linux-kernel - Re: [PATCH 6/6] x86/signal: add SA_{X32,IA32}_ABI sa

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Message-ID: <CALCETrUAyz3EpfZK=kErnPdmS01FCZZzDeZDvEXY=g1UcM85dw@mail.gmail.com>
Date:	Fri, 3 Jun 2016 22:08:04 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Dmitry Safonov <dsafonov@...tuozzo.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Dmitry Safonov <0x7f454c46@...il.com>, khorenko@...tuozzo.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Oleg Nesterov <oleg@...hat.com>, xemul@...tuozzo.com,
	X86 ML <x86@...nel.org>, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 6/6] x86/signal: add SA_{X32,IA32}_ABI sa_flags

On Jun 1, 2016 6:13 AM, "Dmitry Safonov" <dsafonov@...tuozzo.com> wrote:
>
> Introduce new flags that defines which ABI to use on creating sigframe.
> Those flags kernel will set according to sigaction syscall ABI,
> which set handler for the signal being delivered.
>
> So that will drop the dependency on TIF_IA32/TIF_X32 flags on signal deliver.
> Those flags will be used only under CONFIG_COMPAT.
>
> Similar way ARM uses sa_flags to differ in which mode deliver signal
> for 26-bit applications (look at SA_THIRYTWO).
>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Signed-off-by: Dmitry Safonov <dsafonov@...tuozzo.com>
> ---
>  arch/x86/ia32/ia32_signal.c        |  2 +-
>  arch/x86/include/asm/fpu/signal.h  |  6 ++++++
>  arch/x86/include/uapi/asm/signal.h |  6 +++++-
>  arch/x86/kernel/signal.c           | 19 ++++++++++---------
>  arch/x86/kernel/signal_compat.c    | 30 +++++++++++++++++++++++++++---
>  kernel/signal.c                    |  5 +++++
>  6 files changed, 54 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
> index 2f29f4e407c3..cb13c0564ea7 100644
> --- a/arch/x86/ia32/ia32_signal.c
> +++ b/arch/x86/ia32/ia32_signal.c
> @@ -378,7 +378,7 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
>                 put_user_ex(*((u64 *)&code), (u64 __user *)frame->retcode);
>         } put_user_catch(err);
>
> -       err |= copy_siginfo_to_user32(&frame->info, &ksig->info);
> +       err |= __copy_siginfo_to_user32(&frame->info, &ksig->info, false);
>         err |= ia32_setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
>                                      regs, set->sig[0]);
>         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
> diff --git a/arch/x86/include/asm/fpu/signal.h b/arch/x86/include/asm/fpu/signal.h
> index 0e970d00dfcd..20a1fbf7fe4e 100644
> --- a/arch/x86/include/asm/fpu/signal.h
> +++ b/arch/x86/include/asm/fpu/signal.h
> @@ -19,6 +19,12 @@ int ia32_setup_frame(int sig, struct ksignal *ksig,
>  # define ia32_setup_rt_frame   __setup_rt_frame
>  #endif
>
> +#ifdef CONFIG_COMPAT
> +int __copy_siginfo_to_user32(compat_siginfo_t __user *to,
> +               const siginfo_t *from, bool x32_ABI);
> +#endif
> +
> +
>  extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
>                               struct task_struct *tsk);
>  extern void convert_to_fxsr(struct task_struct *tsk,
> diff --git a/arch/x86/include/uapi/asm/signal.h b/arch/x86/include/uapi/asm/signal.h
> index 8264f47cf53e..9c663b6fc023 100644
> --- a/arch/x86/include/uapi/asm/signal.h
> +++ b/arch/x86/include/uapi/asm/signal.h
> @@ -70,6 +70,8 @@ typedef unsigned long sigset_t;
>   * SA_RESETHAND clears the handler when the signal is delivered.
>   * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
>   * SA_NODEFER prevents the current signal from being masked in the handler.
> + * SA_IA32_ABI/SA_X32_ABI indicates ABI for a signal frame,
> + *   if neither is set, the kernel will set them according to a syscall ABI

I would prefer if these weren't in the UAPI header.  If you want a
foreign signal frame type, do a foreign syscall.  This also means that
you should strip these flags if a user sets them directly.

--Andy