bpf, arm64: Fix incorrect runtime stats
When __bpf_prog_enter() returns zero, the arm64 register x20 that stores
prog start time is not assigned to zero, causing incorrect runtime stats.
To fix it, assign the return value of bpf_prog_enter() to x20 register
immediately upon its return.
Fixes: efc9909fdce0 ("bpf, arm64: Add bpf trampoline for arm64")
Reported-by: Ivan Babrou <ivan@cloudflare.com>
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Ivan Babrou <ivan@cloudflare.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240416064208.2919073-2-xukuohai@huaweicloud.com
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 122021f..13eac43 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -1844,15 +1844,15 @@
emit_call(enter_prog, ctx);
+ /* save return value to callee saved register x20 */
+ emit(A64_MOV(1, A64_R(20), A64_R(0)), ctx);
+
/* if (__bpf_prog_enter(prog) == 0)
* goto skip_exec_of_prog;
*/
branch = ctx->image + ctx->idx;
emit(A64_NOP, ctx);
- /* save return value to callee saved register x20 */
- emit(A64_MOV(1, A64_R(20), A64_R(0)), ctx);
-
emit(A64_ADD_I(1, A64_R(0), A64_SP, args_off), ctx);
if (!p->jited)
emit_addr_mov_i64(A64_R(1), (const u64)p->insnsi, ctx);
