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 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 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev