From: Peter Maydell <peter.maydell@linaro.org>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: "Alex Bennée" <alex.bennee@linaro.org>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Laurent Vivier" <laurent@vivier.eu>
Subject: Re: [PATCH v2 10/23] linux-user/i386: Implement setup_sigtramp
Date: Tue, 29 Jun 2021 15:40:40 +0100 [thread overview]
Message-ID: <CAFEAcA9SZmnxcN48_JEcfkSyUDhngcW0Z34DquMpjAaHyPm-cA@mail.gmail.com> (raw)
In-Reply-To: <20210618192951.125651-11-richard.henderson@linaro.org>
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
next prev parent reply other threads:[~2021-06-29 14:46 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-18 19:29 [PATCH v2 00/23] linux-user: Move signal trampolines to new page Richard Henderson
2021-06-18 19:29 ` [PATCH v2 01/23] linux-user: Add infrastructure for a signal trampoline page Richard Henderson
2021-06-19 9:33 ` Philippe Mathieu-Daudé
2021-06-29 13:30 ` Peter Maydell
2021-06-18 19:29 ` [PATCH v2 02/23] linux-user/aarch64: Implement setup_sigtramp Richard Henderson
2021-06-29 13:36 ` Peter Maydell
2021-07-01 19:27 ` Richard Henderson
2021-06-18 19:29 ` [PATCH v2 03/23] linux-user/arm: Split out v2_frame Richard Henderson
2021-06-29 13:53 ` Peter Maydell
2021-06-29 14:30 ` Richard Henderson
2021-06-18 19:29 ` [PATCH v2 04/23] linux-user/arm: Force v2 frames for fdpic Richard Henderson
2021-06-29 13:54 ` Peter Maydell
2021-06-18 19:29 ` [PATCH v2 05/23] linux-user/arm: Implement setup_sigtramp Richard Henderson
2021-06-29 14:09 ` Peter Maydell
2021-06-29 18:32 ` Richard Henderson
2021-06-18 19:29 ` [PATCH v2 06/23] linux-user/alpha: " Richard Henderson
2021-06-18 19:29 ` [PATCH v2 07/23] linux-user/cris: " Richard Henderson
2021-06-19 9:33 ` Philippe Mathieu-Daudé
2021-06-19 12:55 ` Richard Henderson
2021-06-19 14:17 ` Philippe Mathieu-Daudé
2021-06-18 19:29 ` [PATCH v2 08/23] linux-user/hexagon: " Richard Henderson
2021-06-19 9:31 ` Philippe Mathieu-Daudé
2021-06-18 19:29 ` [PATCH v2 09/23] linux-user/hppa: Document non-use of setup_sigtramp Richard Henderson
2021-06-18 19:29 ` [PATCH v2 10/23] linux-user/i386: Implement setup_sigtramp Richard Henderson
2021-06-29 14:40 ` Peter Maydell [this message]
2021-06-29 18:30 ` Richard Henderson
2021-06-18 19:29 ` [PATCH v2 11/23] linux-user/m68k: " Richard Henderson
2021-06-18 19:29 ` [PATCH v2 12/23] linux-user/microblaze: " Richard Henderson
2021-06-18 19:29 ` [PATCH v2 13/23] linux-user/mips: Tidy install_sigtramp Richard Henderson
2021-06-19 9:29 ` Philippe Mathieu-Daudé
2021-06-18 19:29 ` [PATCH v2 14/23] linux-user/mips: Implement setup_sigtramp Richard Henderson
2021-06-18 19:29 ` [PATCH v2 15/23] linux-user/nios2: Document non-use of setup_sigtramp Richard Henderson
2021-06-19 9:35 ` Philippe Mathieu-Daudé
2021-06-18 19:29 ` [PATCH v2 16/23] linux-user/openrisc: Implement setup_sigtramp Richard Henderson
2021-06-18 19:29 ` [PATCH v2 17/23] linux-user/ppc: " Richard Henderson
2021-06-29 14:52 ` Peter Maydell
2021-06-18 19:29 ` [PATCH v2 18/23] linux-user/riscv: " Richard Henderson
2021-06-18 19:29 ` [PATCH v2 19/23] linux-user/s390x: " Richard Henderson
2021-06-18 19:29 ` [PATCH v2 20/23] linux-user/sh4: " Richard Henderson
2021-06-18 19:29 ` [PATCH v2 21/23] linux-user/sparc: " Richard Henderson
2021-07-02 9:05 ` Philippe Mathieu-Daudé
2021-06-18 19:29 ` [PATCH v2 22/23] linux-user/xtensa: " Richard Henderson
2021-06-18 19:29 ` [PATCH v2 23/23] linux-user: Remove default for TARGET_ARCH_HAS_SIGTRAMP_PAGE Richard Henderson
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