[PATCH bpf-next v3 5/6] bpf: specify the old and new poke_type for bpf_arch_text_poke

Menglong Dong
2025-11-18T12:37:21Z

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>
---
v3:
- fix compile error in powerpc

v2:
- add new function parameter to bpf_arch_text_poke instead of introduce
bpf_arch_text_poke_type()
---
arch/arm64/net/bpf_jit_comp.c | 14 ++++++-------
arch/loongarch/net/bpf_jit.c | 9 +++++---
arch/powerpc/net/bpf_jit_comp.c | 10 +++++----
arch/riscv/net/bpf_jit_comp64.c | 9 +++++---
arch/s390/net/bpf_jit_comp.c | 7 ++++---
arch/x86/net/bpf_jit_comp.c | 37 +++++++++++++++++++--------------
include/linux/bpf.h | 6 ++++--
kernel/bpf/core.c | 5 +++--
kernel/bpf/trampoline.c | 20 ++++++++++++------
9 files changed, 71 insertions(+), 46 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 0c9a50a1e73e..c64df579b7e0 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2923,8 +2923,9 @@ static int gen_branch_or_nop(enum aarch64_insn_branch_type type, void *ip,
* The dummy_tramp is used to prevent another CPU from jumping to unknown
* locations during the patching process, making the patching process easier.
*/
-int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
- 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)
{
int ret;
u32 old_insn;
@@ -2968,14 +2969,13 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
!poking_bpf_entry))
return -EINVAL;

- if (poke_type == BPF_MOD_CALL)
- branch_type = AARCH64_INSN_BRANCH_LINK;
- else
- branch_type = AARCH64_INSN_BRANCH_NOLINK;
-
+ branch_type = old_t == BPF_MOD_CALL ? AARCH64_INSN_BRANCH_LINK :
+ AARCH64_INSN_BRANCH_NOLINK;
if (gen_branch_or_nop(branch_type, ip, old_addr, plt, &old_insn) < 0)
return -EFAULT;

+ branch_type = new_t == BPF_MOD_CALL ? AARCH64_INSN_BRANCH_LINK :
+ AARCH64_INSN_BRANCH_NOLINK;
if (gen_branch_or_nop(branch_type, ip, new_addr, plt, &new_insn) < 0)
return -EFAULT;

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index cbe53d0b7fb0..2e7dacbbef5c 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1284,11 +1284,12 @@ void *bpf_arch_text_copy(void *dst, void *src, size_t len)
return ret ? ERR_PTR(-EINVAL) : dst;
}

-int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
- 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)
{
int ret;
- bool is_call = (poke_type == BPF_MOD_CALL);
+ 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};

@@ -1298,6 +1299,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
if (!is_bpf_text_address((unsigned long)ip))
return -ENOTSUPP;

+ is_call = old_t == BPF_MOD_CALL;
ret = emit_jump_or_nops(old_addr, ip, old_insns, is_call);
if (ret)
return ret;
@@ -1305,6 +1307,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
if (memcmp(ip, old_insns, LOONGARCH_LONG_JUMP_NBYTES))
return -EFAULT;

+ is_call = new_t == BPF_MOD_CALL;
ret = emit_jump_or_nops(new_addr, ip, new_insns, is_call);
if (ret)
return ret;
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 88ad5ba7b87f..5e976730b2f5 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -1107,8 +1107,9 @@ static void do_isync(void *info __maybe_unused)
* execute isync (or some CSI) so that they don't go back into the
* trampoline again.
*/
-int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
- 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)
{
unsigned long bpf_func, bpf_func_end, size, offset;
ppc_inst_t old_inst, new_inst;
@@ -1119,7 +1120,6 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
return -EOPNOTSUPP;

bpf_func = (unsigned long)ip;
- branch_flags = poke_type == BPF_MOD_CALL ? BRANCH_SET_LINK : 0;

/* We currently only support poking bpf programs */
if (!__bpf_address_lookup(bpf_func, &size, &offset, name)) {
@@ -1132,7 +1132,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
* an unconditional branch instruction at im->ip_after_call
*/
if (offset) {
- if (poke_type != BPF_MOD_JUMP) {
+ if (old_t == BPF_MOD_CALL || new_t == BPF_MOD_CALL) {
pr_err("%s (0x%lx): calls are not supported in bpf prog body\n", __func__,
bpf_func);
return -EOPNOTSUPP;
@@ -1166,6 +1166,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
}

old_inst = ppc_inst(PPC_RAW_NOP());
+ branch_flags = old_t == BPF_MOD_CALL ? BRANCH_SET_LINK : 0;
if (old_addr) {
if (is_offset_in_branch_range(ip - old_addr))
create_branch(&old_inst, ip, (unsigned long)old_addr, branch_flags);
@@ -1174,6 +1175,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
branch_flags);
}
new_inst = ppc_inst(PPC_RAW_NOP());
+ branch_flags = new_t == BPF_MOD_CALL ? BRANCH_SET_LINK : 0;
if (new_addr) {
if (is_offset_in_branch_range(ip - new_addr))
create_branch(&new_inst, ip, (unsigned long)new_addr, branch_flags);
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 21c70ae3296b..5f9457e910e8 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -852,17 +852,19 @@ static int gen_jump_or_nops(void *target, void *ip, u32 *insns, bool is_call)
return emit_jump_and_link(is_call ? RV_REG_T0 : RV_REG_ZERO, rvoff, false, &ctx);
}

-int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
- 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)
{
u32 old_insns[RV_FENTRY_NINSNS], new_insns[RV_FENTRY_NINSNS];
- bool is_call = poke_type == BPF_MOD_CALL;
+ bool is_call;
int ret;

if (!is_kernel_text((unsigned long)ip) &&
!is_bpf_text_address((unsigned long)ip))
return -ENOTSUPP;

+ is_call = old_t == BPF_MOD_CALL;
ret = gen_jump_or_nops(old_addr, ip, old_insns, is_call);
if (ret)
return ret;
@@ -870,6 +872,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
if (memcmp(ip, old_insns, RV_FENTRY_NBYTES))
return -EFAULT;

+ is_call = new_t == BPF_MOD_CALL;
ret = gen_jump_or_nops(new_addr, ip, new_insns, is_call);
if (ret)
return ret;
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index cf461d76e9da..a2072cabba76 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -2413,8 +2413,9 @@ bool bpf_jit_supports_far_kfunc_call(void)
return true;
}

-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)
{
struct bpf_plt expected_plt, current_plt, new_plt, *plt;
struct {
@@ -2431,7 +2432,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
if (insn.opc != (0xc004 | (old_addr ? 0xf0 : 0)))
return -EINVAL;

- if (t == BPF_MOD_JUMP &&
+ if ((new_t == BPF_MOD_JUMP || old_t == BPF_MOD_JUMP) &&
insn.disp == ((char *)new_addr - (char *)ip) >> 1) {
/*
* The branch already points to the destination,
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 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
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);
}
}
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4187b7578580..d5e2af29c7c8 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3708,12 +3708,14 @@ static inline u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
#endif /* CONFIG_INET */

enum bpf_text_poke_type {
+ BPF_MOD_NOP,
BPF_MOD_CALL,
BPF_MOD_JUMP,
};

-int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
- void *addr1, void *addr2);
+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);

void bpf_arch_poke_desc_update(struct bpf_jit_poke_descriptor *poke,
struct bpf_prog *new, struct bpf_prog *old);
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index ef4448f18aad..c8ae6ab31651 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -3150,8 +3150,9 @@ int __weak skb_copy_bits(const struct sk_buff *skb, int offset, void *to,
return -EFAULT;
}

-int __weak bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
- void *addr1, void *addr2)
+int __weak 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)
{
return -ENOTSUPP;
}
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 04104397c432..0230ad19533e 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -183,7 +183,8 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
if (tr->func.ftrace_managed)
ret = unregister_ftrace_direct(tr->fops, (long)old_addr, false);
else
- ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
+ ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, BPF_MOD_NOP,
+ old_addr, NULL);

return ret;
}
@@ -200,7 +201,10 @@ static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad
else
ret = modify_ftrace_direct_nolock(tr->fops, (long)new_addr);
} else {
- ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
+ ret = bpf_arch_text_poke(ip,
+ old_addr ? BPF_MOD_CALL : BPF_MOD_NOP,
+ new_addr ? BPF_MOD_CALL : BPF_MOD_NOP,
+ old_addr, new_addr);
}
return ret;
}
@@ -225,7 +229,8 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
return ret;
ret = register_ftrace_direct(tr->fops, (long)new_addr);
} else {
- ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
+ ret = bpf_arch_text_poke(ip, BPF_MOD_NOP, BPF_MOD_CALL,
+ NULL, new_addr);
}

return ret;
@@ -336,8 +341,9 @@ static void bpf_tramp_image_put(struct bpf_tramp_image *im)
* call_rcu_tasks() is not necessary.
*/
if (im->ip_after_call) {
- int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP,
- NULL, im->ip_epilogue);
+ int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_NOP,
+ BPF_MOD_JUMP, NULL,
+ im->ip_epilogue);
WARN_ON(err);
if (IS_ENABLED(CONFIG_TASKS_RCU))
call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
@@ -570,7 +576,8 @@ static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link,
if (err)
return err;
tr->extension_prog = link->link.prog;
- return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
+ return bpf_arch_text_poke(tr->func.addr, BPF_MOD_NOP,
+ BPF_MOD_JUMP, NULL,
link->link.prog->bpf_func);
}
if (cnt >= BPF_MAX_TRAMP_LINKS)
@@ -618,6 +625,7 @@ static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link,
if (kind == BPF_TRAMP_REPLACE) {
WARN_ON_ONCE(!tr->extension_prog);
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
+ BPF_MOD_NOP,
tr->extension_prog->bpf_func, NULL);
tr->extension_prog = NULL;
guard(mutex)(&tgt_prog->aux->ext_mutex);
--
2.51.2