[PATCH v3 8/8] perf syscalltbl: Mask off ABI type for MIPS system calls

[Ian Rogers <irogers@google.com>]

Arnd Bergmann described that MIPS system calls don't necessarily start
from 0 as an ABI prefix is applied:
https://lore.kernel.org/lkml/8ed7dfb2-1e4d-4aa4-a04b-0397a89365d1@app.fastmail.com/
When decoding the "id" (aka system call number) for MIPS ignore values
greater-than 1000.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/syscalltbl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/syscalltbl.c b/tools/perf/util/syscalltbl.c
index db0d2b81aed1..ace66e69c1bc 100644
--- a/tools/perf/util/syscalltbl.c
+++ b/tools/perf/util/syscalltbl.c
@@ -46,6 +46,14 @@ const char *syscalltbl__name(int e_machine, int id)
 {
 	const struct syscalltbl *table = find_table(e_machine);
 
+	if (e_machine == EM_MIPS && id > 1000) {
+		/*
+		 * MIPS may encode the N32/64/O32 type in the high part of
+		 * syscall number. Mask this off if present. See the values of
+		 * __NR_N32_Linux, __NR_64_Linux, __NR_O32_Linux and __NR_Linux.
+		 */
+		id = id % 1000;
+	}
 	if (table && id >= 0 && id < table->num_to_name_len)
 		return table->num_to_name[id];
 	return NULL;
-- 
2.48.1.601.g30ceb7b040-goog