1. Patchew
  2. linux
  3. [PATCH V10 00/22] arch: Add basic LoongArch support
  4. View patch

[PATCH V10 19/22] LoongArch: Add VDSO and VSYSCALL support

Huacai Chen posted 22 patches 3 years, 9 months ago
There is a newer version of this series
[PATCH V10 19/22] LoongArch: Add VDSO and VSYSCALL support
Posted by Huacai Chen 3 years, 9 months ago 
Add VDSO and VSYSCALL support (sigreturn, gettimeofday and its friends)
for LoongArch.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 arch/loongarch/include/asm/vdso.h             |  38 +++++
 arch/loongarch/include/asm/vdso/clocksource.h |   8 +
 .../loongarch/include/asm/vdso/gettimeofday.h |  99 +++++++++++++
 arch/loongarch/include/asm/vdso/processor.h   |  14 ++
 arch/loongarch/include/asm/vdso/vdso.h        |  30 ++++
 arch/loongarch/include/asm/vdso/vsyscall.h    |  27 ++++
 arch/loongarch/kernel/vdso.c                  | 138 ++++++++++++++++++
 arch/loongarch/vdso/Makefile                  |  96 ++++++++++++
 arch/loongarch/vdso/elf.S                     |  15 ++
 arch/loongarch/vdso/gen_vdso_offsets.sh       |  13 ++
 arch/loongarch/vdso/sigreturn.S               |  24 +++
 arch/loongarch/vdso/vdso.S                    |  22 +++
 arch/loongarch/vdso/vdso.lds.S                |  72 +++++++++
 arch/loongarch/vdso/vgettimeofday.c           |  25 ++++
 14 files changed, 621 insertions(+)
 create mode 100644 arch/loongarch/include/asm/vdso.h
 create mode 100644 arch/loongarch/include/asm/vdso/clocksource.h
 create mode 100644 arch/loongarch/include/asm/vdso/gettimeofday.h
 create mode 100644 arch/loongarch/include/asm/vdso/processor.h
 create mode 100644 arch/loongarch/include/asm/vdso/vdso.h
 create mode 100644 arch/loongarch/include/asm/vdso/vsyscall.h
 create mode 100644 arch/loongarch/kernel/vdso.c
 create mode 100644 arch/loongarch/vdso/Makefile
 create mode 100644 arch/loongarch/vdso/elf.S
 create mode 100755 arch/loongarch/vdso/gen_vdso_offsets.sh
 create mode 100644 arch/loongarch/vdso/sigreturn.S
 create mode 100644 arch/loongarch/vdso/vdso.S
 create mode 100644 arch/loongarch/vdso/vdso.lds.S
 create mode 100644 arch/loongarch/vdso/vgettimeofday.c

diff --git a/arch/loongarch/include/asm/vdso.h b/arch/loongarch/include/asm/vdso.h
new file mode 100644
index 000000000000..996bddae12dc
--- /dev/null
+++ b/arch/loongarch/include/asm/vdso.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#ifndef __ASM_VDSO_H
+#define __ASM_VDSO_H
+
+#include <linux/mm_types.h>
+#include <vdso/datapage.h>
+
+#include <asm/barrier.h>
+
+/**
+ * struct loongarch_vdso_info - Details of a VDSO image.
+ * @vdso: Pointer to VDSO image (page-aligned).
+ * @size: Size of the VDSO image (page-aligned).
+ * @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.
+ * @code_mapping: Special mapping structure for vdso code.
+ * @code_mapping: Special mapping structure for vdso data.
+ *
+ * This structure contains details of a VDSO image, including the image data
+ * and offsets of certain symbols required by the kernel. It is generated as
+ * part of the VDSO build process, aside from the mapping page array, which is
+ * populated at runtime.
+ */
+struct loongarch_vdso_info {
+	void *vdso;
+	unsigned long size;
+	unsigned long offset_sigreturn;
+	struct vm_special_mapping code_mapping;
+	struct vm_special_mapping data_mapping;
+};
+
+extern struct loongarch_vdso_info vdso_info;
+
+#endif /* __ASM_VDSO_H */
diff --git a/arch/loongarch/include/asm/vdso/clocksource.h b/arch/loongarch/include/asm/vdso/clocksource.h
new file mode 100644
index 000000000000..13cd580d406d
--- /dev/null
+++ b/arch/loongarch/include/asm/vdso/clocksource.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __ASM_VDSOCLOCKSOURCE_H
+#define __ASM_VDSOCLOCKSOURCE_H
+
+#define VDSO_ARCH_CLOCKMODES	\
+	VDSO_CLOCKMODE_CPU
+
+#endif /* __ASM_VDSOCLOCKSOURCE_H */
diff --git a/arch/loongarch/include/asm/vdso/gettimeofday.h b/arch/loongarch/include/asm/vdso/gettimeofday.h
new file mode 100644
index 000000000000..5fc5a746b1c4
--- /dev/null
+++ b/arch/loongarch/include/asm/vdso/gettimeofday.h
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#ifndef __ASM_VDSO_GETTIMEOFDAY_H
+#define __ASM_VDSO_GETTIMEOFDAY_H
+
+#ifndef __ASSEMBLY__
+
+#include <asm/unistd.h>
+#include <asm/vdso/vdso.h>
+
+#define VDSO_HAS_CLOCK_GETRES		1
+
+static __always_inline long gettimeofday_fallback(
+				struct __kernel_old_timeval *_tv,
+				struct timezone *_tz)
+{
+	register struct __kernel_old_timeval *tv asm("a0") = _tv;
+	register struct timezone *tz asm("a1") = _tz;
+	register long nr asm("a7") = __NR_gettimeofday;
+	register long ret asm("v0");
+
+	asm volatile(
+	"       syscall 0\n"
+	: "=r" (ret)
+	: "r" (nr), "r" (tv), "r" (tz)
+	: "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
+	  "$t8", "memory");
+
+	return ret;
+}
+
+static __always_inline long clock_gettime_fallback(
+					clockid_t _clkid,
+					struct __kernel_timespec *_ts)
+{
+	register clockid_t clkid asm("a0") = _clkid;
+	register struct __kernel_timespec *ts asm("a1") = _ts;
+	register long nr asm("a7") = __NR_clock_gettime;
+	register long ret asm("v0");
+
+	asm volatile(
+	"       syscall 0\n"
+	: "=r" (ret)
+	: "r" (nr), "r" (clkid), "r" (ts)
+	: "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
+	  "$t8", "memory");
+
+	return ret;
+}
+
+static __always_inline int clock_getres_fallback(
+					clockid_t _clkid,
+					struct __kernel_timespec *_ts)
+{
+	register clockid_t clkid asm("a0") = _clkid;
+	register struct __kernel_timespec *ts asm("a1") = _ts;
+	register long nr asm("a7") = __NR_clock_getres;
+	register long ret asm("v0");
+
+	asm volatile(
+	"       syscall 0\n"
+	: "=r" (ret)
+	: "r" (nr), "r" (clkid), "r" (ts)
+	: "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
+	  "$t8", "memory");
+
+	return ret;
+}
+
+static __always_inline u64 __arch_get_hw_counter(s32 clock_mode,
+						 const struct vdso_data *vd)
+{
+	unsigned int count;
+
+	__asm__ __volatile__(
+	"	rdtime.d %0, $zero\n"
+	: "=r" (count));
+
+	return count;
+}
+
+static inline bool loongarch_vdso_hres_capable(void)
+{
+	return true;
+}
+#define __arch_vdso_hres_capable loongarch_vdso_hres_capable
+
+static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
+{
+	return get_vdso_data();
+}
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
diff --git a/arch/loongarch/include/asm/vdso/processor.h b/arch/loongarch/include/asm/vdso/processor.h
new file mode 100644
index 000000000000..ef5770b343a0
--- /dev/null
+++ b/arch/loongarch/include/asm/vdso/processor.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#ifndef __ASM_VDSO_PROCESSOR_H
+#define __ASM_VDSO_PROCESSOR_H
+
+#ifndef __ASSEMBLY__
+
+#define cpu_relax()	barrier()
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_PROCESSOR_H */
diff --git a/arch/loongarch/include/asm/vdso/vdso.h b/arch/loongarch/include/asm/vdso/vdso.h
new file mode 100644
index 000000000000..5a01643a65b3
--- /dev/null
+++ b/arch/loongarch/include/asm/vdso/vdso.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#ifndef __ASSEMBLY__
+
+#include <asm/asm.h>
+#include <asm/page.h>
+
+static inline unsigned long get_vdso_base(void)
+{
+	unsigned long addr;
+
+	__asm__(
+	" la.pcrel %0, _start\n"
+	: "=r" (addr)
+	:
+	:);
+
+	return addr;
+}
+
+static inline const struct vdso_data *get_vdso_data(void)
+{
+	return (const struct vdso_data *)(get_vdso_base() - PAGE_SIZE);
+}
+
+#endif /* __ASSEMBLY__ */
diff --git a/arch/loongarch/include/asm/vdso/vsyscall.h b/arch/loongarch/include/asm/vdso/vsyscall.h
new file mode 100644
index 000000000000..5de615383a22
--- /dev/null
+++ b/arch/loongarch/include/asm/vdso/vsyscall.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_VDSO_VSYSCALL_H
+#define __ASM_VDSO_VSYSCALL_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/timekeeper_internal.h>
+#include <vdso/datapage.h>
+
+extern struct vdso_data *vdso_data;
+
+/*
+ * Update the vDSO data page to keep in sync with kernel timekeeping.
+ */
+static __always_inline
+struct vdso_data *__loongarch_get_k_vdso_data(void)
+{
+	return vdso_data;
+}
+#define __arch_get_k_vdso_data __loongarch_get_k_vdso_data
+
+/* The asm-generic header needs to be included after the definitions above */
+#include <asm-generic/vdso/vsyscall.h>
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_VSYSCALL_H */
diff --git a/arch/loongarch/kernel/vdso.c b/arch/loongarch/kernel/vdso.c
new file mode 100644
index 000000000000..e20c8ca87473
--- /dev/null
+++ b/arch/loongarch/kernel/vdso.c
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/binfmts.h>
+#include <linux/elf.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/random.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/timekeeper_internal.h>
+
+#include <asm/page.h>
+#include <asm/vdso.h>
+#include <vdso/helpers.h>
+#include <vdso/vsyscall.h>
+#include <generated/vdso-offsets.h>
+
+extern char vdso_start[], vdso_end[];
+
+/* Kernel-provided data used by the VDSO. */
+static union loongarch_vdso_data {
+	u8 page[PAGE_SIZE];
+	struct vdso_data data[CS_BASES];
+} loongarch_vdso_data __page_aligned_data;
+struct vdso_data *vdso_data = loongarch_vdso_data.data;
+static struct page *vdso_pages[] = { NULL };
+
+static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
+{
+	current->mm->context.vdso = (void *)(new_vma->vm_start);
+
+	return 0;
+}
+
+struct loongarch_vdso_info vdso_info = {
+	.vdso = vdso_start,
+	.size = PAGE_SIZE,
+	.code_mapping = {
+		.name = "[vdso]",
+		.pages = vdso_pages,
+		.mremap = vdso_mremap,
+	},
+	.data_mapping = {
+		.name = "[vvar]",
+	},
+	.offset_sigreturn = vdso_offset_sigreturn,
+};
+
+static int __init init_vdso(void)
+{
+	unsigned long i, pfn;
+
+	BUG_ON(!PAGE_ALIGNED(vdso_info.vdso));
+	BUG_ON(!PAGE_ALIGNED(vdso_info.size));
+
+	pfn = __phys_to_pfn(__pa_symbol(vdso_info.vdso));
+	for (i = 0; i < vdso_info.size / PAGE_SIZE; i++)
+		vdso_info.code_mapping.pages[i] = pfn_to_page(pfn + i);
+
+	return 0;
+}
+subsys_initcall(init_vdso);
+
+static unsigned long vdso_base(void)
+{
+	unsigned long base = STACK_TOP;
+
+	if (current->flags & PF_RANDOMIZE) {
+		base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
+		base = PAGE_ALIGN(base);
+	}
+
+	return base;
+}
+
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+	int ret;
+	unsigned long vvar_size, size, data_addr, vdso_addr;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	struct loongarch_vdso_info *info = current->thread.vdso;
+
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
+	/*
+	 * Determine total area size. This includes the VDSO data itself
+	 * and the data page.
+	 */
+	vvar_size = PAGE_SIZE;
+	size = vvar_size + info->size;
+
+	data_addr = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
+	if (IS_ERR_VALUE(data_addr)) {
+		ret = data_addr;
+		goto out;
+	}
+	vdso_addr = data_addr + PAGE_SIZE;
+
+	vma = _install_special_mapping(mm, data_addr, vvar_size,
+				       VM_READ | VM_MAYREAD,
+				       &info->data_mapping);
+	if (IS_ERR(vma)) {
+		ret = PTR_ERR(vma);
+		goto out;
+	}
+
+	/* Map VDSO data page. */
+	ret = remap_pfn_range(vma, data_addr,
+			      virt_to_phys(vdso_data) >> PAGE_SHIFT,
+			      PAGE_SIZE, PAGE_READONLY);
+	if (ret)
+		goto out;
+
+	/* Map VDSO code page. */
+	vma = _install_special_mapping(mm, vdso_addr, info->size,
+				       VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
+				       &info->code_mapping);
+	if (IS_ERR(vma)) {
+		ret = PTR_ERR(vma);
+		goto out;
+	}
+
+	mm->context.vdso = (void *)vdso_addr;
+	ret = 0;
+
+out:
+	mmap_write_unlock(mm);
+	return ret;
+}
diff --git a/arch/loongarch/vdso/Makefile b/arch/loongarch/vdso/Makefile
new file mode 100644
index 000000000000..6b6e16732c60
--- /dev/null
+++ b/arch/loongarch/vdso/Makefile
@@ -0,0 +1,96 @@
+# SPDX-License-Identifier: GPL-2.0
+# Objects to go into the VDSO.
+
+# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
+# the inclusion of generic Makefile.
+ARCH_REL_TYPE_ABS := R_LARCH_32|R_LARCH_64|R_LARCH_MARK_LA|R_LARCH_JUMP_SLOT
+include $(srctree)/lib/vdso/Makefile
+
+obj-vdso-y := elf.o vgettimeofday.o sigreturn.o
+
+# Common compiler flags between ABIs.
+ccflags-vdso := \
+	$(filter -I%,$(KBUILD_CFLAGS)) \
+	$(filter -E%,$(KBUILD_CFLAGS)) \
+	$(filter -march=%,$(KBUILD_CFLAGS)) \
+	$(filter -m%-float,$(KBUILD_CFLAGS)) \
+	-D__VDSO__
+
+ifeq ($(cc-name),clang)
+ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
+endif
+
+cflags-vdso := $(ccflags-vdso) \
+	$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
+	-O2 -g -fno-strict-aliasing -fno-common -fno-builtin -G0 \
+	-fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
+	$(call cc-option, -fno-asynchronous-unwind-tables) \
+	$(call cc-option, -fno-stack-protector)
+aflags-vdso := $(ccflags-vdso) \
+	-D__ASSEMBLY__ -Wa,-gdwarf-2
+
+ifneq ($(c-gettimeofday-y),)
+  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
+endif
+
+# VDSO linker flags.
+ldflags-y := -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
+	$(filter -E%,$(KBUILD_CFLAGS)) -nostdlib -shared \
+	--hash-style=sysv --build-id -T
+
+GCOV_PROFILE := n
+
+#
+# Shared build commands.
+#
+
+quiet_cmd_vdsold_and_vdso_check = LD      $@
+      cmd_vdsold_and_vdso_check = $(cmd_ld); $(cmd_vdso_check)
+
+quiet_cmd_vdsoas_o_S = AS       $@
+      cmd_vdsoas_o_S = $(CC) $(a_flags) -c -o $@ $<
+
+# Generate VDSO offsets using helper script
+gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
+quiet_cmd_vdsosym = VDSOSYM $@
+      cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
+
+include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
+	$(call if_changed,vdsosym)
+
+#
+# Build native VDSO.
+#
+
+native-abi := $(filter -mabi=%,$(KBUILD_CFLAGS))
+
+targets += $(obj-vdso-y)
+targets += vdso.lds vdso.so.dbg vdso.so
+
+obj-vdso := $(obj-vdso-y:%.o=$(obj)/%.o)
+
+$(obj-vdso): KBUILD_CFLAGS := $(cflags-vdso) $(native-abi)
+$(obj-vdso): KBUILD_AFLAGS := $(aflags-vdso) $(native-abi)
+
+$(obj)/vdso.lds: KBUILD_CPPFLAGS := $(ccflags-vdso) $(native-abi)
+
+$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
+	$(call if_changed,vdsold_and_vdso_check)
+
+$(obj)/vdso.so: OBJCOPYFLAGS := -S
+$(obj)/vdso.so: $(obj)/vdso.so.dbg FORCE
+	$(call if_changed,objcopy)
+
+obj-y += vdso.o
+
+$(obj)/vdso.o : $(obj)/vdso.so
+
+# install commands for the unstripped file
+quiet_cmd_vdso_install = INSTALL $@
+      cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
+
+vdso.so: $(obj)/vdso.so.dbg
+	@mkdir -p $(MODLIB)/vdso
+	$(call cmd,vdso_install)
+
+vdso_install: vdso.so
diff --git a/arch/loongarch/vdso/elf.S b/arch/loongarch/vdso/elf.S
new file mode 100644
index 000000000000..9bb21b9f9583
--- /dev/null
+++ b/arch/loongarch/vdso/elf.S
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <asm/vdso/vdso.h>
+
+#include <linux/elfnote.h>
+#include <linux/version.h>
+
+ELFNOTE_START(Linux, 0, "a")
+	.long LINUX_VERSION_CODE
+ELFNOTE_END
diff --git a/arch/loongarch/vdso/gen_vdso_offsets.sh b/arch/loongarch/vdso/gen_vdso_offsets.sh
new file mode 100755
index 000000000000..1bb4e12642ff
--- /dev/null
+++ b/arch/loongarch/vdso/gen_vdso_offsets.sh
@@ -0,0 +1,13 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+#
+# Derived from RISC-V and ARM64:
+# Author: Will Deacon <will.deacon@arm.com>
+#
+# Match symbols in the DSO that look like VDSO_*; produce a header file
+# of constant offsets into the shared object.
+#
+
+LC_ALL=C sed -n -e 's/^00*/0/' -e \
+'s/^\([0-9a-fA-F]*\) . VDSO_\([a-zA-Z0-9_]*\)$/\#define vdso_offset_\2\t0x\1/p'
diff --git a/arch/loongarch/vdso/sigreturn.S b/arch/loongarch/vdso/sigreturn.S
new file mode 100644
index 000000000000..9cb3c58fad03
--- /dev/null
+++ b/arch/loongarch/vdso/sigreturn.S
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <asm/vdso/vdso.h>
+
+#include <linux/linkage.h>
+#include <uapi/asm/unistd.h>
+
+#include <asm/regdef.h>
+#include <asm/asm.h>
+
+	.section	.text
+	.cfi_sections	.debug_frame
+
+SYM_FUNC_START(__vdso_rt_sigreturn)
+
+	li.w	a7, __NR_rt_sigreturn
+	syscall	0
+
+SYM_FUNC_END(__vdso_rt_sigreturn)
diff --git a/arch/loongarch/vdso/vdso.S b/arch/loongarch/vdso/vdso.S
new file mode 100644
index 000000000000..46789bade6ff
--- /dev/null
+++ b/arch/loongarch/vdso/vdso.S
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ *
+ * Derived from RISC-V:
+ * Copyright (C) 2014 Regents of the University of California
+ */
+
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/page.h>
+
+	__PAGE_ALIGNED_DATA
+
+	.globl vdso_start, vdso_end
+	.balign PAGE_SIZE
+vdso_start:
+	.incbin "arch/loongarch/vdso/vdso.so"
+	.balign PAGE_SIZE
+vdso_end:
+
+	.previous
diff --git a/arch/loongarch/vdso/vdso.lds.S b/arch/loongarch/vdso/vdso.lds.S
new file mode 100644
index 000000000000..955f02de4a2d
--- /dev/null
+++ b/arch/loongarch/vdso/vdso.lds.S
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+OUTPUT_FORMAT("elf64-loongarch", "elf64-loongarch", "elf64-loongarch")
+
+OUTPUT_ARCH(loongarch)
+
+SECTIONS
+{
+	PROVIDE(_start = .);
+	. = SIZEOF_HEADERS;
+
+	.hash		: { *(.hash) }			:text
+	.gnu.hash	: { *(.gnu.hash) }
+	.dynsym		: { *(.dynsym) }
+	.dynstr		: { *(.dynstr) }
+	.gnu.version	: { *(.gnu.version) }
+	.gnu.version_d	: { *(.gnu.version_d) }
+	.gnu.version_r	: { *(.gnu.version_r) }
+
+	.note		: { *(.note.*) }		:text :note
+
+	.text		: { *(.text*) }			:text
+	PROVIDE (__etext = .);
+	PROVIDE (_etext = .);
+	PROVIDE (etext = .);
+
+	.eh_frame_hdr	: { *(.eh_frame_hdr) }		:text :eh_frame_hdr
+	.eh_frame	: { KEEP (*(.eh_frame)) }	:text
+
+	.dynamic	: { *(.dynamic) }		:text :dynamic
+
+	.rodata		: { *(.rodata*) }		:text
+
+	_end = .;
+	PROVIDE(end = .);
+
+	/DISCARD/	: {
+		*(.gnu.attributes)
+		*(.note.GNU-stack)
+		*(.data .data.* .gnu.linkonce.d.* .sdata*)
+		*(.bss .sbss .dynbss .dynsbss)
+	}
+}
+
+PHDRS
+{
+	text		PT_LOAD		FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
+	dynamic		PT_DYNAMIC	FLAGS(4);		/* PF_R */
+	note		PT_NOTE		FLAGS(4);		/* PF_R */
+	eh_frame_hdr	PT_GNU_EH_FRAME;
+}
+
+VERSION
+{
+	LINUX_5.10 {
+	global:
+		__vdso_clock_getres;
+		__vdso_clock_gettime;
+		__vdso_gettimeofday;
+		__vdso_rt_sigreturn;
+	local: *;
+	};
+}
+
+/*
+ * Make the sigreturn code visible to the kernel.
+ */
+VDSO_sigreturn		= __vdso_rt_sigreturn;
diff --git a/arch/loongarch/vdso/vgettimeofday.c b/arch/loongarch/vdso/vgettimeofday.c
new file mode 100644
index 000000000000..b1f4548dae92
--- /dev/null
+++ b/arch/loongarch/vdso/vgettimeofday.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * LoongArch userspace implementations of gettimeofday() and similar.
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#include <linux/types.h>
+
+int __vdso_clock_gettime(clockid_t clock,
+			 struct __kernel_timespec *ts)
+{
+	return __cvdso_clock_gettime(clock, ts);
+}
+
+int __vdso_gettimeofday(struct __kernel_old_timeval *tv,
+			struct timezone *tz)
+{
+	return __cvdso_gettimeofday(tv, tz);
+}
+
+int __vdso_clock_getres(clockid_t clock_id,
+			struct __kernel_timespec *res)
+{
+	return __cvdso_clock_getres(clock_id, res);
+}
-- 
2.27.0
Re: [PATCH V10 19/22] LoongArch: Add VDSO and VSYSCALL support
Posted by WANG Xuerui 3 years, 9 months ago 
Hi,

On 5/14/22 16:03, Huacai Chen wrote:
> Add VDSO and VSYSCALL support (sigreturn, gettimeofday and its friends)
> for LoongArch.
>
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> ---
>   arch/loongarch/include/asm/vdso.h             |  38 +++++
>   arch/loongarch/include/asm/vdso/clocksource.h |   8 +
>   .../loongarch/include/asm/vdso/gettimeofday.h |  99 +++++++++++++
>   arch/loongarch/include/asm/vdso/processor.h   |  14 ++
>   arch/loongarch/include/asm/vdso/vdso.h        |  30 ++++
>   arch/loongarch/include/asm/vdso/vsyscall.h    |  27 ++++
>   arch/loongarch/kernel/vdso.c                  | 138 ++++++++++++++++++
>   arch/loongarch/vdso/Makefile                  |  96 ++++++++++++
>   arch/loongarch/vdso/elf.S                     |  15 ++
>   arch/loongarch/vdso/gen_vdso_offsets.sh       |  13 ++
>   arch/loongarch/vdso/sigreturn.S               |  24 +++
>   arch/loongarch/vdso/vdso.S                    |  22 +++
>   arch/loongarch/vdso/vdso.lds.S                |  72 +++++++++
>   arch/loongarch/vdso/vgettimeofday.c           |  25 ++++
>   14 files changed, 621 insertions(+)
>   create mode 100644 arch/loongarch/include/asm/vdso.h
>   create mode 100644 arch/loongarch/include/asm/vdso/clocksource.h
>   create mode 100644 arch/loongarch/include/asm/vdso/gettimeofday.h
>   create mode 100644 arch/loongarch/include/asm/vdso/processor.h
>   create mode 100644 arch/loongarch/include/asm/vdso/vdso.h
>   create mode 100644 arch/loongarch/include/asm/vdso/vsyscall.h
>   create mode 100644 arch/loongarch/kernel/vdso.c
>   create mode 100644 arch/loongarch/vdso/Makefile
>   create mode 100644 arch/loongarch/vdso/elf.S
>   create mode 100755 arch/loongarch/vdso/gen_vdso_offsets.sh
>   create mode 100644 arch/loongarch/vdso/sigreturn.S
>   create mode 100644 arch/loongarch/vdso/vdso.S
>   create mode 100644 arch/loongarch/vdso/vdso.lds.S
>   create mode 100644 arch/loongarch/vdso/vgettimeofday.c
>
> diff --git a/arch/loongarch/include/asm/vdso.h b/arch/loongarch/include/asm/vdso.h
> new file mode 100644
> index 000000000000..996bddae12dc
> --- /dev/null
> +++ b/arch/loongarch/include/asm/vdso.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Author: Huacai Chen <chenhuacai@loongson.cn>
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +
> +#ifndef __ASM_VDSO_H
> +#define __ASM_VDSO_H
> +
> +#include <linux/mm_types.h>
> +#include <vdso/datapage.h>
> +
> +#include <asm/barrier.h>
> +
> +/**
> + * struct loongarch_vdso_info - Details of a VDSO image.
> + * @vdso: Pointer to VDSO image (page-aligned).
> + * @size: Size of the VDSO image (page-aligned).
> + * @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.
> + * @code_mapping: Special mapping structure for vdso code.
> + * @code_mapping: Special mapping structure for vdso data.
> + *
> + * This structure contains details of a VDSO image, including the image data
> + * and offsets of certain symbols required by the kernel. It is generated as
> + * part of the VDSO build process, aside from the mapping page array, which is
> + * populated at runtime.
> + */
> +struct loongarch_vdso_info {
> +	void *vdso;
> +	unsigned long size;
> +	unsigned long offset_sigreturn;
> +	struct vm_special_mapping code_mapping;
> +	struct vm_special_mapping data_mapping;
> +};
> +
> +extern struct loongarch_vdso_info vdso_info;
> +
> +#endif /* __ASM_VDSO_H */
> diff --git a/arch/loongarch/include/asm/vdso/clocksource.h b/arch/loongarch/include/asm/vdso/clocksource.h
> new file mode 100644
> index 000000000000..13cd580d406d
> --- /dev/null
> +++ b/arch/loongarch/include/asm/vdso/clocksource.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef __ASM_VDSOCLOCKSOURCE_H
> +#define __ASM_VDSOCLOCKSOURCE_H
> +
> +#define VDSO_ARCH_CLOCKMODES	\
> +	VDSO_CLOCKMODE_CPU
> +
> +#endif /* __ASM_VDSOCLOCKSOURCE_H */
> diff --git a/arch/loongarch/include/asm/vdso/gettimeofday.h b/arch/loongarch/include/asm/vdso/gettimeofday.h
> new file mode 100644
> index 000000000000..5fc5a746b1c4
> --- /dev/null
> +++ b/arch/loongarch/include/asm/vdso/gettimeofday.h
> @@ -0,0 +1,99 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Author: Huacai Chen <chenhuacai@loongson.cn>
> + *
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +#ifndef __ASM_VDSO_GETTIMEOFDAY_H
> +#define __ASM_VDSO_GETTIMEOFDAY_H
> +
> +#ifndef __ASSEMBLY__
> +
> +#include <asm/unistd.h>
> +#include <asm/vdso/vdso.h>
> +
> +#define VDSO_HAS_CLOCK_GETRES		1
> +
> +static __always_inline long gettimeofday_fallback(
> +				struct __kernel_old_timeval *_tv,
> +				struct timezone *_tz)
> +{
> +	register struct __kernel_old_timeval *tv asm("a0") = _tv;
> +	register struct timezone *tz asm("a1") = _tz;
> +	register long nr asm("a7") = __NR_gettimeofday;
> +	register long ret asm("v0");
> +
> +	asm volatile(
> +	"       syscall 0\n"
> +	: "=r" (ret)
> +	: "r" (nr), "r" (tv), "r" (tz)
> +	: "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
> +	  "$t8", "memory");
Here ret is being hinted to register $v0, which is in fact the same 
register as $a0; so I'm afraid the "=r" constraint wouldn't prevent the 
$a0 from being clobbered before the syscall insn? Changing "v0" to "a0", 
then "=r" to "+r", could do it, although I cannot build-test it (due to 
the boot protocol being incompatible with existing shipped systems). 
Please check this for me...
> +
> +	return ret;
> +}
> +
> +static __always_inline long clock_gettime_fallback(
> +					clockid_t _clkid,
> +					struct __kernel_timespec *_ts)
> +{
> +	register clockid_t clkid asm("a0") = _clkid;
> +	register struct __kernel_timespec *ts asm("a1") = _ts;
> +	register long nr asm("a7") = __NR_clock_gettime;
> +	register long ret asm("v0");
> +
> +	asm volatile(
> +	"       syscall 0\n"
> +	: "=r" (ret)
> +	: "r" (nr), "r" (clkid), "r" (ts)
> +	: "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
> +	  "$t8", "memory");
> +
> +	return ret;
> +}
> +
> +static __always_inline int clock_getres_fallback(
> +					clockid_t _clkid,
> +					struct __kernel_timespec *_ts)
> +{
> +	register clockid_t clkid asm("a0") = _clkid;
> +	register struct __kernel_timespec *ts asm("a1") = _ts;
> +	register long nr asm("a7") = __NR_clock_getres;
> +	register long ret asm("v0");
> +
> +	asm volatile(
> +	"       syscall 0\n"
> +	: "=r" (ret)
> +	: "r" (nr), "r" (clkid), "r" (ts)
> +	: "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
> +	  "$t8", "memory");
> +
> +	return ret;
> +}
> +
> +static __always_inline u64 __arch_get_hw_counter(s32 clock_mode,
> +						 const struct vdso_data *vd)
> +{
> +	unsigned int count;
> +
> +	__asm__ __volatile__(
> +	"	rdtime.d %0, $zero\n"
> +	: "=r" (count));
> +
> +	return count;
> +}
> +
> +static inline bool loongarch_vdso_hres_capable(void)
> +{
> +	return true;
> +}
> +#define __arch_vdso_hres_capable loongarch_vdso_hres_capable
> +
> +static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
> +{
> +	return get_vdso_data();
> +}
> +
> +#endif /* !__ASSEMBLY__ */
> +
> +#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
> diff --git a/arch/loongarch/include/asm/vdso/processor.h b/arch/loongarch/include/asm/vdso/processor.h
> new file mode 100644
> index 000000000000..ef5770b343a0
> --- /dev/null
> +++ b/arch/loongarch/include/asm/vdso/processor.h
> @@ -0,0 +1,14 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +#ifndef __ASM_VDSO_PROCESSOR_H
> +#define __ASM_VDSO_PROCESSOR_H
> +
> +#ifndef __ASSEMBLY__
> +
> +#define cpu_relax()	barrier()
> +
> +#endif /* __ASSEMBLY__ */
> +
> +#endif /* __ASM_VDSO_PROCESSOR_H */
> diff --git a/arch/loongarch/include/asm/vdso/vdso.h b/arch/loongarch/include/asm/vdso/vdso.h
> new file mode 100644
> index 000000000000..5a01643a65b3
> --- /dev/null
> +++ b/arch/loongarch/include/asm/vdso/vdso.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Author: Huacai Chen <chenhuacai@loongson.cn>
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +
> +#ifndef __ASSEMBLY__
> +
> +#include <asm/asm.h>
> +#include <asm/page.h>
> +
> +static inline unsigned long get_vdso_base(void)
> +{
> +	unsigned long addr;
> +
> +	__asm__(
> +	" la.pcrel %0, _start\n"
> +	: "=r" (addr)
> +	:
> +	:);
> +
> +	return addr;
> +}
> +
> +static inline const struct vdso_data *get_vdso_data(void)
> +{
> +	return (const struct vdso_data *)(get_vdso_base() - PAGE_SIZE);
> +}
> +
> +#endif /* __ASSEMBLY__ */
> diff --git a/arch/loongarch/include/asm/vdso/vsyscall.h b/arch/loongarch/include/asm/vdso/vsyscall.h
> new file mode 100644
> index 000000000000..5de615383a22
> --- /dev/null
> +++ b/arch/loongarch/include/asm/vdso/vsyscall.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __ASM_VDSO_VSYSCALL_H
> +#define __ASM_VDSO_VSYSCALL_H
> +
> +#ifndef __ASSEMBLY__
> +
> +#include <linux/timekeeper_internal.h>
> +#include <vdso/datapage.h>
> +
> +extern struct vdso_data *vdso_data;
> +
> +/*
> + * Update the vDSO data page to keep in sync with kernel timekeeping.
> + */
> +static __always_inline
> +struct vdso_data *__loongarch_get_k_vdso_data(void)
> +{
> +	return vdso_data;
> +}
> +#define __arch_get_k_vdso_data __loongarch_get_k_vdso_data
> +
> +/* The asm-generic header needs to be included after the definitions above */
> +#include <asm-generic/vdso/vsyscall.h>
> +
> +#endif /* !__ASSEMBLY__ */
> +
> +#endif /* __ASM_VDSO_VSYSCALL_H */
> diff --git a/arch/loongarch/kernel/vdso.c b/arch/loongarch/kernel/vdso.c
> new file mode 100644
> index 000000000000..e20c8ca87473
> --- /dev/null
> +++ b/arch/loongarch/kernel/vdso.c
> @@ -0,0 +1,138 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Author: Huacai Chen <chenhuacai@loongson.cn>
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +
> +#include <linux/binfmts.h>
> +#include <linux/elf.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/ioport.h>
> +#include <linux/kernel.h>
> +#include <linux/mm.h>
> +#include <linux/random.h>
> +#include <linux/sched.h>
> +#include <linux/slab.h>
> +#include <linux/timekeeper_internal.h>
> +
> +#include <asm/page.h>
> +#include <asm/vdso.h>
> +#include <vdso/helpers.h>
> +#include <vdso/vsyscall.h>
> +#include <generated/vdso-offsets.h>
> +
> +extern char vdso_start[], vdso_end[];
> +
> +/* Kernel-provided data used by the VDSO. */
> +static union loongarch_vdso_data {
> +	u8 page[PAGE_SIZE];
> +	struct vdso_data data[CS_BASES];
> +} loongarch_vdso_data __page_aligned_data;
> +struct vdso_data *vdso_data = loongarch_vdso_data.data;
> +static struct page *vdso_pages[] = { NULL };
> +
> +static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
> +{
> +	current->mm->context.vdso = (void *)(new_vma->vm_start);
> +
> +	return 0;
> +}
> +
> +struct loongarch_vdso_info vdso_info = {
> +	.vdso = vdso_start,
> +	.size = PAGE_SIZE,
> +	.code_mapping = {
> +		.name = "[vdso]",
> +		.pages = vdso_pages,
> +		.mremap = vdso_mremap,
> +	},
> +	.data_mapping = {
> +		.name = "[vvar]",
> +	},
> +	.offset_sigreturn = vdso_offset_sigreturn,
> +};
> +
> +static int __init init_vdso(void)
> +{
> +	unsigned long i, pfn;
> +
> +	BUG_ON(!PAGE_ALIGNED(vdso_info.vdso));
> +	BUG_ON(!PAGE_ALIGNED(vdso_info.size));
> +
> +	pfn = __phys_to_pfn(__pa_symbol(vdso_info.vdso));
> +	for (i = 0; i < vdso_info.size / PAGE_SIZE; i++)
> +		vdso_info.code_mapping.pages[i] = pfn_to_page(pfn + i);
> +
> +	return 0;
> +}
> +subsys_initcall(init_vdso);
> +
> +static unsigned long vdso_base(void)
> +{
> +	unsigned long base = STACK_TOP;
> +
> +	if (current->flags & PF_RANDOMIZE) {
> +		base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
> +		base = PAGE_ALIGN(base);
> +	}
> +
> +	return base;
> +}
> +
> +int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
> +{
> +	int ret;
> +	unsigned long vvar_size, size, data_addr, vdso_addr;
> +	struct mm_struct *mm = current->mm;
> +	struct vm_area_struct *vma;
> +	struct loongarch_vdso_info *info = current->thread.vdso;
> +
> +	if (mmap_write_lock_killable(mm))
> +		return -EINTR;
> +
> +	/*
> +	 * Determine total area size. This includes the VDSO data itself
> +	 * and the data page.
> +	 */
> +	vvar_size = PAGE_SIZE;
> +	size = vvar_size + info->size;
> +
> +	data_addr = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
> +	if (IS_ERR_VALUE(data_addr)) {
> +		ret = data_addr;
> +		goto out;
> +	}
> +	vdso_addr = data_addr + PAGE_SIZE;
> +
> +	vma = _install_special_mapping(mm, data_addr, vvar_size,
> +				       VM_READ | VM_MAYREAD,
> +				       &info->data_mapping);
> +	if (IS_ERR(vma)) {
> +		ret = PTR_ERR(vma);
> +		goto out;
> +	}
> +
> +	/* Map VDSO data page. */
> +	ret = remap_pfn_range(vma, data_addr,
> +			      virt_to_phys(vdso_data) >> PAGE_SHIFT,
> +			      PAGE_SIZE, PAGE_READONLY);
> +	if (ret)
> +		goto out;
> +
> +	/* Map VDSO code page. */
> +	vma = _install_special_mapping(mm, vdso_addr, info->size,
> +				       VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
> +				       &info->code_mapping);
> +	if (IS_ERR(vma)) {
> +		ret = PTR_ERR(vma);
> +		goto out;
> +	}
> +
> +	mm->context.vdso = (void *)vdso_addr;
> +	ret = 0;
> +
> +out:
> +	mmap_write_unlock(mm);
> +	return ret;
> +}
> diff --git a/arch/loongarch/vdso/Makefile b/arch/loongarch/vdso/Makefile
> new file mode 100644
> index 000000000000..6b6e16732c60
> --- /dev/null
> +++ b/arch/loongarch/vdso/Makefile
> @@ -0,0 +1,96 @@
> +# SPDX-License-Identifier: GPL-2.0
> +# Objects to go into the VDSO.
> +
> +# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
> +# the inclusion of generic Makefile.
> +ARCH_REL_TYPE_ABS := R_LARCH_32|R_LARCH_64|R_LARCH_MARK_LA|R_LARCH_JUMP_SLOT
> +include $(srctree)/lib/vdso/Makefile
> +
> +obj-vdso-y := elf.o vgettimeofday.o sigreturn.o
> +
> +# Common compiler flags between ABIs.
> +ccflags-vdso := \
> +	$(filter -I%,$(KBUILD_CFLAGS)) \
> +	$(filter -E%,$(KBUILD_CFLAGS)) \
> +	$(filter -march=%,$(KBUILD_CFLAGS)) \
> +	$(filter -m%-float,$(KBUILD_CFLAGS)) \
> +	-D__VDSO__
> +
> +ifeq ($(cc-name),clang)
> +ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
> +endif
> +
> +cflags-vdso := $(ccflags-vdso) \
> +	$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
> +	-O2 -g -fno-strict-aliasing -fno-common -fno-builtin -G0 \
> +	-fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
> +	$(call cc-option, -fno-asynchronous-unwind-tables) \
> +	$(call cc-option, -fno-stack-protector)
> +aflags-vdso := $(ccflags-vdso) \
> +	-D__ASSEMBLY__ -Wa,-gdwarf-2
> +
> +ifneq ($(c-gettimeofday-y),)
> +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> +endif
> +
> +# VDSO linker flags.
> +ldflags-y := -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
> +	$(filter -E%,$(KBUILD_CFLAGS)) -nostdlib -shared \
> +	--hash-style=sysv --build-id -T
> +
> +GCOV_PROFILE := n
> +
> +#
> +# Shared build commands.
> +#
> +
> +quiet_cmd_vdsold_and_vdso_check = LD      $@
> +      cmd_vdsold_and_vdso_check = $(cmd_ld); $(cmd_vdso_check)
> +
> +quiet_cmd_vdsoas_o_S = AS       $@
> +      cmd_vdsoas_o_S = $(CC) $(a_flags) -c -o $@ $<
> +
> +# Generate VDSO offsets using helper script
> +gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
> +quiet_cmd_vdsosym = VDSOSYM $@
> +      cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
> +
> +include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
> +	$(call if_changed,vdsosym)
> +
> +#
> +# Build native VDSO.
> +#
> +
> +native-abi := $(filter -mabi=%,$(KBUILD_CFLAGS))
> +
> +targets += $(obj-vdso-y)
> +targets += vdso.lds vdso.so.dbg vdso.so
> +
> +obj-vdso := $(obj-vdso-y:%.o=$(obj)/%.o)
> +
> +$(obj-vdso): KBUILD_CFLAGS := $(cflags-vdso) $(native-abi)
> +$(obj-vdso): KBUILD_AFLAGS := $(aflags-vdso) $(native-abi)
> +
> +$(obj)/vdso.lds: KBUILD_CPPFLAGS := $(ccflags-vdso) $(native-abi)
> +
> +$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
> +	$(call if_changed,vdsold_and_vdso_check)
> +
> +$(obj)/vdso.so: OBJCOPYFLAGS := -S
> +$(obj)/vdso.so: $(obj)/vdso.so.dbg FORCE
> +	$(call if_changed,objcopy)
> +
> +obj-y += vdso.o
> +
> +$(obj)/vdso.o : $(obj)/vdso.so
> +
> +# install commands for the unstripped file
> +quiet_cmd_vdso_install = INSTALL $@
> +      cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
> +
> +vdso.so: $(obj)/vdso.so.dbg
> +	@mkdir -p $(MODLIB)/vdso
> +	$(call cmd,vdso_install)
> +
> +vdso_install: vdso.so
> diff --git a/arch/loongarch/vdso/elf.S b/arch/loongarch/vdso/elf.S
> new file mode 100644
> index 000000000000..9bb21b9f9583
> --- /dev/null
> +++ b/arch/loongarch/vdso/elf.S
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Author: Huacai Chen <chenhuacai@loongson.cn>
> + *
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +
> +#include <asm/vdso/vdso.h>
> +
> +#include <linux/elfnote.h>
> +#include <linux/version.h>
> +
> +ELFNOTE_START(Linux, 0, "a")
> +	.long LINUX_VERSION_CODE
> +ELFNOTE_END
> diff --git a/arch/loongarch/vdso/gen_vdso_offsets.sh b/arch/loongarch/vdso/gen_vdso_offsets.sh
> new file mode 100755
> index 000000000000..1bb4e12642ff
> --- /dev/null
> +++ b/arch/loongarch/vdso/gen_vdso_offsets.sh
> @@ -0,0 +1,13 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +
> +#
> +# Derived from RISC-V and ARM64:
> +# Author: Will Deacon <will.deacon@arm.com>
> +#
> +# Match symbols in the DSO that look like VDSO_*; produce a header file
> +# of constant offsets into the shared object.
> +#
> +
> +LC_ALL=C sed -n -e 's/^00*/0/' -e \
> +'s/^\([0-9a-fA-F]*\) . VDSO_\([a-zA-Z0-9_]*\)$/\#define vdso_offset_\2\t0x\1/p'
> diff --git a/arch/loongarch/vdso/sigreturn.S b/arch/loongarch/vdso/sigreturn.S
> new file mode 100644
> index 000000000000..9cb3c58fad03
> --- /dev/null
> +++ b/arch/loongarch/vdso/sigreturn.S
> @@ -0,0 +1,24 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Author: Huacai Chen <chenhuacai@loongson.cn>
> + *
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +
> +#include <asm/vdso/vdso.h>
> +
> +#include <linux/linkage.h>
> +#include <uapi/asm/unistd.h>
> +
> +#include <asm/regdef.h>
> +#include <asm/asm.h>
> +
> +	.section	.text
> +	.cfi_sections	.debug_frame
> +
> +SYM_FUNC_START(__vdso_rt_sigreturn)
> +
> +	li.w	a7, __NR_rt_sigreturn
> +	syscall	0
> +
> +SYM_FUNC_END(__vdso_rt_sigreturn)
> diff --git a/arch/loongarch/vdso/vdso.S b/arch/loongarch/vdso/vdso.S
> new file mode 100644
> index 000000000000..46789bade6ff
> --- /dev/null
> +++ b/arch/loongarch/vdso/vdso.S
> @@ -0,0 +1,22 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + *
> + * Derived from RISC-V:
> + * Copyright (C) 2014 Regents of the University of California
> + */
> +
> +#include <linux/init.h>
> +#include <linux/linkage.h>
> +#include <asm/page.h>
> +
> +	__PAGE_ALIGNED_DATA
> +
> +	.globl vdso_start, vdso_end
> +	.balign PAGE_SIZE
> +vdso_start:
> +	.incbin "arch/loongarch/vdso/vdso.so"
> +	.balign PAGE_SIZE
> +vdso_end:
> +
> +	.previous
> diff --git a/arch/loongarch/vdso/vdso.lds.S b/arch/loongarch/vdso/vdso.lds.S
> new file mode 100644
> index 000000000000..955f02de4a2d
> --- /dev/null
> +++ b/arch/loongarch/vdso/vdso.lds.S
> @@ -0,0 +1,72 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Author: Huacai Chen <chenhuacai@loongson.cn>
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +
> +OUTPUT_FORMAT("elf64-loongarch", "elf64-loongarch", "elf64-loongarch")
> +
> +OUTPUT_ARCH(loongarch)
> +
> +SECTIONS
> +{
> +	PROVIDE(_start = .);
> +	. = SIZEOF_HEADERS;
> +
> +	.hash		: { *(.hash) }			:text
> +	.gnu.hash	: { *(.gnu.hash) }
> +	.dynsym		: { *(.dynsym) }
> +	.dynstr		: { *(.dynstr) }
> +	.gnu.version	: { *(.gnu.version) }
> +	.gnu.version_d	: { *(.gnu.version_d) }
> +	.gnu.version_r	: { *(.gnu.version_r) }
> +
> +	.note		: { *(.note.*) }		:text :note
> +
> +	.text		: { *(.text*) }			:text
> +	PROVIDE (__etext = .);
> +	PROVIDE (_etext = .);
> +	PROVIDE (etext = .);
> +
> +	.eh_frame_hdr	: { *(.eh_frame_hdr) }		:text :eh_frame_hdr
> +	.eh_frame	: { KEEP (*(.eh_frame)) }	:text
> +
> +	.dynamic	: { *(.dynamic) }		:text :dynamic
> +
> +	.rodata		: { *(.rodata*) }		:text
> +
> +	_end = .;
> +	PROVIDE(end = .);
> +
> +	/DISCARD/	: {
> +		*(.gnu.attributes)
> +		*(.note.GNU-stack)
> +		*(.data .data.* .gnu.linkonce.d.* .sdata*)
> +		*(.bss .sbss .dynbss .dynsbss)
> +	}
> +}
> +
> +PHDRS
> +{
> +	text		PT_LOAD		FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
> +	dynamic		PT_DYNAMIC	FLAGS(4);		/* PF_R */
> +	note		PT_NOTE		FLAGS(4);		/* PF_R */
> +	eh_frame_hdr	PT_GNU_EH_FRAME;
> +}
> +
> +VERSION
> +{
> +	LINUX_5.10 {
> +	global:
> +		__vdso_clock_getres;
> +		__vdso_clock_gettime;
> +		__vdso_gettimeofday;
> +		__vdso_rt_sigreturn;
> +	local: *;
> +	};
> +}
> +
> +/*
> + * Make the sigreturn code visible to the kernel.
> + */
> +VDSO_sigreturn		= __vdso_rt_sigreturn;
> diff --git a/arch/loongarch/vdso/vgettimeofday.c b/arch/loongarch/vdso/vgettimeofday.c
> new file mode 100644
> index 000000000000..b1f4548dae92
> --- /dev/null
> +++ b/arch/loongarch/vdso/vgettimeofday.c
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * LoongArch userspace implementations of gettimeofday() and similar.
> + *
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +#include <linux/types.h>
> +
> +int __vdso_clock_gettime(clockid_t clock,
> +			 struct __kernel_timespec *ts)
> +{
> +	return __cvdso_clock_gettime(clock, ts);
> +}
> +
> +int __vdso_gettimeofday(struct __kernel_old_timeval *tv,
> +			struct timezone *tz)
> +{
> +	return __cvdso_gettimeofday(tv, tz);
> +}
> +
> +int __vdso_clock_getres(clockid_t clock_id,
> +			struct __kernel_timespec *res)
> +{
> +	return __cvdso_clock_getres(clock_id, res);
> +}

Other bits look familiar (it's generic vDSO but shows MIPS heritage 
too); from my experience with the MIPS vDSO this feels correct as well. 
Also I think an earlier version of the code is already deployed on my 
system and obviously working.

The only minor nit is, the proper capitalization "VDSO" should be "vDSO" 
-- it's short for "virtual DSO" after all. But the all-caps "VDSO" also 
has many occurrences so I guess it's down to preferences. Either would 
be okay for me, although I'd personally prefer "vDSO".

With the *other* bit (regarding asm constraints) addressed:

Reviewed-by: WANG Xuerui <git@xen0n.name>
Re: [PATCH V10 19/22] LoongArch: Add VDSO and VSYSCALL support
Posted by Huacai Chen 3 years, 9 months ago 
Hi, Xuerui,

On Sun, May 15, 2022 at 10:47 PM WANG Xuerui <kernel@xen0n.name> wrote:
>
> Hi,
>
> On 5/14/22 16:03, Huacai Chen wrote:
> > Add VDSO and VSYSCALL support (sigreturn, gettimeofday and its friends)
> > for LoongArch.
> >
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > ---
> >   arch/loongarch/include/asm/vdso.h             |  38 +++++
> >   arch/loongarch/include/asm/vdso/clocksource.h |   8 +
> >   .../loongarch/include/asm/vdso/gettimeofday.h |  99 +++++++++++++
> >   arch/loongarch/include/asm/vdso/processor.h   |  14 ++
> >   arch/loongarch/include/asm/vdso/vdso.h        |  30 ++++
> >   arch/loongarch/include/asm/vdso/vsyscall.h    |  27 ++++
> >   arch/loongarch/kernel/vdso.c                  | 138 ++++++++++++++++++
> >   arch/loongarch/vdso/Makefile                  |  96 ++++++++++++
> >   arch/loongarch/vdso/elf.S                     |  15 ++
> >   arch/loongarch/vdso/gen_vdso_offsets.sh       |  13 ++
> >   arch/loongarch/vdso/sigreturn.S               |  24 +++
> >   arch/loongarch/vdso/vdso.S                    |  22 +++
> >   arch/loongarch/vdso/vdso.lds.S                |  72 +++++++++
> >   arch/loongarch/vdso/vgettimeofday.c           |  25 ++++
> >   14 files changed, 621 insertions(+)
> >   create mode 100644 arch/loongarch/include/asm/vdso.h
> >   create mode 100644 arch/loongarch/include/asm/vdso/clocksource.h
> >   create mode 100644 arch/loongarch/include/asm/vdso/gettimeofday.h
> >   create mode 100644 arch/loongarch/include/asm/vdso/processor.h
> >   create mode 100644 arch/loongarch/include/asm/vdso/vdso.h
> >   create mode 100644 arch/loongarch/include/asm/vdso/vsyscall.h
> >   create mode 100644 arch/loongarch/kernel/vdso.c
> >   create mode 100644 arch/loongarch/vdso/Makefile
> >   create mode 100644 arch/loongarch/vdso/elf.S
> >   create mode 100755 arch/loongarch/vdso/gen_vdso_offsets.sh
> >   create mode 100644 arch/loongarch/vdso/sigreturn.S
> >   create mode 100644 arch/loongarch/vdso/vdso.S
> >   create mode 100644 arch/loongarch/vdso/vdso.lds.S
> >   create mode 100644 arch/loongarch/vdso/vgettimeofday.c
> >
> > diff --git a/arch/loongarch/include/asm/vdso.h b/arch/loongarch/include/asm/vdso.h
> > new file mode 100644
> > index 000000000000..996bddae12dc
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/vdso.h
> > @@ -0,0 +1,38 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Author: Huacai Chen <chenhuacai@loongson.cn>
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#ifndef __ASM_VDSO_H
> > +#define __ASM_VDSO_H
> > +
> > +#include <linux/mm_types.h>
> > +#include <vdso/datapage.h>
> > +
> > +#include <asm/barrier.h>
> > +
> > +/**
> > + * struct loongarch_vdso_info - Details of a VDSO image.
> > + * @vdso: Pointer to VDSO image (page-aligned).
> > + * @size: Size of the VDSO image (page-aligned).
> > + * @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.
> > + * @code_mapping: Special mapping structure for vdso code.
> > + * @code_mapping: Special mapping structure for vdso data.
> > + *
> > + * This structure contains details of a VDSO image, including the image data
> > + * and offsets of certain symbols required by the kernel. It is generated as
> > + * part of the VDSO build process, aside from the mapping page array, which is
> > + * populated at runtime.
> > + */
> > +struct loongarch_vdso_info {
> > +     void *vdso;
> > +     unsigned long size;
> > +     unsigned long offset_sigreturn;
> > +     struct vm_special_mapping code_mapping;
> > +     struct vm_special_mapping data_mapping;
> > +};
> > +
> > +extern struct loongarch_vdso_info vdso_info;
> > +
> > +#endif /* __ASM_VDSO_H */
> > diff --git a/arch/loongarch/include/asm/vdso/clocksource.h b/arch/loongarch/include/asm/vdso/clocksource.h
> > new file mode 100644
> > index 000000000000..13cd580d406d
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/vdso/clocksource.h
> > @@ -0,0 +1,8 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef __ASM_VDSOCLOCKSOURCE_H
> > +#define __ASM_VDSOCLOCKSOURCE_H
> > +
> > +#define VDSO_ARCH_CLOCKMODES \
> > +     VDSO_CLOCKMODE_CPU
> > +
> > +#endif /* __ASM_VDSOCLOCKSOURCE_H */
> > diff --git a/arch/loongarch/include/asm/vdso/gettimeofday.h b/arch/loongarch/include/asm/vdso/gettimeofday.h
> > new file mode 100644
> > index 000000000000..5fc5a746b1c4
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/vdso/gettimeofday.h
> > @@ -0,0 +1,99 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Author: Huacai Chen <chenhuacai@loongson.cn>
> > + *
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#ifndef __ASM_VDSO_GETTIMEOFDAY_H
> > +#define __ASM_VDSO_GETTIMEOFDAY_H
> > +
> > +#ifndef __ASSEMBLY__
> > +
> > +#include <asm/unistd.h>
> > +#include <asm/vdso/vdso.h>
> > +
> > +#define VDSO_HAS_CLOCK_GETRES                1
> > +
> > +static __always_inline long gettimeofday_fallback(
> > +                             struct __kernel_old_timeval *_tv,
> > +                             struct timezone *_tz)
> > +{
> > +     register struct __kernel_old_timeval *tv asm("a0") = _tv;
> > +     register struct timezone *tz asm("a1") = _tz;
> > +     register long nr asm("a7") = __NR_gettimeofday;
> > +     register long ret asm("v0");
> > +
> > +     asm volatile(
> > +     "       syscall 0\n"
> > +     : "=r" (ret)
> > +     : "r" (nr), "r" (tv), "r" (tz)
> > +     : "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
> > +       "$t8", "memory");
> Here ret is being hinted to register $v0, which is in fact the same
> register as $a0; so I'm afraid the "=r" constraint wouldn't prevent the
> $a0 from being clobbered before the syscall insn? Changing "v0" to "a0",
> then "=r" to "+r", could do it, although I cannot build-test it (due to
> the boot protocol being incompatible with existing shipped systems).
> Please check this for me...
Thanks, all v0 will be replaced.

Huacai
> > +
> > +     return ret;
> > +}
> > +
> > +static __always_inline long clock_gettime_fallback(
> > +                                     clockid_t _clkid,
> > +                                     struct __kernel_timespec *_ts)
> > +{
> > +     register clockid_t clkid asm("a0") = _clkid;
> > +     register struct __kernel_timespec *ts asm("a1") = _ts;
> > +     register long nr asm("a7") = __NR_clock_gettime;
> > +     register long ret asm("v0");
> > +
> > +     asm volatile(
> > +     "       syscall 0\n"
> > +     : "=r" (ret)
> > +     : "r" (nr), "r" (clkid), "r" (ts)
> > +     : "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
> > +       "$t8", "memory");
> > +
> > +     return ret;
> > +}
> > +
> > +static __always_inline int clock_getres_fallback(
> > +                                     clockid_t _clkid,
> > +                                     struct __kernel_timespec *_ts)
> > +{
> > +     register clockid_t clkid asm("a0") = _clkid;
> > +     register struct __kernel_timespec *ts asm("a1") = _ts;
> > +     register long nr asm("a7") = __NR_clock_getres;
> > +     register long ret asm("v0");
> > +
> > +     asm volatile(
> > +     "       syscall 0\n"
> > +     : "=r" (ret)
> > +     : "r" (nr), "r" (clkid), "r" (ts)
> > +     : "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7",
> > +       "$t8", "memory");
> > +
> > +     return ret;
> > +}
> > +
> > +static __always_inline u64 __arch_get_hw_counter(s32 clock_mode,
> > +                                              const struct vdso_data *vd)
> > +{
> > +     unsigned int count;
> > +
> > +     __asm__ __volatile__(
> > +     "       rdtime.d %0, $zero\n"
> > +     : "=r" (count));
> > +
> > +     return count;
> > +}
> > +
> > +static inline bool loongarch_vdso_hres_capable(void)
> > +{
> > +     return true;
> > +}
> > +#define __arch_vdso_hres_capable loongarch_vdso_hres_capable
> > +
> > +static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
> > +{
> > +     return get_vdso_data();
> > +}
> > +
> > +#endif /* !__ASSEMBLY__ */
> > +
> > +#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
> > diff --git a/arch/loongarch/include/asm/vdso/processor.h b/arch/loongarch/include/asm/vdso/processor.h
> > new file mode 100644
> > index 000000000000..ef5770b343a0
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/vdso/processor.h
> > @@ -0,0 +1,14 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#ifndef __ASM_VDSO_PROCESSOR_H
> > +#define __ASM_VDSO_PROCESSOR_H
> > +
> > +#ifndef __ASSEMBLY__
> > +
> > +#define cpu_relax()  barrier()
> > +
> > +#endif /* __ASSEMBLY__ */
> > +
> > +#endif /* __ASM_VDSO_PROCESSOR_H */
> > diff --git a/arch/loongarch/include/asm/vdso/vdso.h b/arch/loongarch/include/asm/vdso/vdso.h
> > new file mode 100644
> > index 000000000000..5a01643a65b3
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/vdso/vdso.h
> > @@ -0,0 +1,30 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +/*
> > + * Author: Huacai Chen <chenhuacai@loongson.cn>
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#ifndef __ASSEMBLY__
> > +
> > +#include <asm/asm.h>
> > +#include <asm/page.h>
> > +
> > +static inline unsigned long get_vdso_base(void)
> > +{
> > +     unsigned long addr;
> > +
> > +     __asm__(
> > +     " la.pcrel %0, _start\n"
> > +     : "=r" (addr)
> > +     :
> > +     :);
> > +
> > +     return addr;
> > +}
> > +
> > +static inline const struct vdso_data *get_vdso_data(void)
> > +{
> > +     return (const struct vdso_data *)(get_vdso_base() - PAGE_SIZE);
> > +}
> > +
> > +#endif /* __ASSEMBLY__ */
> > diff --git a/arch/loongarch/include/asm/vdso/vsyscall.h b/arch/loongarch/include/asm/vdso/vsyscall.h
> > new file mode 100644
> > index 000000000000..5de615383a22
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/vdso/vsyscall.h
> > @@ -0,0 +1,27 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __ASM_VDSO_VSYSCALL_H
> > +#define __ASM_VDSO_VSYSCALL_H
> > +
> > +#ifndef __ASSEMBLY__
> > +
> > +#include <linux/timekeeper_internal.h>
> > +#include <vdso/datapage.h>
> > +
> > +extern struct vdso_data *vdso_data;
> > +
> > +/*
> > + * Update the vDSO data page to keep in sync with kernel timekeeping.
> > + */
> > +static __always_inline
> > +struct vdso_data *__loongarch_get_k_vdso_data(void)
> > +{
> > +     return vdso_data;
> > +}
> > +#define __arch_get_k_vdso_data __loongarch_get_k_vdso_data
> > +
> > +/* The asm-generic header needs to be included after the definitions above */
> > +#include <asm-generic/vdso/vsyscall.h>
> > +
> > +#endif /* !__ASSEMBLY__ */
> > +
> > +#endif /* __ASM_VDSO_VSYSCALL_H */
> > diff --git a/arch/loongarch/kernel/vdso.c b/arch/loongarch/kernel/vdso.c
> > new file mode 100644
> > index 000000000000..e20c8ca87473
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/vdso.c
> > @@ -0,0 +1,138 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Author: Huacai Chen <chenhuacai@loongson.cn>
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#include <linux/binfmts.h>
> > +#include <linux/elf.h>
> > +#include <linux/err.h>
> > +#include <linux/init.h>
> > +#include <linux/ioport.h>
> > +#include <linux/kernel.h>
> > +#include <linux/mm.h>
> > +#include <linux/random.h>
> > +#include <linux/sched.h>
> > +#include <linux/slab.h>
> > +#include <linux/timekeeper_internal.h>
> > +
> > +#include <asm/page.h>
> > +#include <asm/vdso.h>
> > +#include <vdso/helpers.h>
> > +#include <vdso/vsyscall.h>
> > +#include <generated/vdso-offsets.h>
> > +
> > +extern char vdso_start[], vdso_end[];
> > +
> > +/* Kernel-provided data used by the VDSO. */
> > +static union loongarch_vdso_data {
> > +     u8 page[PAGE_SIZE];
> > +     struct vdso_data data[CS_BASES];
> > +} loongarch_vdso_data __page_aligned_data;
> > +struct vdso_data *vdso_data = loongarch_vdso_data.data;
> > +static struct page *vdso_pages[] = { NULL };
> > +
> > +static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
> > +{
> > +     current->mm->context.vdso = (void *)(new_vma->vm_start);
> > +
> > +     return 0;
> > +}
> > +
> > +struct loongarch_vdso_info vdso_info = {
> > +     .vdso = vdso_start,
> > +     .size = PAGE_SIZE,
> > +     .code_mapping = {
> > +             .name = "[vdso]",
> > +             .pages = vdso_pages,
> > +             .mremap = vdso_mremap,
> > +     },
> > +     .data_mapping = {
> > +             .name = "[vvar]",
> > +     },
> > +     .offset_sigreturn = vdso_offset_sigreturn,
> > +};
> > +
> > +static int __init init_vdso(void)
> > +{
> > +     unsigned long i, pfn;
> > +
> > +     BUG_ON(!PAGE_ALIGNED(vdso_info.vdso));
> > +     BUG_ON(!PAGE_ALIGNED(vdso_info.size));
> > +
> > +     pfn = __phys_to_pfn(__pa_symbol(vdso_info.vdso));
> > +     for (i = 0; i < vdso_info.size / PAGE_SIZE; i++)
> > +             vdso_info.code_mapping.pages[i] = pfn_to_page(pfn + i);
> > +
> > +     return 0;
> > +}
> > +subsys_initcall(init_vdso);
> > +
> > +static unsigned long vdso_base(void)
> > +{
> > +     unsigned long base = STACK_TOP;
> > +
> > +     if (current->flags & PF_RANDOMIZE) {
> > +             base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
> > +             base = PAGE_ALIGN(base);
> > +     }
> > +
> > +     return base;
> > +}
> > +
> > +int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
> > +{
> > +     int ret;
> > +     unsigned long vvar_size, size, data_addr, vdso_addr;
> > +     struct mm_struct *mm = current->mm;
> > +     struct vm_area_struct *vma;
> > +     struct loongarch_vdso_info *info = current->thread.vdso;
> > +
> > +     if (mmap_write_lock_killable(mm))
> > +             return -EINTR;
> > +
> > +     /*
> > +      * Determine total area size. This includes the VDSO data itself
> > +      * and the data page.
> > +      */
> > +     vvar_size = PAGE_SIZE;
> > +     size = vvar_size + info->size;
> > +
> > +     data_addr = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
> > +     if (IS_ERR_VALUE(data_addr)) {
> > +             ret = data_addr;
> > +             goto out;
> > +     }
> > +     vdso_addr = data_addr + PAGE_SIZE;
> > +
> > +     vma = _install_special_mapping(mm, data_addr, vvar_size,
> > +                                    VM_READ | VM_MAYREAD,
> > +                                    &info->data_mapping);
> > +     if (IS_ERR(vma)) {
> > +             ret = PTR_ERR(vma);
> > +             goto out;
> > +     }
> > +
> > +     /* Map VDSO data page. */
> > +     ret = remap_pfn_range(vma, data_addr,
> > +                           virt_to_phys(vdso_data) >> PAGE_SHIFT,
> > +                           PAGE_SIZE, PAGE_READONLY);
> > +     if (ret)
> > +             goto out;
> > +
> > +     /* Map VDSO code page. */
> > +     vma = _install_special_mapping(mm, vdso_addr, info->size,
> > +                                    VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
> > +                                    &info->code_mapping);
> > +     if (IS_ERR(vma)) {
> > +             ret = PTR_ERR(vma);
> > +             goto out;
> > +     }
> > +
> > +     mm->context.vdso = (void *)vdso_addr;
> > +     ret = 0;
> > +
> > +out:
> > +     mmap_write_unlock(mm);
> > +     return ret;
> > +}
> > diff --git a/arch/loongarch/vdso/Makefile b/arch/loongarch/vdso/Makefile
> > new file mode 100644
> > index 000000000000..6b6e16732c60
> > --- /dev/null
> > +++ b/arch/loongarch/vdso/Makefile
> > @@ -0,0 +1,96 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Objects to go into the VDSO.
> > +
> > +# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
> > +# the inclusion of generic Makefile.
> > +ARCH_REL_TYPE_ABS := R_LARCH_32|R_LARCH_64|R_LARCH_MARK_LA|R_LARCH_JUMP_SLOT
> > +include $(srctree)/lib/vdso/Makefile
> > +
> > +obj-vdso-y := elf.o vgettimeofday.o sigreturn.o
> > +
> > +# Common compiler flags between ABIs.
> > +ccflags-vdso := \
> > +     $(filter -I%,$(KBUILD_CFLAGS)) \
> > +     $(filter -E%,$(KBUILD_CFLAGS)) \
> > +     $(filter -march=%,$(KBUILD_CFLAGS)) \
> > +     $(filter -m%-float,$(KBUILD_CFLAGS)) \
> > +     -D__VDSO__
> > +
> > +ifeq ($(cc-name),clang)
> > +ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
> > +endif
> > +
> > +cflags-vdso := $(ccflags-vdso) \
> > +     $(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
> > +     -O2 -g -fno-strict-aliasing -fno-common -fno-builtin -G0 \
> > +     -fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
> > +     $(call cc-option, -fno-asynchronous-unwind-tables) \
> > +     $(call cc-option, -fno-stack-protector)
> > +aflags-vdso := $(ccflags-vdso) \
> > +     -D__ASSEMBLY__ -Wa,-gdwarf-2
> > +
> > +ifneq ($(c-gettimeofday-y),)
> > +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > +endif
> > +
> > +# VDSO linker flags.
> > +ldflags-y := -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
> > +     $(filter -E%,$(KBUILD_CFLAGS)) -nostdlib -shared \
> > +     --hash-style=sysv --build-id -T
> > +
> > +GCOV_PROFILE := n
> > +
> > +#
> > +# Shared build commands.
> > +#
> > +
> > +quiet_cmd_vdsold_and_vdso_check = LD      $@
> > +      cmd_vdsold_and_vdso_check = $(cmd_ld); $(cmd_vdso_check)
> > +
> > +quiet_cmd_vdsoas_o_S = AS       $@
> > +      cmd_vdsoas_o_S = $(CC) $(a_flags) -c -o $@ $<
> > +
> > +# Generate VDSO offsets using helper script
> > +gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
> > +quiet_cmd_vdsosym = VDSOSYM $@
> > +      cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
> > +
> > +include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
> > +     $(call if_changed,vdsosym)
> > +
> > +#
> > +# Build native VDSO.
> > +#
> > +
> > +native-abi := $(filter -mabi=%,$(KBUILD_CFLAGS))
> > +
> > +targets += $(obj-vdso-y)
> > +targets += vdso.lds vdso.so.dbg vdso.so
> > +
> > +obj-vdso := $(obj-vdso-y:%.o=$(obj)/%.o)
> > +
> > +$(obj-vdso): KBUILD_CFLAGS := $(cflags-vdso) $(native-abi)
> > +$(obj-vdso): KBUILD_AFLAGS := $(aflags-vdso) $(native-abi)
> > +
> > +$(obj)/vdso.lds: KBUILD_CPPFLAGS := $(ccflags-vdso) $(native-abi)
> > +
> > +$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
> > +     $(call if_changed,vdsold_and_vdso_check)
> > +
> > +$(obj)/vdso.so: OBJCOPYFLAGS := -S
> > +$(obj)/vdso.so: $(obj)/vdso.so.dbg FORCE
> > +     $(call if_changed,objcopy)
> > +
> > +obj-y += vdso.o
> > +
> > +$(obj)/vdso.o : $(obj)/vdso.so
> > +
> > +# install commands for the unstripped file
> > +quiet_cmd_vdso_install = INSTALL $@
> > +      cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
> > +
> > +vdso.so: $(obj)/vdso.so.dbg
> > +     @mkdir -p $(MODLIB)/vdso
> > +     $(call cmd,vdso_install)
> > +
> > +vdso_install: vdso.so
> > diff --git a/arch/loongarch/vdso/elf.S b/arch/loongarch/vdso/elf.S
> > new file mode 100644
> > index 000000000000..9bb21b9f9583
> > --- /dev/null
> > +++ b/arch/loongarch/vdso/elf.S
> > @@ -0,0 +1,15 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Author: Huacai Chen <chenhuacai@loongson.cn>
> > + *
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#include <asm/vdso/vdso.h>
> > +
> > +#include <linux/elfnote.h>
> > +#include <linux/version.h>
> > +
> > +ELFNOTE_START(Linux, 0, "a")
> > +     .long LINUX_VERSION_CODE
> > +ELFNOTE_END
> > diff --git a/arch/loongarch/vdso/gen_vdso_offsets.sh b/arch/loongarch/vdso/gen_vdso_offsets.sh
> > new file mode 100755
> > index 000000000000..1bb4e12642ff
> > --- /dev/null
> > +++ b/arch/loongarch/vdso/gen_vdso_offsets.sh
> > @@ -0,0 +1,13 @@
> > +#!/bin/sh
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +#
> > +# Derived from RISC-V and ARM64:
> > +# Author: Will Deacon <will.deacon@arm.com>
> > +#
> > +# Match symbols in the DSO that look like VDSO_*; produce a header file
> > +# of constant offsets into the shared object.
> > +#
> > +
> > +LC_ALL=C sed -n -e 's/^00*/0/' -e \
> > +'s/^\([0-9a-fA-F]*\) . VDSO_\([a-zA-Z0-9_]*\)$/\#define vdso_offset_\2\t0x\1/p'
> > diff --git a/arch/loongarch/vdso/sigreturn.S b/arch/loongarch/vdso/sigreturn.S
> > new file mode 100644
> > index 000000000000..9cb3c58fad03
> > --- /dev/null
> > +++ b/arch/loongarch/vdso/sigreturn.S
> > @@ -0,0 +1,24 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Author: Huacai Chen <chenhuacai@loongson.cn>
> > + *
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#include <asm/vdso/vdso.h>
> > +
> > +#include <linux/linkage.h>
> > +#include <uapi/asm/unistd.h>
> > +
> > +#include <asm/regdef.h>
> > +#include <asm/asm.h>
> > +
> > +     .section        .text
> > +     .cfi_sections   .debug_frame
> > +
> > +SYM_FUNC_START(__vdso_rt_sigreturn)
> > +
> > +     li.w    a7, __NR_rt_sigreturn
> > +     syscall 0
> > +
> > +SYM_FUNC_END(__vdso_rt_sigreturn)
> > diff --git a/arch/loongarch/vdso/vdso.S b/arch/loongarch/vdso/vdso.S
> > new file mode 100644
> > index 000000000000..46789bade6ff
> > --- /dev/null
> > +++ b/arch/loongarch/vdso/vdso.S
> > @@ -0,0 +1,22 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + *
> > + * Derived from RISC-V:
> > + * Copyright (C) 2014 Regents of the University of California
> > + */
> > +
> > +#include <linux/init.h>
> > +#include <linux/linkage.h>
> > +#include <asm/page.h>
> > +
> > +     __PAGE_ALIGNED_DATA
> > +
> > +     .globl vdso_start, vdso_end
> > +     .balign PAGE_SIZE
> > +vdso_start:
> > +     .incbin "arch/loongarch/vdso/vdso.so"
> > +     .balign PAGE_SIZE
> > +vdso_end:
> > +
> > +     .previous
> > diff --git a/arch/loongarch/vdso/vdso.lds.S b/arch/loongarch/vdso/vdso.lds.S
> > new file mode 100644
> > index 000000000000..955f02de4a2d
> > --- /dev/null
> > +++ b/arch/loongarch/vdso/vdso.lds.S
> > @@ -0,0 +1,72 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Author: Huacai Chen <chenhuacai@loongson.cn>
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +OUTPUT_FORMAT("elf64-loongarch", "elf64-loongarch", "elf64-loongarch")
> > +
> > +OUTPUT_ARCH(loongarch)
> > +
> > +SECTIONS
> > +{
> > +     PROVIDE(_start = .);
> > +     . = SIZEOF_HEADERS;
> > +
> > +     .hash           : { *(.hash) }                  :text
> > +     .gnu.hash       : { *(.gnu.hash) }
> > +     .dynsym         : { *(.dynsym) }
> > +     .dynstr         : { *(.dynstr) }
> > +     .gnu.version    : { *(.gnu.version) }
> > +     .gnu.version_d  : { *(.gnu.version_d) }
> > +     .gnu.version_r  : { *(.gnu.version_r) }
> > +
> > +     .note           : { *(.note.*) }                :text :note
> > +
> > +     .text           : { *(.text*) }                 :text
> > +     PROVIDE (__etext = .);
> > +     PROVIDE (_etext = .);
> > +     PROVIDE (etext = .);
> > +
> > +     .eh_frame_hdr   : { *(.eh_frame_hdr) }          :text :eh_frame_hdr
> > +     .eh_frame       : { KEEP (*(.eh_frame)) }       :text
> > +
> > +     .dynamic        : { *(.dynamic) }               :text :dynamic
> > +
> > +     .rodata         : { *(.rodata*) }               :text
> > +
> > +     _end = .;
> > +     PROVIDE(end = .);
> > +
> > +     /DISCARD/       : {
> > +             *(.gnu.attributes)
> > +             *(.note.GNU-stack)
> > +             *(.data .data.* .gnu.linkonce.d.* .sdata*)
> > +             *(.bss .sbss .dynbss .dynsbss)
> > +     }
> > +}
> > +
> > +PHDRS
> > +{
> > +     text            PT_LOAD         FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
> > +     dynamic         PT_DYNAMIC      FLAGS(4);               /* PF_R */
> > +     note            PT_NOTE         FLAGS(4);               /* PF_R */
> > +     eh_frame_hdr    PT_GNU_EH_FRAME;
> > +}
> > +
> > +VERSION
> > +{
> > +     LINUX_5.10 {
> > +     global:
> > +             __vdso_clock_getres;
> > +             __vdso_clock_gettime;
> > +             __vdso_gettimeofday;
> > +             __vdso_rt_sigreturn;
> > +     local: *;
> > +     };
> > +}
> > +
> > +/*
> > + * Make the sigreturn code visible to the kernel.
> > + */
> > +VDSO_sigreturn               = __vdso_rt_sigreturn;
> > diff --git a/arch/loongarch/vdso/vgettimeofday.c b/arch/loongarch/vdso/vgettimeofday.c
> > new file mode 100644
> > index 000000000000..b1f4548dae92
> > --- /dev/null
> > +++ b/arch/loongarch/vdso/vgettimeofday.c
> > @@ -0,0 +1,25 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * LoongArch userspace implementations of gettimeofday() and similar.
> > + *
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#include <linux/types.h>
> > +
> > +int __vdso_clock_gettime(clockid_t clock,
> > +                      struct __kernel_timespec *ts)
> > +{
> > +     return __cvdso_clock_gettime(clock, ts);
> > +}
> > +
> > +int __vdso_gettimeofday(struct __kernel_old_timeval *tv,
> > +                     struct timezone *tz)
> > +{
> > +     return __cvdso_gettimeofday(tv, tz);
> > +}
> > +
> > +int __vdso_clock_getres(clockid_t clock_id,
> > +                     struct __kernel_timespec *res)
> > +{
> > +     return __cvdso_clock_getres(clock_id, res);
> > +}
>
> Other bits look familiar (it's generic vDSO but shows MIPS heritage
> too); from my experience with the MIPS vDSO this feels correct as well.
> Also I think an earlier version of the code is already deployed on my
> system and obviously working.
>
> The only minor nit is, the proper capitalization "VDSO" should be "vDSO"
> -- it's short for "virtual DSO" after all. But the all-caps "VDSO" also
> has many occurrences so I guess it's down to preferences. Either would
> be okay for me, although I'd personally prefer "vDSO".
>
> With the *other* bit (regarding asm constraints) addressed:
>
> Reviewed-by: WANG Xuerui <git@xen0n.name>
>

Patchew 2.1-devel-b67e4c2

© 2016 - 2026 Red Hat, Inc.