only attach when necessary

Don't attach before we are sure there are patches.

Signed-off-by: Pavel Boldin <[email protected]>

Author: paboldin

src/kpatch_process.c

@@ -622,6 +622,10 @@ kpatch_process_mem_open(kpatch_process_t *proc, int mode)
 {
 	char path[sizeof("/proc/0123456789/mem")];
 
+	if (proc->memfd >= 0) {
+		close(proc->memfd);
+	}
+
 	snprintf(path, sizeof(path), "/proc/%d/mem", proc->pid);
 	proc->memfd = open(path, mode == MEM_WRITE ? O_RDWR : O_RDONLY);
 	if (proc->memfd < 0) {
@@ -883,6 +887,12 @@ kpatch_process_load_libraries(kpatch_process_t *proc)
 	if (!proc->is_just_started)
 		return 0;
 
+	ret = kpatch_process_attach(proc);
+	if (ret < 0) {
+		kperr("unable to attach to just started process\n");
+		return -1;
+	}
+
 	if (proc->send_fd != -1) {
 		ret = kpatch_process_kickstart_execve_wrapper(proc);
 		if (ret < 0) {

src/kpatch_user.c

@@ -1010,7 +1010,7 @@ static int process_patch(int pid, void *_data)
 
 	kpatch_process_print_short(proc);
 
-	ret = kpatch_process_attach(proc);
+	ret = kpatch_process_mem_open(proc, MEM_READ);
 	if (ret < 0)
 		goto out_free;
 
@@ -1030,11 +1030,10 @@ static int process_patch(int pid, void *_data)
 		goto out_free;
 
 	/*
-	 * For each object file that we want to patch (either binary
-	 * itself or shared library) we need its ELF structure
-	 * to perform relocations. Because we know uniq BuildID of
-	 * the object the section addresses stored in the patch
-	 * are valid for the original object.
+	 * For each object file that we want to patch (either binary itself or
+	 * shared library) we need its ELF structure to perform relocations.
+	 * Because we know uniq BuildID of the object the section addresses
+	 * stored in the patch are valid for the original object.
 	 */
 	ret = kpatch_process_map_object_files(proc);
 	if (ret < 0)
@@ -1047,6 +1046,11 @@ static int process_patch(int pid, void *_data)
 	if (ret <= 0)
 		goto out_free;
 
+	/* Finally, attach to process */
+	ret = kpatch_process_attach(proc);
+	if (ret < 0)
+		goto out_free;
+
 	ret = kpatch_coroutines_find(proc);
 	if (ret < 0)
 		goto out_free;