linux-kernel - Re: [PATCH v2] perf: Fix display of kernel symbols

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <590b2f02-f7f0-48b2-b45e-8a31bbadef2a@csgroup.eu>
Date: Wed, 8 Jan 2025 18:06:03 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>, linux-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, linux-perf-users@...r.kernel.org,
 Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH v2] perf: Fix display of kernel symbols



Le 08/01/2025 à 15:53, Arnaldo Carvalho de Melo a écrit :
> On Wed, Jan 08, 2025 at 10:54:20AM +0100, Christophe Leroy wrote:
>> Since commit 659ad3492b91 ("perf maps: Switch from rbtree to lazily
>> sorted array for addresses"), perf doesn't display anymore kernel
>> symbols on powerpc, allthough it still detects them as kernel addresses.
>>
>> 	# Overhead  Command     Shared Object  Symbol
>> 	# ........  ..........  ............. ......................................
>> 	#
>> 	    80.49%  Coeur main  [unknown]      [k] 0xc005f0f8
>> 	     3.91%  Coeur main  gau            [.] engine_loop.constprop.0.isra.0
>> 	     1.72%  Coeur main  [unknown]      [k] 0xc005f11c
>> 	     1.09%  Coeur main  [unknown]      [k] 0xc01f82c8
>> 	     0.44%  Coeur main  libc.so.6      [.] epoll_wait
>> 	     0.38%  Coeur main  [unknown]      [k] 0xc0011718
>> 	     0.36%  Coeur main  [unknown]      [k] 0xc01f45c0
>>
>> This is because function maps__find_next_entry() now returns current
>> entry instead of next entry, leading to kernel map end address
>> getting mis-configured with its own start address instead of the
>> start address of the following map.
>>
>> Fix it by really taking the next entry, also make sure that entry
>> follows current one by making sure entries are sorted.
>>
>> Fixes: 659ad3492b91 ("perf maps: Switch from rbtree to lazily sorted array for addresses")
>> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
>> Reviewed-by: Arnaldo Carvalho de Melo <acme@...hat.com>
>> ---
>> v2: Make sure the entries are sorted, if not sort them.
> 
> Since you have changed what I reviewed I'll have to re-review :-) Will
> try to do it after some calls.

Ah yes sorry, should have removed your Reviewed-by.

Based on Ian's feedback "Using the next entry in this way won't work if 
the entries aren't sorted", I added the following block in front of the 
initial change:

+	while (!maps__maps_by_address_sorted(maps)) {
+		up_read(maps__lock(maps));
+		maps__sort_by_address(maps);
+		down_read(maps__lock(maps));
+	}

Christophe