Re: [PATCH v4 6/7] LoongArch: BPF: Enhance the bpf_arch_text_poke() function

On Sat, Dec 20, 2025 at 10:07:25PM +0800, Hengqi Chen wrote:

On Wed, Dec 17, 2025 at 2:15 PM Chenghao Duan [off-list ref] wrote:

quoted

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.

Signed-off-by: Chenghao Duan <redacted>
---
 arch/loongarch/net/bpf_jit.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 3dbabacc8856..0c16a1b18e8f 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c

@@ -1290,6 +1290,10 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
                       void *new_addr)

The signature of bpf_arch_text_poke() was changed in v6.19 ([1]), please rebase.

  [1]: https://github.com/torvalds/linux/commit/ae4a3160d19cd16b874737ebc1798c7bc2fe3c9e

Thank you for your review and for pointing out the API change in v6.19.

I believe my patch series already accounts for this. It was developed on
top of commit ae4a3160d19c ("bpf: specify the old and new poke_type for bpf_arch_text_poke"),
so all modifications to bpf_arch_text_poke() call sites within my
patches should already be using the updated signature.

Please let me know if you find any inconsistencies or if further
adjustments are needed.

Best regards,
Chenghao

quoted

 {
        int ret;
+       unsigned long size = 0;
+       unsigned long offset = 0;
+       char namebuf[KSYM_NAME_LEN];
+       void *image = NULL;
        bool is_call;
        u32 old_insns[LOONGARCH_LONG_JUMP_NINSNS] = {[0 ... 4] = INSN_NOP};
        u32 new_insns[LOONGARCH_LONG_JUMP_NINSNS] = {[0 ... 4] = INSN_NOP};

@@ -1297,9 +1301,18 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
        /* 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)
--

2.25.1