Author: jhb
Date: Wed Mar 9 18:45:41 2016
New Revision: 296571
URL: https://svnweb.freebsd.org/changeset/base/296571
Log:
Use ptrace(2) LWP events to track threads reliably in truss.
- truss can now log the system call invoked by a thread during a
voluntary process exit. No return value is logged, but the value passed
to exit() is included in the trace output. Arguments passed to thread
exit system calls such as thr_exit() are not logged as voluntary thread
exits cannot be distinguished from involuntary thread exits during a
system call.
- New events are now reported for thread births and exits similar to the
recently added events for new child processes when following forks.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D5561
Modified:
head/usr.bin/truss/setup.c
head/usr.bin/truss/syscalls.c
head/usr.bin/truss/truss.h
Modified: head/usr.bin/truss/setup.c
==============================================================================
--- head/usr.bin/truss/setup.c Wed Mar 9 18:38:30 2016 (r296570)
+++ head/usr.bin/truss/setup.c Wed Mar 9 18:45:41 2016 (r296571)
@@ -61,7 +61,9 @@ SET_DECLARE(procabi, struct procabi);
static sig_atomic_t detaching;
-static void new_proc(struct trussinfo *, pid_t);
+static void enter_syscall(struct trussinfo *, struct threadinfo *,
+ struct ptrace_lwpinfo *);
+static void new_proc(struct trussinfo *, pid_t, lwpid_t);
/*
* setup_and_wait() is called to start a process. All it really does
@@ -87,7 +89,7 @@ setup_and_wait(struct trussinfo *info, c
if (waitpid(pid, NULL, 0) < 0)
err(1, "unexpect stop in waitpid");
- new_proc(info, pid);
+ new_proc(info, pid, 0);
}
/*
@@ -109,7 +111,7 @@ start_tracing(struct trussinfo *info, pi
if (waitpid(pid, NULL, 0) < 0)
err(1, "Unexpect stop in waitpid");
- new_proc(info, pid);
+ new_proc(info, pid, 0);
}
/*
@@ -170,14 +172,71 @@ find_abi(pid_t pid)
return (NULL);
}
+static struct threadinfo *
+new_thread(struct procinfo *p, lwpid_t lwpid)
+{
+ struct threadinfo *nt;
+
+ /*
+ * If this happens it means there is a bug in truss. Unfortunately
+ * this will kill any processes truss is attached to.
+ */
+ LIST_FOREACH(nt, &p->threadlist, entries) {
+ if (nt->tid == lwpid)
+ errx(1, "Duplicate thread for LWP %ld", (long)lwpid);
+ }
+
+ nt = calloc(1, sizeof(struct threadinfo));
+ if (nt == NULL)
+ err(1, "calloc() failed");
+ nt->proc = p;
+ nt->tid = lwpid;
+ LIST_INSERT_HEAD(&p->threadlist, nt, entries);
+ return (nt);
+}
+
+static void
+free_thread(struct threadinfo *t)
+{
+
+ LIST_REMOVE(t, entries);
+ free(t);
+}
+
static void
-new_proc(struct trussinfo *info, pid_t pid)
+add_threads(struct trussinfo *info, struct procinfo *p)
+{
+ struct ptrace_lwpinfo pl;
+ struct threadinfo *t;
+ lwpid_t *lwps;
+ int i, nlwps;
+
+ nlwps = ptrace(PT_GETNUMLWPS, p->pid, NULL, 0);
+ if (nlwps == -1)
+ err(1, "Unable to fetch number of LWPs");
+ assert(nlwps > 0);
+ lwps = calloc(nlwps, sizeof(*lwps));
+ nlwps = ptrace(PT_GETLWPLIST, p->pid, (caddr_t)lwps, nlwps);
+ if (nlwps == -1)
+ err(1, "Unable to fetch LWP list");
+ for (i = 0; i < nlwps; i++) {
+ t = new_thread(p, lwps[i]);
+ if (ptrace(PT_LWPINFO, lwps[i], (caddr_t)&pl, sizeof(pl)) == -1)
+ err(1, "ptrace(PT_LWPINFO)");
+ if (pl.pl_flags & PL_FLAG_SCE)
+ enter_syscall(info, t, &pl);
+ }
+ free(lwps);
+}
+
+static void
+new_proc(struct trussinfo *info, pid_t pid, lwpid_t lwpid)
{
struct procinfo *np;
/*
* If this happens it means there is a bug in truss. Unfortunately
- * this will kill any processes are attached to.
+ * this will kill any processes truss is attached to.
*/
LIST_FOREACH(np, &info->proclist, entries) {
if (np->pid == pid)
@@ -187,11 +246,18 @@ new_proc(struct trussinfo *info, pid_t p
if (info->flags & FOLLOWFORKS)
if (ptrace(PT_FOLLOW_FORK, pid, NULL, 1) == -1)
err(1, "Unable to follow forks for pid %ld", (long)pid);
+ if (ptrace(PT_LWP_EVENTS, pid, NULL, 1) == -1)
+ err(1, "Unable to enable LWP events for pid %ld", (long)pid);
np = calloc(1, sizeof(struct procinfo));
np->pid = pid;
np->abi = find_abi(pid);
- SLIST_INIT(&np->threadlist);
+ LIST_INIT(&np->threadlist);
LIST_INSERT_HEAD(&info->proclist, np, entries);
+
+ if (lwpid != 0)
+ new_thread(np, lwpid);
+ else
+ add_threads(info, np);
}
static void
@@ -199,7 +265,7 @@ free_proc(struct procinfo *p)
{
struct threadinfo *t, *t2;
- SLIST_FOREACH_SAFE(t, &p->threadlist, entries, t2) {
+ LIST_FOREACH_SAFE(t, &p->threadlist, entries, t2) {
free(t);
}
LIST_REMOVE(p, entries);
@@ -232,7 +298,6 @@ find_proc(struct trussinfo *info, pid_t
/*
* Change curthread member based on (pid, lwpid).
- * If it is a new thread, create a threadinfo structure.
*/
static void
find_thread(struct trussinfo *info, pid_t pid, lwpid_t lwpid)
@@ -243,55 +308,30 @@ find_thread(struct trussinfo *info, pid_
np = find_proc(info, pid);
assert(np != NULL);
- SLIST_FOREACH(nt, &np->threadlist, entries) {
+ LIST_FOREACH(nt, &np->threadlist, entries) {
if (nt->tid == lwpid) {
info->curthread = nt;
return;
}
}
-
- nt = calloc(1, sizeof(struct threadinfo));
- if (nt == NULL)
- err(1, "calloc() failed");
- nt->proc = np;
- nt->tid = lwpid;
- SLIST_INSERT_HEAD(&np->threadlist, nt, entries);
- info->curthread = nt;
+ errx(1, "could not find thread");
}
/*
- * When a process exits, it no longer has any threads left. However,
- * the main loop expects a valid curthread. In cases when a thread
- * triggers the termination (e.g. calling exit or triggering a fault)
- * we would ideally use that thread. However, if a process is killed
- * by a signal sent from another process then there is no "correct"
- * thread. We just punt and use the first thread.
+ * When a process exits, it should have exactly one thread left.
+ * All of the other threads should have reported thread exit events.
*/
static void
find_exit_thread(struct trussinfo *info, pid_t pid)
{
- struct procinfo *np;
- struct threadinfo *nt;
+ struct procinfo *p;
- np = find_proc(info, pid);
- assert(np != NULL);
+ p = find_proc(info, pid);
+ assert(p != NULL);
- if (SLIST_EMPTY(&np->threadlist)) {
- /*
- * If an existing process exits right after we attach
- * to it but before it posts any events, there won't
- * be any threads. Create a dummy thread and set its
- * "before" time to the global start time.
- */
- nt = calloc(1, sizeof(struct threadinfo));
- if (nt == NULL)
- err(1, "calloc() failed");
- nt->proc = np;
- nt->tid = 0;
- SLIST_INSERT_HEAD(&np->threadlist, nt, entries);
- nt->before = info->start_time;
- }
- info->curthread = SLIST_FIRST(&np->threadlist);
+ info->curthread = LIST_FIRST(&p->threadlist);
+ assert(info->curthread != NULL);
+ assert(LIST_NEXT(info->curthread, entries) == NULL);
}
static void
@@ -322,13 +362,12 @@ free_syscall(struct threadinfo *t)
}
static void
-enter_syscall(struct trussinfo *info, struct ptrace_lwpinfo *pl)
+enter_syscall(struct trussinfo *info, struct threadinfo *t,
+ struct ptrace_lwpinfo *pl)
{
- struct threadinfo *t;
struct syscall *sc;
u_int i, narg;
- t = info->curthread;
alloc_syscall(t, pl);
narg = MIN(pl->pl_syscall_narg, nitems(t->cs.args));
if (narg != 0 && t->proc->abi->fetch_args(info, narg) != 0) {
@@ -377,6 +416,28 @@ enter_syscall(struct trussinfo *info, st
clock_gettime(CLOCK_REALTIME, &t->before);
}
+/*
+ * When a thread exits voluntarily (including when a thread calls
+ * exit() to trigger a process exit), the thread's internal state
+ * holds the arguments passed to the exit system call. When the
+ * thread's exit is reported, log that system call without a return
+ * value.
+ */
+static void
+thread_exit_syscall(struct trussinfo *info)
+{
+ struct threadinfo *t;
+
+ t = info->curthread;
+ if (!t->in_syscall)
+ return;
+
+ clock_gettime(CLOCK_REALTIME, &t->after);
+
+ print_syscall_ret(info, 0, NULL);
+ free_syscall(t);
+}
+
static void
exit_syscall(struct trussinfo *info, struct ptrace_lwpinfo *pl)
{
@@ -430,6 +491,7 @@ exit_syscall(struct trussinfo *info, str
* new ABI isn't supported, stop tracing this process.
*/
if (pl->pl_flags & PL_FLAG_EXEC) {
+ assert(LIST_NEXT(LIST_FIRST(&p->threadlist), entries) == NULL);
p->abi = find_abi(p->pid);
if (p->abi == NULL) {
if (ptrace(PT_DETACH, p->pid, (caddr_t)1, 0) < 0)
@@ -472,6 +534,29 @@ print_line_prefix(struct trussinfo *info
}
static void
+report_thread_death(struct trussinfo *info)
+{
+ struct threadinfo *t;
+
+ t = info->curthread;
+ clock_gettime(CLOCK_REALTIME, &t->after);
+ print_line_prefix(info);
+ fprintf(info->outfile, "<thread %ld exited>\n", (long)t->tid);
+}
+
+static void
+report_thread_birth(struct trussinfo *info)
+{
+ struct threadinfo *t;
+
+ t = info->curthread;
+ clock_gettime(CLOCK_REALTIME, &t->after);
+ t->before = t->after;
+ print_line_prefix(info);
+ fprintf(info->outfile, "<new thread %ld>\n", (long)t->tid);
+}
+
+static void
report_exit(struct trussinfo *info, siginfo_t *si)
{
struct threadinfo *t;
@@ -544,8 +629,11 @@ eventloop(struct trussinfo *info)
case CLD_KILLED:
case CLD_DUMPED:
find_exit_thread(info, si.si_pid);
- if ((info->flags & COUNTONLY) == 0)
+ if ((info->flags & COUNTONLY) == 0) {
+ if (si.si_code == CLD_EXITED)
+ thread_exit_syscall(info);
report_exit(info, &si);
+ }
free_proc(info->curthread->proc);
info->curthread = NULL;
break;
@@ -555,16 +643,27 @@ eventloop(struct trussinfo *info)
err(1, "ptrace(PT_LWPINFO)");
if (pl.pl_flags & PL_FLAG_CHILD) {
- new_proc(info, si.si_pid);
+ new_proc(info, si.si_pid, pl.pl_lwpid);
assert(LIST_FIRST(&info->proclist)->abi !=
NULL);
- }
+ } else if (pl.pl_flags & PL_FLAG_BORN)
+ new_thread(find_proc(info, si.si_pid),
+ pl.pl_lwpid);
find_thread(info, si.si_pid, pl.pl_lwpid);
if (si.si_status == SIGTRAP &&
- (pl.pl_flags & (PL_FLAG_SCE|PL_FLAG_SCX)) != 0) {
- if (pl.pl_flags & PL_FLAG_SCE)
- enter_syscall(info, &pl);
+ (pl.pl_flags & (PL_FLAG_BORN|PL_FLAG_EXITED|
+ PL_FLAG_SCE|PL_FLAG_SCX)) != 0) {
+ if (pl.pl_flags & PL_FLAG_BORN) {
+ if ((info->flags & COUNTONLY) == 0)
+ report_thread_birth(info);
+ } else if (pl.pl_flags & PL_FLAG_EXITED) {
+ if ((info->flags & COUNTONLY) == 0)
+ report_thread_death(info);
+ free_thread(info->curthread);
+ info->curthread = NULL;
+ } else if (pl.pl_flags & PL_FLAG_SCE)
+ enter_syscall(info, info->curthread,
&pl);
else if (pl.pl_flags & PL_FLAG_SCX)
exit_syscall(info, &pl);
pending_signal = 0;
Modified: head/usr.bin/truss/syscalls.c
==============================================================================
--- head/usr.bin/truss/syscalls.c Wed Mar 9 18:38:30 2016
(r296570)
+++ head/usr.bin/truss/syscalls.c Wed Mar 9 18:45:41 2016
(r296571)
@@ -2054,6 +2054,16 @@ print_syscall_ret(struct trussinfo *trus
print_syscall(trussinfo);
fflush(trussinfo->outfile);
+
+ if (retval == NULL) {
+ /*
+ * This system call resulted in the current thread's exit,
+ * so there is no return value or error to display.
+ */
+ fprintf(trussinfo->outfile, "\n");
+ return;
+ }
+
if (errorp) {
error = sysdecode_abi_to_freebsd_errno(t->proc->abi->abi,
retval[0]);
Modified: head/usr.bin/truss/truss.h
==============================================================================
--- head/usr.bin/truss/truss.h Wed Mar 9 18:38:30 2016 (r296570)
+++ head/usr.bin/truss/truss.h Wed Mar 9 18:45:41 2016 (r296571)
@@ -73,7 +73,7 @@ struct current_syscall {
struct threadinfo
{
- SLIST_ENTRY(threadinfo) entries;
+ LIST_ENTRY(threadinfo) entries;
struct procinfo *proc;
lwpid_t tid;
int in_syscall;
@@ -87,7 +87,7 @@ struct procinfo {
pid_t pid;
struct procabi *abi;
- SLIST_HEAD(, threadinfo) threadlist;
+ LIST_HEAD(, threadinfo) threadlist;
};
struct trussinfo
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