bpf: make bpf_get_branch_snapshot() architecture-agnostic

perf_snapshot_branch_stack is set up in an architecture-agnostic way, so
there is no reason for BPF subsystem to keep track of which
architectures do support LBR or not. E.g., it looks like ARM64 might soon
get support for BRBE ([0]), which (with proper integration) should be
possible to utilize using this BPF helper.

perf_snapshot_branch_stack static call will point to
__static_call_return0() by default, which just returns zero, which will
lead to -ENOENT, as expected. So no need to guard anything here.

  [0] https://lore.kernel.org/linux-arm-kernel/20240125094119.2542332-1-anshuman.khandual@arm.com/

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240404002640.1774210-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 6d0c95638e1bf9f53710324dcea5ad2125dc4df8..afb232b1d7c237a82634c3e57e9577db496154ed 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1188,9 +1188,6 @@ static const struct bpf_func_proto bpf_get_attach_cookie_proto_tracing = {
 
 BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags)
 {
-#ifndef CONFIG_X86
-       return -ENOENT;
-#else
        static const u32 br_entry_size = sizeof(struct perf_branch_entry);
        u32 entry_cnt = size / br_entry_size;
 
@@ -1203,7 +1200,6 @@ BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags)
                return -ENOENT;
 
        return entry_cnt * br_entry_size;
-#endif
 }
 
 static const struct bpf_func_proto bpf_get_branch_snapshot_proto = {