Skip to content

Commit

Permalink
perf symbols: Fix symbol size calculation condition
Browse files Browse the repository at this point in the history
commit 3cf6a32 upstream.

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.

Fixes: 3b01a41 ("perf symbols: Improve kallsyms symbol end addr calculation")
Signed-off-by: Michael Petlan <mpetlan@redhat.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: http://lore.kernel.org/lkml/20220317135536.805-1-mpetlan@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  • Loading branch information
Michael Petlan authored and Greg Kroah-Hartman committed Mar 23, 2022
1 parent fc8033a commit 01064d8
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion tools/perf/util/symbol.c
Original file line number Diff line number Diff line change
Expand Up @@ -224,7 +224,7 @@ void symbols__fixup_end(struct rb_root *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);
}

Expand Down

0 comments on commit 01064d8

Please sign in to comment.