Merge "tracing: fix race condition reading saved tgids" (f0c7cce9) · Commits · e / devices / android_kernel_fairphone_FP3

kernel/trace/trace.c

+81 −20

Original line number	Diff line number	Diff line
		@@ -1599,11 +1599,11 @@ void tracing_reset_all_online_cpus(void)

		#define SAVED_CMDLINES_DEFAULT 128
		#define NO_CMDLINE_MAP UINT_MAX
		static unsigned saved_tgids[SAVED_CMDLINES_DEFAULT];
		static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
		struct saved_cmdlines_buffer {
		unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
		unsigned *map_cmdline_to_pid;
		unsigned *map_cmdline_to_tgid;
		unsigned cmdline_num;
		int cmdline_idx;
		char *saved_cmdlines;
		@@ -1637,12 +1637,23 @@ static int allocate_cmdlines_buffer(unsigned int val,
		return -ENOMEM;
		}

		s->map_cmdline_to_tgid = kmalloc_array(val,
		sizeof(*s->map_cmdline_to_tgid),
		GFP_KERNEL);
		if (!s->map_cmdline_to_tgid) {
		kfree(s->map_cmdline_to_pid);
		kfree(s->saved_cmdlines);
		return -ENOMEM;
		}

		s->cmdline_idx = 0;
		s->cmdline_num = val;
		memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
		sizeof(s->map_pid_to_cmdline));
		memset(s->map_cmdline_to_pid, NO_CMDLINE_MAP,
		val * sizeof(*s->map_cmdline_to_pid));
		memset(s->map_cmdline_to_tgid, NO_CMDLINE_MAP,
		val * sizeof(*s->map_cmdline_to_tgid));

		return 0;
		}
		@@ -1808,14 +1819,17 @@ static int trace_save_cmdline(struct task_struct *tsk)
		if (!tsk->pid \|\| unlikely(tsk->pid > PID_MAX_DEFAULT))
		return 0;

		preempt_disable();
		/*
		* It's not the end of the world if we don't get
		* the lock, but we also don't want to spin
		* nor do we want to disable interrupts,
		* so if we miss here, then better luck next time.
		*/
		if (!arch_spin_trylock(&trace_cmdline_lock))
		if (!arch_spin_trylock(&trace_cmdline_lock)) {
		preempt_enable();
		return 0;
		}

		idx = savedcmd->map_pid_to_cmdline[tsk->pid];
		if (idx == NO_CMDLINE_MAP) {
		@@ -1838,8 +1852,9 @@ static int trace_save_cmdline(struct task_struct *tsk)
		}

		set_cmdline(idx, tsk->comm);
		saved_tgids[idx] = tsk->tgid;
		savedcmd->map_cmdline_to_tgid[idx] = tsk->tgid;
		arch_spin_unlock(&trace_cmdline_lock);
		preempt_enable();

		return 1;
		}
		@@ -1881,19 +1896,29 @@ void trace_find_cmdline(int pid, char comm[])
		preempt_enable();
		}

		int trace_find_tgid(int pid)
		static int __find_tgid_locked(int pid)
		{
		unsigned map;
		int tgid;

		preempt_disable();
		arch_spin_lock(&trace_cmdline_lock);
		map = savedcmd->map_pid_to_cmdline[pid];
		if (map != NO_CMDLINE_MAP)
		tgid = saved_tgids[map];
		tgid = savedcmd->map_cmdline_to_tgid[map];
		else
		tgid = -1;

		return tgid;
		}

		int trace_find_tgid(int pid)
		{
		int tgid;

		preempt_disable();
		arch_spin_lock(&trace_cmdline_lock);

		tgid = __find_tgid_locked(pid);

		arch_spin_unlock(&trace_cmdline_lock);
		preempt_enable();

		@@ -4386,10 +4411,15 @@ tracing_saved_cmdlines_size_read(struct file filp, char __user ubuf,
		{
		char buf[64];
		int r;
		unsigned int n;

		preempt_disable();
		arch_spin_lock(&trace_cmdline_lock);
		r = scnprintf(buf, sizeof(buf), "%u\n", savedcmd->cmdline_num);
		n = savedcmd->cmdline_num;
		arch_spin_unlock(&trace_cmdline_lock);
		preempt_enable();

		r = scnprintf(buf, sizeof(buf), "%u\n", n);

		return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
		}
		@@ -4398,6 +4428,7 @@ static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s)
		{
		kfree(s->saved_cmdlines);
		kfree(s->map_cmdline_to_pid);
		kfree(s->map_cmdline_to_tgid);
		kfree(s);
		}

		@@ -4414,10 +4445,12 @@ static int tracing_resize_saved_cmdlines(unsigned int val)
		return -ENOMEM;
		}

		preempt_disable();
		arch_spin_lock(&trace_cmdline_lock);
		savedcmd_temp = savedcmd;
		savedcmd = s;
		arch_spin_unlock(&trace_cmdline_lock);
		preempt_enable();
		free_saved_cmdlines_buffer(savedcmd_temp);

		return 0;
		@@ -4636,33 +4669,61 @@ tracing_saved_tgids_read(struct file file, char __user ubuf,
		char *file_buf;
		char *buf;
		int len = 0;
		int pid;
		int i;
		int *pids;
		int n = 0;

		file_buf = kmalloc(SAVED_CMDLINES_DEFAULT*(16+1+16), GFP_KERNEL);
		if (!file_buf)
		return -ENOMEM;
		preempt_disable();
		arch_spin_lock(&trace_cmdline_lock);

		buf = file_buf;
		pids = kmalloc_array(savedcmd->cmdline_num, 2*sizeof(int), GFP_KERNEL);
		if (!pids) {
		arch_spin_unlock(&trace_cmdline_lock);
		preempt_enable();
		return -ENOMEM;
		}

		for (i = 0; i < SAVED_CMDLINES_DEFAULT; i++) {
		int tgid;
		int r;
		for (i = 0; i < savedcmd->cmdline_num; i++) {
		int pid;

		pid = savedcmd->map_cmdline_to_pid[i];
		if (pid == -1 \|\| pid == NO_CMDLINE_MAP)
		continue;

		tgid = trace_find_tgid(pid);
		r = sprintf(buf, "%d %d\n", pid, tgid);
		pids[n] = pid;
		pids[n+1] = __find_tgid_locked(pid);
		n += 2;
		}
		arch_spin_unlock(&trace_cmdline_lock);
		preempt_enable();

		if (n == 0) {
		kfree(pids);
		return 0;
		}

		/* enough to hold max pair of pids + space, lr and nul */
		len = n * 12;
		file_buf = kmalloc(len, GFP_KERNEL);
		if (!file_buf) {
		kfree(pids);
		return -ENOMEM;
		}

		buf = file_buf;
		for (i = 0; i < n && len > 0; i += 2) {
		int r;

		r = snprintf(buf, len, "%d %d\n", pids[i], pids[i+1]);
		buf += r;
		len += r;
		len -= r;
		}

		len = simple_read_from_buffer(ubuf, cnt, ppos,
		file_buf, len);
		file_buf, buf - file_buf);

		kfree(file_buf);
		kfree(pids);

		return len;
		}