linux-kernel - [tip:perf/urgent] x86/oprofile: Fix uninitialized variable use in debug printk

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Date:	Mon, 25 Oct 2010 06:52:03 GMT
From:	tip-bot for Ingo Molnar <mingo@...e.hu>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	torvalds@...ux-foundation.org, robert.richter@....com,
	tglx@...utronix.de, sfr@...b.auug.org.au, mingo@...e.hu
Subject: [tip:perf/urgent] x86/oprofile: Fix uninitialized variable use in debug printk

Commit-ID:  2c78ffeca98fcd5a1dfd4a322438944506ed5e64
Gitweb:     http://git.kernel.org/tip/2c78ffeca98fcd5a1dfd4a322438944506ed5e64
Author:     Ingo Molnar <mingo@...e.hu>
AuthorDate: Mon, 25 Oct 2010 08:41:09 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Mon, 25 Oct 2010 08:46:20 +0200

x86/oprofile: Fix uninitialized variable use in debug printk

Stephen Rothwell reported this build warning:

  arch/x86/oprofile/op_model_amd.c: In function 'ibs_eilvt_valid':
  arch/x86/oprofile/op_model_amd.c:289: warning: 'offset' may be used uninitialized in this function

And correctly observed that indeed the variable is used uninitialized in
this function. The result of this bug can be a debug printk with a bogus
value.

Also fix a few more small details that made this function hard to read
and which probably contributed to the bug being introduced to begin with:

 - Use more symmetric error conditions

 - Remove the !0 obfuscation

 - Add newlines to the printk output

 - Remove bogus linebreaks in printk strings and elsewhere

Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Cc: Robert Richter <robert.richter@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
LKML-Reference: <20101025115736.41d51abe.sfr@...b.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/x86/oprofile/op_model_amd.c |   26 +++++++++++---------------
 1 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/arch/x86/oprofile/op_model_amd.c b/arch/x86/oprofile/op_model_amd.c
index 42fb46f..68759e7 100644
--- a/arch/x86/oprofile/op_model_amd.c
+++ b/arch/x86/oprofile/op_model_amd.c
@@ -281,29 +281,25 @@ static inline int eilvt_is_available(int offset)
 
 static inline int ibs_eilvt_valid(void)
 {
-	u64 val;
 	int offset;
+	u64 val;
 
 	rdmsrl(MSR_AMD64_IBSCTL, val);
+	offset = val & IBSCTL_LVT_OFFSET_MASK;
+
 	if (!(val & IBSCTL_LVT_OFFSET_VALID)) {
-		pr_err(FW_BUG "cpu %d, invalid IBS "
-		       "interrupt offset %d (MSR%08X=0x%016llx)",
-		       smp_processor_id(), offset,
-		       MSR_AMD64_IBSCTL, val);
+		pr_err(FW_BUG "cpu %d, invalid IBS interrupt offset %d (MSR%08X=0x%016llx)\n",
+		       smp_processor_id(), offset, MSR_AMD64_IBSCTL, val);
 		return 0;
 	}
 
-	offset = val & IBSCTL_LVT_OFFSET_MASK;
-
-	if (eilvt_is_available(offset))
-		return !0;
-
-	pr_err(FW_BUG "cpu %d, IBS interrupt offset %d "
-	       "not available (MSR%08X=0x%016llx)",
-	       smp_processor_id(), offset,
-	       MSR_AMD64_IBSCTL, val);
+	if (!eilvt_is_available(offset)) {
+		pr_err(FW_BUG "cpu %d, IBS interrupt offset %d not available (MSR%08X=0x%016llx)\n",
+		       smp_processor_id(), offset, MSR_AMD64_IBSCTL, val);
+		return 0;
+	}
 
-	return 0;
+	return 1;
 }
 
 static inline int get_ibs_offset(void)
--
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