[patch 1/4] powerpc: fix for OProfile callgraph for Power 64 bit user apps
michael at ellerman.id.au
Thu May 15 10:20:44 EST 2008
On Wed, 2008-05-14 at 16:12 -0700, akpm at linux-foundation.org wrote:
> From: Carl Love <cel at us.ibm.com>
> Fix the 64 bit user code backtrace which currently may hang the system.
> Signed-off-by: Carl Love <carll at us.ibm.com>
> Cc: Maynard Johnson <maynardj at us.ibm.com>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
I'm a bit confused by this change ..
> 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;
> + 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.
__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
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?
Also 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".
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