[PATCH] trace-cmd:show: be picky on user argument 'cpu'

[Federico Vaga]

Before this patch the following command worked without errors:

    trace-cmd show -c b

This command opens the CPU0 files. From `strace(1)`:

    openat(AT_FDCWD, "/sys/kernel/tracing/per_cpu/cpu0/trace", O_RDONLY) = 3

Signed-off-by: Federico Vaga <federico.v...@vaga.pv.it>
---
 trace-show.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/trace-show.c b/trace-show.c
index f13db31..7d04012 100644
--- a/trace-show.c
+++ b/trace-show.c
@@ -149,7 +149,14 @@ void trace_show(int argc, char **argv)
                file = "snapshot";
 
        if (cpu) {
-               snprintf(cpu_path, 128, "per_cpu/cpu%d/%s", atoi(cpu), file);
+               char *endptr;
+               long val;
+
+               errno = 0;
+               val = strtol(cpu, &endptr, 0);
+               if (errno || cpu == endptr)
+                       die("Invalid CPU index '%s'", cpu);
+               snprintf(cpu_path, 128, "per_cpu/cpu%ld/%s", val, file);
                file = cpu_path;
        }
 
-- 
2.14.3