perf tools: Fixup module symbol end address properly

I got a strange error on ARM to fail on processing FINISHED_ROUND
record.  It turned out that it was failing in symbol__alloc_hist()
because the symbol size is too big.

When a sample is captured on a specific BPF program, it failed.  I've
added a debug code and found the end address of the symbol is from
the next module which is placed far way.

  ffff800008795778-ffff80000879d6d8: bpf_prog_1bac53b8aac4bc58_netcg_sock    [bpf]
  ffff80000879d6d8-ffff80000ad656b4: bpf_prog_76867454b5944e15_netcg_getsockopt      [bpf]
  ffff80000ad656b4-ffffd69b7af74048: bpf_prog_1d50286d2eb1be85_hn_egress     [bpf]   <---------- here
  ffffd69b7af74048-ffffd69b7af74048: $x.5    [sha3_generic]
  ffffd69b7af74048-ffffd69b7af740b8: crypto_sha3_init        [sha3_generic]
  ffffd69b7af740b8-ffffd69b7af741e0: crypto_sha3_update      [sha3_generic]

The logic in symbols__fixup_end() just uses curr->start to update the
prev->end.  But in this case, it won't work as it's too different.

I think ARM has a different kernel memory layout for modules and BPF
than on x86.  Actually there's a logic to handle kernel and module
boundary.  Let's do the same for symbols between different modules.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Leo Yan <leo.yan@linux.dev>
Cc: Will Deacon <will@kernel.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20240212233322.1855161-1-namhyung@kernel.org

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 35975189999b1f0e4362c5fc62ed5dd047781975..9ebdb8e13c0b84604b64a475c6be680d9ff211c1 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -248,14 +248,31 @@ void symbols__fixup_end(struct rb_root_cached *symbols, bool is_kallsyms)
                 * segment is very big.  Therefore do not fill this gap and do
                 * not assign it to the kernel dso map (kallsyms).
                 *
+                * Also BPF code can be allocated separately from text segments
+                * and modules.  So the last entry in a module should not fill
+                * the gap too.
+                *
                 * In kallsyms, it determines module symbols using '[' character
                 * like in:
                 *   ffffffffc1937000 T hdmi_driver_init  [snd_hda_codec_hdmi]
                 */
                if (prev->end == prev->start) {
+                       const char *prev_mod;
+                       const char *curr_mod;
+
+                       if (!is_kallsyms) {
+                               prev->end = curr->start;
+                               continue;
+                       }
+
+                       prev_mod = strchr(prev->name, '[');
+                       curr_mod = strchr(curr->name, '[');
+
                        /* Last kernel/module symbol mapped to end of page */
-                       if (is_kallsyms && (!strchr(prev->name, '[') !=
-                                           !strchr(curr->name, '[')))
+                       if (!prev_mod != !curr_mod)
+                               prev->end = roundup(prev->end + 4096, 4096);
+                       /* Last symbol in the previous module */
+                       else if (prev_mod && strcmp(prev_mod, curr_mod))
                                prev->end = roundup(prev->end + 4096, 4096);
                        else
                                prev->end = curr->start;