From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752554AbcHQJhA (ORCPT ); Wed, 17 Aug 2016 05:37:00 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:59435 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752054AbcHQJg6 (ORCPT ); Wed, 17 Aug 2016 05:36:58 -0400 X-IBM-Helo: d28dlp03.in.ibm.com X-IBM-MailFrom: maddy@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: Madhavan Srinivasan To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, peterz@infradead.org, acme@kernel.org Cc: Madhavan Srinivasan , Yury Norov , Ingo Molnar , Alexander Shishkin , Jiri Olsa , Michael Ellerman Subject: [PATCH v2 2/2] perf/core: Fix the mask in perf_output_sample_regs Date: Wed, 17 Aug 2016 15:06:08 +0530 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1471426568-31051-1-git-send-email-maddy@linux.vnet.ibm.com> References: <1471426568-31051-1-git-send-email-maddy@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16081709-0008-0000-0000-0000030CC9C9 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16081709-0009-0000-0000-00000EC6D4C7 Message-Id: <1471426568-31051-2-git-send-email-maddy@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-08-17_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1608170108 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Reviewed-by: Yury Norov Cc: Yury Norov Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Alexander Shishkin Cc: Jiri Olsa Cc: Michael Ellerman Signed-off-by: Madhavan Srinivasan --- 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