LoongArch: BPF: Enhance the bpf_arch_text_poke() function

Enhance the bpf_arch_text_poke() function to enable accurate location
of BPF program entry points.

When modifying the entry point of a BPF program, skip the "move t0, ra"
instruction to ensure the correct logic and copy of the jump address.

Cc: stable@vger.kernel.org
Fixes: 677e6123e3d2 ("LoongArch: BPF: Disable trampoline for kernel module function trace")
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 9f6e93343b6e3a00dea60ec81761221757c7ca10..d1d5a65308b9eb2db571b77d50ea38be53151f25 100644 (file)
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1309,15 +1309,30 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
 {
        int ret;
        bool is_call;
+       unsigned long size = 0;
+       unsigned long offset = 0;
+       void *image = NULL;
+       char namebuf[KSYM_NAME_LEN];
        u32 old_insns[LOONGARCH_LONG_JUMP_NINSNS] = {[0 ... 4] = INSN_NOP};
        u32 new_insns[LOONGARCH_LONG_JUMP_NINSNS] = {[0 ... 4] = INSN_NOP};
 
        /* Only poking bpf text is supported. Since kernel function entry
         * is set up by ftrace, we rely on ftrace to poke kernel functions.
         */
-       if (!is_bpf_text_address((unsigned long)ip))
+       if (!__bpf_address_lookup((unsigned long)ip, &size, &offset, namebuf))
                return -ENOTSUPP;
 
+       image = ip - offset;
+
+       /* zero offset means we're poking bpf prog entry */
+       if (offset == 0) {
+               /* skip to the nop instruction in bpf prog entry:
+                * move t0, ra
+                * nop
+                */
+               ip = image + LOONGARCH_INSN_SIZE;
+       }
+
        is_call = old_t == BPF_MOD_CALL;
        ret = emit_jump_or_nops(old_addr, ip, old_insns, is_call);
        if (ret)