From: Vincent Donnefort <vincent.donnefort@xxxxxxx>
kptr_restrict might prevent trace-cmd from accessing /proc/kallsyms,
leading to a trace without the kernel function names resolved.
Signed-off-by: Vincent Donnefort <vincent.donnefort@xxxxxxx>
diff --git a/lib/trace-cmd/trace-output.c b/lib/trace-cmd/trace-output.c
index 41932ee..be4d3f5 100644
--- a/lib/trace-cmd/trace-output.c
+++ b/lib/trace-cmd/trace-output.c
@@ -674,6 +674,46 @@ static int read_event_files(struct tracecmd_output *handle,
return ret;
}
+#define KPTR_UNINITIALIZED 'X'
+
+static void set_proc_kptr_restrict(int reset)
+{
+ char *path = "/proc/sys/kernel/kptr_restrict";
+ static char saved = KPTR_UNINITIALIZED;
+ int fd, ret = -1;
+ struct stat st;
+ char buf;
+
+ if ((reset && saved == KPTR_UNINITIALIZED) ||
+ (stat(path, &st) < 0))
+ return;
+
+ fd = open(path, O_RDONLY);
+ if (fd < 0)
+ goto err;
+
+ if (reset) {
+ buf = saved;
+ } else {
+ if (read(fd, &buf, 1) < 0)
+ goto err;
+ saved = buf;
+ buf = '0';
+ }
+ close(fd);
+
+ fd = open(path, O_WRONLY);
+ if (fd < 0)
+ goto err;
+ if (write(fd, &buf, 1) > 0)
+ ret = 0;
+err:
+ if (fd > 0)
+ close(fd);
+ if (ret)
+ warning("can't set kptr_restrict");
+}
+
static int read_proc_kallsyms(struct tracecmd_output *handle,
const char *kallsyms)
{
@@ -698,12 +738,16 @@ static int read_proc_kallsyms(struct tracecmd_output *handle,
endian4 = convert_endian_4(handle, size);
if (do_write_check(handle, &endian4, 4))
return -1;
+
+ set_proc_kptr_restrict(0);
check_size = copy_file(handle, path);
if (size != check_size) {
errno = EINVAL;
warning("error in size of file '%s'", path);
+ set_proc_kptr_restrict(1);
return -1;
}
+ set_proc_kptr_restrict(1);
return 0;
}
--
2.7.4
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