[LTP] [PATCH] thp01: Find largest arguments size

[Richard Palethorpe]

Because of kernel commit da029c11e6b1 the arguments size for exec has been
reduced considerably. This causes exec to fail with E2BIG, so we call it
repeatedly with a decreasing number of arguments until it is successful.

As far as I know, there is no other reliable and easy way to determine the
maximum argument length.

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
 testcases/kernel/mem/thp/thp01.c | 83 ++++++++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 33 deletions(-)

diff --git a/testcases/kernel/mem/thp/thp01.c b/testcases/kernel/mem/thp/thp01.c
index 101a9b5c8..b90b9b637 100644
--- a/testcases/kernel/mem/thp/thp01.c
+++ b/testcases/kernel/mem/thp/thp01.c
@@ -30,6 +30,7 @@
  * ....
  */
 
+#include <errno.h>
 #include <sys/types.h>
 #include <sys/resource.h>
 #include <sys/wait.h>
@@ -38,56 +39,72 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include "mem.h"
+#include "tst_minmax.h"
+#include "tst_safe_sysv_ipc.h"
 
-#define ARRAY_SZ	256
+#define ARGS_SZ	256
 
-static int ps;
-static long length;
-static char *array[ARRAY_SZ];
+static int shm_id;
+static char *args[ARGS_SZ];
 static char *arg;
-static struct rlimit rl = {
-	.rlim_cur = RLIM_INFINITY,
-	.rlim_max = RLIM_INFINITY,
-};
+static long *arg_count;
 
 static void thp_test(void)
 {
-	int i;
-	pid_t pid;
-
-	switch (pid = SAFE_FORK()) {
-	case 0:
-		memset(arg, 'c', length - 1);
-		arg[length - 1] = '\0';
-		array[0] = "true";
-		for (i = 1; i < ARRAY_SZ - 1; i++)
-			array[i] = arg;
-		array[ARRAY_SZ - 1] = NULL;
-		if (setrlimit(RLIMIT_STACK, &rl) == -1) {
-			perror("setrlimit");
-			exit(1);
-		}
-		if (execvp("true", array) == -1) {
-			perror("execvp");
-			exit(1);
-		}
-	default:
-		tst_reap_children();
+	pid_t pid = SAFE_FORK();
+
+	if (!arg_count)
+		tst_brk(TBROK, "No shared memory");
+
+	if (!pid) {
+		args[*arg_count] = NULL;
+
+		do {
+			TEST(execvp("true", args));
+			args[--(*arg_count)] = NULL;
+		} while (*arg_count > 0 && TEST_ERRNO == E2BIG);
+
+		tst_brk(TBROK | TTERRNO, "execvp(\"true\", ...)");
 	}
 
+	tst_reap_children();
 	tst_res(TPASS, "system didn't crash, pass.");
 }
 
 static void setup(void)
 {
-	ps = sysconf(_SC_PAGESIZE);
-	length = 32 * ps;
-	arg = SAFE_MALLOC(length);
+	struct rlimit rl = {
+		.rlim_cur = RLIM_INFINITY,
+		.rlim_max = RLIM_INFINITY,
+	};
+	int i;
+	long arg_len;
+
+	shm_id = SAFE_SHMGET(IPC_PRIVATE, sizeof(long),
+				 IPC_CREAT | IPC_EXCL);
+	arg_count = SAFE_SHMAT(shm_id, NULL, 0);
+
+	arg_len = 32 * sysconf(_SC_PAGESIZE);
+	arg = SAFE_MALLOC(arg_len);
+	memset(arg, 'c', arg_len - 1);
+	arg[arg_len - 1] = '\0';
+
+	args[0] = "true";
+	*arg_count = ARGS_SZ - 1;
+	for (i = 1; i < *arg_count; i++)
+		args[i] = arg;
+
+	SAFE_SETRLIMIT(RLIMIT_STACK, &rl);
 }
 
 static void cleanup(void)
 {
-	free(arg);
+	if (arg)
+		free(arg);
+	if (arg_count)
+		SAFE_SHMDT(arg_count);
+	if (shm_id)
+		SAFE_SHMCTL(shm_id, IPC_RMID, NULL);
 }
 
 static struct tst_test test = {
-- 
2.14.1