kcsan: Simplify constant string handling

Simplify checking prefixes and length calculation of constant strings.
For the former, the kernel provides str_has_prefix(), and the latter we
should just use strlen("..") because GCC and Clang have optimizations
that optimize these into constants.

No functional change intended.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c
index 3a9566a..116bdd8 100644 (file)
--- a/kernel/kcsan/debugfs.c
+++ b/kernel/kcsan/debugfs.c
@@ -300,16 +300,16 @@ debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *o
                WRITE_ONCE(kcsan_enabled, true);
        } else if (!strcmp(arg, "off")) {
                WRITE_ONCE(kcsan_enabled, false);
-       } else if (!strncmp(arg, "microbench=", sizeof("microbench=") - 1)) {
+       } else if (str_has_prefix(arg, "microbench=")) {
                unsigned long iters;
 
-               if (kstrtoul(&arg[sizeof("microbench=") - 1], 0, &iters))
+               if (kstrtoul(&arg[strlen("microbench=")], 0, &iters))
                        return -EINVAL;
                microbenchmark(iters);
-       } else if (!strncmp(arg, "test=", sizeof("test=") - 1)) {
+       } else if (str_has_prefix(arg, "test=")) {
                unsigned long iters;
 
-               if (kstrtoul(&arg[sizeof("test=") - 1], 0, &iters))
+               if (kstrtoul(&arg[strlen("test=")], 0, &iters))
                        return -EINVAL;
                test_thread(iters);
        } else if (!strcmp(arg, "whitelist")) {

diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
index 3e83a69..bf1d594 100644 (file)
--- a/kernel/kcsan/report.c
+++ b/kernel/kcsan/report.c
@@ -279,8 +279,8 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries
 
                cur = strnstr(buf, "kcsan_", len);
                if (cur) {
-                       cur += sizeof("kcsan_") - 1;
-                       if (strncmp(cur, "test", sizeof("test") - 1))
+                       cur += strlen("kcsan_");
+                       if (!str_has_prefix(cur, "test"))
                                continue; /* KCSAN runtime function. */
                        /* KCSAN related test. */
                }