From b3b9cf7dc1912c4df8c9d8dd740144dab8050bff Mon Sep 17 00:00:00 2001
From: Mattias Andrée <maandree@kth.se>
Date: Sat, 30 May 2020 23:18:42 +0200
Subject: Add support for tracing threads
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Signed-off-by: Mattias Andrée <maandree@kth.se>
---
 common.h  |  3 +++
 sctrace.c | 16 ++++++++++++----
 util.c    | 15 +++++++++++----
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/common.h b/common.h
index 996b9ef..d3df014 100644
--- a/common.h
+++ b/common.h
@@ -67,8 +67,10 @@ enum type {
 enum state {
 	Normal,
 	Syscall,
+	CloneChild,
 	ForkChild,
 	VforkChild,
+	CloneParent,
 	ForkParent,
 	VforkParent,
 	Exec
@@ -76,6 +78,7 @@ enum state {
 
 struct process {
 	pid_t pid;
+	pid_t thread_group_leader;
 	struct process *next;
 	struct process *prev;
 	enum state state;
diff --git a/sctrace.c b/sctrace.c
index f027a77..65216a5 100644
--- a/sctrace.c
+++ b/sctrace.c
@@ -8,7 +8,7 @@ char *argv0;
 static void
 usage(void)
 {
-	fprintf(stderr, "usage: %s [-o trace-output-file] [-f] (command | -0 command argv0) [argument] ...\n", argv0);
+	fprintf(stderr, "usage: %s [-o trace-output-file] [-ft] (command | -0 command argv0) [argument] ...\n", argv0);
 	exit(1);
 }
 
@@ -42,6 +42,7 @@ handle_syscall(struct process *proc)
 		break;
 
 	case Syscall:
+	case CloneParent:
 	case ForkParent:
 		/* Get system call result */
 		if (ptrace(PTRACE_GETREGS, proc->pid, NULL, &regs))
@@ -82,6 +83,7 @@ handle_syscall(struct process *proc)
 		proc->state = Syscall;
 		break;
 
+	case CloneChild:
 	case ForkChild:
 	case VforkChild:
 		tprintf(proc, "= 0\n");
@@ -104,7 +106,6 @@ main(int argc, char **argv)
 	struct process *proc, *proc2;
 	unsigned long int event;
 
-	/* TODO add option to trace threads (-t) */
 	/* TODO add option to trace signals (-s) */
 	ARGBEGIN {
 	case '0':
@@ -118,6 +119,9 @@ main(int argc, char **argv)
 	case 'f':
 		trace_options |= PTRACE_O_TRACEFORK;
 		trace_options |= PTRACE_O_TRACEVFORK;
+		/* fall through */
+	case 't':
+		trace_options |= PTRACE_O_TRACECLONE;
 		multiprocess = 1;
 		break;
 	default:
@@ -226,20 +230,24 @@ have_outfp:
 					tprintf(proc, "\nProcess stopped by vfork until child exits or exec(2)s\n");
 					/* fall thought */
 				case PTRACE_EVENT_FORK:
+				case PTRACE_EVENT_CLONE:
 					if (ptrace(PTRACE_GETEVENTMSG, proc->pid, NULL, &event))
 						eprintf("ptrace PTRACE_GETEVENTMSG %ju NULL <buffer>:", (uintmax_t)proc->pid);
 					proc2 = add_process((pid_t)event, trace_options);
+					if (trace_event == PTRACE_EVENT_CLONE)
+						proc2->thread_group_leader = proc->pid;
 					proc->ret = event;
 					if (trace_event == PTRACE_EVENT_VFORK) {
 						proc2->continue_on_exit = proc;
 						proc->vfork_waiting_on = proc2;
 						proc->state = VforkParent;
 					} else {
-						proc->state = ForkParent;
+						proc->state = trace_event == PTRACE_EVENT_CLONE ? CloneParent : ForkParent;
 						handle_syscall(proc);
 					}
 					tprintf(proc2, "\nTracing new process\n");
-					proc2->state = trace_event == PTRACE_EVENT_FORK ? ForkChild : VforkChild;
+					proc2->state = trace_event == PTRACE_EVENT_FORK ? ForkChild :
+					               trace_event == PTRACE_EVENT_VFORK ? VforkChild : CloneChild;
 					handle_syscall(proc2);
 					break;
 
diff --git a/util.c b/util.c
index 7ee9c51..521f73a 100644
--- a/util.c
+++ b/util.c
@@ -25,10 +25,17 @@ tprintf(struct process *proc, const char *fmt, ...)
 		fmt = &fmt[1];
 	}
 	if (multiproctrace) {
-		if (last_char == '\n')
-			fprintf(trace_fp, "[%ju] ", (uintmax_t)proc->pid);
-		else if (proc->pid != last_pid)
-			fprintf(trace_fp, "\n[%ju] ", (uintmax_t)proc->pid);
+		if (proc->thread_group_leader) {
+			if (last_char == '\n')
+				fprintf(trace_fp, "[%ju, %ju] ", (uintmax_t)proc->thread_group_leader, (uintmax_t)proc->pid);
+			else if (proc->pid != last_pid)
+				fprintf(trace_fp, "\n[%ju, %ju] ", (uintmax_t)proc->thread_group_leader, (uintmax_t)proc->pid);
+		} else {
+			if (last_char == '\n')
+				fprintf(trace_fp, "[%ju] ", (uintmax_t)proc->pid);
+			else if (proc->pid != last_pid)
+				fprintf(trace_fp, "\n[%ju] ", (uintmax_t)proc->pid);
+		}
 	}
 	va_start(ap, fmt);
 	vfprintf(trace_fp, fmt, ap);
-- 
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