[PATCH] selftests/proc/proc-empty-vm.c: Test for unmapped process

[Siddharth Menon <simeddon@gmail.com>]

Check if VMsize is 0 to determine whether the process has been unmapped.
The child process cannot signal the parent that it has unmapped itself,
as it no longer exists. This includes unmapping the text segment,
preventing the child from proceeding to the next instruction.

Signed-off-by: Siddharth Menon <simeddon@gmail.com>
---
 tools/testing/selftests/proc/proc-empty-vm.c | 50 ++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/tools/testing/selftests/proc/proc-empty-vm.c b/tools/testing/selftests/proc/proc-empty-vm.c
index b3f898aab4ab..8ee000b0ddd7 100644
--- a/tools/testing/selftests/proc/proc-empty-vm.c
+++ b/tools/testing/selftests/proc/proc-empty-vm.c
@@ -213,6 +213,53 @@ static void vsyscall(void)
 }
 #endif
 
+static int test_proc_pid_mem(pid_t pid)
+{
+	char buf[4096];
+	char *line;
+	int vm_size = -1;
+
+	snprintf(buf, sizeof(buf), "/proc/%d/status", pid);
+	int fd = open(buf, O_RDONLY);
+
+	if (fd == -1) {
+		if (errno == ENOENT) {
+			// Process does not exist
+			return EXIT_SUCCESS;
+		}
+	perror("open /proc/[pid]/status");
+	return EXIT_FAILURE;
+	}
+
+	ssize_t rv = read(fd, buf, sizeof(buf) - 1);
+
+	if (rv == -1) {
+		perror("read");
+		close(fd);
+		return EXIT_FAILURE;
+	}
+	buf[rv] = '\0';
+
+	line = strtok(buf, "\n");
+	while (line != NULL) {
+		// Check for VmSize
+		if (strncmp(line, "VmSize:", 7) == 0) {
+			sscanf(line, "VmSize: %d", &vm_size);
+			break;
+		}
+		line = strtok(NULL, "\n");
+	}
+
+	close(fd);
+
+	// Check if VmSize is 0
+	if (vm_size == 0) {
+		return EXIT_SUCCESS;
+	}
+
+	return EXIT_FAILURE;
+}
+
 static int test_proc_pid_maps(pid_t pid)
 {
 	char buf[4096];
@@ -508,6 +555,9 @@ int main(void)
 		 */
 		sleep(1);
 
+		if (rv == EXIT_SUCCESS) {
+			rv = test_proc_pid_mem(pid);
+		}
 		if (rv == EXIT_SUCCESS) {
 			rv = test_proc_pid_maps(pid);
 		}
-- 
2.39.5