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bpf, arm64: Fix incorrect runtime stats

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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: efc9909fdc ("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
This commit is contained in:
Xu Kuohai
2024-04-16 14:42:07 +08:00
committed by Daniel Borkmann
parent 37eacb9f6e
commit dc7d7447b5
1 changed files with 3 additions and 3 deletions
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6
arch/arm64/net/bpf_jit_comp.c
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@@ -1844,15 +1844,15 @@ static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
emit_call(enter_prog, ctx); 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) /* if (__bpf_prog_enter(prog) == 0)
* goto skip_exec_of_prog; * goto skip_exec_of_prog;
*/ */
branch = ctx->image + ctx->idx; branch = ctx->image + ctx->idx;
emit(A64_NOP, ctx); 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); emit(A64_ADD_I(1, A64_R(0), A64_SP, args_off), ctx);
if (!p->jited) if (!p->jited)
emit_addr_mov_i64(A64_R(1), (const u64)p->insnsi, ctx); emit_addr_mov_i64(A64_R(1), (const u64)p->insnsi, ctx);