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Message-Id: <1466521000-11329-1-git-send-email-maddy@linux.vnet.ibm.com>
Date: Tue, 21 Jun 2016 20:26:40 +0530
From: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
Yury Norov <ynorov@...iumnetworks.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...el.com>,
Wang Nan <wangnan0@...wei.com>,
Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH v3] tools/perf: Fix the mask in regs_dump__printf and print_sample_iregs
When decoding the perf_regs mask in regs_dump__printf(),
we loop through the mask using find_first_bit and find_next_bit functions.
"mask" is of type "u64", but sent as a "unsigned long *" to
lib functions along with sizeof().
While the exisitng code works fine in most of the case,
the logic is broken when using a 32bit perf on a 64bit kernel (Big Endian).
When reading u64 using (u32 *)(&val)[0], perf (lib/find_*_bit()) assumes it gets
lower 32bits of u64 which is wrong. Proposed fix is to swap the words
of the u64 to handle this case. This is _not_ endianess swap.
Suggested-by: Yury Norov <ynorov@...iumnetworks.com>
Cc: Yury Norov <ynorov@...iumnetworks.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Kan Liang <kan.liang@...el.com>
Cc: Wang Nan <wangnan0@...wei.com>
Cc: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
---
Changelog v2:
1)Moved the swap code to a common function
2)Added more comments in the code
Changelog v1:
1)updated commit message and patch subject
2)Add the fix to print_sample_iregs() in builtin-script.c
tools/include/linux/bitmap.h | 9 +++++++++
tools/perf/builtin-script.c | 16 +++++++++++++++-
tools/perf/util/session.c | 16 +++++++++++++++-
3 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/tools/include/linux/bitmap.h b/tools/include/linux/bitmap.h
index 28f5493da491..79998b26eb04 100644
--- a/tools/include/linux/bitmap.h
+++ b/tools/include/linux/bitmap.h
@@ -2,6 +2,7 @@
#define _PERF_BITOPS_H
#include <string.h>
+#include <limits.h>
#include <linux/bitops.h>
#define DECLARE_BITMAP(name,bits) \
@@ -22,6 +23,14 @@ void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
#define small_const_nbits(nbits) \
(__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG)
+static inline void bitmap_from_u64(unsigned long *_mask, u64 mask)
+{
+ _mask[0] = mask & ULONG_MAX;
+
+ if (sizeof(mask) > sizeof(unsigned long))
+ _mask[1] = mask >> 32;
+}
+
static inline void bitmap_zero(unsigned long *dst, int nbits)
{
if (small_const_nbits(nbits))
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index e3ce2f34d3ad..73928310fd91 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -412,11 +412,25 @@ static void print_sample_iregs(struct perf_sample *sample,
struct regs_dump *regs = &sample->intr_regs;
uint64_t mask = attr->sample_regs_intr;
unsigned i = 0, r;
+ unsigned long _mask[sizeof(mask)/sizeof(unsigned long)];
if (!regs)
return;
- for_each_set_bit(r, (unsigned long *) &mask, sizeof(mask) * 8) {
+ /*
+ * Since u64 is passed as 'unsigned long *', check
+ * to see whether we need to swap words within u64.
+ * Reason being, in 32 bit big endian userspace on a
+ * 64bit kernel, 'unsigned long' is 32 bits.
+ * When reading u64 using (u32 *)(&val)[0] and (u32 *)(&val)[1],
+ * we will get wrong value for the mask. This is what
+ * find_first_bit() and find_next_bit() is doing.
+ * Issue here is "(u32 *)(&val)[0]" gets upper 32 bits of u64,
+ * but perf assumes it gets lower 32bits of u64. Hence the check
+ * and swap.
+ */
+ bitmap_from_u64(_mask, mask);
+ for_each_set_bit(r, _mask, sizeof(mask) * 8) {
u64 val = regs->regs[i++];
printf("%5s:0x%"PRIx64" ", perf_reg_name(r), val);
}
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 5214974e841a..1337b1c73f82 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -940,8 +940,22 @@ static void branch_stack__printf(struct perf_sample *sample)
static void regs_dump__printf(u64 mask, u64 *regs)
{
unsigned rid, i = 0;
+ unsigned long _mask[sizeof(mask)/sizeof(unsigned long)];
- for_each_set_bit(rid, (unsigned long *) &mask, sizeof(mask) * 8) {
+ /*
+ * Since u64 is passed as 'unsigned long *', check
+ * to see whether we need to swap words within u64.
+ * Reason being, in 32 bit big endian userspace on a
+ * 64bit kernel, 'unsigned long' is 32 bits.
+ * When reading u64 using (u32 *)(&val)[0] and (u32 *)(&val)[1],
+ * we will get wrong value for the mask. This is what
+ * find_first_bit() and find_next_bit() is doing.
+ * Issue here is "(u32 *)(&val)[0]" gets upper 32 bits of u64,
+ * but perf assumes it gets lower 32bits of u64. Hence the check
+ * and swap.
+ */
+ bitmap_from_u64(_mask, mask);
+ for_each_set_bit(rid, _mask, sizeof(mask) * 8) {
u64 val = regs[i++];
printf(".... %-5s 0x%" PRIx64 "\n",
--
1.9.1
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