[PATCH bpf-next 1/2] bpf: implement bpf_send_signal_pid/tgid() helpers

[Puranjay Mohan <puranjay@kernel.org>]

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