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Subject[PATCH 11/13] tools/perf: Fix the mask in regs_dump__printf and print_sample_iregs
Date
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@caviumnetworks.com>
Reviewed-by: Yury Norov <ynorov@caviumnetworks.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Yury Norov <ynorov@caviumnetworks.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
---
Fix already posted, but yet to be pulled in. This is needed
for the subsequent patches.

https://patchwork.kernel.org/patch/9285421/

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 43c1c5021e4b..998ac95a8ddd 100644
--- a/tools/include/linux/bitmap.h
+++ b/tools/include/linux/bitmap.h
@@ -4,10 +4,12 @@
#include <string.h>
#include <linux/bitops.h>
#include <stdlib.h>
+#include <limits.h>

#define DECLARE_BITMAP(name,bits) \
unsigned long name[BITS_TO_LONGS(bits)]

+void bitmap_from_u64(unsigned long *dst, u64 mask);
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);
diff --git a/tools/lib/bitmap.c b/tools/lib/bitmap.c
index 38748b0e342f..21e17730c35f 100644
--- a/tools/lib/bitmap.c
+++ b/tools/lib/bitmap.c
@@ -73,3 +73,21 @@ int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
BITMAP_LAST_WORD_MASK(bits));
return result != 0;
}
+
+/*
+ * 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 6b3c8b0d3276..db270b4f892a 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -421,11 +421,13 @@ 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 5d61242a6e64..440a9fb2a6fb 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -944,8 +944,10 @@ 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",
--
2.7.4
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