From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3rVZS71mcvzDqjc for ; Thu, 16 Jun 2016 17:16:23 +1000 (AEST) Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u5G7DoRQ072075 for ; Thu, 16 Jun 2016 03:16:20 -0400 Received: from e23smtp08.au.ibm.com (e23smtp08.au.ibm.com [202.81.31.141]) by mx0b-001b2d01.pphosted.com with ESMTP id 23jswc5nj8-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 16 Jun 2016 03:16:19 -0400 Received: from localhost by e23smtp08.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 16 Jun 2016 17:16:16 +1000 Received: from d23relay09.au.ibm.com (d23relay09.au.ibm.com [9.185.63.181]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 6630F3578057 for ; Thu, 16 Jun 2016 17:16:14 +1000 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay09.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u5G7GEYW18939942 for ; Thu, 16 Jun 2016 17:16:14 +1000 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u5G7GD4d004212 for ; Thu, 16 Jun 2016 17:16:14 +1000 Subject: Re: [PATCH] tools/perf: fix the word selected in find_*_bit To: Yury Norov References: <1465990973-31483-1-git-send-email-maddy@linux.vnet.ibm.com> <20160615195127.GA6039@yury-N73SV> Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Arnaldo Carvalho de Melo , Adrian Hunter , Borislav Petkov , David Ahern , George Spelvin , Jiri Olsa , Namhyung Kim , Rasmus Villemoes , Wang Nan , Yury Norov , Michael Ellerman From: Madhavan Srinivasan Date: Thu, 16 Jun 2016 12:45:55 +0530 MIME-Version: 1.0 In-Reply-To: <20160615195127.GA6039@yury-N73SV> Content-Type: text/plain; charset=windows-1252 Message-Id: <37638e17-ab3f-2045-d3f6-faff11e8e87c@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thursday 16 June 2016 01:21 AM, Yury Norov wrote: > Hi Madhavan, > > On Wed, Jun 15, 2016 at 05:12:53PM +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. >> And mask is of type "u64". But "u64" is send as a "unsigned long *" to >> lib functions along with sizeof(). >> >> While the exisitng code works fine in most of the case, when using a 32bit perf >> on a 64bit kernel (Big Endian), we end reading the wrong word. In find_first_bit(), >> one word at a time (based on BITS_PER_LONG) is loaded and >> checked for any bit set. In 32bit BE userspace, >> BITS_PER_LONG turns out to be 32, and for a mask value of >> "0x00000000000000ff", find_first_bit will return 32, instead of 0. >> Reason for this is that, value in the word0 is all zeros and value >> in word1 is 0xff. Ideally, second word in the mask should be loaded >> and searched. Patch swaps the word to look incase of 32bit BE. > I think this is not a problem of find_bit() at all. You have wrong > typecast as the source of problem (tools/perf/util/session.c"): > > 940 static void regs_dump__printf(u64 mask, u64 *regs) > 941 { > 942 unsigned rid, i = 0; > 943 > 944 for_each_set_bit(rid, (unsigned long *) &mask, sizeof(mask) * 8) { > ^^^^ Here ^^^^ > 945 u64 val = regs[i++]; > 946 > 947 printf(".... %-5s 0x%" PRIx64 "\n", > 948 perf_reg_name(rid), val); > 949 } > 950 } > > But for some reason you change correct find_bit()... > > Though proper fix is like this for me: > > static void regs_dump__printf(u64 mask, u64 *regs) > { > unsigned rid, i = 0; > unsigned long _mask[sizeof(mask)/sizeof(unsigned long)]; > > _mask[0] = mask & ULONG_MAX; > if (sizeof(mask) > sizeof(unsigned long)) > _mask[1] = mask >> BITS_PER_LONG; > > for_each_set_bit(rid, _mask, sizeof(mask) * BITS_PER_BYTE) { > u64 val = regs[i++]; > > printf(".... %-5s 0x%" PRIx64 "\n", > perf_reg_name(rid), val); > } > } > > Maybe there already is some macro doing the conversion for you... Agreed, but reason for proposing fix in lib side is to avoid conversion on each case (if any in future). I will repost the fix as suggested. Maddy > Yury. > >> Cc: Arnaldo Carvalho de Melo >> Cc: Adrian Hunter >> Cc: Borislav Petkov >> Cc: David Ahern >> Cc: George Spelvin >> Cc: Jiri Olsa >> Cc: Namhyung Kim >> Cc: Rasmus Villemoes >> Cc: Wang Nan >> Cc: Yury Norov >> Cc: Michael Ellerman >> Signed-off-by: Madhavan Srinivasan >> --- >> tools/lib/find_bit.c | 17 +++++++++++++++++ >> 1 file changed, 17 insertions(+) >> >> diff --git a/tools/lib/find_bit.c b/tools/lib/find_bit.c >> index 9122a9e80046..996b3e04324f 100644 >> --- a/tools/lib/find_bit.c >> +++ b/tools/lib/find_bit.c >> @@ -37,7 +37,12 @@ static unsigned long _find_next_bit(const unsigned long *addr, >> if (!nbits || start >= nbits) >> return nbits; >> >> +#if (__BYTE_ORDER == __BIG_ENDIAN) && (BITS_PER_LONG != 64) >> + tmp = addr[(((nbits - 1)/BITS_PER_LONG) - (start / BITS_PER_LONG))] >> + ^ invert; >> +#else >> tmp = addr[start / BITS_PER_LONG] ^ invert; >> +#endif >> >> /* Handle 1st word. */ >> tmp &= BITMAP_FIRST_WORD_MASK(start); >> @@ -48,7 +53,12 @@ static unsigned long _find_next_bit(const unsigned long *addr, >> if (start >= nbits) >> return nbits; >> >> +#if (__BYTE_ORDER == __BIG_ENDIAN) && (BITS_PER_LONG != 64) >> + tmp = addr[(((nbits - 1)/BITS_PER_LONG) - (start / BITS_PER_LONG))] >> + ^ invert; >> +#else >> tmp = addr[start / BITS_PER_LONG] ^ invert; >> +#endif >> } >> >> return min(start + __ffs(tmp), nbits); >> @@ -75,8 +85,15 @@ unsigned long find_first_bit(const unsigned long *addr, unsigned long size) >> unsigned long idx; >> >> for (idx = 0; idx * BITS_PER_LONG < size; idx++) { >> +#if (__BYTE_ORDER == __BIG_ENDIAN) && (BITS_PER_LONG != 64) >> + if (addr[(((size-1)/BITS_PER_LONG) - idx)]) >> + return min(idx * BITS_PER_LONG + >> + __ffs(addr[(((size-1)/BITS_PER_LONG) - idx)]), >> + size); >> +#else >> if (addr[idx]) >> return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size); >> +#endif >> } >> >> return size; >> -- >> 1.9.1