Implement the bpf_arch_text_poke function for the LoongArch
architecture. On LoongArch, since symbol addresses in the direct mapping
region cannot be reached via relative jump instructions from the paged
mapping region, we use the move_imm+jirl instruction pair as absolute
jump instructions. These require 2-5 instructions, so we reserve 5 NOP
instructions in the program as placeholders for function jumps.

Signed-off-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
---
 arch/loongarch/net/bpf_jit.c | 64 ++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index ea357a3ed..0e31d4d66 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -4,6 +4,7 @@
  *
  * Copyright (C) 2022 Loongson Technology Corporation Limited
  */
+#include <linux/memory.h>
 #include "bpf_jit.h"
 
 #define REG_TCC		LOONGARCH_GPR_A6
@@ -1351,3 +1352,66 @@ bool bpf_jit_supports_subprog_tailcalls(void)
 {
 	return true;
 }
+
+static int emit_jump_and_link(struct jit_ctx *ctx, u8 rd, u64 ip, u64 target)
+{
+	s64 offset = (s64)(target - ip);
+
+	if (offset && (offset >= -SZ_128M && offset < SZ_128M)) {
+		emit_insn(ctx, bl, offset >> 2);
+	} else {
+		move_imm(ctx, LOONGARCH_GPR_T1, target, false);
+		emit_insn(ctx, jirl, rd, LOONGARCH_GPR_T1, 0);
+	}
+
+	return 0;
+}
+
+static int gen_jump_or_nops(void *target, void *ip, u32 *insns, bool is_call)
+{
+	s64 off = 0;
+	struct jit_ctx ctx;
+
+	ctx.idx = 0;
+	ctx.image = (union loongarch_instruction *)insns;
+
+	if (!target) {
+		emit_insn((&ctx), NOP);
+		emit_insn((&ctx), NOP);
+		return 0;
+	}
+
+	off = (s64)(target - ip);
+	return emit_jump_and_link(&ctx, is_call ? LOONGARCH_GPR_T0 : LOONGARCH_GPR_ZERO,
+					(unsigned long)ip, (unsigned long)target);
+}
+
+int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
+			void *old_addr, void *new_addr)
+{
+	u32 old_insns[5] = {[0 ... 4] = INSN_NOP};
+	u32 new_insns[5] = {[0 ... 4] = INSN_NOP};
+	bool is_call = poke_type == BPF_MOD_CALL;
+	int ret;
+
+	if (!is_kernel_text((unsigned long)ip) &&
+		!is_bpf_text_address((unsigned long)ip))
+		return -ENOTSUPP;
+
+	ret = gen_jump_or_nops(old_addr, ip, old_insns, is_call);
+	if (ret)
+		return ret;
+
+	if (memcmp(ip, old_insns, 5 * 4))
+		return -EFAULT;
+
+	ret = gen_jump_or_nops(new_addr, ip, new_insns, is_call);
+	if (ret)
+		return ret;
+
+	mutex_lock(&text_mutex);
+	if (memcmp(ip, new_insns, 5 * 4))
+		ret = larch_insn_text_copy(ip, new_insns, 5 * 4);
+	mutex_unlock(&text_mutex);
+	return ret;
+}
-- 
2.25.1

Hi Chenghao,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/net]
[also build test WARNING on bpf-next/master bpf/master linus/master v6.16-rc1 next-20250611]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Chenghao-Duan/LoongArch-Support-fixmap/20250611-133843
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git net
patch link:    https://lore.kernel.org/r/20250611053625.352091-4-duanchenghao%40kylinos.cn
patch subject: [PATCH v1 3/5] LoongArch: BPF: Add bpf_arch_text_poke support for Loongarch
config: loongarch-randconfig-002-20250612 (https://download.01.org/0day-ci/archive/20250612/202506120407.Dqc4kJYr-lkp@intel.com/config)
compiler: loongarch64-linux-gcc (GCC) 12.4.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250612/202506120407.Dqc4kJYr-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202506120407.Dqc4kJYr-lkp@intel.com/

All warnings (new ones prefixed by >>):

   arch/loongarch/net/bpf_jit.c: In function 'gen_jump_or_nops':
>> arch/loongarch/net/bpf_jit.c:1380:13: warning: variable 'off' set but not used [-Wunused-but-set-variable]
    1380 |         s64 off = 0;
         |             ^~~


vim +/off +1380 arch/loongarch/net/bpf_jit.c

  1377	
  1378	static int gen_jump_or_nops(void *target, void *ip, u32 *insns, bool is_call)
  1379	{
> 1380		s64 off = 0;
  1381		struct jit_ctx ctx;
  1382	
  1383		ctx.idx = 0;
  1384		ctx.image = (union loongarch_instruction *)insns;
  1385	
  1386		if (!target) {
  1387			emit_insn((&ctx), NOP);
  1388			emit_insn((&ctx), NOP);
  1389			return 0;
  1390		}
  1391	
  1392		off = (s64)(target - ip);
  1393		return emit_jump_and_link(&ctx, is_call ? LOONGARCH_GPR_T0 : LOONGARCH_GPR_ZERO,
  1394						(unsigned long)ip, (unsigned long)target);
  1395	}
  1396	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki