linux-kernel - [PATCH] recordmcount: Fix handling of elf64 big-endian objects.

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Date:	Mon, 19 Dec 2011 17:42:42 -0800
From:	David Daney <ddaney.cavm@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, David Daney <david.daney@...ium.com>
Subject: [PATCH] recordmcount: Fix handling of elf64 big-endian objects.

From: David Daney <david.daney@...ium.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.

Signed-off-by: David Daney <david.daney@...ium.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;
 }
-- 
1.7.2.3

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