From: Michael Petlan <mpetlan@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-perf-users@vger.kernel.org, acme@kernel.org,
jolsa@kernel.org, atrajeev@linux.vnet.ibm.com,
maddy@linux.ibm.com, kjain@linux.ibm.com
Subject: [PATCH] perf symbols: Fix symbol size calculation condition
Date: Thu, 17 Mar 2022 14:55:36 +0100 [thread overview]
Message-ID: <20220317135536.805-1-mpetlan@redhat.com> (raw)
Before this patch, the symbol end address fixup to be called, needed two
conditions being met:
if (prev->end == prev->start && prev->end != curr->start)
Where
"prev->end == prev->start" means that prev is zero-long
(and thus needs a fixup)
and
"prev->end != curr->start" means that fixup hasn't been applied yet
However, this logic is incorrect in the following situation:
*curr = {rb_node = {__rb_parent_color = 278218928,
rb_right = 0x0, rb_left = 0x0},
start = 0xc000000000062354,
end = 0xc000000000062354, namelen = 40, type = 2 '\002',
binding = 0 '\000', idle = 0 '\000', ignore = 0 '\000',
inlined = 0 '\000', arch_sym = 0 '\000', annotate2 = false,
name = 0x1159739e "kprobe_optinsn_page\t[__builtin__kprobes]"}
*prev = {rb_node = {__rb_parent_color = 278219041,
rb_right = 0x109548b0, rb_left = 0x109547c0},
start = 0xc000000000062354,
end = 0xc000000000062354, namelen = 12, type = 2 '\002',
binding = 1 '\001', idle = 0 '\000', ignore = 0 '\000',
inlined = 0 '\000', arch_sym = 0 '\000', annotate2 = false,
name = 0x1095486e "optinsn_slot"}
In this case, prev->start == prev->end == curr->start == curr->end,
thus the condition above thinks that "we need a fixup due to zero
length of prev symbol, but it has been probably done, since the
prev->end == curr->start", which is wrong.
After the patch, the execution path proceeds to arch__symbols__fixup_end
function which fixes up the size of prev symbol by adding page_size to
its end offset.
Signed-off-by: Michael Petlan <mpetlan@redhat.com>
---
tools/perf/util/symbol.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index fb075aa8f8f2..dea0fc495185 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -231,7 +231,7 @@ void symbols__fixup_end(struct rb_root_cached *symbols)
prev = curr;
curr = rb_entry(nd, struct symbol, rb_node);
- if (prev->end == prev->start && prev->end != curr->start)
+ if (prev->end == prev->start || prev->end != curr->start)
arch__symbols__fixup_end(prev, curr);
}
--
2.18.4
next reply other threads:[~2022-03-17 13:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-17 13:55 Michael Petlan [this message]
2022-03-17 15:37 ` [PATCH] perf symbols: Fix symbol size calculation condition Arnaldo Carvalho de Melo
2022-03-17 17:49 ` Michael Petlan
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