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SubjectRe: [PATCH] oprofile, x86: allow backtrace for 32bit apps under 64bit kernel
On 13.09.10 08:15:17, Jiri Olsa wrote:
> hi,
>
> adding support for backtrace of ia32 applications under 64bit kernels.
>
> wbr,
> jirka
>
>
>
> Signed-off-by: Jiri Olsa <jolsa@redhat.com>
> Signed-off-by: Tom Marshall <tdm.rhbz@gmail.com>
> ---
> arch/x86/oprofile/backtrace.c | 42 +++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 42 insertions(+), 0 deletions(-)

Jirka,

see my comments below.

Please, provide a more meaningful commit message.

>
> diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c
> index 3855096..3e443ad 100644
> --- a/arch/x86/oprofile/backtrace.c
> +++ b/arch/x86/oprofile/backtrace.c
> @@ -73,6 +73,38 @@ static struct frame_head *dump_user_backtrace(struct frame_head *head)
> return bufhead[0].bp;
> }
>
> +#ifdef CONFIG_X86_64
> +struct frame_head_32 {
> + __u32 ebp;
> + __u32 ret;
> +} __attribute__((packed));

There exists already struct stack_frame_ia32.

Please, also change the code to reuse struct stack_frame for 64 bit
processes.

> +
> +static struct frame_head *
> +dump_user_backtrace_32(struct frame_head *head)
> +{
> + struct frame_head_32 bufhead_32[2];
> + unsigned long bp, ret;
> +
> + /* Also check accessibility of one struct frame_head beyond */
> + if (!access_ok(VERIFY_READ, head, sizeof(bufhead_32)))
> + return NULL;
> + if (__copy_from_user_inatomic(bufhead_32, head, sizeof(bufhead_32)))
> + return NULL;
> +
> + bp = bufhead_32[0].ebp;
> + ret = bufhead_32[0].ret;
> +
> + oprofile_add_trace(ret);
> +
> + /* frame pointers should strictly progress back up the stack
> + * (towards higher addresses) */
> + if (head >= (struct frame_head *) bp)

You are mixing up struct frame_head and struct frame_head_32 here.

> + return NULL;
> +
> + return (struct frame_head *) bp;
> +}
> +#endif
> +
> void
> x86_backtrace(struct pt_regs * const regs, unsigned int depth)
> {
> @@ -86,6 +118,16 @@ x86_backtrace(struct pt_regs * const regs, unsigned int depth)
> return;
> }
>
> +#ifdef CONFIG_X86_64

Rather use CONFIG_COMPAT here.

> + if (current && test_thread_flag(TIF_IA32)) {
> + /* User process is 32-bit */
> + head = (struct frame_head *)(regs->bp & 0xffffffff);

Same is provided with compat_ptr().

> + while (depth-- && head)
> + head = dump_user_backtrace_32(head);
> + return;
> + }
> +#endif

Please avoid inline macros and make this an inline function (maybe
x86_backtrace_32) with a function stub for the !CONFIG_COMPAT case.

If possible, try to avoid duplicate code for 32 and 64 bit backtraces.

Thanks,

-Robert

> +
> while (depth-- && head)
> head = dump_user_backtrace(head);
> }
> --
> 1.7.1
>
>

--
Advanced Micro Devices, Inc.
Operating System Research Center



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