linux-kernel - Re: [RFC 2/3] x86/coredump: use core regs, rather that TIF

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Date:	Mon, 25 Apr 2016 09:51:38 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Dmitry Safonov <dsafonov@...tuozzo.com>,
	Oleg Nesterov <oleg@...hat.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dmitry Safonov <0x7f454c46@...il.com>,
	Andy Lutomirski <luto@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	X86 ML <x86@...nel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: [RFC 2/3] x86/coredump: use core regs, rather that TIF_IA32 flag

On Mon, Apr 25, 2016 at 9:12 AM, Dmitry Safonov <dsafonov@...tuozzo.com> wrote:
> As we have here core registers, use them to determine application's
> mode and sizes of register set and elf_prstatus.

Looks fine to me, but I'm not that familiar with this code.  Oleg?

>
> 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: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: x86@...nel.org
> Cc: linux-fsdevel@...r.kernel.org
> Signed-off-by: Dmitry Safonov <dsafonov@...tuozzo.com>
> ---
>  arch/x86/include/asm/compat.h |  8 ++++----
>  fs/binfmt_elf.c               | 18 ++++++++++--------
>  2 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
> index 5a3b2c119ed0..d0b517fc77ff 100644
> --- a/arch/x86/include/asm/compat.h
> +++ b/arch/x86/include/asm/compat.h
> @@ -264,10 +264,10 @@ struct compat_shmid64_ds {
>  #ifdef CONFIG_X86_X32_ABI
>  typedef struct user_regs_struct compat_elf_gregset_t;
>
> -#define PR_REG_SIZE(S) (test_thread_flag(TIF_IA32) ? 68 : 216)
> -#define PRSTATUS_SIZE(S) (test_thread_flag(TIF_IA32) ? 144 : 296)
> -#define SET_PR_FPVALID(S,V) \
> -  do { *(int *) (((void *) &((S)->pr_reg)) + PR_REG_SIZE(0)) = (V); } \
> +#define PR_REG_SIZE(S, R) (!user_64bit_mode(R) ? 68 : 216)
> +#define PRSTATUS_SIZE(S, R) (!user_64bit_mode(R) ? 144 : 296)
> +#define SET_PR_FPVALID(S, V, R) \
> +  do { *(int *) (((void *) &((S)->pr_reg)) + PR_REG_SIZE(0, R)) = (V); } \
>    while (0)
>
>  #define COMPAT_USE_64BIT_TIME \
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 81381cc0dd17..6be281ef34f9 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1621,11 +1621,11 @@ static void do_thread_regset_writeback(struct task_struct *task,
>  }
>
>  #ifndef PR_REG_SIZE
> -#define PR_REG_SIZE(S) sizeof(S)
> +#define PR_REG_SIZE(S, R) sizeof(S)
>  #endif
>
>  #ifndef PRSTATUS_SIZE
> -#define PRSTATUS_SIZE(S) sizeof(S)
> +#define PRSTATUS_SIZE(S, R) sizeof(S)
>  #endif
>
>  #ifndef PR_REG_PTR
> @@ -1633,12 +1633,13 @@ static void do_thread_regset_writeback(struct task_struct *task,
>  #endif
>
>  #ifndef SET_PR_FPVALID
> -#define SET_PR_FPVALID(S, V) ((S)->pr_fpvalid = (V))
> +#define SET_PR_FPVALID(S, V, R) ((S)->pr_fpvalid = (V))
>  #endif
>
>  static int fill_thread_core_info(struct elf_thread_core_info *t,
>                                  const struct user_regset_view *view,
> -                                long signr, size_t *total)
> +                                long signr, size_t *total,
> +                                struct pt_regs *regs __maybe_unused)
>  {
>         unsigned int i;
>
> @@ -1650,11 +1651,11 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
>          */
>         fill_prstatus(&t->prstatus, t->task, signr);
>         (void) view->regsets[0].get(t->task, &view->regsets[0],
> -                                   0, PR_REG_SIZE(t->prstatus.pr_reg),
> +                                   0, PR_REG_SIZE(t->prstatus.pr_reg, regs),
>                                     PR_REG_PTR(&t->prstatus), NULL);
>
>         fill_note(&t->notes[0], "CORE", NT_PRSTATUS,
> -                 PRSTATUS_SIZE(t->prstatus), &t->prstatus);
> +                 PRSTATUS_SIZE(t->prstatus, regs), &t->prstatus);
>         *total += notesize(&t->notes[0]);
>
>         do_thread_regset_writeback(t->task, &view->regsets[0]);
> @@ -1684,7 +1685,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
>                                                   regset->core_note_type,
>                                                   size, data);
>                                 else {
> -                                       SET_PR_FPVALID(&t->prstatus, 1);
> +                                       SET_PR_FPVALID(&t->prstatus, 1, regs);
>                                         fill_note(&t->notes[i], "CORE",
>                                                   NT_PRFPREG, size, data);
>                                 }
> @@ -1770,7 +1771,8 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
>          * Now fill in each thread's information.
>          */
>         for (t = info->thread; t != NULL; t = t->next)
> -               if (!fill_thread_core_info(t, view, siginfo->si_signo, &info->size))
> +               if (!fill_thread_core_info(t, view, siginfo->si_signo,
> +                                       &info->size, regs))
>                         return 0;
>
>         /*
> --
> 2.8.0
>



-- 
Andy Lutomirski
AMA Capital Management, LLC