linux-kernel - [50/90] recordmcount: Fix handling of elf64 big-endian objects.

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Date:	Mon, 23 Jan 2012 15:39:36 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, David Daney <david.daney@...ium.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [50/90] recordmcount: Fix handling of elf64 big-endian objects.

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit 2e885057b7f75035f0b85e02f737891482815a81 upstream.

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.

Link: http://lkml.kernel.org/r/1324345362-12230-1-git-send-email-ddaney.cavm@gmail.com

Signed-off-by: David Daney <david.daney@...ium.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 scripts/recordmcount.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/scripts/recordmcount.h
+++ b/scripts/recordmcount.h
@@ -462,7 +462,7 @@ __has_rel_mcount(Elf_Shdr const *const r
 		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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