[PATCH v7 6/6] selftests: prctl: Add test for long thread names
From: André Almeida <andrealmeid@igalia.com>
Date: 2026-09-12 01:24:58
Also in:
linux-mm, linux-trace-kernel, lkml
Subsystem:
kernel selftest framework, the rest · Maintainers:
Shuah Khan, Shuah Khan, Linus Torvalds
Add tests for the new interface to set and get long thread names. The kernel should accept the LONG_NAME and returning it accordingly. For the old PR_GET_NAME interface, the kernel should truncate the name up to 16 chars. /proc/<task>/comm should return the same string ad PR_GET_NAME. While here, fix the check_is_name_correct() logic. It currently returns 1 for success, or a negative number for error. EXPECT_TRUE() evaluates any non-zero value as true, so the error will be evaluated as a success. Make the logic more robust and straightforward by returning the results of strcmp() and expecting zero as success. Signed-off-by: André Almeida <andrealmeid@igalia.com> --- Changes in v5: - fix check_is_name_correct() return logic --- tools/testing/selftests/prctl/set-process-name.c | 57 +++++++++++++++++++++--- 1 file changed, 50 insertions(+), 7 deletions(-)
diff --git a/tools/testing/selftests/prctl/set-process-name.c b/tools/testing/selftests/prctl/set-process-name.c
index 3f7b146d36df..f05053aaba85 100644
--- a/tools/testing/selftests/prctl/set-process-name.c
+++ b/tools/testing/selftests/prctl/set-process-name.c@@ -9,9 +9,17 @@ #include "kselftest_harness.h" +#ifndef PR_SET_EXT_NAME +# define PR_SET_EXT_NAME 17 +# define PR_GET_EXT_NAME 18 +#endif + #define CHANGE_NAME "changename" +#define LONG_NAME "change_to_very_long_extended_name" +#define LONG_NAME_CAP "change_to_very_" #define EMPTY_NAME "" #define TASK_COMM_LEN 16 +#define TASK_COMM_EXT_LEN 64 #define MAX_PATH_LEN 50 int set_name(char *name)
@@ -25,6 +33,20 @@ int set_name(char *name) return res; } +int set_ext_name(char *name) +{ + int res; + + res = prctl(PR_SET_EXT_NAME, name, NULL, NULL, NULL); + + if (res < 0) + return -errno; + return res; +} + +/* + * Return 0 if strings match + */ int check_is_name_correct(char *check_name) { char name[TASK_COMM_LEN];
@@ -35,7 +57,23 @@ int check_is_name_correct(char *check_name) if (res < 0) return -errno; - return !strcmp(name, check_name); + return strcmp(name, check_name); +} + +/* + * Return 0 if strings match + */ +int check_is_ext_name_correct(char *check_name) +{ + char name[TASK_COMM_EXT_LEN]; + int res; + + res = prctl(PR_GET_EXT_NAME, name, NULL, NULL, NULL); + + if (res < 0) + return -errno; + + return strcmp(name, check_name); } int check_null_pointer(char *check_name)
@@ -56,8 +94,8 @@ int check_name(void) pid = getpid(); FILE *fptr = NULL; char path[MAX_PATH_LEN] = {}; - char name[TASK_COMM_LEN] = {}; - char output[TASK_COMM_LEN] = {}; + char name[TASK_COMM_EXT_LEN] = {}; + char output[TASK_COMM_EXT_LEN] = {}; int j; j = snprintf(path, MAX_PATH_LEN, "/proc/self/task/%d/comm", pid);
@@ -74,21 +112,26 @@ int check_name(void) if (res < 0) return -errno; - return !strcmp(output, name); + return strcmp(output, name); } TEST(rename_process) { EXPECT_GE(set_name(CHANGE_NAME), 0); - EXPECT_TRUE(check_is_name_correct(CHANGE_NAME)); + EXPECT_FALSE(check_is_name_correct(CHANGE_NAME)); + + EXPECT_GE(set_ext_name(LONG_NAME), 0); + EXPECT_FALSE(check_is_ext_name_correct(LONG_NAME)); + EXPECT_FALSE(check_is_name_correct(LONG_NAME_CAP)); + EXPECT_FALSE(check_name()); EXPECT_GE(set_name(EMPTY_NAME), 0); - EXPECT_TRUE(check_is_name_correct(EMPTY_NAME)); + EXPECT_FALSE(check_is_name_correct(EMPTY_NAME)); EXPECT_GE(set_name(CHANGE_NAME), 0); EXPECT_LT(check_null_pointer(CHANGE_NAME), 0); - EXPECT_TRUE(check_name()); + EXPECT_FALSE(check_name()); } TEST_HARNESS_MAIN
--
2.55.0