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* [PATCH bpf-next 1/2] bpf: implement bpf_send_signal_pid/tgid() helpers
@ 2024-07-24 11:39 Puranjay Mohan
  2024-07-24 11:39 ` [PATCH bpf-next 2/2] selftests/bpf: Augment send_signal test with remote signaling Puranjay Mohan
  2024-07-24 23:23 ` [PATCH bpf-next 1/2] bpf: implement bpf_send_signal_pid/tgid() helpers Alexei Starovoitov
  0 siblings, 2 replies; 3+ messages in thread
From: Puranjay Mohan @ 2024-07-24 11:39 UTC (permalink / raw)
  To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa,
	Matt Bobrowski, Steven Rostedt, Masami Hiramatsu,
	Mathieu Desnoyers, Puranjay Mohan, Abhishek Chauhan, bpf,
	linux-kernel, linux-trace-kernel

Implement bpf_send_signal_pid and bpf_send_signal_tgid helpers which are
similar to bpf_send_signal_thread and bpf_send_signal helpers
respectively but can be used to send signals to other threads and
processes.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
---
 include/uapi/linux/bpf.h       | 37 ++++++++++++++++++++++++
 kernel/trace/bpf_trace.c       | 53 +++++++++++++++++++++++++++++-----
 tools/include/uapi/linux/bpf.h | 37 ++++++++++++++++++++++++
 3 files changed, 120 insertions(+), 7 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 35bcf52dbc65..7b29003c079c 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5792,6 +5792,41 @@ union bpf_attr {
  *		0 on success.
  *
  *		**-ENOENT** if the bpf_local_storage cannot be found.
+ *
+ * long bpf_send_signal_pid(u32 sig, u32 pid)
+ *	Description
+ *		Send signal *sig* to the thread corresponding to the
+ *		process id *pid*.
+ *	Return
+ *		0 on success or successfully queued.
+ *
+ *		**-EBUSY** if work queue under nmi is full.
+ *
+ *		**-EINVAL** if *sig* is invalid.
+ *
+ *		**-EPERM** if no permission to send the *sig*.
+ *
+ *		**-EAGAIN** if bpf program can try again.
+ *
+ *		**-ESRCH** if *pid* is invalid.
+ *
+ * long bpf_send_signal_tgid(u32 sig, u32 tgid)
+ *	Description
+ *		Send signal *sig* to the process corresponding to the
+ *		thread group id *tgid*.
+ *		The signal may be delivered to any of this process's threads.
+ *	Return
+ *		0 on success or successfully queued.
+ *
+ *		**-EBUSY** if work queue under nmi is full.
+ *
+ *		**-EINVAL** if *sig* is invalid.
+ *
+ *		**-EPERM** if no permission to send the *sig*.
+ *
+ *		**-EAGAIN** if bpf program can try again.
+ *
+ *		**-ESRCH** if *tgid* is invalid.
  */
 #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
 	FN(unspec, 0, ##ctx)				\
@@ -6006,6 +6041,8 @@ union bpf_attr {
 	FN(user_ringbuf_drain, 209, ##ctx)		\
 	FN(cgrp_storage_get, 210, ##ctx)		\
 	FN(cgrp_storage_delete, 211, ##ctx)		\
+	FN(send_signal_pid, 212, ##ctx)		\
+	FN(send_signal_tgid, 213, ##ctx)		\
 	/* */
 
 /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index cd098846e251..f1e58122600d 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -839,21 +839,30 @@ static void do_bpf_send_signal(struct irq_work *entry)
 	put_task_struct(work->task);
 }
 
-static int bpf_send_signal_common(u32 sig, enum pid_type type)
+static int bpf_send_signal_common(u32 sig, enum pid_type type, u32 pid)
 {
 	struct send_signal_irq_work *work = NULL;
+	struct task_struct *tsk;
+
+	if (pid) {
+		tsk = find_task_by_vpid(pid);
+		if (!tsk)
+			return -ESRCH;
+	} else {
+		tsk = current;
+	}
 
 	/* Similar to bpf_probe_write_user, task needs to be
 	 * in a sound condition and kernel memory access be
 	 * permitted in order to send signal to the current
 	 * task.
 	 */
-	if (unlikely(current->flags & (PF_KTHREAD | PF_EXITING)))
+	if (unlikely(tsk->flags & (PF_KTHREAD | PF_EXITING)))
 		return -EPERM;
 	if (unlikely(!nmi_uaccess_okay()))
 		return -EPERM;
 	/* Task should not be pid=1 to avoid kernel panic. */
-	if (unlikely(is_global_init(current)))
+	if (unlikely(is_global_init(tsk)))
 		return -EPERM;
 
 	if (irqs_disabled()) {
@@ -871,19 +880,19 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
 		 * to the irq_work. The current task may change when queued
 		 * irq works get executed.
 		 */
-		work->task = get_task_struct(current);
+		work->task = get_task_struct(tsk);
 		work->sig = sig;
 		work->type = type;
 		irq_work_queue(&work->irq_work);
 		return 0;
 	}
 
-	return group_send_sig_info(sig, SEND_SIG_PRIV, current, type);
+	return group_send_sig_info(sig, SEND_SIG_PRIV, tsk, type);
 }
 
 BPF_CALL_1(bpf_send_signal, u32, sig)
 {
-	return bpf_send_signal_common(sig, PIDTYPE_TGID);
+	return bpf_send_signal_common(sig, PIDTYPE_TGID, 0);
 }
 
 static const struct bpf_func_proto bpf_send_signal_proto = {
@@ -895,7 +904,7 @@ static const struct bpf_func_proto bpf_send_signal_proto = {
 
 BPF_CALL_1(bpf_send_signal_thread, u32, sig)
 {
-	return bpf_send_signal_common(sig, PIDTYPE_PID);
+	return bpf_send_signal_common(sig, PIDTYPE_PID, 0);
 }
 
 static const struct bpf_func_proto bpf_send_signal_thread_proto = {
@@ -905,6 +914,32 @@ static const struct bpf_func_proto bpf_send_signal_thread_proto = {
 	.arg1_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_2(bpf_send_signal_pid, u32, sig, u32, pid)
+{
+	return bpf_send_signal_common(sig, PIDTYPE_PID, pid);
+}
+
+static const struct bpf_func_proto bpf_send_signal_pid_proto = {
+	.func		= bpf_send_signal_pid,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING,
+};
+
+BPF_CALL_2(bpf_send_signal_tgid, u32, sig, u32, tgid)
+{
+	return bpf_send_signal_common(sig, PIDTYPE_TGID, tgid);
+}
+
+static const struct bpf_func_proto bpf_send_signal_tgid_proto = {
+	.func		= bpf_send_signal_tgid,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING,
+};
+
 BPF_CALL_3(bpf_d_path, struct path *, path, char *, buf, u32, sz)
 {
 	struct path copy;
@@ -1583,6 +1618,10 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_send_signal_proto;
 	case BPF_FUNC_send_signal_thread:
 		return &bpf_send_signal_thread_proto;
+	case BPF_FUNC_send_signal_pid:
+		return &bpf_send_signal_pid_proto;
+	case BPF_FUNC_send_signal_tgid:
+		return &bpf_send_signal_tgid_proto;
 	case BPF_FUNC_perf_event_read_value:
 		return &bpf_perf_event_read_value_proto;
 	case BPF_FUNC_ringbuf_output:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 35bcf52dbc65..7b29003c079c 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5792,6 +5792,41 @@ union bpf_attr {
  *		0 on success.
  *
  *		**-ENOENT** if the bpf_local_storage cannot be found.
+ *
+ * long bpf_send_signal_pid(u32 sig, u32 pid)
+ *	Description
+ *		Send signal *sig* to the thread corresponding to the
+ *		process id *pid*.
+ *	Return
+ *		0 on success or successfully queued.
+ *
+ *		**-EBUSY** if work queue under nmi is full.
+ *
+ *		**-EINVAL** if *sig* is invalid.
+ *
+ *		**-EPERM** if no permission to send the *sig*.
+ *
+ *		**-EAGAIN** if bpf program can try again.
+ *
+ *		**-ESRCH** if *pid* is invalid.
+ *
+ * long bpf_send_signal_tgid(u32 sig, u32 tgid)
+ *	Description
+ *		Send signal *sig* to the process corresponding to the
+ *		thread group id *tgid*.
+ *		The signal may be delivered to any of this process's threads.
+ *	Return
+ *		0 on success or successfully queued.
+ *
+ *		**-EBUSY** if work queue under nmi is full.
+ *
+ *		**-EINVAL** if *sig* is invalid.
+ *
+ *		**-EPERM** if no permission to send the *sig*.
+ *
+ *		**-EAGAIN** if bpf program can try again.
+ *
+ *		**-ESRCH** if *tgid* is invalid.
  */
 #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
 	FN(unspec, 0, ##ctx)				\
@@ -6006,6 +6041,8 @@ union bpf_attr {
 	FN(user_ringbuf_drain, 209, ##ctx)		\
 	FN(cgrp_storage_get, 210, ##ctx)		\
 	FN(cgrp_storage_delete, 211, ##ctx)		\
+	FN(send_signal_pid, 212, ##ctx)		\
+	FN(send_signal_tgid, 213, ##ctx)		\
 	/* */
 
 /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
-- 
2.40.1


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2024-07-24 11:39 [PATCH bpf-next 1/2] bpf: implement bpf_send_signal_pid/tgid() helpers Puranjay Mohan
2024-07-24 11:39 ` [PATCH bpf-next 2/2] selftests/bpf: Augment send_signal test with remote signaling Puranjay Mohan
2024-07-24 23:23 ` [PATCH bpf-next 1/2] bpf: implement bpf_send_signal_pid/tgid() helpers Alexei Starovoitov

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