[PATCH v1 2/5] perf trace: Return error if a system call doesn't exist

[Leo Yan <leo.yan@linaro.org>]

When a system call is not detected, the reason is either because the
system call ID is out of scope or failure to find the corresponding path
in the sysfs, trace__read_syscall_info() returns zero.  Finally, without
returning an error value it introduces confusion for the caller.

This patch lets the function trace__read_syscall_info() to return
-EEXIST when a system call doesn't exist.

Fixes: b8b1033fcaa0 ("perf trace: Mark syscall ids that are not allocated to avoid unnecessary error messages")
Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 tools/perf/builtin-trace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 22008a31684b..bd5513b15cde 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1796,11 +1796,11 @@ static int trace__read_syscall_info(struct trace *trace, int id)
 #endif
 	sc = trace->syscalls.table + id;
 	if (sc->nonexistent)
-		return 0;
+		return -EEXIST;
 
 	if (name == NULL) {
 		sc->nonexistent = true;
-		return 0;
+		return -EEXIST;
 	}
 
 	sc->name = name;
-- 
2.34.1