On Mon, 2008-06-09 at 16:26 -0700, [EMAIL PROTECTED] wrote:
> From: Carl Love <[EMAIL PROTECTED]>
>
> Fix the 64 bit user code backtrace which currently may hang the system.
>
> Signed-off-by: Carl Love <[EMAIL PROTECTED]>
> Cc: Maynard Johnson <[EMAIL PROTECTED]>
That looks weird. I doubt it's the right fix for the problem. Paul,
I remember this was discussed earlier, did we come up with a proper fix
already ?
Cheers,
Ben.
> On Thu, 15 May 2008 10:20:44 +1000
> Michael Ellerman <[EMAIL PROTECTED]> wrote:
> >
> > __copy_from_user_inatomic() accepts any value for n, it just has a
> > special case for 1, 2, 4 and 8 - but it should still work for other
> > values.
> >
> > The old code copied 24 bytes from sp, and the new code copies 8 bytes
> > from sp and 8 bytes from sp + 16 - so I don't see where the 48 bytes
> > comes in to it?
> >
> > \ufeffAlso the comment is a little hard to parse, I think you mean "Issue:
> > the ..", but I read "Issue" as a verb in that sentence. And "Don't read
> > more then" should be "than".
>
> Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
> ---
>
> arch/powerpc/oprofile/backtrace.c | 33 ++++++++++++++++++++++------
> 1 file changed, 27 insertions(+), 6 deletions(-)
>
> diff -puN
> arch/powerpc/oprofile/backtrace.c~powerpc-fix-for-oprofile-callgraph-for-power-64-bit-user-apps
> arch/powerpc/oprofile/backtrace.c
> ---
> a/arch/powerpc/oprofile/backtrace.c~powerpc-fix-for-oprofile-callgraph-for-power-64-bit-user-apps
> +++ a/arch/powerpc/oprofile/backtrace.c
> @@ -53,19 +53,40 @@ static unsigned int user_getsp32(unsigne
> #ifdef CONFIG_PPC64
> static unsigned long user_getsp64(unsigned long sp, int is_first)
> {
> - unsigned long stack_frame[3];
> + unsigned long stk_frm_lr;
> + unsigned long stk_frm_sp;
> + unsigned long size;
> +
> + /* Issue the __copy_from_user_inatomic() third argument currently
> + * only takes sizes 1, 2, 4 or 8 bytes. Don't read more then the
> + * first 48 bytes of the stack frame. That is all that is
> + * guaranteed to exist. Reading more may cause the system to hang.
> + *
> + * 64 bit stack frame layout:
> + * 0-7 bytes is the pointer to previous stack
> + * 8-15 bytes condition register save area
> + * 16-23 bytes link register save area
> + */
> + size = sizeof(unsigned long);
> + if (!access_ok(VERIFY_READ, (void __user *)sp, size))
> + return 0;
>
> - if (!access_ok(VERIFY_READ, (void __user *)sp, sizeof(stack_frame)))
> + if (__copy_from_user_inatomic(&stk_frm_sp, (void __user *)sp,
> + size))
> return 0;
>
> - if (__copy_from_user_inatomic(stack_frame, (void __user *)sp,
> - sizeof(stack_frame)))
> + /* get the LR from the user stack */
> + if (!access_ok(VERIFY_READ, (void __user *)(sp+16), size))
> + return 0;
> +
> + if (__copy_from_user_inatomic(&stk_frm_lr, (void __user *)(sp+16),
> + size))
> return 0;
>
> if (!is_first)
> - oprofile_add_trace(STACK_LR64(stack_frame));
> + oprofile_add_trace(stk_frm_lr);
>
> - return STACK_SP(stack_frame);
> + return stk_frm_sp;
> }
> #endif
>
> _
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