LoongArch: BPF: Make trampoline size stable

commit ea645cfd3d5f74a2bd40a60003f113b3c467975d upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 68b93ce5f3821c6e2902345f8fbc967a98f9399a..8d534a0dad87c8b844d2b940f8ffdee6de4b6b2b 100644 (file)
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1632,7 +1632,7 @@ 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;
@@ -1682,7 +1682,7 @@ 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;