[PATCH v6 1/2] tools/perf: Fix the mask in regs_dump__printf and print_sample_iregs

[PATCH v6 1/2] tools/perf: Fix the mask in regs_dump__printf and print_sample_iregs

[Madhavan Srinivasan]

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>
---
Changelog v5:
1)No logic change, just upstream rebasing

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 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 9c640a8081c7..4b8de4f99a11 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -418,11 +418,13 @@ 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

[PATCH v2 2/2] perf/core: Fix the mask in perf_output_sample_regs

[Madhavan Srinivasan]

When decoding the perf_regs mask in perf_output_sample_regs(),
we loop through the mask using find_first_bit and find_next_bit functions.
While the exisitng code works fine in most of the case,
the logic is broken for 32bit kernel (Big Endian).
When reading u64 mask using (u32 *)(&val)[0], find_*_bit() assumes it gets
lower 32bits of u64 but instead gets upper 32bits which is wrong.
Proposed fix is to swap the words of the u64 to handle this case.
This is _not_ endianness swap.

Suggested-by: Yury Norov <ynorov@caviumnetworks.com>
Reviewed-by: Yury Norov <ynorov@caviumnetworks.com>
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: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
---
Changelog v1:
1)bitmap_from_u64() is inline now

 include/linux/bitmap.h | 18 ++++++++++++++++++
 kernel/events/core.c   |  5 +++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 598bc999f4c2..a9ea992161a1 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -339,6 +339,24 @@ static inline int bitmap_parse(const char *buf, unsigned int buflen,
 	return __bitmap_parse(buf, buflen, 0, maskp, nmaskbits);
 }
 
+/*
+ * bitmap_from_u64 - Check and swap words within u64.
+ *  @mask: source bitmap
+ *  @dst:  destination bitmap
+ *
+ * In 32bit Big Endian kernel, when using (u32 *)(&val)[*]
+ * to read u64 mask, we will get wrong word.
+ * That is "(u32 *)(&val)[0]" gets upper 32 bits,
+ * but expected could be lower 32bits of u64.
+ */
+static inline void bitmap_from_u64(unsigned long *dst, u64 mask)
+{
+	dst[0] = mask & ULONG_MAX;
+
+	if (sizeof(mask) > sizeof(unsigned long))
+		dst[1] = mask >> 32;
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __LINUX_BITMAP_H */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1903b8f3a705..de32e9bd8189 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5292,9 +5292,10 @@ perf_output_sample_regs(struct perf_output_handle *handle,
 			struct pt_regs *regs, u64 mask)
 {
 	int bit;
+	DECLARE_BITMAP(_mask, 64);
 
-	for_each_set_bit(bit, (const unsigned long *) &mask,
-			 sizeof(mask) * BITS_PER_BYTE) {
+	bitmap_from_u64(_mask, mask);
+	for_each_set_bit(bit, _mask, sizeof(mask) * BITS_PER_BYTE) {
 		u64 val;
 
 		val = perf_reg_value(regs, bit);
-- 
2.7.4