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    SubjectRe: [PATCH] recordmcount: Fix handling of elf64 big-endian objects.
    On 12/19/2011 07:09 PM, Steven Rostedt wrote:
    > On Mon, 2011-12-19 at 17:42 -0800, David Daney wrote:
    >> From: David Daney<david.daney@cavium.com>
    >>
    >> In ELF64, the sh_flags field is 64-bits wide. recordmcount was
    >> erroneously treating it as a 32-bit wide field. For little endian
    >> objects this works because the flags of interest (SHF_EXECINSTR)
    >> reside in the lower 32 bits of the word, and you get the same result
    >> with either a 32-bit or 64-bit read. Big endian objects on the
    >> other hand do not work at all with this error.
    >>
    >> The fix: Correctly treat sh_flags as 64-bits wide in elf64 objects.
    >>
    >> The symptom I observed was that my
    >> __start_mcount_loc..__stop_mcount_loc was empty even though ftrace
    >> function tracing was enabled.
    >>
    >
    > OUCH!
    >
    > This looks like something that needs to go to stable. Let me play with
    > this on my PPC64 tomorrow.
    >

    Hi Steven,

    Any more feedback on this patch? Should I look for it to appear in 3.3?

    Thanks,
    David Daney

    > Thanks!
    >
    > -- Steve
    >
    >> Signed-off-by: David Daney<david.daney@cavium.com>
    >> ---
    >> scripts/recordmcount.h | 2 +-
    >> 1 files changed, 1 insertions(+), 1 deletions(-)
    >>
    >> diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
    >> index f40a6af6..54e35c1 100644
    >> --- a/scripts/recordmcount.h
    >> +++ b/scripts/recordmcount.h
    >> @@ -462,7 +462,7 @@ __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */
    >> succeed_file();
    >> }
    >> if (w(txthdr->sh_type) != SHT_PROGBITS ||
    >> - !(w(txthdr->sh_flags)& SHF_EXECINSTR))
    >> + !(_w(txthdr->sh_flags)& SHF_EXECINSTR))
    >> return NULL;
    >> return txtname;
    >> }
    >
    >



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