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 <yno...@caviumnetworks.com>
Cc: Yury Norov <yno...@caviumnetworks.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Jiri Olsa <jo...@kernel.org>
Cc: Adrian Hunter <adrian.hun...@intel.com>
Cc: Kan Liang <kan.li...@intel.com>
Cc: Wang Nan <wangn...@huawei.com>
Cc: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Madhavan Srinivasan <ma...@linux.vnet.ibm.com>
---
Changelog v4:
1) Removed the new macro and resued the DECLARE_BITMAP
Changelog v3:
1)Moved the swap function to lib/bitmap.c
2)Added a macro for declaration
3)Added the comments
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 | 2 ++
tools/lib/bitmap.c | 18 ++++++++++++++++++
tools/perf/builtin-script.c | 4 +++-
tools/perf/util/session.c | 4 +++-
4 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/tools/include/linux/bitmap.h b/tools/include/linux/bitmap.h
index 28f5493da491..5e98525387dc 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) \
@@ -10,6 +11,7 @@
int __bitmap_weight(const unsigned long *bitmap, int bits);
void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
const unsigned long *bitmap2, int bits);
+void bitmap_from_u64(unsigned long *dst, u64 mask);
#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
diff --git a/tools/lib/bitmap.c b/tools/lib/bitmap.c
index 0a1adc1111fd..464a0cc63e6a 100644
--- a/tools/lib/bitmap.c
+++ b/tools/lib/bitmap.c
@@ -29,3 +29,21 @@ void __bitmap_or(unsigned long *dst, const unsigned long
*bitmap1,
for (k = 0; k < nr; k++)
dst[k] = bitmap1[k] | bitmap2[k];
}
+
+/*
+ * bitmap_from_u64 - Check and swap words within u64.
+ * @mask: source bitmap
+ * @dst: destination bitmap
+ *
+ * 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. That is "(u32 *)(&val)[0]"
+ * gets upper 32 bits of u64, but perf may expect lower 32bits of u64.
+ */
+void bitmap_from_u64(unsigned long *dst, u64 mask)
+{
+ dst[0] = mask & ULONG_MAX;
+
+ if (sizeof(mask) > sizeof(unsigned long))
+ dst[1] = mask >> 32;
+}
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index e3ce2f34d3ad..132a4bb70c31 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -412,11 +412,13 @@ 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;
+ DECLARE_BITMAP(_mask, 64);
if (!regs)
return;
- for_each_set_bit(r, (unsigned long *) &mask, sizeof(mask) * 8) {
+ 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..35722226bf13 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -940,8 +940,10 @@ static void branch_stack__printf(struct perf_sample
*sample)
static void regs_dump__printf(u64 mask, u64 *regs)
{
unsigned rid, i = 0;
+ DECLARE_BITMAP(_mask, 64);
- for_each_set_bit(rid, (unsigned long *) &mask, sizeof(mask) * 8) {
+ 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
