perf session: Fix handling when buffer exceeds 2 GiB

If a user specifies an AUX buffer larger than 2 GiB, the returned size
may exceed 0x80000000. Since the err variable is defined as a signed
32-bit integer, such a value overflows and becomes negative.

As a result, the perf record command reports an error:

  0x146e8 [0x30]: failed to process type: 71 [Unknown error 183711232]

Change the type of the err variable to a signed 64-bit integer to
accommodate large buffer sizes correctly.

Fixes: d5652d8 ("perf session: Add ability to skip 4GiB or more")
Reported-by: Tamas Zsoldos <tamas.zsoldos@arm.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20250808-perf_fix_big_buffer_size-v1-1-45f45444a9a4@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: Leo-Yan

tools/perf/util/session.c

@@ -1402,7 +1402,7 @@ static s64 perf_session__process_user_event(struct perf_session *session,
 	const struct perf_tool *tool = session->tool;
 	struct perf_sample sample;
 	int fd = perf_data__fd(session->data);
-	int err;
+	s64 err;
 
 	perf_sample__init(&sample, /*all=*/true);
 	if ((event->header.type != PERF_RECORD_COMPRESSED &&