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[PATCH v4 01/10] LoongArch/ftrace: Add basic support

Qing Zhang posted 10 patches 3 years, 6 months ago
Only 8 patches received!
There is a newer version of this series
[PATCH v4 01/10] LoongArch/ftrace: Add basic support
Posted by Qing Zhang 3 years, 6 months ago 
This patch contains basic ftrace support for LoongArch.
Specifically, function tracer (HAVE_FUNCTION_TRACER), function graph
tracer (HAVE_FUNCTION_GRAPH_TRACER) are implemented following the
instructions in Documentation/trace/ftrace-design.txt.

Use `-pg` makes stub like a child function `void _mcount(void *ra)`.
Thus, it can be seen store RA and open stack before `call _mcount`.
Find `open stack` at first, and then find `store RA`

Note that the functions in both inst.c and time.c should not be
hooked with the compiler's -pg option: to prevent infinite self-
referencing for the former, and to ignore early setup stuff for the
latter.

Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
---
 arch/loongarch/Kconfig              |  2 +
 arch/loongarch/Makefile             |  5 ++
 arch/loongarch/include/asm/ftrace.h | 18 ++++++
 arch/loongarch/kernel/Makefile      |  8 +++
 arch/loongarch/kernel/ftrace.c      | 74 +++++++++++++++++++++++
 arch/loongarch/kernel/mcount.S      | 94 +++++++++++++++++++++++++++++
 6 files changed, 201 insertions(+)
 create mode 100644 arch/loongarch/include/asm/ftrace.h
 create mode 100644 arch/loongarch/kernel/ftrace.c
 create mode 100644 arch/loongarch/kernel/mcount.S

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 9b1f2ab878e9..95eab9611191 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -90,6 +90,8 @@ config LOONGARCH
 	select HAVE_EBPF_JIT
 	select HAVE_EXIT_THREAD
 	select HAVE_FAST_GUP
+        select HAVE_FUNCTION_GRAPH_TRACER
+        select HAVE_FUNCTION_TRACER
 	select HAVE_GENERIC_VDSO
 	select HAVE_IOREMAP_PROT
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index 69b39ba3a09d..1149a17dc04f 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -33,6 +33,11 @@ ifneq ($(SUBARCH),$(ARCH))
   endif
 endif
 
+ifdef CONFIG_DYNAMIC_FTRACE
+  KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
+  CC_FLAGS_FTRACE := -fpatchable-function-entry=2
+endif
+
 ifdef CONFIG_64BIT
 ld-emul			= $(64bit-emul)
 cflags-y		+= -mabi=lp64s
diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
new file mode 100644
index 000000000000..6a3e76234618
--- /dev/null
+++ b/arch/loongarch/include/asm/ftrace.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#ifndef _ASM_LOONGARCH_FTRACE_H
+#define _ASM_LOONGARCH_FTRACE_H
+
+#ifdef CONFIG_FUNCTION_TRACER
+#define MCOUNT_INSN_SIZE 4		/* sizeof mcount call */
+
+#ifndef __ASSEMBLY__
+extern void _mcount(void);
+#define mcount _mcount
+
+#endif /* __ASSEMBLY__ */
+#endif /* CONFIG_FUNCTION_TRACER */
+#endif /* _ASM_LOONGARCH_FTRACE_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 7225916dd378..7db7ab152f71 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -14,6 +14,14 @@ obj-$(CONFIG_EFI) 		+= efi.o
 
 obj-$(CONFIG_CPU_HAS_FPU)	+= fpu.o
 
+ifdef CONFIG_FUNCTION_TRACER
+    obj-y += mcount.o ftrace.o
+    CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)
+  CFLAGS_REMOVE_inst.o = $(CC_FLAGS_FTRACE)
+  CFLAGS_REMOVE_time.o = $(CC_FLAGS_FTRACE)
+  CFLAGS_REMOVE_perf_event.o = $(CC_FLAGS_FTRACE)
+endif
+
 obj-$(CONFIG_MODULES)		+= module.o module-sections.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 
diff --git a/arch/loongarch/kernel/ftrace.c b/arch/loongarch/kernel/ftrace.c
new file mode 100644
index 000000000000..c8ddc5f11f32
--- /dev/null
+++ b/arch/loongarch/kernel/ftrace.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <linux/ftrace.h>
+#include <linux/syscalls.h>
+
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/cacheflush.h>
+#include <asm/inst.h>
+#include <asm/loongarch.h>
+#include <asm/syscall.h>
+#include <asm/unistd.h>
+
+#include <asm-generic/sections.h>
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+/*
+ * As `call _mcount` follows LoongArch psABI, ra-saved operation and
+ * stack operation can be found before this insn.
+ */
+
+static int ftrace_get_parent_ra_addr(unsigned long insn_addr, int *ra_off)
+{
+	union loongarch_instruction *insn;
+	int limit = 32;
+
+	insn = (union loongarch_instruction *)insn_addr;
+
+	do {
+		insn--;
+		limit--;
+
+		if (is_ra_save_ins(insn))
+			*ra_off = -((1 << 12) - insn->reg2i12_format.immediate);
+
+	} while (!is_stack_alloc_ins(insn) && limit);
+
+	if (!limit)
+		return -EINVAL;
+
+	return 0;
+}
+
+void prepare_ftrace_return(unsigned long self_addr,
+		unsigned long callsite_sp, unsigned long old)
+{
+	int ra_off;
+	unsigned long return_hooker = (unsigned long)&return_to_handler;
+
+	if (unlikely(ftrace_graph_is_dead()))
+		return;
+
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		return;
+
+	if (ftrace_get_parent_ra_addr(self_addr, &ra_off))
+		goto out;
+
+	if (!function_graph_enter(old, self_addr, 0, NULL))
+		*(unsigned long *)(callsite_sp + ra_off) = return_hooker;
+
+	return;
+
+out:
+	ftrace_graph_stop();
+	WARN_ON(1);
+}
+#endif	/* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S
new file mode 100644
index 000000000000..3de7c2d7fd12
--- /dev/null
+++ b/arch/loongarch/kernel/mcount.S
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * LoongArch specific _mcount support
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#include <asm/export.h>
+#include <asm/regdef.h>
+#include <asm/stackframe.h>
+#include <asm/ftrace.h>
+
+	.text
+
+#define MCOUNT_STACK_SIZE	(2 * SZREG)
+#define MCOUNT_S0_OFFSET	(0)
+#define MCOUNT_RA_OFFSET	(SZREG)
+
+	.macro MCOUNT_SAVE_REGS
+	PTR_ADDI sp, sp, -MCOUNT_STACK_SIZE
+	PTR_S	s0, sp, MCOUNT_S0_OFFSET
+	PTR_S	ra, sp, MCOUNT_RA_OFFSET
+	move	s0, a0
+	.endm
+
+	.macro MCOUNT_RESTORE_REGS
+	move	a0, s0
+	PTR_L	ra, sp, MCOUNT_RA_OFFSET
+	PTR_L	s0, sp, MCOUNT_S0_OFFSET
+	PTR_ADDI sp, sp, MCOUNT_STACK_SIZE
+	.endm
+
+
+SYM_FUNC_START(_mcount)
+	la.pcrel	t1, ftrace_stub
+	la.pcrel	t2, ftrace_trace_function	/* Prepare t2 for (1) */
+	PTR_L	t2, t2, 0
+	beq	t1, t2, fgraph_trace
+
+	MCOUNT_SAVE_REGS
+
+	move	a0, ra				/* arg0: self return address */
+	move	a1, s0				/* arg1: parent's return address */
+	jirl	ra, t2, 0			/* (1) call *ftrace_trace_function */
+
+	MCOUNT_RESTORE_REGS
+
+fgraph_trace:
+#ifdef	CONFIG_FUNCTION_GRAPH_TRACER
+	la.pcrel	t1, ftrace_stub
+	la.pcrel	t3, ftrace_graph_return
+	PTR_L	t3, t3, 0
+	bne	t1, t3, ftrace_graph_caller
+	la.pcrel	t1, ftrace_graph_entry_stub
+	la.pcrel	t3, ftrace_graph_entry
+	PTR_L	t3, t3, 0
+	bne	t1, t3, ftrace_graph_caller
+#endif
+
+	.globl ftrace_stub
+ftrace_stub:
+	jr	ra
+SYM_FUNC_END(_mcount)
+EXPORT_SYMBOL(_mcount)
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+SYM_FUNC_START(ftrace_graph_caller)
+	MCOUNT_SAVE_REGS
+
+	PTR_ADDI	a0, ra, -4			/* arg0: Callsite self return addr */
+	PTR_ADDI	a1, sp, MCOUNT_STACK_SIZE	/* arg1: Callsite sp */
+	move	a2, s0					/* arg2: Callsite parent ra */
+	bl	prepare_ftrace_return
+
+	MCOUNT_RESTORE_REGS
+	jr	ra
+SYM_FUNC_END(ftrace_graph_caller)
+
+SYM_FUNC_START(return_to_handler)
+	PTR_ADDI sp, sp, -2 * SZREG
+	PTR_S	a0, sp, 0
+	PTR_S	a1, sp, SZREG
+
+	bl	ftrace_return_to_handler
+
+	/* restore the real parent address: a0 -> ra */
+	move	ra, a0
+
+	PTR_L	a0, sp, 0
+	PTR_L	a1, sp, SZREG
+	PTR_ADDI	sp, sp, 2 * SZREG
+	jr	ra
+SYM_FUNC_END(return_to_handler)
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
-- 
2.36.1
Re: [PATCH v4 01/10] LoongArch/ftrace: Add basic support
Posted by Huacai Chen 3 years, 6 months ago 
Hi, Qing,

On Fri, Sep 16, 2022 at 10:55 AM Qing Zhang <zhangqing@loongson.cn> wrote:
>
> This patch contains basic ftrace support for LoongArch.
> Specifically, function tracer (HAVE_FUNCTION_TRACER), function graph
> tracer (HAVE_FUNCTION_GRAPH_TRACER) are implemented following the
> instructions in Documentation/trace/ftrace-design.txt.
>
> Use `-pg` makes stub like a child function `void _mcount(void *ra)`.
> Thus, it can be seen store RA and open stack before `call _mcount`.
> Find `open stack` at first, and then find `store RA`
>
> Note that the functions in both inst.c and time.c should not be
> hooked with the compiler's -pg option: to prevent infinite self-
> referencing for the former, and to ignore early setup stuff for the
> latter.
>
> Co-developed-by: Jinyang He <hejinyang@loongson.cn>
> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
> Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
> ---
>  arch/loongarch/Kconfig              |  2 +
>  arch/loongarch/Makefile             |  5 ++
>  arch/loongarch/include/asm/ftrace.h | 18 ++++++
>  arch/loongarch/kernel/Makefile      |  8 +++
>  arch/loongarch/kernel/ftrace.c      | 74 +++++++++++++++++++++++
>  arch/loongarch/kernel/mcount.S      | 94 +++++++++++++++++++++++++++++
>  6 files changed, 201 insertions(+)
>  create mode 100644 arch/loongarch/include/asm/ftrace.h
>  create mode 100644 arch/loongarch/kernel/ftrace.c
>  create mode 100644 arch/loongarch/kernel/mcount.S
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 9b1f2ab878e9..95eab9611191 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -90,6 +90,8 @@ config LOONGARCH
>         select HAVE_EBPF_JIT
>         select HAVE_EXIT_THREAD
>         select HAVE_FAST_GUP
> +        select HAVE_FUNCTION_GRAPH_TRACER
> +        select HAVE_FUNCTION_TRACER
The indentation is obviously wrong here, and some other patches have
the same problem.


Huacai

>         select HAVE_GENERIC_VDSO
>         select HAVE_IOREMAP_PROT
>         select HAVE_IRQ_EXIT_ON_IRQ_STACK
> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> index 69b39ba3a09d..1149a17dc04f 100644
> --- a/arch/loongarch/Makefile
> +++ b/arch/loongarch/Makefile
> @@ -33,6 +33,11 @@ ifneq ($(SUBARCH),$(ARCH))
>    endif
>  endif
>
> +ifdef CONFIG_DYNAMIC_FTRACE
> +  KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
> +  CC_FLAGS_FTRACE := -fpatchable-function-entry=2
> +endif
> +
>  ifdef CONFIG_64BIT
>  ld-emul                        = $(64bit-emul)
>  cflags-y               += -mabi=lp64s
> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
> new file mode 100644
> index 000000000000..6a3e76234618
> --- /dev/null
> +++ b/arch/loongarch/include/asm/ftrace.h
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +
> +#ifndef _ASM_LOONGARCH_FTRACE_H
> +#define _ASM_LOONGARCH_FTRACE_H
> +
> +#ifdef CONFIG_FUNCTION_TRACER
> +#define MCOUNT_INSN_SIZE 4             /* sizeof mcount call */
> +
> +#ifndef __ASSEMBLY__
> +extern void _mcount(void);
> +#define mcount _mcount
> +
> +#endif /* __ASSEMBLY__ */
> +#endif /* CONFIG_FUNCTION_TRACER */
> +#endif /* _ASM_LOONGARCH_FTRACE_H */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 7225916dd378..7db7ab152f71 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -14,6 +14,14 @@ obj-$(CONFIG_EFI)            += efi.o
>
>  obj-$(CONFIG_CPU_HAS_FPU)      += fpu.o
>
> +ifdef CONFIG_FUNCTION_TRACER
> +    obj-y += mcount.o ftrace.o
> +    CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)
> +  CFLAGS_REMOVE_inst.o = $(CC_FLAGS_FTRACE)
> +  CFLAGS_REMOVE_time.o = $(CC_FLAGS_FTRACE)
> +  CFLAGS_REMOVE_perf_event.o = $(CC_FLAGS_FTRACE)
> +endif
> +
>  obj-$(CONFIG_MODULES)          += module.o module-sections.o
>  obj-$(CONFIG_STACKTRACE)       += stacktrace.o
>
> diff --git a/arch/loongarch/kernel/ftrace.c b/arch/loongarch/kernel/ftrace.c
> new file mode 100644
> index 000000000000..c8ddc5f11f32
> --- /dev/null
> +++ b/arch/loongarch/kernel/ftrace.c
> @@ -0,0 +1,74 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +
> +#include <linux/uaccess.h>
> +#include <linux/init.h>
> +#include <linux/ftrace.h>
> +#include <linux/syscalls.h>
> +
> +#include <asm/asm.h>
> +#include <asm/asm-offsets.h>
> +#include <asm/cacheflush.h>
> +#include <asm/inst.h>
> +#include <asm/loongarch.h>
> +#include <asm/syscall.h>
> +#include <asm/unistd.h>
> +
> +#include <asm-generic/sections.h>
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +
> +/*
> + * As `call _mcount` follows LoongArch psABI, ra-saved operation and
> + * stack operation can be found before this insn.
> + */
> +
> +static int ftrace_get_parent_ra_addr(unsigned long insn_addr, int *ra_off)
> +{
> +       union loongarch_instruction *insn;
> +       int limit = 32;
> +
> +       insn = (union loongarch_instruction *)insn_addr;
> +
> +       do {
> +               insn--;
> +               limit--;
> +
> +               if (is_ra_save_ins(insn))
> +                       *ra_off = -((1 << 12) - insn->reg2i12_format.immediate);
> +
> +       } while (!is_stack_alloc_ins(insn) && limit);
> +
> +       if (!limit)
> +               return -EINVAL;
> +
> +       return 0;
> +}
> +
> +void prepare_ftrace_return(unsigned long self_addr,
> +               unsigned long callsite_sp, unsigned long old)
> +{
> +       int ra_off;
> +       unsigned long return_hooker = (unsigned long)&return_to_handler;
> +
> +       if (unlikely(ftrace_graph_is_dead()))
> +               return;
> +
> +       if (unlikely(atomic_read(&current->tracing_graph_pause)))
> +               return;
> +
> +       if (ftrace_get_parent_ra_addr(self_addr, &ra_off))
> +               goto out;
> +
> +       if (!function_graph_enter(old, self_addr, 0, NULL))
> +               *(unsigned long *)(callsite_sp + ra_off) = return_hooker;
> +
> +       return;
> +
> +out:
> +       ftrace_graph_stop();
> +       WARN_ON(1);
> +}
> +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S
> new file mode 100644
> index 000000000000..3de7c2d7fd12
> --- /dev/null
> +++ b/arch/loongarch/kernel/mcount.S
> @@ -0,0 +1,94 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * LoongArch specific _mcount support
> + *
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +
> +#include <asm/export.h>
> +#include <asm/regdef.h>
> +#include <asm/stackframe.h>
> +#include <asm/ftrace.h>
> +
> +       .text
> +
> +#define MCOUNT_STACK_SIZE      (2 * SZREG)
> +#define MCOUNT_S0_OFFSET       (0)
> +#define MCOUNT_RA_OFFSET       (SZREG)
> +
> +       .macro MCOUNT_SAVE_REGS
> +       PTR_ADDI sp, sp, -MCOUNT_STACK_SIZE
> +       PTR_S   s0, sp, MCOUNT_S0_OFFSET
> +       PTR_S   ra, sp, MCOUNT_RA_OFFSET
> +       move    s0, a0
> +       .endm
> +
> +       .macro MCOUNT_RESTORE_REGS
> +       move    a0, s0
> +       PTR_L   ra, sp, MCOUNT_RA_OFFSET
> +       PTR_L   s0, sp, MCOUNT_S0_OFFSET
> +       PTR_ADDI sp, sp, MCOUNT_STACK_SIZE
> +       .endm
> +
> +
> +SYM_FUNC_START(_mcount)
> +       la.pcrel        t1, ftrace_stub
> +       la.pcrel        t2, ftrace_trace_function       /* Prepare t2 for (1) */
> +       PTR_L   t2, t2, 0
> +       beq     t1, t2, fgraph_trace
> +
> +       MCOUNT_SAVE_REGS
> +
> +       move    a0, ra                          /* arg0: self return address */
> +       move    a1, s0                          /* arg1: parent's return address */
> +       jirl    ra, t2, 0                       /* (1) call *ftrace_trace_function */
> +
> +       MCOUNT_RESTORE_REGS
> +
> +fgraph_trace:
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +       la.pcrel        t1, ftrace_stub
> +       la.pcrel        t3, ftrace_graph_return
> +       PTR_L   t3, t3, 0
> +       bne     t1, t3, ftrace_graph_caller
> +       la.pcrel        t1, ftrace_graph_entry_stub
> +       la.pcrel        t3, ftrace_graph_entry
> +       PTR_L   t3, t3, 0
> +       bne     t1, t3, ftrace_graph_caller
> +#endif
> +
> +       .globl ftrace_stub
> +ftrace_stub:
> +       jr      ra
> +SYM_FUNC_END(_mcount)
> +EXPORT_SYMBOL(_mcount)
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +SYM_FUNC_START(ftrace_graph_caller)
> +       MCOUNT_SAVE_REGS
> +
> +       PTR_ADDI        a0, ra, -4                      /* arg0: Callsite self return addr */
> +       PTR_ADDI        a1, sp, MCOUNT_STACK_SIZE       /* arg1: Callsite sp */
> +       move    a2, s0                                  /* arg2: Callsite parent ra */
> +       bl      prepare_ftrace_return
> +
> +       MCOUNT_RESTORE_REGS
> +       jr      ra
> +SYM_FUNC_END(ftrace_graph_caller)
> +
> +SYM_FUNC_START(return_to_handler)
> +       PTR_ADDI sp, sp, -2 * SZREG
> +       PTR_S   a0, sp, 0
> +       PTR_S   a1, sp, SZREG
> +
> +       bl      ftrace_return_to_handler
> +
> +       /* restore the real parent address: a0 -> ra */
> +       move    ra, a0
> +
> +       PTR_L   a0, sp, 0
> +       PTR_L   a1, sp, SZREG
> +       PTR_ADDI        sp, sp, 2 * SZREG
> +       jr      ra
> +SYM_FUNC_END(return_to_handler)
> +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> --
> 2.36.1
>

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