This makes sure that wchan contains a sensible symbol when a process is blocked. Specifically this calls the sleep() syscall, and expects the architecture to have called schedule() from a function that has "sleep" somewhere in its name. For example, on the architectures I tested (x86_64, arm64, arm, mips, and powerpc) this is "hrtimer_nanosleep":
$ tools/testing/selftests/proc/proc-pid-wchan ok: found 'sleep' in wchan 'hrtimer_nanosleep'
Cc: Peter Zijlstra peterz@infradead.org Cc: Mark Rutland mark.rutland@arm.com Cc: Shuah Khan shuah@kernel.org Cc: Alexey Dobriyan adobriyan@gmail.com Cc: linux-kselftest@vger.kernel.org Signed-off-by: Kees Cook keescook@chromium.org --- Hi Peter,
Can you add this to the wchan series, please? This should help wchan from regressing in the future, and allow us to notice if the depth accidentally changes, like Mark saw. --- tools/testing/selftests/proc/Makefile | 1 + tools/testing/selftests/proc/proc-pid-wchan.c | 69 +++++++++++++++++++ 2 files changed, 70 insertions(+) create mode 100644 tools/testing/selftests/proc/proc-pid-wchan.c
diff --git a/tools/testing/selftests/proc/Makefile b/tools/testing/selftests/proc/Makefile index 1054e40a499a..45cf35703ece 100644 --- a/tools/testing/selftests/proc/Makefile +++ b/tools/testing/selftests/proc/Makefile @@ -8,6 +8,7 @@ TEST_GEN_PROGS += fd-002-posix-eq TEST_GEN_PROGS += fd-003-kthread TEST_GEN_PROGS += proc-loadavg-001 TEST_GEN_PROGS += proc-pid-vm +TEST_GEN_PROGS += proc-pid-wchan TEST_GEN_PROGS += proc-self-map-files-001 TEST_GEN_PROGS += proc-self-map-files-002 TEST_GEN_PROGS += proc-self-syscall diff --git a/tools/testing/selftests/proc/proc-pid-wchan.c b/tools/testing/selftests/proc/proc-pid-wchan.c new file mode 100644 index 000000000000..7d7870c31cef --- /dev/null +++ b/tools/testing/selftests/proc/proc-pid-wchan.c @@ -0,0 +1,69 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Make sure that wchan returns a reasonable symbol when blocked. + */ +#include <sys/types.h> +#include <sys/stat.h> +#include <errno.h> +#include <fcntl.h> +#include <signal.h> +#include <stdio.h> +#include <string.h> +#include <unistd.h> +#include <sys/wait.h> + +#define perror_exit(str) do { perror(str); _exit(1); } while (0) + +int main(void) +{ + char buf[64]; + pid_t child; + int sync[2], fd; + + if (pipe(sync) < 0) + perror_exit("pipe"); + + child = fork(); + if (child < 0) + perror_exit("fork"); + if (child == 0) { + /* Child */ + if (close(sync[0]) < 0) + perror_exit("child close sync[0]"); + if (close(sync[1]) < 0) + perror_exit("child close sync[1]"); + sleep(10); + _exit(0); + } + /* Parent */ + if (close(sync[1]) < 0) + perror_exit("parent close sync[1]"); + if (read(sync[0], buf, 1) != 0) + perror_exit("parent read sync[0]"); + + snprintf(buf, sizeof(buf), "/proc/%d/wchan", child); + fd = open(buf, O_RDONLY); + if (fd < 0) { + if (errno == ENOENT) + return 4; + perror_exit(buf); + } + + memset(buf, 0, sizeof(buf)); + if (read(fd, buf, sizeof(buf) - 1) < 1) + perror_exit(buf); + if (strstr(buf, "sleep") == NULL) { + fprintf(stderr, "FAIL: did not find 'sleep' in wchan '%s'\n", buf); + return 1; + } + printf("ok: found 'sleep' in wchan '%s'\n", buf); + + if (kill(child, SIGKILL) < 0) + perror_exit("kill"); + if (waitpid(child, NULL, 0) != child) { + fprintf(stderr, "waitpid: got the wrong child!?\n"); + return 1; + } + + return 0; +}