Re: [PATCH v3 08/19] unwind/x86: Enable CONFIG_HAVE_UNWIND_USER_FP

From: Peter Zijlstra
Date: Tue Oct 29 2024 - 09:13:30 EST


On Mon, Oct 28, 2024 at 02:47:35PM -0700, Josh Poimboeuf wrote:
> Use ARCH_INIT_USER_FP_FRAME to describe how frame pointers are unwound
> on x86, and enable CONFIG_HAVE_UNWIND_USER_FP accordingly so the
> unwind_user interfaces can be used.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/include/asm/unwind_user.h | 11 +++++++++++
> 2 files changed, 12 insertions(+)
> create mode 100644 arch/x86/include/asm/unwind_user.h
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 0bdb7a394f59..f91098d6f535 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -289,6 +289,7 @@ config X86
> select HAVE_SYSCALL_TRACEPOINTS
> select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
> select HAVE_UNSTABLE_SCHED_CLOCK
> + select HAVE_UNWIND_USER_FP if X86_64
> select HAVE_USER_RETURN_NOTIFIER
> select HAVE_GENERIC_VDSO
> select VDSO_GETRANDOM if X86_64
> diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_user.h
> new file mode 100644
> index 000000000000..19df26a65132
> --- /dev/null
> +++ b/arch/x86/include/asm/unwind_user.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_X86_UNWIND_USER_H
> +#define _ASM_X86_UNWIND_USER_H
> +
> +#define ARCH_INIT_USER_FP_FRAME \
> + .ra_off = (s32)sizeof(long) * -1, \
> + .cfa_off = (s32)sizeof(long) * 2, \
> + .fp_off = (s32)sizeof(long) * -2, \
> + .use_fp = true,
> +
> +#endif /* _ASM_X86_UNWIND_USER_H */

What about compat / 32bit userspace?