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Sun, 22 Jun 2025 14:33:29 -0700 (PDT) Received: by ikb-h07-29-noble.in.iijlab.net (Postfix, from userid 1010) id 5F881EF1EB0; Mon, 23 Jun 2025 06:33:27 +0900 (JST) From: Hajime Tazaki To: linux-um@lists.infradead.org Cc: thehajime@gmail.com, ricarkol@google.com, Liam.Howlett@oracle.com, linux-kernel@vger.kernel.org Subject: [PATCH v10 06/13] x86/um: nommu: process/thread handling Date: Mon, 23 Jun 2025 06:33:04 +0900 Message-ID: <92ad19005df45ac15452be94c9cb522c87c8ee1c.1750594487.git.thehajime@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Since ptrace facility isn't used under !MMU of UML, there is different code path to invoke processes/threads; there are no external process used, and need to properly configure some of registers (fs segment register for TLS, etc) on every context switch, etc. Signals aren't delivered in non-ptrace syscall entry/leave so, we also need to handle pending signal by ourselves. ptrace related syscalls are not tested yet so, marked arch_has_single_step() unsupported in !MMU environment. Signed-off-by: Hajime Tazaki Signed-off-by: Ricardo Koller --- arch/um/include/asm/ptrace-generic.h | 2 +- arch/x86/um/Makefile | 3 +- arch/x86/um/nommu/Makefile | 2 +- arch/x86/um/nommu/entry_64.S | 22 ++++++++++++++ arch/x86/um/nommu/syscalls_64.c | 44 ++++++++++++++++++++++++++++ 5 files changed, 70 insertions(+), 3 deletions(-) create mode 100644 arch/x86/um/nommu/syscalls_64.c diff --git a/arch/um/include/asm/ptrace-generic.h b/arch/um/include/asm/ptr= ace-generic.h index 4ff844bcb1cd..a9778c9a59a3 100644 --- a/arch/um/include/asm/ptrace-generic.h +++ b/arch/um/include/asm/ptrace-generic.h @@ -14,7 +14,7 @@ struct pt_regs { struct uml_pt_regs regs; }; =20 -#define arch_has_single_step() (1) +#define arch_has_single_step() (IS_ENABLED(CONFIG_MMU)) =20 #define EMPTY_REGS { .regs =3D EMPTY_UML_PT_REGS } =20 diff --git a/arch/x86/um/Makefile b/arch/x86/um/Makefile index 227af2a987e2..53c9ebb3c41c 100644 --- a/arch/x86/um/Makefile +++ b/arch/x86/um/Makefile @@ -27,7 +27,8 @@ subarch-y +=3D ../kernel/sys_ia32.o =20 else =20 -obj-y +=3D syscalls_64.o vdso/ +obj-y +=3D vdso/ +obj-$(CONFIG_MMU) +=3D syscalls_64.o =20 subarch-y =3D ../lib/csum-partial_64.o ../lib/memcpy_64.o \ ../lib/memmove_64.o ../lib/memset_64.o diff --git a/arch/x86/um/nommu/Makefile b/arch/x86/um/nommu/Makefile index ebe47d4836f4..4018d9e0aba0 100644 --- a/arch/x86/um/nommu/Makefile +++ b/arch/x86/um/nommu/Makefile @@ -5,4 +5,4 @@ else BITS :=3D 64 endif =20 -obj-y =3D do_syscall_$(BITS).o entry_$(BITS).o os-Linux/ +obj-y =3D do_syscall_$(BITS).o entry_$(BITS).o syscalls_$(BITS).o os-Linux/ diff --git a/arch/x86/um/nommu/entry_64.S b/arch/x86/um/nommu/entry_64.S index e9bfc7b93c84..950447dfa66b 100644 --- a/arch/x86/um/nommu/entry_64.S +++ b/arch/x86/um/nommu/entry_64.S @@ -89,3 +89,25 @@ ENTRY(__kernel_vsyscall) jmp *%rcx =20 END(__kernel_vsyscall) + +// void userspace(struct uml_pt_regs *regs) +ENTRY(userspace) + + /* align the stack for x86_64 ABI */ + and $-0x10, %rsp + /* Handle any immediate reschedules or signals */ + call interrupt_end + + movq current_ptregs, %rsp + + POP_REGS + + addq $8, %rsp /* skip orig_ax */ + popq %r11 /* pt_regs->ip */ + addq $8, %rsp /* skip cs */ + addq $8, %rsp /* skip flags */ + popq %rsp + + jmp *%r11 + +END(userspace) diff --git a/arch/x86/um/nommu/syscalls_64.c b/arch/x86/um/nommu/syscalls_6= 4.c new file mode 100644 index 000000000000..e88e93e9d80a --- /dev/null +++ b/arch/x86/um/nommu/syscalls_64.c @@ -0,0 +1,44 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) + * Copyright 2003 PathScale, Inc. + * + * Licensed under the GPL + */ + +#include +#include +#include +#include +#include /* XXX This should get the constants from libc */ +#include +#include +#include "syscalls.h" + +void arch_switch_to(struct task_struct *to) +{ + /* + * In !CONFIG_MMU, it doesn't ptrace thus, + * The FS_BASE registers are saved here. + */ + current_top_of_stack =3D task_top_of_stack(to); + current_ptregs =3D (long)task_pt_regs(to); + + if ((to->thread.regs.regs.gp[FS_BASE / sizeof(unsigned long)] =3D=3D 0) || + (to->mm =3D=3D NULL)) + return; + + /* this changes the FS on every context switch */ + arch_prctl(to, ARCH_SET_FS, + (void __user *) to->thread.regs.regs.gp[FS_BASE / sizeof(unsigned lon= g)]); +} + +SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, + unsigned long, prot, unsigned long, flags, + unsigned long, fd, unsigned long, off) +{ + if (off & ~PAGE_MASK) + return -EINVAL; + + return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT); +} --=20 2.43.0