[PATCH 01/13] bpf: Add bpf_stream_print_stack stack dumping kfunc

[Emil Tsalapatis <etsal@meta.com>]

Add a new kfunc called bpf_stream_print_stack to be used by programs
that need to print out their current BPF stack. The kfunc is essentially
a wrapper around the existing bpf_stream_dump_stack functionality used
to generate stack traces for error events like may_goto violations and
BPF-side arena page faults.

Signed-off-by: Emil Tsalapatis (Meta) <emil@etsalapatis.com>
---
 kernel/bpf/helpers.c        |  1 +
 kernel/bpf/stream.c         | 13 +++++++++++++
 tools/lib/bpf/bpf_helpers.h |  2 ++
 3 files changed, 16 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index f8aa1320e2f7..0e131283780f 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -4534,6 +4534,7 @@ BTF_ID_FLAGS(func, bpf_strncasestr);
 BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU)
 #endif
 BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_IMPLICIT_ARGS)
+BTF_ID_FLAGS(func, bpf_stream_print_stack, KF_IMPLICIT_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_IMPLICIT_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_IMPLICIT_ARGS)
 BTF_ID_FLAGS(func, bpf_dynptr_from_file)
diff --git a/kernel/bpf/stream.c b/kernel/bpf/stream.c
index 24730df55e69..6e2cbe5f34e7 100644
--- a/kernel/bpf/stream.c
+++ b/kernel/bpf/stream.c
@@ -245,6 +245,19 @@ __bpf_kfunc int bpf_stream_vprintk(int stream_id, const char *fmt__str, const vo
 	return ret;
 }
 
+/* Directly trigger a stack dump from the program. */
+__bpf_kfunc void bpf_stream_print_stack(struct bpf_prog_aux *aux)
+{
+	struct bpf_stream_stage ss;
+	struct bpf_prog *prog;
+
+	prog = aux->main_prog_aux->prog;
+
+	bpf_stream_stage(ss, prog, BPF_STDERR, ({
+		bpf_stream_dump_stack(ss);
+	}));
+}
+
 __bpf_kfunc_end_defs();
 
 /* Added kfunc to common_btf_ids */
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index c145da05a67c..6d8ae3887618 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -343,6 +343,8 @@ extern int bpf_stream_vprintk(int stream_id, const char *fmt__str, const void *a
 /* Helper macro to print out debug messages */
 #define bpf_printk(fmt, args...) ___bpf_pick_printk(args)(fmt, ##args)
 
+extern void bpf_stream_print_stack(void) __weak __ksym;
+
 struct bpf_iter_num;
 
 extern int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end) __weak __ksym;
-- 
2.47.3