uftrace: Apply dynamic (un)patching at runtime

Add support for the '--patch' and '--unpatch' options in the client. When used, the agent patches or unpatches symbols on the fly. Co-authored-by: Gabriel-Andrew Pollo-Guilbert <[email protected]> Signed-off-by: Clément Guidi <[email protected]>
namhyung · Jul 6, 2023 · fe06e08 · fe06e08
1 parent 06d2cdf
commit fe06e08
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Showing 3 changed files with 15 additions and 2 deletions.
diff --git a/cmds/live.c b/cmds/live.c
@@ -361,7 +361,7 @@ static int forward_options(struct uftrace_opts *opts)
 	}
 
 	/* provide a pattern type for options that need it */
-	if (opts->filter || opts->caller || opts->trigger) {
+	if (opts->filter || opts->caller || opts->trigger || opts->patch) {
 		status = forward_option(sfd, capabilities, UFTRACE_AGENT_OPT_PATTERN,
 					&opts->patt_type, sizeof(opts->patt_type));
 		if (status < 0)
@@ -389,6 +389,13 @@ static int forward_options(struct uftrace_opts *opts)
 			goto close;
 	}
 
+	if (opts->patch) {
+		status = forward_option(sfd, capabilities, UFTRACE_AGENT_OPT_PATCH, opts->patch,
+					strlen(opts->patch) + 1);
+		if (status < 0)
+			goto close;
+	}
+
 close:
 	status_close = agent_message_send(sfd, UFTRACE_MSG_AGENT_CLOSE, NULL, 0);
 	if (status_close == 0) {

diff --git a/libmcount/mcount.c b/libmcount/mcount.c
@@ -107,7 +107,7 @@ static volatile bool agent_run = false;
 #define MCOUNT_AGENT_CAPABILITIES                                                                  \
 	(UFTRACE_AGENT_OPT_TRACE | UFTRACE_AGENT_OPT_DEPTH | UFTRACE_AGENT_OPT_THRESHOLD |         \
 	 UFTRACE_AGENT_OPT_PATTERN | UFTRACE_AGENT_OPT_FILTER | UFTRACE_AGENT_OPT_CALLER |         \
-	 UFTRACE_AGENT_OPT_TRIGGER)
+	 UFTRACE_AGENT_OPT_TRIGGER | UFTRACE_AGENT_OPT_PATCH)
 
 __weak void dynamic_return(void)
 {
@@ -1988,6 +1988,11 @@ static int agent_apply_option(int opt, void *value, size_t size,
 		agent_setup_trigger(value, triggers);
 		break;
 
+	case UFTRACE_AGENT_OPT_PATCH:
+		pr_dbg3("apply patch '%s' (size=%d)\n", value, size);
+		mcount_dynamic_update(&mcount_sym_info, value, mcount_filter_setting.ptype);
+		break;
+
 	default:
 		ret = -1;
 	}

diff --git a/uftrace.h b/uftrace.h
@@ -466,6 +466,7 @@ enum uftrace_agent_opt {
 	UFTRACE_AGENT_OPT_FILTER = (1U << 4), /* tracing filters */
 	UFTRACE_AGENT_OPT_CALLER = (1U << 5), /* tracing caller filters */
 	UFTRACE_AGENT_OPT_TRIGGER = (1U << 6), /* tracing trigger actions */
+	UFTRACE_AGENT_OPT_PATCH = (1U << 7), /* patch string */
 };
 
 extern struct uftrace_session *first_session;