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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@elte.hu>
AuthorDate: Mon, 25 Oct 2010 08:41:09 +0200
Committer: Ingo Molnar <mingo@elte.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@canb.auug.org.au>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20101025115736.41d51abe.sfr@canb.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@elte.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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