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LoongArch: BPF: Enhance the bpf_arch_text_poke() function

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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>
This commit is contained in:
Chenghao Duan 2025-12-31 15:19:21 +08:00 committed by Huacai Chen
parent 26138762d9
commit 73721d8676
1 changed files with 16 additions and 1 deletions
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17
arch/loongarch/net/bpf_jit.c
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@ -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)