Add new BPF helper, bpf_get_user_ctx(), which can be used by BPF programs to
get access to the user_ctx value, specified during BPF program attachment (BPF
link creation) time.
Currently all perf_event-backed BPF program types support bpf_get_user_ctx()
helper. Follow-up patches will add support for fentry/fexit programs as well.
While at it, mark bpf_tracing_func_proto() as static to make it obvious that
it's only used from within the kernel/trace/bpf_trace.c.
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
include/linux/bpf.h | 3 ---
include/uapi/linux/bpf.h | 16 ++++++++++++++++
kernel/trace/bpf_trace.c | 35 +++++++++++++++++++++++++++++++++-
tools/include/uapi/linux/bpf.h | 16 ++++++++++++++++
4 files changed, 66 insertions(+), 4 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 74b35faf0b73..94ebedc1e13a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2110,9 +2110,6 @@ extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
-const struct bpf_func_proto *bpf_tracing_func_proto(
- enum bpf_func_id func_id, const struct bpf_prog *prog);
-
const struct bpf_func_proto *tracing_prog_func_proto(
enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index bc1fd54a8f58..96afeced3467 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4856,6 +4856,21 @@ union bpf_attr {
* Get address of the traced function (for tracing and kprobe programs).
* Return
* Address of the traced function.
+ *
+ * u64 bpf_get_user_ctx(void *ctx)
+ * Description
+ * Get user_ctx value provided (optionally) during the program
+ * attachment. It might be different for each individual
+ * attachment, even if BPF program itself is the same.
+ * Expects BPF program context *ctx* as a first argument.
+ *
+ * Supported for the following program types:
+ * - kprobe/uprobe;
+ * - tracepoint;
+ * - perf_event.
+ * Return
+ * Value specified by user at BPF link creation/attachment time
+ * or 0, if it was not specified.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5032,6 +5047,7 @@ union bpf_attr {
FN(timer_start), \
FN(timer_cancel), \
FN(get_func_ip), \
+ FN(get_user_ctx), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index c9cf6a0d0fb3..b14978b3f6fb 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -975,7 +975,34 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = {
.arg1_type = ARG_PTR_TO_CTX,
};
-const struct bpf_func_proto *
+BPF_CALL_1(bpf_get_user_ctx_trace, void *, ctx)
+{
+ struct bpf_trace_run_ctx *run_ctx;
+
+ run_ctx = container_of(current->bpf_ctx, struct bpf_trace_run_ctx, run_ctx);
+ return run_ctx->user_ctx;
+}
+
+static const struct bpf_func_proto bpf_get_user_ctx_proto_trace = {
+ .func = bpf_get_user_ctx_trace,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+};
+
+BPF_CALL_1(bpf_get_user_ctx_pe, struct bpf_perf_event_data_kern *, ctx)
+{
+ return ctx->event->user_ctx;
+}
+
+static const struct bpf_func_proto bpf_get_user_ctx_proto_pe = {
+ .func = bpf_get_user_ctx_pe,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+};
+
+static const struct bpf_func_proto *
bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
switch (func_id) {
@@ -1108,6 +1135,8 @@ kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
#endif
case BPF_FUNC_get_func_ip:
return &bpf_get_func_ip_proto_kprobe;
+ case BPF_FUNC_get_user_ctx:
+ return &bpf_get_user_ctx_proto_trace;
default:
return bpf_tracing_func_proto(func_id, prog);
}
@@ -1218,6 +1247,8 @@ tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_get_stackid_proto_tp;
case BPF_FUNC_get_stack:
return &bpf_get_stack_proto_tp;
+ case BPF_FUNC_get_user_ctx:
+ return &bpf_get_user_ctx_proto_trace;
default:
return bpf_tracing_func_proto(func_id, prog);
}
@@ -1325,6 +1356,8 @@ pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_perf_prog_read_value_proto;
case BPF_FUNC_read_branch_records:
return &bpf_read_branch_records_proto;
+ case BPF_FUNC_get_user_ctx:
+ return &bpf_get_user_ctx_proto_pe;
default:
return bpf_tracing_func_proto(func_id, prog);
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index bc1fd54a8f58..96afeced3467 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4856,6 +4856,21 @@ union bpf_attr {
* Get address of the traced function (for tracing and kprobe programs).
* Return
* Address of the traced function.
+ *
+ * u64 bpf_get_user_ctx(void *ctx)
+ * Description
+ * Get user_ctx value provided (optionally) during the program
+ * attachment. It might be different for each individual
+ * attachment, even if BPF program itself is the same.
+ * Expects BPF program context *ctx* as a first argument.
+ *
+ * Supported for the following program types:
+ * - kprobe/uprobe;
+ * - tracepoint;
+ * - perf_event.
+ * Return
+ * Value specified by user at BPF link creation/attachment time
+ * or 0, if it was not specified.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5032,6 +5047,7 @@ union bpf_attr {
FN(timer_start), \
FN(timer_cancel), \
FN(get_func_ip), \
+ FN(get_user_ctx), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.30.2
