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Re: [PATCH v2 10/23] linux-user/i386: Implement setup_sigtramp
From: |
Peter Maydell |
Subject: |
Re: [PATCH v2 10/23] linux-user/i386: Implement setup_sigtramp |
Date: |
Tue, 29 Jun 2021 15:40:40 +0100 |
On Fri, 18 Jun 2021 at 20:38, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Create and record the two signal trampolines.
> Use them when the guest does not use SA_RESTORER.
> Note that x86_64 does not use this code.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> linux-user/i386/target_signal.h | 2 ++
> linux-user/x86_64/target_signal.h | 3 +++
> linux-user/i386/signal.c | 42 ++++++++++++++++++-------------
> 3 files changed, 29 insertions(+), 18 deletions(-)
>
> diff --git a/linux-user/i386/target_signal.h b/linux-user/i386/target_signal.h
> index 50361af874..64d09f2e75 100644
> --- a/linux-user/i386/target_signal.h
> +++ b/linux-user/i386/target_signal.h
> @@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
> #include "../generic/signal.h"
>
> #define TARGET_ARCH_HAS_SETUP_FRAME
> +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
> +
> #endif /* I386_TARGET_SIGNAL_H */
> diff --git a/linux-user/x86_64/target_signal.h
> b/linux-user/x86_64/target_signal.h
> index 4ea74f20dd..4673c5a886 100644
> --- a/linux-user/x86_64/target_signal.h
> +++ b/linux-user/x86_64/target_signal.h
> @@ -21,4 +21,7 @@ typedef struct target_sigaltstack {
>
> #include "../generic/signal.h"
>
> +/* For x86_64, use of SA_RESTORER is mandatory. */
> +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
> +
> #endif /* X86_64_TARGET_SIGNAL_H */
> diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c
> index 8701774e37..a83ecba54f 100644
> --- a/linux-user/i386/signal.c
> +++ b/linux-user/i386/signal.c
> @@ -337,16 +337,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
> if (ka->sa_flags & TARGET_SA_RESTORER) {
> __put_user(ka->sa_restorer, &frame->pretcode);
> } else {
> - uint16_t val16;
> - abi_ulong retcode_addr;
> - retcode_addr = frame_addr + offsetof(struct sigframe, retcode);
> - __put_user(retcode_addr, &frame->pretcode);
> - /* This is popl %eax ; movl $,%eax ; int $0x80 */
> - val16 = 0xb858;
> - __put_user(val16, (uint16_t *)(frame->retcode+0));
> - __put_user(TARGET_NR_sigreturn, (int *)(frame->retcode+2));
> - val16 = 0x80cd;
> - __put_user(val16, (uint16_t *)(frame->retcode+6));
> + __put_user(default_sigreturn, &frame->pretcode);
>
In the kernel in arch/x86/kernel/signal.c there is a comment:
/*
* This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
*
* WE DO NOT USE IT ANY MORE! It's only left here for historical
* reasons and because gdb uses it as a signature to notice
* signal handler stack frames.
*/
which suggests that we also should continue to fill in the
retcode bytes in the signal frame for gdb's benefit even though
we don't actually execute them any more.
thanks
-- PMM
- [PATCH v2 07/23] linux-user/cris: Implement setup_sigtramp, (continued)
- [PATCH v2 12/23] linux-user/microblaze: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 16/23] linux-user/openrisc: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 20/23] linux-user/sh4: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 14/23] linux-user/mips: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 11/23] linux-user/m68k: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 10/23] linux-user/i386: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- Re: [PATCH v2 10/23] linux-user/i386: Implement setup_sigtramp,
Peter Maydell <=
- [PATCH v2 17/23] linux-user/ppc: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 21/23] linux-user/sparc: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 23/23] linux-user: Remove default for TARGET_ARCH_HAS_SIGTRAMP_PAGE, Richard Henderson, 2021/06/18
- [PATCH v2 19/23] linux-user/s390x: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 15/23] linux-user/nios2: Document non-use of setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 22/23] linux-user/xtensa: Implement setup_sigtramp, Richard Henderson, 2021/06/18
- [PATCH v2 18/23] linux-user/riscv: Implement setup_sigtramp, Richard Henderson, 2021/06/18