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LoongArch: BPF: Make trampoline size stable

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When attach fentry/fexit BPF programs, __arch_prepare_bpf_trampoline()
is called twice with different `struct bpf_tramp_image *im`:

    bpf_trampoline_update()
        -> arch_bpf_trampoline_size()
            -> __arch_prepare_bpf_trampoline()
        -> arch_prepare_bpf_trampoline()
            -> __arch_prepare_bpf_trampoline()

Use move_imm() will emit unstable instruction sequences, so let's use
move_addr() instead to prevent subtle bugs.

(I observed this while debugging other issues with printk.)

Cc: stable@vger.kernel.org
Tested-by: Vincent Li <vincent.mc.li@gmail.com>
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Hengqi Chen
2025-10-02 22:39:52 +08:00
committed by Huacai Chen
parent a04731cbee
commit ea645cfd3d
1 changed files with 2 additions and 2 deletions
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4
arch/loongarch/net/bpf_jit.c
View File

@@ -1595,7 +1595,7 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
orig_call += LOONGARCH_BPF_FENTRY_NBYTES;
if (flags & BPF_TRAMP_F_CALL_ORIG) {
move_imm(ctx, LOONGARCH_GPR_A0, (const s64)im, false);
move_addr(ctx, LOONGARCH_GPR_A0, (const u64)im);
ret = emit_call(ctx, (const u64)__bpf_tramp_enter);
if (ret)
return ret;
@@ -1645,7 +1645,7 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
if (flags & BPF_TRAMP_F_CALL_ORIG) {
im->ip_epilogue = ctx->ro_image + ctx->idx;
move_imm(ctx, LOONGARCH_GPR_A0, (const s64)im, false);
move_addr(ctx, LOONGARCH_GPR_A0, (const u64)im);
ret = emit_call(ctx, (const u64)__bpf_tramp_exit);
if (ret)
goto out;