[PATCH bpf-next 8/9] bpf: Remove trace_in argument from __bpf_get_stack

[Jiri Olsa <jolsa@kernel.org>]

Now with the new callchain_* helper functions we can process trace_in
case directly in bpf_get_stack_pe function and remove it from
__bpf_get_stack which makes things easier for preemption fix in
following change.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/bpf/stackmap.c | 50 +++++++++++++++++++++++++++++++------------
 1 file changed, 36 insertions(+), 14 deletions(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index eea7b781300c..57cd4c33403b 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -784,7 +784,6 @@ static long callchain_finalize(void *buf, u32 size, u32 trace_nr, u32 elem_size,
 }
 
 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
-			    struct perf_callchain_entry *trace_in,
 			    void *buf, u32 size, u64 flags, bool may_fault)
 {
 	bool user_build_id = flags & BPF_F_USER_BUILD_ID;
@@ -823,10 +822,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 	if (may_fault)
 		rcu_read_lock(); /* need RCU for perf's callchain below */
 
-	if (trace_in) {
-		trace = trace_in;
-		trace->nr = min_t(u32, trace->nr, max_depth);
-	} else if (kernel && task) {
+	if (kernel && task) {
 		trace = get_callchain_entry_for_task(task, max_depth);
 	} else {
 		trace = get_perf_callchain(regs, kernel, user, max_depth,
@@ -857,7 +853,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 	   u64, flags)
 {
-	return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, false /* !may_fault */);
+	return __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */);
 }
 
 const struct bpf_func_proto bpf_get_stack_proto = {
@@ -873,7 +869,7 @@ const struct bpf_func_proto bpf_get_stack_proto = {
 BPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size,
 	   u64, flags)
 {
-	return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, true /* may_fault */);
+	return __bpf_get_stack(regs, NULL, buf, size, flags, true /* may_fault */);
 }
 
 const struct bpf_func_proto bpf_get_stack_sleepable_proto = {
@@ -897,7 +893,7 @@ static long __bpf_get_task_stack(struct task_struct *task, void *buf, u32 size,
 
 	regs = task_pt_regs(task);
 	if (regs)
-		res = __bpf_get_stack(regs, task, NULL, buf, size, flags, may_fault);
+		res = __bpf_get_stack(regs, task, buf, size, flags, may_fault);
 	put_task_stack(task);
 
 	return res;
@@ -937,6 +933,33 @@ const struct bpf_func_proto bpf_get_task_stack_sleepable_proto = {
 	.arg4_type	= ARG_ANYTHING,
 };
 
+static int __bpf_get_stack_pe(struct perf_callchain_entry *trace, void *buf, u32 size,
+			      u64 flags)
+{
+	bool user_build_id = flags & BPF_F_USER_BUILD_ID;
+	u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
+	bool user = flags & BPF_F_USER_STACK;
+	u32 elem_size, max_depth, nr_trace;
+	bool kernel = !user;
+
+	if (kernel && user_build_id)
+		return -EINVAL;
+
+	elem_size = user_build_id ? sizeof(struct bpf_stack_build_id) : sizeof(u64);
+	if (unlikely(size % elem_size))
+		return -EINVAL;
+
+	max_depth = stack_map_calculate_max_depth(size, elem_size, flags);
+	trace->nr = min_t(u32, trace->nr, max_depth);
+
+	if (trace->nr < skip)
+		return -EFAULT;
+
+	nr_trace = callchain_store(trace, buf, size, elem_size, flags);
+	return callchain_finalize(buf, size, nr_trace, elem_size, user_build_id,
+				  user, false /* !may_fault */);
+}
+
 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 	   void *, buf, u32, size, u64, flags)
 {
@@ -948,7 +971,7 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 	__u64 nr_kernel;
 
 	if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
-		return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, false /* !may_fault */);
+		return __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */);
 
 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 			       BPF_F_USER_BUILD_ID)))
@@ -968,7 +991,7 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 		__u64 nr = trace->nr;
 
 		trace->nr = nr_kernel;
-		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags, false /* !may_fault */);
+		err = __bpf_get_stack_pe(trace, buf, size, flags);
 
 		/* restore nr */
 		trace->nr = nr;
@@ -978,14 +1001,13 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 		skip += nr_kernel;
 		if (skip > BPF_F_SKIP_FIELD_MASK)
 			goto clear;
-
 		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
-		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags, false /* !may_fault */);
+		err = __bpf_get_stack_pe(trace, buf, size, flags);
 	}
-	return err;
 
 clear:
-	memset(buf, 0, size);
+	if (err < 0)
+		memset(buf, 0, size);
 	return err;
 
 }
-- 
2.54.0