From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946015AbcHRKxy (ORCPT ); Thu, 18 Aug 2016 06:53:54 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57914 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945892AbcHRKxw (ORCPT ); Thu, 18 Aug 2016 06:53:52 -0400 Date: Thu, 18 Aug 2016 03:53:01 -0700 From: tip-bot for Madhavan Srinivasan Message-ID: Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, peterz@infradead.org, vincent.weaver@maine.edu, mingo@kernel.org, eranian@google.com, acme@redhat.com, torvalds@linux-foundation.org, jolsa@kernel.org, ynorov@caviumnetworks.com, acme@kernel.org, jolsa@redhat.com, alexander.shishkin@linux.intel.com, hpa@zytor.com, mpe@ellerman.id.au, maddy@linux.vnet.ibm.com Reply-To: vincent.weaver@maine.edu, peterz@infradead.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org, jolsa@redhat.com, acme@kernel.org, ynorov@caviumnetworks.com, jolsa@kernel.org, acme@redhat.com, torvalds@linux-foundation.org, eranian@google.com, maddy@linux.vnet.ibm.com, mpe@ellerman.id.au, hpa@zytor.com, alexander.shishkin@linux.intel.com In-Reply-To: <1471426568-31051-2-git-send-email-maddy@linux.vnet.ibm.com> References: <1471426568-31051-2-git-send-email-maddy@linux.vnet.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] bitmap.h, perf/core: Fix the mask in perf_output_sample_regs() Git-Commit-ID: 29dd3288705f26cc27663e79061209dabce2d5b9 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 29dd3288705f26cc27663e79061209dabce2d5b9 Gitweb: http://git.kernel.org/tip/29dd3288705f26cc27663e79061209dabce2d5b9 Author: Madhavan Srinivasan AuthorDate: Wed, 17 Aug 2016 15:06:08 +0530 Committer: Ingo Molnar CommitDate: Thu, 18 Aug 2016 10:44:20 +0200 bitmap.h, perf/core: Fix the mask in perf_output_sample_regs() 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 exisiting code works fine in most of the case, the logic is broken for big-endian 32-bit kernels. When reading a u64 mask using (u32 *)(&val)[0], find_*_bit() assumes that it gets the lower 32 bits of u64, but instead it gets the upper 32 bits - which is wrong. The fix is to swap the words of the u64 to handle this case. This is _not_ a regular endianness swap. Suggested-by: Yury Norov Signed-off-by: Madhavan Srinivasan Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Yury Norov Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Jiri Olsa Cc: Linus Torvalds Cc: Michael Ellerman Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/1471426568-31051-2-git-send-email-maddy@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- 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 598bc99..3b77588 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 32-bit Big Endian kernel, when using (u32 *)(&val)[*] + * to read u64 mask, we will get the wrong word. + * That is "(u32 *)(&val)[0]" gets the upper 32 bits, + * but we expect the lower 32-bits 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 ca4fde5..849919c 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5340,9 +5340,10 @@ 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);