Commit bacefe0c authored by Namhyung Kim's avatar Namhyung Kim
Browse files

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: default avatarNamhyung Kim <namhyung@kernel.org>
Reviewed-by: default avatarLeo 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
parent 6f146b24

tools/perf/util/symbol.c

+19 −2
Original line number Diff line number Diff line
@@ -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;