perf symbols: Fix symbol size calculation condition

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: d7291137178e8707 ("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>

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index b2ed3140a1faaa1acda190707e236a6a873b156c..dfde9eada224afd31d81842054b108ea576873f2 100644 (file)
--- 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);
        }