Pass external callchain entry to get_perf_callchain

include/linux/perf_event.h

@@ -67,6 +67,7 @@ struct perf_callchain_entry_ctx {
 	u32				nr;
 	short				contexts;
 	bool				contexts_maxed;
+	bool				add_mark;
 };
 
 typedef unsigned long (*perf_copy_f)(void *dst, const void *src,
@@ -1718,6 +1719,14 @@ DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry);
 
 extern void perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
 extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
+
+extern void __init_perf_callchain_ctx(struct perf_callchain_entry_ctx *ctx,
+				      struct perf_callchain_entry *entry,
+				      u32 max_stack, bool add_mark);
+
+extern void __get_perf_callchain_kernel(struct perf_callchain_entry_ctx *ctx, struct pt_regs *regs);
+extern void __get_perf_callchain_user(struct perf_callchain_entry_ctx *ctx, struct pt_regs *regs);
+
 extern struct perf_callchain_entry *
 get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
 		   u32 max_stack, bool crosstask, bool add_mark);

kernel/bpf/stackmap.c

@@ -210,13 +210,12 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 }
 
 static struct perf_callchain_entry *
-get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
+get_callchain_entry_for_task(int *rctx, struct task_struct *task, u32 max_depth)
 {
 #ifdef CONFIG_STACKTRACE
 	struct perf_callchain_entry *entry;
-	int rctx;
 
-	entry = get_callchain_entry(&rctx);
+	entry = get_callchain_entry(rctx);
 
 	if (!entry)
 		return NULL;
@@ -238,8 +237,6 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
 			to[i] = (u64)(from[i]);
 	}
 
-	put_callchain_entry(rctx);
-
 	return entry;
 #else /* CONFIG_STACKTRACE */
 	return NULL;
@@ -320,6 +317,31 @@ static long __bpf_get_stackid(struct bpf_map *map,
 	return id;
 }
 
+static struct perf_callchain_entry *
+bpf_get_perf_callchain(int *rctx, struct pt_regs *regs, bool kernel, bool user,
+		       int max_stack, bool crosstask)
+{
+	struct perf_callchain_entry_ctx ctx;
+	struct perf_callchain_entry *entry;
+
+	entry = get_callchain_entry(rctx);
+	if (unlikely(!entry))
+		return NULL;
+
+	__init_perf_callchain_ctx(&ctx, entry, max_stack, false);
+	if (kernel)
+		__get_perf_callchain_kernel(&ctx, regs);
+	if (user && !crosstask)
+		__get_perf_callchain_user(&ctx, regs);
+
+	return entry;
+}
+
+static void bpf_put_perf_callchain(int rctx)
+{
+	put_callchain_entry(rctx);
+}
+
 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 	   u64, flags)
 {
@@ -328,20 +350,24 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 	struct perf_callchain_entry *trace;
 	bool kernel = !user;
 	u32 max_depth;
+	int rctx, ret;
 
 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 		return -EINVAL;
 
 	max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags);
-	trace = get_perf_callchain(regs, kernel, user, max_depth,
-				   false, false);
+	trace = bpf_get_perf_callchain(&rctx, regs, kernel, user, max_depth,
+				       false);
 
 	if (unlikely(!trace))
 		/* couldn't fetch the stack trace */
 		return -EFAULT;
 
-	return __bpf_get_stackid(map, trace, flags);
+	ret = __bpf_get_stackid(map, trace, flags);
+	bpf_put_perf_callchain(rctx);
+
+	return ret;
 }
 
 const struct bpf_func_proto bpf_get_stackid_proto = {
@@ -435,6 +461,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 	bool kernel = !user;
 	int err = -EINVAL;
 	u64 *ips;
+	int rctx;
 
 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 			       BPF_F_USER_BUILD_ID)))
@@ -467,18 +494,26 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 		trace = trace_in;
 		trace->nr = min_t(u32, trace->nr, max_depth);
 	} else if (kernel && task) {
-		trace = get_callchain_entry_for_task(task, max_depth);
+		trace = get_callchain_entry_for_task(&rctx, task, max_depth);
 	} else {
-		trace = get_perf_callchain(regs, kernel, user, max_depth,
-					   crosstask, false);
+		trace = bpf_get_perf_callchain(&rctx, regs, kernel, user, max_depth,
+					       crosstask);
 	}
 
-	if (unlikely(!trace) || trace->nr < skip) {
+	if (unlikely(!trace)) {
 		if (may_fault)
 			rcu_read_unlock();
 		goto err_fault;
 	}
 
+	if (trace->nr < skip) {
+		if (may_fault)
+			rcu_read_unlock();
+		if (!trace_in)
+			bpf_put_perf_callchain(rctx);
+		goto err_fault;
+	}
+
 	trace_nr = trace->nr - skip;
 	copy_len = trace_nr * elem_size;
 
@@ -497,6 +532,9 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 	if (may_fault)
 		rcu_read_unlock();
 
+	if (!trace_in)
+		bpf_put_perf_callchain(rctx);
+
 	if (user_build_id)
 		stack_map_get_build_id_offset(buf, trace_nr, user, may_fault);
 

kernel/events/callchain.c

@@ -216,13 +216,54 @@ static void fixup_uretprobe_trampoline_entries(struct perf_callchain_entry *entr
 #endif
 }
 
+void __init_perf_callchain_ctx(struct perf_callchain_entry_ctx *ctx,
+			       struct perf_callchain_entry *entry,
+			       u32 max_stack, bool add_mark)
+
+{
+	ctx->entry		= entry;
+	ctx->max_stack		= max_stack;
+	ctx->nr			= entry->nr = 0;
+	ctx->contexts		= 0;
+	ctx->contexts_maxed	= false;
+	ctx->add_mark		= add_mark;
+}
+
+void __get_perf_callchain_kernel(struct perf_callchain_entry_ctx *ctx, struct pt_regs *regs)
+{
+	if (user_mode(regs))
+		return;
+
+	if (ctx->add_mark)
+		perf_callchain_store_context(ctx, PERF_CONTEXT_KERNEL);
+	perf_callchain_kernel(ctx, regs);
+}
+
+void __get_perf_callchain_user(struct perf_callchain_entry_ctx *ctx, struct pt_regs *regs)
+{
+	int start_entry_idx;
+
+	if (!user_mode(regs)) {
+		if (current->flags & (PF_KTHREAD | PF_USER_WORKER))
+			return;
+		regs = task_pt_regs(current);
+	}
+
+	if (ctx->add_mark)
+		perf_callchain_store_context(ctx, PERF_CONTEXT_USER);
+
+	start_entry_idx = ctx->nr;
+	perf_callchain_user(ctx, regs);
+	fixup_uretprobe_trampoline_entries(ctx->entry, start_entry_idx);
+}
+
 struct perf_callchain_entry *
 get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
 		   u32 max_stack, bool crosstask, bool add_mark)
 {
 	struct perf_callchain_entry *entry;
 	struct perf_callchain_entry_ctx ctx;
-	int rctx, start_entry_idx;
+	int rctx;
 
 	/* crosstask is not supported for user stacks */
 	if (crosstask && user && !kernel)
@@ -232,34 +273,14 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
 	if (!entry)
 		return NULL;
 
-	ctx.entry		= entry;
-	ctx.max_stack		= max_stack;
-	ctx.nr			= entry->nr = 0;
-	ctx.contexts		= 0;
-	ctx.contexts_maxed	= false;
+	__init_perf_callchain_ctx(&ctx, entry, max_stack, add_mark);
 
-	if (kernel && !user_mode(regs)) {
-		if (add_mark)
-			perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL);
-		perf_callchain_kernel(&ctx, regs);
-	}
-
-	if (user && !crosstask) {
-		if (!user_mode(regs)) {
-			if (current->flags & (PF_KTHREAD | PF_USER_WORKER))
-				goto exit_put;
-			regs = task_pt_regs(current);
-		}
+	if (kernel)
+		__get_perf_callchain_kernel(&ctx, regs);
 
-		if (add_mark)
-			perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
-
-		start_entry_idx = entry->nr;
-		perf_callchain_user(&ctx, regs);
-		fixup_uretprobe_trampoline_entries(entry, start_entry_idx);
-	}
+	if (user && !crosstask)
+		__get_perf_callchain_user(&ctx, regs);
 
-exit_put:
 	put_callchain_entry(rctx);
 
 	return entry;

kernel/events/internal.h

@@ -214,12 +214,9 @@ static inline int get_recursion_context(u8 *recursion)
 {
 	unsigned char rctx = interrupt_context_level();
 
-	if (recursion[rctx])
+	if (cmpxchg(&recursion[rctx], 0, 1) != 0)
 		return -1;
 
-	recursion[rctx]++;
-	barrier();
-
 	return rctx;
 }