Commit dc7d7447 authored by Xu Kuohai's avatar Xu Kuohai Committed by Daniel Borkmann
Browse files

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: efc9909f ("bpf, arm64: Add bpf trampoline for arm64")
Reported-by: default avatarIvan Babrou <ivan@cloudflare.com>
Signed-off-by: default avatarXu Kuohai <xukuohai@huawei.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Tested-by: default avatarIvan Babrou <ivan@cloudflare.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240416064208.2919073-2-xukuohai@huaweicloud.com
parent 37eacb9f

arch/arm64/net/bpf_jit_comp.c

+3 −3
Original line number Diff line number Diff line
@@ -1844,15 +1844,15 @@ static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l, 


	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);