From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751951AbcFVDwb (ORCPT ); Tue, 21 Jun 2016 23:52:31 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:22940 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751347AbcFVDwa (ORCPT ); Tue, 21 Jun 2016 23:52:30 -0400 X-IBM-Helo: d28dlp02.in.ibm.com X-IBM-MailFrom: maddy@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] tools/perf: Fix the mask in regs_dump__printf and print_sample_iregs To: Yury Norov References: <1466521000-11329-1-git-send-email-maddy@linux.vnet.ibm.com> <20160621153531.GA32361@yury-N73SV> Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Adrian Hunter , Kan Liang , Wang Nan , Michael Ellerman From: Madhavan Srinivasan Date: Wed, 22 Jun 2016 09:20:43 +0530 User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <20160621153531.GA32361@yury-N73SV> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16062203-0012-0000-0000-000002A2F1D4 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16062203-0013-0000-0000-00000D4BEBA9 Message-Id: <11fbc51b-6560-bebb-0aff-c9f9c51fd176@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-22_02:,, 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-1606220041 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 21 June 2016 09:05 PM, Yury Norov wrote: > On Tue, Jun 21, 2016 at 08:26:40PM +0530, Madhavan Srinivasan wrote: >> 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 >> Cc: Yury Norov >> Cc: Peter Zijlstra >> Cc: Ingo Molnar >> Cc: Arnaldo Carvalho de Melo >> Cc: Alexander Shishkin >> Cc: Jiri Olsa >> Cc: Adrian Hunter >> Cc: Kan Liang >> Cc: Wang Nan >> Cc: Michael Ellerman >> Signed-off-by: Madhavan Srinivasan >> --- >> 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 +++++++++ > What about include/linux/bitmap.h? I think we'd place it there first. Wanted to handle that separately. > >> 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 >> +#include >> #include >> >> #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) > Inline is not required. Some people don't not like it. Underscored parameter in Not sure why you say that. IIUC we can avoid a function call overhead, also rest of the functions in the file likes it. > function declaration is not the best idea as well. Try: > static void bitmap_from_u64(unsigned long *bitmap, 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 we start with it, I think we'd hide declaration machinery as well: > > #define DECLARE_L64_BITMAP(__name) unsigned long __name[sizeof(u64)/sizeof(unsigned long)] > or > #define L64_BITMAP_SIZE (sizeof(u64)/sizeof(unsigned long)) > > Or both :) Whatever you prefer. ok > >> >> 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. >> + */ > Identical comments... I'd prefer to see it in commit message, or > better in function description. For me it's pretty straightforward in > understanding what happens here in-place without comments. I would prefer the comments here. When reading/understanding the code, we can avoid a jump to another file :). Maddy >> + 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