bpf: specify the old and new poke_type for bpf_arch_text_poke

In the origin logic, the bpf_arch_text_poke() assume that the old and new
instructions have the same opcode. However, they can have different opcode
if we want to replace a "call" insn with a "jmp" insn.

Therefore, add the new function parameter "old_t" along with the "new_t",
which are used to indicate the old and new poke type. Meanwhile, adjust
the implement of bpf_arch_text_poke() for all the archs.

"BPF_MOD_NOP" is added to make the code more readable. In
bpf_arch_text_poke(), we still check if the new and old address is NULL to
determine if nop insn should be used, which I think is more safe.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Link: https://lore.kernel.org/r/20251118123639.688444-6-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 21 insertions, 16 deletions

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 632a83381c2d..b69dc7194e2c 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -597,7 +597,8 @@ static int emit_jump(u8 **pprog, void *func, void *ip)
 	return emit_patch(pprog, func, ip, 0xE9);
 }
 
-static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
+static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
+				enum bpf_text_poke_type new_t,
 				void *old_addr, void *new_addr)
 {
 	const u8 *nop_insn = x86_nops[5];
@@ -607,9 +608,9 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 	int ret;
 
 	memcpy(old_insn, nop_insn, X86_PATCH_SIZE);
-	if (old_addr) {
+	if (old_t != BPF_MOD_NOP && old_addr) {
 		prog = old_insn;
-		ret = t == BPF_MOD_CALL ?
+		ret = old_t == BPF_MOD_CALL ?
 		      emit_call(&prog, old_addr, ip) :
 		      emit_jump(&prog, old_addr, ip);
 		if (ret)
@@ -617,9 +618,9 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 	}
 
 	memcpy(new_insn, nop_insn, X86_PATCH_SIZE);
-	if (new_addr) {
+	if (new_t != BPF_MOD_NOP && new_addr) {
 		prog = new_insn;
-		ret = t == BPF_MOD_CALL ?
+		ret = new_t == BPF_MOD_CALL ?
 		      emit_call(&prog, new_addr, ip) :
 		      emit_jump(&prog, new_addr, ip);
 		if (ret)
@@ -640,8 +641,9 @@ out:
 	return ret;
 }
 
-int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
-		       void *old_addr, void *new_addr)
+int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
+		       enum bpf_text_poke_type new_t, void *old_addr,
+		       void *new_addr)
 {
 	if (!is_kernel_text((long)ip) &&
 	    !is_bpf_text_address((long)ip))
@@ -655,7 +657,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 	if (is_endbr(ip))
 		ip += ENDBR_INSN_SIZE;
 
-	return __bpf_arch_text_poke(ip, t, old_addr, new_addr);
+	return __bpf_arch_text_poke(ip, old_t, new_t, old_addr, new_addr);
 }
 
 #define EMIT_LFENCE()	EMIT3(0x0F, 0xAE, 0xE8)
@@ -897,12 +899,13 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
 		target = array->ptrs[poke->tail_call.key];
 		if (target) {
 			ret = __bpf_arch_text_poke(poke->tailcall_target,
-						   BPF_MOD_JUMP, NULL,
+						   BPF_MOD_NOP, BPF_MOD_JUMP,
+						   NULL,
 						   (u8 *)target->bpf_func +
 						   poke->adj_off);
 			BUG_ON(ret < 0);
 			ret = __bpf_arch_text_poke(poke->tailcall_bypass,
-						   BPF_MOD_JUMP,
+						   BPF_MOD_JUMP, BPF_MOD_NOP,
 						   (u8 *)poke->tailcall_target +
 						   X86_PATCH_SIZE, NULL);
 			BUG_ON(ret < 0);
@@ -3985,6 +3988,7 @@ void bpf_arch_poke_desc_update(struct bpf_jit_poke_descriptor *poke,
 			       struct bpf_prog *new, struct bpf_prog *old)
 {
 	u8 *old_addr, *new_addr, *old_bypass_addr;
+	enum bpf_text_poke_type t;
 	int ret;
 
 	old_bypass_addr = old ? NULL : poke->bypass_addr;
@@ -3997,21 +4001,22 @@ void bpf_arch_poke_desc_update(struct bpf_jit_poke_descriptor *poke,
 	 * the kallsyms check.
 	 */
 	if (new) {
+		t = old_addr ? BPF_MOD_JUMP : BPF_MOD_NOP;
 		ret = __bpf_arch_text_poke(poke->tailcall_target,
-					   BPF_MOD_JUMP,
+					   t, BPF_MOD_JUMP,
 					   old_addr, new_addr);
 		BUG_ON(ret < 0);
 		if (!old) {
 			ret = __bpf_arch_text_poke(poke->tailcall_bypass,
-						   BPF_MOD_JUMP,
+						   BPF_MOD_JUMP, BPF_MOD_NOP,
 						   poke->bypass_addr,
 						   NULL);
 			BUG_ON(ret < 0);
 		}
 	} else {
+		t = old_bypass_addr ? BPF_MOD_JUMP : BPF_MOD_NOP;
 		ret = __bpf_arch_text_poke(poke->tailcall_bypass,
-					   BPF_MOD_JUMP,
-					   old_bypass_addr,
+					   t, BPF_MOD_JUMP, old_bypass_addr,
 					   poke->bypass_addr);
 		BUG_ON(ret < 0);
 		/* let other CPUs finish the execution of program
@@ -4020,9 +4025,9 @@ void bpf_arch_poke_desc_update(struct bpf_jit_poke_descriptor *poke,
 		 */
 		if (!ret)
 			synchronize_rcu();
+		t = old_addr ? BPF_MOD_JUMP : BPF_MOD_NOP;
 		ret = __bpf_arch_text_poke(poke->tailcall_target,
-					   BPF_MOD_JUMP,
-					   old_addr, NULL);
+					   t, BPF_MOD_NOP, old_addr, NULL);
 		BUG_ON(ret < 0);
 	}
 }