libdrgn: examples: add --pre-exec and --post-exec options to load_deb…

…ug_info

These can be used for benchmarking.

Signed-off-by: Omar Sandoval <[email protected]>

libdrgn/examples/load_debug_info.c

@@ -3,13 +3,50 @@
 
 #include <errno.h>
 #include <getopt.h>
+#include <spawn.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdnoreturn.h>
+#include <sys/wait.h>
 #include <time.h>
 #include <unistd.h>
 
 #include "drgn.h"
+#include "util.h"
+
+extern char **environ;
+
+static struct drgn_error *run_command(const char *which, const char *command)
+{
+	if (!command)
+		return NULL;
+
+	char pid_arg[max_decimal_length(long)];
+	sprintf(pid_arg, "%ld", (long)getpid());
+	const char * const argv[] = {"sh", "-c", command, "sh", pid_arg, NULL};
+
+	pid_t pid;
+	int errnum =
+		posix_spawnp(&pid, "sh", NULL, NULL, (char **)argv, environ);
+	if (errnum)
+		return drgn_error_create_os("posix_spawnp", errnum, "sh");
+
+	int wstatus;
+	if (waitpid(pid, &wstatus, 0) < 0)
+		return drgn_error_create_os("waitpid", errno, NULL);
+
+	if (!WIFEXITED(wstatus)) {
+		return drgn_error_format(DRGN_ERROR_OTHER,
+					 "%s-exec command exited abnormally: %d",
+					 which, wstatus);
+	}
+	if (WEXITSTATUS(wstatus) != 0) {
+		return drgn_error_format(DRGN_ERROR_OTHER,
+					 "%s-exec command exited with status %d",
+					 which, WEXITSTATUS(wstatus));
+	}
+	return NULL;
+}
 
 static inline struct timespec timespec_sub(struct timespec a, struct timespec b)
 {
@@ -29,7 +66,7 @@ static inline struct timespec timespec_sub(struct timespec a, struct timespec b)
 noreturn static void usage(bool error)
 {
 	fprintf(error ? stderr : stdout,
-		"usage: load_debug_info [-k|-c CORE|-p PID] [PATH...]\n"
+		"usage: load_debug_info [OPTION...] [-k|-c CORE|-p PID] [PATH...]\n"
 		"\n"
 		"Example libdrgn program that loads default debug information\n"
 		"\n"
@@ -38,6 +75,10 @@ noreturn static void usage(bool error)
 		"  -c PATH, --core PATH    debug the given core dump\n"
 		"  -p PID, --pid PID       debug the running process with the given PID\n"
 		"  -T, --time              print how long loading debug info took in seconds\n"
+		"  --pre-exec CMD          before loading debug info, execute shell command with\n"
+		"                          PID of this process as argument\n"
+		"  --post-exec CMD         after loading debug info, execute shell command with\n"
+		"                          PID of this process as argument\n"
 		"  -h, --help              display this help message and exit\n");
 	exit(error ? EXIT_FAILURE : EXIT_SUCCESS);
 }
@@ -49,13 +90,17 @@ int main(int argc, char **argv)
 		{"core", required_argument, NULL, 'c'},
 		{"pid", required_argument, NULL, 'p'},
 		{"time", no_argument, NULL, 'T'},
+		{"pre-exec", required_argument, NULL, 'x'},
+		{"post-exec", required_argument, NULL, 'X'},
 		{"help", no_argument, NULL, 'h'},
 		{},
 	};
 	bool kernel = false;
 	const char *core = NULL;
 	const char *pid = NULL;
 	bool print_time = false;
+	const char *pre_exec = NULL;
+	const char *post_exec = NULL;
 	for (;;) {
 		int c = getopt_long(argc, argv, "kc:p:Th", long_options, NULL);
 		if (c == -1)
@@ -73,6 +118,12 @@ int main(int argc, char **argv)
 		case 'T':
 			print_time = true;
 			break;
+		case 'x':
+			pre_exec = optarg;
+			break;
+		case 'X':
+			post_exec = optarg;
+			break;
 		case 'h':
 			usage(false);
 		default:
@@ -98,6 +149,10 @@ int main(int argc, char **argv)
 	if (err)
 		goto out;
 
+	err = run_command("pre", pre_exec);
+	if (err)
+		goto out;
+
 	struct timespec start, end;
 	if (print_time && clock_gettime(CLOCK_MONOTONIC, &start))
 		abort();
@@ -110,18 +165,20 @@ int main(int argc, char **argv)
 		struct timespec diff = timespec_sub(end, start);
 		printf("%lld.%09ld\n", (long long)diff.tv_sec, diff.tv_nsec);
 	}
+	if (err && err->code == DRGN_ERROR_MISSING_DEBUG_INFO) {
+		drgn_error_fwrite(stderr, err);
+		drgn_error_destroy(err);
+	}
+
+	err = run_command("post", post_exec);
+	if (err)
+		goto out;
 
 out:;
-	int status;
+	int status = err ? EXIT_FAILURE : EXIT_SUCCESS;
 	if (err) {
-		if (err->code == DRGN_ERROR_MISSING_DEBUG_INFO)
-			status = EXIT_SUCCESS;
-		else
-			status = EXIT_FAILURE;
 		drgn_error_fwrite(stderr, err);
 		drgn_error_destroy(err);
-	} else {
-		status = EXIT_SUCCESS;
 	}
 	drgn_program_destroy(prog);
 	return status;