Merge branch 'emit-endbr-bti-instructions-for-indirect'

Xu Kuohai says:

====================
emit ENDBR/BTI instructions for indirect

On architectures with CFI protection enabled that require landing pad
instructions at indirect jump targets, such as x86 with CET/IBT enabled
and arm64 with BTI enabled, kernel panics when an indirect jump lands on
a target without landing pad. Therefore, the JIT must emit landing pad
instructions for indirect jump targets.

The verifier already recognizes which instructions are indirect jump
targets during the verification phase. So we can store this information
in env->insn_aux_data and pass it to the JIT as new parameter, allowing
the JIT to consult env->insn_aux_data to determine which instructions are
indirect jump targets.

During JIT, constants blinding is performed. It rewrites the private copy
of instructions for the JITed program, but it does not adjust the global
env->insn_aux_data array. As a result, after constants blinding, the
instruction indexes used by JIT may no longer match the indexes in
env->insn_aux_data, so the JIT can not use env->insn_aux_data directly.

To avoid this mismatch, and given that all existing arch-specific JITs
already implement constants blinding with largely duplicated code, move
constants blinding from JIT to generic code.

v15:
- Rebase and target bpf tree
- Resotre subprog_start of the fake 'exit' subprog on failure
- Fix wrong function name used in comment

v14: https://lore.kernel.org/all/cover.1776062885.git.xukuohai@hotmail.com/
- Rebase
- Fix comment style
- Fix incorrect variable and function name used in commit message

v13: https://lore.kernel.org/bpf/20260411133847.1042658-1-xukuohai@huaweicloud.com
- Use vmalloc to allocate memory for insn_aux_data copies to match with vfree
- Do not free the copied memory of insn_aux_data when restoring from failure
- Code cleanup

v12: https://lore.kernel.org/bpf/20260403132811.753894-1-xukuohai@huaweicloud.com
- Restore env->insn_aux_data on JIT failure
- Fix incorrect error code sign (-EFAULT vs EFAULT)
- Fix incorrect prog used in the restore path

v11: https://lore.kernel.org/bpf/20260403090915.473493-1-xukuohai@huaweicloud.com
- Restore env->subprog_info after jit_subprogs() fails
- Clear prog->jit_requested and prog->blinding_requested on failure
- Use the actual env->insn_aux_data size in clear_insn_aux_data() on failure

v10: https://lore.kernel.org/bpf/20260324122052.342751-1-xukuohai@huaweicloud.com
- Fix the incorrect call_imm restore in jit_subprogs
- Define a dummy void version of bpf_jit_prog_release_other and
  bpf_patch_insn_data when the corresponding config is not set
- Remove the unnecessary #ifdef in x86_64 JIT (Leon Hwang)

v9: https://lore.kernel.org/bpf/20260312170255.3427799-1-xukuohai@huaweicloud.com
- Make constant blinding available for classic bpf (Eduard)
- Clear prog->bpf_func, prog->jited ... on the error path of extra pass (Eduard)
- Fix spelling errors and remove unused parameter (Anton Protopopov)

v8: https://lore.kernel.org/bpf/20260309140044.2652538-1-xukuohai@huaweicloud.com
- Define void bpf_jit_blind_constants() function when CONFIG_BPF_JIT is not set
- Move indirect_target fixup for insn patching from bpf_jit_blind_constants()
  to adjust_insn_aux_data()

v7: https://lore.kernel.org/bpf/20260307103949.2340104-1-xukuohai@huaweicloud.com
- Move constants blinding logic back to bpf/core.c
- Compute ip address before switch statement in x86 JIT
- Clear JIT state from error path on arm64 and loongarch

v6: https://lore.kernel.org/bpf/20260306102329.2056216-1-xukuohai@huaweicloud.com
- Move constants blinding from JIT to verifier
- Move call to bpf_prog_select_runtime from bpf_prog_load to verifier

v5: https://lore.kernel.org/bpf/20260302102726.1126019-1-xukuohai@huaweicloud.com
- Switch to pass env to JIT directly to get rid of copying private insn_aux_data for
  each prog

v4: https://lore.kernel.org/all/20260114093914.2403982-1-xukuohai@huaweicloud.com
- Switch to the approach proposed by Eduard, using insn_aux_data to identify indirect
  jump targets, and emit ENDBR on x86

v3: https://lore.kernel.org/bpf/20251227081033.240336-1-xukuohai@huaweicloud.com
- Get rid of unnecessary enum definition (Yonghong Song, Anton Protopopov)

v2: https://lore.kernel.org/bpf/20251223085447.139301-1-xukuohai@huaweicloud.com
- Exclude instruction arrays not used for indirect jumps (Anton Protopopov)

v1: https://lore.kernel.org/bpf/20251127140318.3944249-1-xukuohai@huaweicloud.com
====================

Link: https://patch.msgid.link/20260416064341.151802-1-xukuohai@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 55 insertions, 6 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0136a108d083..b4b703c90ca9 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1541,6 +1541,8 @@ bool bpf_has_frame_pointer(unsigned long ip);
 int bpf_jit_charge_modmem(u32 size);
 void bpf_jit_uncharge_modmem(u32 size);
 bool bpf_prog_has_trampoline(const struct bpf_prog *prog);
+bool bpf_insn_is_indirect_target(const struct bpf_verifier_env *env, const struct bpf_prog *prog,
+				 int insn_idx);
 #else
 static inline int bpf_trampoline_link_prog(struct bpf_tramp_link *link,
 					   struct bpf_trampoline *tr,
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 53e8664cb566..b148f816f25b 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -630,16 +630,17 @@ struct bpf_insn_aux_data {
 
 	/* below fields are initialized once */
 	unsigned int orig_idx; /* original instruction index */
-	bool jmp_point;
-	bool prune_point;
+	u32 jmp_point:1;
+	u32 prune_point:1;
 	/* ensure we check state equivalence and save state checkpoint and
 	 * this instruction, regardless of any heuristics
 	 */
-	bool force_checkpoint;
+	u32 force_checkpoint:1;
 	/* true if instruction is a call to a helper function that
 	 * accepts callback function as a parameter.
 	 */
-	bool calls_callback;
+	u32 calls_callback:1;
+	u32 indirect_target:1; /* if it is an indirect jump target */
 	/*
 	 * CFG strongly connected component this instruction belongs to,
 	 * zero if it is a singleton SCC.
diff --git a/include/linux/filter.h b/include/linux/filter.h
index f552170eacf4..1ec6d5ba64cc 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1108,6 +1108,8 @@ sk_filter_reason(struct sock *sk, struct sk_buff *skb)
 	return sk_filter_trim_cap(sk, skb, 1);
 }
 
+struct bpf_prog *__bpf_prog_select_runtime(struct bpf_verifier_env *env, struct bpf_prog *fp,
+					   int *err);
 struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err);
 void bpf_prog_free(struct bpf_prog *fp);
 
@@ -1153,7 +1155,7 @@ u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 	((u64 (*)(u64, u64, u64, u64, u64, const struct bpf_insn *)) \
 	 (void *)__bpf_call_base)
 
-struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog);
+struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_prog *prog);
 void bpf_jit_compile(struct bpf_prog *prog);
 bool bpf_jit_needs_zext(void);
 bool bpf_jit_inlines_helper_call(s32 imm);
@@ -1184,6 +1186,31 @@ static inline bool bpf_dump_raw_ok(const struct cred *cred)
 
 struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
 				       const struct bpf_insn *patch, u32 len);
+
+#ifdef CONFIG_BPF_SYSCALL
+struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off,
+				     const struct bpf_insn *patch, u32 len);
+struct bpf_insn_aux_data *bpf_dup_insn_aux_data(struct bpf_verifier_env *env);
+void bpf_restore_insn_aux_data(struct bpf_verifier_env *env,
+			       struct bpf_insn_aux_data *orig_insn_aux);
+#else
+static inline struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off,
+						   const struct bpf_insn *patch, u32 len)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+
+static inline struct bpf_insn_aux_data *bpf_dup_insn_aux_data(struct bpf_verifier_env *env)
+{
+	return NULL;
+}
+
+static inline void bpf_restore_insn_aux_data(struct bpf_verifier_env *env,
+					     struct bpf_insn_aux_data *orig_insn_aux)
+{
+}
+#endif /* CONFIG_BPF_SYSCALL */
+
 int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt);
 
 static inline bool xdp_return_frame_no_direct(void)
@@ -1310,9 +1337,14 @@ int bpf_jit_get_func_addr(const struct bpf_prog *prog,
 
 const char *bpf_jit_get_prog_name(struct bpf_prog *prog);
 
-struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *fp);
+struct bpf_prog *bpf_jit_blind_constants(struct bpf_verifier_env *env, struct bpf_prog *prog);
 void bpf_jit_prog_release_other(struct bpf_prog *fp, struct bpf_prog *fp_other);
 
+static inline bool bpf_prog_need_blind(const struct bpf_prog *prog)
+{
+	return prog->blinding_requested && !prog->blinded;
+}
+
 static inline void bpf_jit_dump(unsigned int flen, unsigned int proglen,
 				u32 pass, void *image)
 {
@@ -1451,6 +1483,20 @@ static inline void bpf_prog_kallsyms_del(struct bpf_prog *fp)
 {
 }
 
+static inline bool bpf_prog_need_blind(const struct bpf_prog *prog)
+{
+	return false;
+}
+
+static inline
+struct bpf_prog *bpf_jit_blind_constants(struct bpf_verifier_env *env, struct bpf_prog *prog)
+{
+	return prog;
+}
+
+static inline void bpf_jit_prog_release_other(struct bpf_prog *fp, struct bpf_prog *fp_other)
+{
+}
 #endif /* CONFIG_BPF_JIT */
 
 void bpf_prog_kallsyms_del_all(struct bpf_prog *fp);