Merge branch 'exceptions-1-2'

Kumar Kartikeya Dwivedi says:

====================
Exceptions - 1/2

This series implements the _first_ part of the runtime and verifier
support needed to enable BPF exceptions. Exceptions thrown from programs
are processed as an immediate exit from the program, which unwinds all
the active stack frames until the main stack frame, and returns to the
BPF program's caller. The ability to perform this unwinding safely
allows the program to test conditions that are always true at runtime
but which the verifier has no visibility into.

Thus, it also reduces verification effort by safely terminating
redundant paths that can be taken within a program.

The patches to perform runtime resource cleanup during the
frame-by-frame unwinding will be posted as a follow-up to this set.

It must be noted that exceptions are not an error handling mechanism for
unlikely runtime conditions, but a way to safely terminate the execution
of a program in presence of conditions that should never occur at
runtime. They are meant to serve higher-level primitives such as program
assertions.

The following kfuncs and macros are introduced:

Assertion macros are also introduced, please see patch 13 for their
documentation.

/* Description
 *	Throw a BPF exception from the program, immediately terminating its
 *	execution and unwinding the stack. The supplied 'cookie' parameter
 *	will be the return value of the program when an exception is thrown,
 *	and the default exception callback is used. Otherwise, if an exception
 *	callback is set using the '__exception_cb(callback)' declaration tag
 *	on the main program, the 'cookie' parameter will be the callback's only
 *	input argument.
 *
 *	Thus, in case of default exception callback, 'cookie' is subjected to
 *	constraints on the program's return value (as with R0 on exit).
 *	Otherwise, the return value of the marked exception callback will be
 *	subjected to the same checks.
 *
 *	Note that throwing an exception with lingering resources (locks,
 *	references, etc.) will lead to a verification error.
 *
 *	Note that callbacks *cannot* call this helper.
 * Returns
 *	Never.
 * Throws
 *	An exception with the specified 'cookie' value.
 */
extern void bpf_throw(u64 cookie) __ksym;

/* This macro must be used to mark the exception callback corresponding to the
 * main program. For example:
 *
 * int exception_cb(u64 cookie) {
 *	return cookie;
 * }
 *
 * SEC("tc")
 * __exception_cb(exception_cb)
 * int main_prog(struct __sk_buff *ctx) {
 *	...
 *	return TC_ACT_OK;
 * }
 *
 * Here, exception callback for the main program will be 'exception_cb'. Note
 * that this attribute can only be used once, and multiple exception callbacks
 * specified for the main program will lead to verification error.
 */
\#define __exception_cb(name) __attribute__((btf_decl_tag("exception_callback:" #name)))

As such, a program can only install an exception handler once for the
lifetime of a BPF program, and this handler cannot be changed at
runtime. The purpose of the handler is to simply interpret the cookie
value supplied by the bpf_throw call, and execute user-defined logic
corresponding to it. The primary purpose of allowing a handler is to
control the return value of the program. The default handler returns the
cookie value passed to bpf_throw when an exception is thrown.

Fixing the handler for the lifetime of the program eliminates tricky and
expensive handling in case of runtime changes of the handler callback
when programs begin to nest, where it becomes more complex to save and
restore the active handler at runtime.

This version of offline unwinding based BPF exceptions is truly zero
overhead, with the exception of generation of a default callback which
contains a few instructions to return a default return value (0) when no
exception callback is supplied by the user.

Callbacks are disallowed from throwing BPF exceptions for now, since
such exceptions need to cross the callback helper boundary (and
therefore must care about unwinding kernel state), however it is
possible to lift this restriction in the future follow-up.

Exceptions terminate propogating at program boundaries, hence both
BPF_PROG_TYPE_EXT and tail call targets return to their caller context
the return value of the exception callback, in the event that they throw
an exception. Thus, exceptions do not cross extension or tail call
boundary.

However, this is mostly an implementation choice, and can be changed to
suit more user-friendly semantics.

Changelog:
----------
v2 -> v3
v2: https://lore.kernel.org/bpf/20230809114116.3216687-1-memxor@gmail.com

 * Add Dave's Acked-by.
 * Address all comments from Alexei.
   * Use bpf_is_subprog to check for main prog in bpf_stack_walker.
   * Drop accidental leftover hunk in libbpf patch.
   * Split libbpf patch's refactoring to aid review
   * Disable fentry/fexit in addition to freplace for exception cb.
   * Add selftests for fentry/fexit/freplace on exception cb and main prog.
 * Use btf_find_by_name_kind in bpf_find_exception_callback_insn_off (Martin)
 * Split KASAN patch into two to aid backporting (Andrey)
 * Move exception callback append step to bpf_object__reloacte (Andrii)
 * Ensure that the exception callback name is unique (Andrii)
 * Keep ASM implementation of assertion macros instead of C, as it does
   not achieve intended results for bpf_assert_range and other cases.

v1 -> v2
v1: https://lore.kernel.org/bpf/20230713023232.1411523-1-memxor@gmail.com

 * Address all comments from Alexei.
 * Fix a few bugs and corner cases in the implementations found during
   testing. Also add new selftests for these cases.
 * Reinstate patch to consider ksym.end part of the program (but
   reworked to cover other corner cases).
 * Implement new style of tagging exception callbacks, add libbpf
   support for the new declaration tag.
 * Limit support to 64-bit integer types for assertion macros. The
   compiler ends up performing shifts or bitwise and operations when
   finally making use of the value, which defeats the purpose of the
   macro. On noalu32 mode, the shifts may also happen before use,
   hurting reliability.
 * Comprehensively test assertion macros and their side effects on the
   verifier state, register bounds, etc.
 * Fix a KASAN false positive warning.

RFC v1 -> v1
RFC v1: https://lore.kernel.org/bpf/20230405004239.1375399-1-memxor@gmail.com

 * Completely rework the unwinding infrastructure to use offline
   unwinding support.
 * Remove the runtime exception state and program rewriting code.
 * Make bpf_set_exception_callback idempotent to avoid vexing
   synchronization and state clobbering issues in presence of program
   nesting.
 * Disable bpf_throw within callback functions, for now.
 * Allow bpf_throw in tail call programs and extension programs,
   removing limitations of rewrite based unwinding.
 * Expand selftests.
====================

Link: https://lore.kernel.org/r/20230912233214.1518551-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

5 files changed, 473 insertions, 83 deletions

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 187b57276fec..f93e835d90af 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3310,10 +3310,10 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
 	return BTF_FIELD_FOUND;
 }
 
-static const char *btf_find_decl_tag_value(const struct btf *btf,
-					   const struct btf_type *pt,
-					   int comp_idx, const char *tag_key)
+const char *btf_find_decl_tag_value(const struct btf *btf, const struct btf_type *pt,
+				    int comp_idx, const char *tag_key)
 {
+	const char *value = NULL;
 	int i;
 
 	for (i = 1; i < btf_nr_types(btf); i++) {
@@ -3327,9 +3327,14 @@ static const char *btf_find_decl_tag_value(const struct btf *btf,
 			continue;
 		if (strncmp(__btf_name_by_offset(btf, t->name_off), tag_key, len))
 			continue;
-		return __btf_name_by_offset(btf, t->name_off) + len;
+		/* Prevent duplicate entries for same type */
+		if (value)
+			return ERR_PTR(-EEXIST);
+		value = __btf_name_by_offset(btf, t->name_off) + len;
 	}
-	return NULL;
+	if (!value)
+		return ERR_PTR(-ENOENT);
+	return value;
 }
 
 static int
@@ -3347,7 +3352,7 @@ btf_find_graph_root(const struct btf *btf, const struct btf_type *pt,
 	if (t->size != sz)
 		return BTF_FIELD_IGNORE;
 	value_type = btf_find_decl_tag_value(btf, pt, comp_idx, "contains:");
-	if (!value_type)
+	if (IS_ERR(value_type))
 		return -EINVAL;
 	node_field_name = strstr(value_type, ":");
 	if (!node_field_name)
@@ -6954,7 +6959,7 @@ int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
  * (either PTR_TO_CTX or SCALAR_VALUE).
  */
 int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
-			  struct bpf_reg_state *regs)
+			  struct bpf_reg_state *regs, bool is_ex_cb)
 {
 	struct bpf_verifier_log *log = &env->log;
 	struct bpf_prog *prog = env->prog;
@@ -7011,7 +7016,7 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
 			tname, nargs, MAX_BPF_FUNC_REG_ARGS);
 		return -EINVAL;
 	}
-	/* check that function returns int */
+	/* check that function returns int, exception cb also requires this */
 	t = btf_type_by_id(btf, t->type);
 	while (btf_type_is_modifier(t))
 		t = btf_type_by_id(btf, t->type);
@@ -7060,6 +7065,14 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
 			i, btf_type_str(t), tname);
 		return -EINVAL;
 	}
+	/* We have already ensured that the callback returns an integer, just
+	 * like all global subprogs. We need to determine it only has a single
+	 * scalar argument.
+	 */
+	if (is_ex_cb && (nargs != 1 || regs[BPF_REG_1].type != SCALAR_VALUE)) {
+		bpf_log(log, "exception cb only supports single integer argument\n");
+		return -EINVAL;
+	}
 	return 0;
 }
 
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 95599df82ee4..8f921b6d6981 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -212,7 +212,7 @@ void bpf_prog_fill_jited_linfo(struct bpf_prog *prog,
 	const struct bpf_line_info *linfo;
 	void **jited_linfo;
 
-	if (!prog->aux->jited_linfo)
+	if (!prog->aux->jited_linfo || prog->aux->func_idx > prog->aux->func_cnt)
 		/* Userspace did not provide linfo */
 		return;
 
@@ -539,7 +539,7 @@ static void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp)
 {
 	int i;
 
-	for (i = 0; i < fp->aux->func_cnt; i++)
+	for (i = 0; i < fp->aux->real_func_cnt; i++)
 		bpf_prog_kallsyms_del(fp->aux->func[i]);
 }
 
@@ -589,7 +589,7 @@ bpf_prog_ksym_set_name(struct bpf_prog *prog)
 	sym  = bin2hex(sym, prog->tag, sizeof(prog->tag));
 
 	/* prog->aux->name will be ignored if full btf name is available */
-	if (prog->aux->func_info_cnt) {
+	if (prog->aux->func_info_cnt && prog->aux->func_idx < prog->aux->func_info_cnt) {
 		type = btf_type_by_id(prog->aux->btf,
 				      prog->aux->func_info[prog->aux->func_idx].type_id);
 		func_name = btf_name_by_offset(prog->aux->btf, type->name_off);
@@ -623,7 +623,11 @@ static __always_inline int bpf_tree_comp(void *key, struct latch_tree_node *n)
 
 	if (val < ksym->start)
 		return -1;
-	if (val >= ksym->end)
+	/* Ensure that we detect return addresses as part of the program, when
+	 * the final instruction is a call for a program part of the stack
+	 * trace. Therefore, do val > ksym->end instead of val >= ksym->end.
+	 */
+	if (val > ksym->end)
 		return  1;
 
 	return 0;
@@ -733,7 +737,7 @@ bool is_bpf_text_address(unsigned long addr)
 	return ret;
 }
 
-static struct bpf_prog *bpf_prog_ksym_find(unsigned long addr)
+struct bpf_prog *bpf_prog_ksym_find(unsigned long addr)
 {
 	struct bpf_ksym *ksym = bpf_ksym_find(addr);
 
@@ -1208,7 +1212,7 @@ int bpf_jit_get_func_addr(const struct bpf_prog *prog,
 		if (!extra_pass)
 			addr = NULL;
 		else if (prog->aux->func &&
-			 off >= 0 && off < prog->aux->func_cnt)
+			 off >= 0 && off < prog->aux->real_func_cnt)
 			addr = (u8 *)prog->aux->func[off]->bpf_func;
 		else
 			return -EINVAL;
@@ -2721,7 +2725,7 @@ static void bpf_prog_free_deferred(struct work_struct *work)
 #endif
 	if (aux->dst_trampoline)
 		bpf_trampoline_put(aux->dst_trampoline);
-	for (i = 0; i < aux->func_cnt; i++) {
+	for (i = 0; i < aux->real_func_cnt; i++) {
 		/* We can just unlink the subprog poke descriptor table as
 		 * it was originally linked to the main program and is also
 		 * released along with it.
@@ -2729,7 +2733,7 @@ static void bpf_prog_free_deferred(struct work_struct *work)
 		aux->func[i]->aux->poke_tab = NULL;
 		bpf_jit_free(aux->func[i]);
 	}
-	if (aux->func_cnt) {
+	if (aux->real_func_cnt) {
 		kfree(aux->func);
 		bpf_prog_unlock_free(aux->prog);
 	} else {
@@ -2914,6 +2918,15 @@ int __weak bpf_arch_text_invalidate(void *dst, size_t len)
 	return -ENOTSUPP;
 }
 
+bool __weak bpf_jit_supports_exceptions(void)
+{
+	return false;
+}
+
+void __weak arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, u64 bp), void *cookie)
+{
+}
+
 #ifdef CONFIG_BPF_SYSCALL
 static int __init bpf_global_ma_init(void)
 {
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index b0a9834f1051..7ff2a42f1996 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -22,6 +22,7 @@
 #include <linux/security.h>
 #include <linux/btf_ids.h>
 #include <linux/bpf_mem_alloc.h>
+#include <linux/kasan.h>
 
 #include "../../lib/kstrtox.h"
 
@@ -2449,6 +2450,49 @@ __bpf_kfunc void bpf_rcu_read_unlock(void)
 	rcu_read_unlock();
 }
 
+struct bpf_throw_ctx {
+	struct bpf_prog_aux *aux;
+	u64 sp;
+	u64 bp;
+	int cnt;
+};
+
+static bool bpf_stack_walker(void *cookie, u64 ip, u64 sp, u64 bp)
+{
+	struct bpf_throw_ctx *ctx = cookie;
+	struct bpf_prog *prog;
+
+	if (!is_bpf_text_address(ip))
+		return !ctx->cnt;
+	prog = bpf_prog_ksym_find(ip);
+	ctx->cnt++;
+	if (bpf_is_subprog(prog))
+		return true;
+	ctx->aux = prog->aux;
+	ctx->sp = sp;
+	ctx->bp = bp;
+	return false;
+}
+
+__bpf_kfunc void bpf_throw(u64 cookie)
+{
+	struct bpf_throw_ctx ctx = {};
+
+	arch_bpf_stack_walk(bpf_stack_walker, &ctx);
+	WARN_ON_ONCE(!ctx.aux);
+	if (ctx.aux)
+		WARN_ON_ONCE(!ctx.aux->exception_boundary);
+	WARN_ON_ONCE(!ctx.bp);
+	WARN_ON_ONCE(!ctx.cnt);
+	/* Prevent KASAN false positives for CONFIG_KASAN_STACK by unpoisoning
+	 * deeper stack depths than ctx.sp as we do not return from bpf_throw,
+	 * which skips compiler generated instrumentation to do the same.
+	 */
+	kasan_unpoison_task_stack_below((void *)ctx.sp);
+	ctx.aux->bpf_exception_cb(cookie, ctx.sp, ctx.bp);
+	WARN(1, "A call to BPF exception callback should never return\n");
+}
+
 __diag_pop();
 
 BTF_SET8_START(generic_btf_ids)
@@ -2478,6 +2522,7 @@ BTF_ID_FLAGS(func, bpf_cgroup_from_id, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_throw)
 BTF_SET8_END(generic_btf_ids)
 
 static const struct btf_kfunc_id_set generic_kfunc_set = {
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6a692f3bea15..85c1d908f70f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2749,7 +2749,7 @@ free_used_maps:
 	 * period before we can tear down JIT memory since symbols
 	 * are already exposed under kallsyms.
 	 */
-	__bpf_prog_put_noref(prog, prog->aux->func_cnt);
+	__bpf_prog_put_noref(prog, prog->aux->real_func_cnt);
 	return err;
 free_prog_sec:
 	free_uid(prog->aux->user);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 18e673c0ac15..a7178ecf676d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -543,6 +543,7 @@ static bool is_dynptr_ref_function(enum bpf_func_id func_id)
 }
 
 static bool is_callback_calling_kfunc(u32 btf_id);
+static bool is_bpf_throw_kfunc(struct bpf_insn *insn);
 
 static bool is_callback_calling_function(enum bpf_func_id func_id)
 {
@@ -1748,7 +1749,9 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state,
 		return -ENOMEM;
 	dst_state->jmp_history_cnt = src->jmp_history_cnt;
 
-	/* if dst has more stack frames then src frame, free them */
+	/* if dst has more stack frames then src frame, free them, this is also
+	 * necessary in case of exceptional exits using bpf_throw.
+	 */
 	for (i = src->curframe + 1; i <= dst_state->curframe; i++) {
 		free_func_state(dst_state->frame[i]);
 		dst_state->frame[i] = NULL;
@@ -2454,6 +2457,68 @@ static int add_subprog(struct bpf_verifier_env *env, int off)
 	return env->subprog_cnt - 1;
 }
 
+static int bpf_find_exception_callback_insn_off(struct bpf_verifier_env *env)
+{
+	struct bpf_prog_aux *aux = env->prog->aux;
+	struct btf *btf = aux->btf;
+	const struct btf_type *t;
+	u32 main_btf_id, id;
+	const char *name;
+	int ret, i;
+
+	/* Non-zero func_info_cnt implies valid btf */
+	if (!aux->func_info_cnt)
+		return 0;
+	main_btf_id = aux->func_info[0].type_id;
+
+	t = btf_type_by_id(btf, main_btf_id);
+	if (!t) {
+		verbose(env, "invalid btf id for main subprog in func_info\n");
+		return -EINVAL;
+	}
+
+	name = btf_find_decl_tag_value(btf, t, -1, "exception_callback:");
+	if (IS_ERR(name)) {
+		ret = PTR_ERR(name);
+		/* If there is no tag present, there is no exception callback */
+		if (ret == -ENOENT)
+			ret = 0;
+		else if (ret == -EEXIST)
+			verbose(env, "multiple exception callback tags for main subprog\n");
+		return ret;
+	}
+
+	ret = btf_find_by_name_kind(btf, name, BTF_KIND_FUNC);
+	if (ret < 0) {
+		verbose(env, "exception callback '%s' could not be found in BTF\n", name);
+		return ret;
+	}
+	id = ret;
+	t = btf_type_by_id(btf, id);
+	if (btf_func_linkage(t) != BTF_FUNC_GLOBAL) {
+		verbose(env, "exception callback '%s' must have global linkage\n", name);
+		return -EINVAL;
+	}
+	ret = 0;
+	for (i = 0; i < aux->func_info_cnt; i++) {
+		if (aux->func_info[i].type_id != id)
+			continue;
+		ret = aux->func_info[i].insn_off;
+		/* Further func_info and subprog checks will also happen
+		 * later, so assume this is the right insn_off for now.
+		 */
+		if (!ret) {
+			verbose(env, "invalid exception callback insn_off in func_info: 0\n");
+			ret = -EINVAL;
+		}
+	}
+	if (!ret) {
+		verbose(env, "exception callback type id not found in func_info\n");
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
 #define MAX_KFUNC_DESCS 256
 #define MAX_KFUNC_BTFS	256
 
@@ -2793,8 +2858,8 @@ bpf_jit_find_kfunc_model(const struct bpf_prog *prog,
 static int add_subprog_and_kfunc(struct bpf_verifier_env *env)
 {
 	struct bpf_subprog_info *subprog = env->subprog_info;
+	int i, ret, insn_cnt = env->prog->len, ex_cb_insn;
 	struct bpf_insn *insn = env->prog->insnsi;
-	int i, ret, insn_cnt = env->prog->len;
 
 	/* Add entry function. */
 	ret = add_subprog(env, 0);
@@ -2820,6 +2885,26 @@ static int add_subprog_and_kfunc(struct bpf_verifier_env *env)
 			return ret;
 	}
 
+	ret = bpf_find_exception_callback_insn_off(env);
+	if (ret < 0)
+		return ret;
+	ex_cb_insn = ret;
+
+	/* If ex_cb_insn > 0, this means that the main program has a subprog
+	 * marked using BTF decl tag to serve as the exception callback.
+	 */
+	if (ex_cb_insn) {
+		ret = add_subprog(env, ex_cb_insn);
+		if (ret < 0)
+			return ret;
+		for (i = 1; i < env->subprog_cnt; i++) {
+			if (env->subprog_info[i].start != ex_cb_insn)
+				continue;
+			env->exception_callback_subprog = i;
+			break;
+		}
+	}
+
 	/* Add a fake 'exit' subprog which could simplify subprog iteration
 	 * logic. 'subprog_cnt' should not be increased.
 	 */
@@ -2868,7 +2953,7 @@ next:
 		if (i == subprog_end - 1) {
 			/* to avoid fall-through from one subprog into another
 			 * the last insn of the subprog should be either exit
-			 * or unconditional jump back
+			 * or unconditional jump back or bpf_throw call
 			 */
 			if (code != (BPF_JMP | BPF_EXIT) &&
 			    code != (BPF_JMP32 | BPF_JA) &&
@@ -5661,6 +5746,27 @@ continue_func:
 	for (; i < subprog_end; i++) {
 		int next_insn, sidx;
 
+		if (bpf_pseudo_kfunc_call(insn + i) && !insn[i].off) {
+			bool err = false;
+
+			if (!is_bpf_throw_kfunc(insn + i))
+				continue;
+			if (subprog[idx].is_cb)
+				err = true;
+			for (int c = 0; c < frame && !err; c++) {
+				if (subprog[ret_prog[c]].is_cb) {
+					err = true;
+					break;
+				}
+			}
+			if (!err)
+				continue;
+			verbose(env,
+				"bpf_throw kfunc (insn %d) cannot be called from callback subprog %d\n",
+				i, idx);
+			return -EINVAL;
+		}
+
 		if (!bpf_pseudo_call(insn + i) && !bpf_pseudo_func(insn + i))
 			continue;
 		/* remember insn and function to return to */
@@ -5683,6 +5789,10 @@ continue_func:
 			/* async callbacks don't increase bpf prog stack size unless called directly */
 			if (!bpf_pseudo_call(insn + i))
 				continue;
+			if (subprog[sidx].is_exception_cb) {
+				verbose(env, "insn %d cannot call exception cb directly\n", i);
+				return -EINVAL;
+			}
 		}
 		i = next_insn;
 		idx = sidx;
@@ -5704,8 +5814,13 @@ continue_func:
 	 * tail call counter throughout bpf2bpf calls combined with tailcalls
 	 */
 	if (tail_call_reachable)
-		for (j = 0; j < frame; j++)
+		for (j = 0; j < frame; j++) {
+			if (subprog[ret_prog[j]].is_exception_cb) {
+				verbose(env, "cannot tail call within exception cb\n");
+				return -EINVAL;
+			}
 			subprog[ret_prog[j]].tail_call_reachable = true;
+		}
 	if (subprog[0].tail_call_reachable)
 		env->prog->aux->tail_call_reachable = true;
 
@@ -8919,6 +9034,7 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	 * callbacks
 	 */
 	if (set_callee_state_cb != set_callee_state) {
+		env->subprog_info[subprog].is_cb = true;
 		if (bpf_pseudo_kfunc_call(insn) &&
 		    !is_callback_calling_kfunc(insn->imm)) {
 			verbose(env, "verifier bug: kfunc %s#%d not marked as callback-calling\n",
@@ -9308,7 +9424,8 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
 		verbose(env, "to caller at %d:\n", *insn_idx);
 		print_verifier_state(env, caller, true);
 	}
-	/* clear everything in the callee */
+	/* clear everything in the callee. In case of exceptional exits using
+	 * bpf_throw, this will be done by copy_verifier_state for extra frames. */
 	free_func_state(callee);
 	state->frame[state->curframe--] = NULL;
 	return 0;
@@ -9432,17 +9549,17 @@ record_func_key(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
 	return 0;
 }
 
-static int check_reference_leak(struct bpf_verifier_env *env)
+static int check_reference_leak(struct bpf_verifier_env *env, bool exception_exit)
 {
 	struct bpf_func_state *state = cur_func(env);
 	bool refs_lingering = false;
 	int i;
 
-	if (state->frameno && !state->in_callback_fn)
+	if (!exception_exit && state->frameno && !state->in_callback_fn)
 		return 0;
 
 	for (i = 0; i < state->acquired_refs; i++) {
-		if (state->in_callback_fn && state->refs[i].callback_ref != state->frameno)
+		if (!exception_exit && state->in_callback_fn && state->refs[i].callback_ref != state->frameno)
 			continue;
 		verbose(env, "Unreleased reference id=%d alloc_insn=%d\n",
 			state->refs[i].id, state->refs[i].insn_idx);
@@ -9697,7 +9814,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 
 	switch (func_id) {
 	case BPF_FUNC_tail_call:
-		err = check_reference_leak(env);
+		err = check_reference_leak(env, false);
 		if (err) {
 			verbose(env, "tail_call would lead to reference leak\n");
 			return err;
@@ -10332,6 +10449,7 @@ enum special_kfunc_type {
 	KF_bpf_dynptr_clone,
 	KF_bpf_percpu_obj_new_impl,
 	KF_bpf_percpu_obj_drop_impl,
+	KF_bpf_throw,
 };
 
 BTF_SET_START(special_kfunc_set)
@@ -10354,6 +10472,7 @@ BTF_ID(func, bpf_dynptr_slice_rdwr)
 BTF_ID(func, bpf_dynptr_clone)
 BTF_ID(func, bpf_percpu_obj_new_impl)
 BTF_ID(func, bpf_percpu_obj_drop_impl)
+BTF_ID(func, bpf_throw)
 BTF_SET_END(special_kfunc_set)
 
 BTF_ID_LIST(special_kfunc_list)
@@ -10378,6 +10497,7 @@ BTF_ID(func, bpf_dynptr_slice_rdwr)
 BTF_ID(func, bpf_dynptr_clone)
 BTF_ID(func, bpf_percpu_obj_new_impl)
 BTF_ID(func, bpf_percpu_obj_drop_impl)
+BTF_ID(func, bpf_throw)
 
 static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
 {
@@ -10695,6 +10815,12 @@ static bool is_callback_calling_kfunc(u32 btf_id)
 	return btf_id == special_kfunc_list[KF_bpf_rbtree_add_impl];
 }
 
+static bool is_bpf_throw_kfunc(struct bpf_insn *insn)
+{
+	return bpf_pseudo_kfunc_call(insn) && insn->off == 0 &&
+	       insn->imm == special_kfunc_list[KF_bpf_throw];
+}
+
 static bool is_rbtree_lock_required_kfunc(u32 btf_id)
 {
 	return is_bpf_rbtree_api_kfunc(btf_id);
@@ -11281,6 +11407,10 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 			break;
 		}
 		case KF_ARG_PTR_TO_CALLBACK:
+			if (reg->type != PTR_TO_FUNC) {
+				verbose(env, "arg%d expected pointer to func\n", i);
+				return -EINVAL;
+			}
 			meta->subprogno = reg->subprogno;
 			break;
 		case KF_ARG_PTR_TO_REFCOUNTED_KPTR:
@@ -11359,6 +11489,8 @@ static int fetch_kfunc_meta(struct bpf_verifier_env *env,
 	return 0;
 }
 
+static int check_return_code(struct bpf_verifier_env *env, int regno);
+
 static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			    int *insn_idx_p)
 {
@@ -11480,6 +11612,24 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		}
 	}
 
+	if (meta.func_id == special_kfunc_list[KF_bpf_throw]) {
+		if (!bpf_jit_supports_exceptions()) {
+			verbose(env, "JIT does not support calling kfunc %s#%d\n",
+				func_name, meta.func_id);
+			return -ENOTSUPP;
+		}
+		env->seen_exception = true;
+
+		/* In the case of the default callback, the cookie value passed
+		 * to bpf_throw becomes the return value of the program.
+		 */
+		if (!env->exception_callback_subprog) {
+			err = check_return_code(env, BPF_REG_1);
+			if (err < 0)
+				return err;
+		}
+	}
+
 	for (i = 0; i < CALLER_SAVED_REGS; i++)
 		mark_reg_not_init(env, regs, caller_saved[i]);
 
@@ -14525,7 +14675,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	 * gen_ld_abs() may terminate the program at runtime, leading to
 	 * reference leak.
 	 */
-	err = check_reference_leak(env);
+	err = check_reference_leak(env, false);
 	if (err) {
 		verbose(env, "BPF_LD_[ABS|IND] cannot be mixed with socket references\n");
 		return err;
@@ -14574,7 +14724,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	return 0;
 }
 
-static int check_return_code(struct bpf_verifier_env *env)
+static int check_return_code(struct bpf_verifier_env *env, int regno)
 {
 	struct tnum enforce_attach_type_range = tnum_unknown;
 	const struct bpf_prog *prog = env->prog;
@@ -14586,7 +14736,7 @@ static int check_return_code(struct bpf_verifier_env *env)
 	const bool is_subprog = frame->subprogno;
 
 	/* LSM and struct_ops func-ptr's return type could be "void" */
-	if (!is_subprog) {
+	if (!is_subprog || frame->in_exception_callback_fn) {
 		switch (prog_type) {
 		case BPF_PROG_TYPE_LSM:
 			if (prog->expected_attach_type == BPF_LSM_CGROUP)
@@ -14608,22 +14758,22 @@ static int check_return_code(struct bpf_verifier_env *env)
 	 * of bpf_exit, which means that program wrote
 	 * something into it earlier
 	 */
-	err = check_reg_arg(env, BPF_REG_0, SRC_OP);
+	err = check_reg_arg(env, regno, SRC_OP);
 	if (err)
 		return err;
 
-	if (is_pointer_value(env, BPF_REG_0)) {
-		verbose(env, "R0 leaks addr as return value\n");
+	if (is_pointer_value(env, regno)) {
+		verbose(env, "R%d leaks addr as return value\n", regno);
 		return -EACCES;
 	}
 
-	reg = cur_regs(env) + BPF_REG_0;
+	reg = cur_regs(env) + regno;
 
 	if (frame->in_async_callback_fn) {
 		/* enforce return zero from async callbacks like timer */
 		if (reg->type != SCALAR_VALUE) {
-			verbose(env, "In async callback the register R0 is not a known value (%s)\n",
-				reg_type_str(env, reg->type));
+			verbose(env, "In async callback the register R%d is not a known value (%s)\n",
+				regno, reg_type_str(env, reg->type));
 			return -EINVAL;
 		}
 
@@ -14634,10 +14784,10 @@ static int check_return_code(struct bpf_verifier_env *env)
 		return 0;
 	}
 
-	if (is_subprog) {
+	if (is_subprog && !frame->in_exception_callback_fn) {
 		if (reg->type != SCALAR_VALUE) {
-			verbose(env, "At subprogram exit the register R0 is not a scalar value (%s)\n",
-				reg_type_str(env, reg->type));
+			verbose(env, "At subprogram exit the register R%d is not a scalar value (%s)\n",
+				regno, reg_type_str(env, reg->type));
 			return -EINVAL;
 		}
 		return 0;
@@ -14719,8 +14869,8 @@ static int check_return_code(struct bpf_verifier_env *env)
 	}
 
 	if (reg->type != SCALAR_VALUE) {
-		verbose(env, "At program exit the register R0 is not a known value (%s)\n",
-			reg_type_str(env, reg->type));
+		verbose(env, "At program exit the register R%d is not a known value (%s)\n",
+			regno, reg_type_str(env, reg->type));
 		return -EINVAL;
 	}
 
@@ -14991,8 +15141,8 @@ static int check_cfg(struct bpf_verifier_env *env)
 {
 	int insn_cnt = env->prog->len;
 	int *insn_stack, *insn_state;
-	int ret = 0;
-	int i;
+	int ex_insn_beg, i, ret = 0;
+	bool ex_done = false;
 
 	insn_state = env->cfg.insn_state = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
 	if (!insn_state)
@@ -15008,6 +15158,7 @@ static int check_cfg(struct bpf_verifier_env *env)
 	insn_stack[0] = 0; /* 0 is the first instruction */
 	env->cfg.cur_stack = 1;
 
+walk_cfg:
 	while (env->cfg.cur_stack > 0) {
 		int t = insn_stack[env->cfg.cur_stack - 1];
 
@@ -15034,6 +15185,16 @@ static int check_cfg(struct bpf_verifier_env *env)
 		goto err_free;
 	}
 
+	if (env->exception_callback_subprog && !ex_done) {
+		ex_insn_beg = env->subprog_info[env->exception_callback_subprog].start;
+
+		insn_state[ex_insn_beg] = DISCOVERED;
+		insn_stack[0] = ex_insn_beg;
+		env->cfg.cur_stack = 1;
+		ex_done = true;
+		goto walk_cfg;
+	}
+
 	for (i = 0; i < insn_cnt; i++) {
 		if (insn_state[i] != EXPLORED) {
 			verbose(env, "unreachable insn %d\n", i);
@@ -15071,20 +15232,18 @@ static int check_abnormal_return(struct bpf_verifier_env *env)
 #define MIN_BPF_FUNCINFO_SIZE	8
 #define MAX_FUNCINFO_REC_SIZE	252
 
-static int check_btf_func(struct bpf_verifier_env *env,
-			  const union bpf_attr *attr,
-			  bpfptr_t uattr)
+static int check_btf_func_early(struct bpf_verifier_env *env,
+				const union bpf_attr *attr,
+				bpfptr_t uattr)
 {
-	const struct btf_type *type, *func_proto, *ret_type;
-	u32 i, nfuncs, urec_size, min_size;
 	u32 krec_size = sizeof(struct bpf_func_info);
+	const struct btf_type *type, *func_proto;
+	u32 i, nfuncs, urec_size, min_size;
 	struct bpf_func_info *krecord;
-	struct bpf_func_info_aux *info_aux = NULL;
 	struct bpf_prog *prog;
 	const struct btf *btf;
-	bpfptr_t urecord;
 	u32 prev_offset = 0;
-	bool scalar_return;
+	bpfptr_t urecord;
 	int ret = -ENOMEM;
 
 	nfuncs = attr->func_info_cnt;
@@ -15094,11 +15253,6 @@ static int check_btf_func(struct bpf_verifier_env *env,
 		return 0;
 	}
 
-	if (nfuncs != env->subprog_cnt) {
-		verbose(env, "number of funcs in func_info doesn't match number of subprogs\n");
-		return -EINVAL;
-	}
-
 	urec_size = attr->func_info_rec_size;
 	if (urec_size < MIN_BPF_FUNCINFO_SIZE ||
 	    urec_size > MAX_FUNCINFO_REC_SIZE ||
@@ -15116,9 +15270,6 @@ static int check_btf_func(struct bpf_verifier_env *env,
 	krecord = kvcalloc(nfuncs, krec_size, GFP_KERNEL | __GFP_NOWARN);
 	if (!krecord)
 		return -ENOMEM;
-	info_aux = kcalloc(nfuncs, sizeof(*info_aux), GFP_KERNEL | __GFP_NOWARN);
-	if (!info_aux)
-		goto err_free;
 
 	for (i = 0; i < nfuncs; i++) {
 		ret = bpf_check_uarg_tail_zero(urecord, krec_size, urec_size);
@@ -15157,11 +15308,6 @@ static int check_btf_func(struct bpf_verifier_env *env,
 			goto err_free;
 		}
 
-		if (env->subprog_info[i].start != krecord[i].insn_off) {
-			verbose(env, "func_info BTF section doesn't match subprog layout in BPF program\n");
-			goto err_free;
-		}
-
 		/* check type_id */
 		type = btf_type_by_id(btf, krecord[i].type_id);
 		if (!type || !btf_type_is_func(type)) {
@@ -15169,12 +15315,80 @@ static int check_btf_func(struct bpf_verifier_env *env,
 				krecord[i].type_id);
 			goto err_free;
 		}
-		info_aux[i].linkage = BTF_INFO_VLEN(type->info);
 
 		func_proto = btf_type_by_id(btf, type->type);
 		if (unlikely(!func_proto || !btf_type_is_func_proto(func_proto)))
 			/* btf_func_check() already verified it during BTF load */
 			goto err_free;
+
+		prev_offset = krecord[i].insn_off;
+		bpfptr_add(&urecord, urec_size);
+	}
+
+	prog->aux->func_info = krecord;
+	prog->aux->func_info_cnt = nfuncs;
+	return 0;
+
+err_free:
+	kvfree(krecord);
+	return ret;
+}
+
+static int check_btf_func(struct bpf_verifier_env *env,
+			  const union bpf_attr *attr,
+			  bpfptr_t uattr)
+{
+	const struct btf_type *type, *func_proto, *ret_type;
+	u32 i, nfuncs, urec_size, min_size;
+	u32 krec_size = sizeof(struct bpf_func_info);
+	struct bpf_func_info *krecord;
+	struct bpf_func_info_aux *info_aux = NULL;
+	struct bpf_prog *prog;
+	const struct btf *btf;
+	bpfptr_t urecord;
+	u32 prev_offset = 0;
+	bool scalar_return;
+	int ret = -ENOMEM;
+
+	nfuncs = attr->func_info_cnt;
+	if (!nfuncs) {
+		if (check_abnormal_return(env))
+			return -EINVAL;
+		return 0;
+	}
+	if (nfuncs != env->subprog_cnt) {
+		verbose(env, "number of funcs in func_info doesn't match number of subprogs\n");
+		return -EINVAL;
+	}
+
+	urec_size = attr->func_info_rec_size;
+
+	prog = env->prog;
+	btf = prog->aux->btf;
+
+	urecord = make_bpfptr(attr->func_info, uattr.is_kernel);
+	min_size = min_t(u32, krec_size, urec_size);
+
+	krecord = prog->aux->func_info;
+	info_aux = kcalloc(nfuncs, sizeof(*info_aux), GFP_KERNEL | __GFP_NOWARN);
+	if (!info_aux)
+		return -ENOMEM;
+
+	for (i = 0; i < nfuncs; i++) {
+		/* check insn_off */
+		ret = -EINVAL;
+
+		if (env->subprog_info[i].start != krecord[i].insn_off) {
+			verbose(env, "func_info BTF section doesn't match subprog layout in BPF program\n");
+			goto err_free;
+		}
+
+		/* Already checked type_id */
+		type = btf_type_by_id(btf, krecord[i].type_id);
+		info_aux[i].linkage = BTF_INFO_VLEN(type->info);
+		/* Already checked func_proto */
+		func_proto = btf_type_by_id(btf, type->type);
+
 		ret_type = btf_type_skip_modifiers(btf, func_proto->type, NULL);
 		scalar_return =
 			btf_type_is_small_int(ret_type) || btf_is_any_enum(ret_type);
@@ -15191,13 +15405,10 @@ static int check_btf_func(struct bpf_verifier_env *env,
 		bpfptr_add(&urecord, urec_size);
 	}
 
-	prog->aux->func_info = krecord;
-	prog->aux->func_info_cnt = nfuncs;
 	prog->aux->func_info_aux = info_aux;
 	return 0;
 
 err_free:
-	kvfree(krecord);
 	kfree(info_aux);
 	return ret;
 }
@@ -15210,7 +15421,8 @@ static void adjust_btf_func(struct bpf_verifier_env *env)
 	if (!aux->func_info)
 		return;
 
-	for (i = 0; i < env->subprog_cnt; i++)
+	/* func_info is not available for hidden subprogs */
+	for (i = 0; i < env->subprog_cnt - env->hidden_subprog_cnt; i++)
 		aux->func_info[i].insn_off = env->subprog_info[i].start;
 }
 
@@ -15414,9 +15626,9 @@ static int check_core_relo(struct bpf_verifier_env *env,
 	return err;
 }
 
-static int check_btf_info(struct bpf_verifier_env *env,
-			  const union bpf_attr *attr,
-			  bpfptr_t uattr)
+static int check_btf_info_early(struct bpf_verifier_env *env,
+				const union bpf_attr *attr,
+				bpfptr_t uattr)
 {
 	struct btf *btf;
 	int err;
@@ -15436,6 +15648,24 @@ static int check_btf_info(struct bpf_verifier_env *env,
 	}
 	env->prog->aux->btf = btf;
 
+	err = check_btf_func_early(env, attr, uattr);
+	if (err)
+		return err;
+	return 0;
+}
+
+static int check_btf_info(struct bpf_verifier_env *env,
+			  const union bpf_attr *attr,
+			  bpfptr_t uattr)
+{
+	int err;
+
+	if (!attr->func_info_cnt && !attr->line_info_cnt) {
+		if (check_abnormal_return(env))
+			return -EINVAL;
+		return 0;
+	}
+
 	err = check_btf_func(env, attr, uattr);
 	if (err)
 		return err;
@@ -16538,6 +16768,7 @@ static int do_check(struct bpf_verifier_env *env)
 	int prev_insn_idx = -1;
 
 	for (;;) {
+		bool exception_exit = false;
 		struct bpf_insn *insn;
 		u8 class;
 		int err;
@@ -16752,12 +16983,17 @@ static int do_check(struct bpf_verifier_env *env)
 						return -EINVAL;
 					}
 				}
-				if (insn->src_reg == BPF_PSEUDO_CALL)
+				if (insn->src_reg == BPF_PSEUDO_CALL) {
 					err = check_func_call(env, insn, &env->insn_idx);
-				else if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL)
+				} else if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
 					err = check_kfunc_call(env, insn, &env->insn_idx);
-				else
+					if (!err && is_bpf_throw_kfunc(insn)) {
+						exception_exit = true;
+						goto process_bpf_exit_full;
+					}
+				} else {
 					err = check_helper_call(env, insn, &env->insn_idx);
+				}
 				if (err)
 					return err;
 
@@ -16787,7 +17023,7 @@ static int do_check(struct bpf_verifier_env *env)
 					verbose(env, "BPF_EXIT uses reserved fields\n");
 					return -EINVAL;
 				}
-
+process_bpf_exit_full:
 				if (env->cur_state->active_lock.ptr &&
 				    !in_rbtree_lock_required_cb(env)) {
 					verbose(env, "bpf_spin_unlock is missing\n");
@@ -16806,10 +17042,23 @@ static int do_check(struct bpf_verifier_env *env)
 				 * function, for which reference_state must
 				 * match caller reference state when it exits.
 				 */
-				err = check_reference_leak(env);
+				err = check_reference_leak(env, exception_exit);
 				if (err)
 					return err;
 
+				/* The side effect of the prepare_func_exit
+				 * which is being skipped is that it frees
+				 * bpf_func_state. Typically, process_bpf_exit
+				 * will only be hit with outermost exit.
+				 * copy_verifier_state in pop_stack will handle
+				 * freeing of any extra bpf_func_state left over
+				 * from not processing all nested function
+				 * exits. We also skip return code checks as
+				 * they are not needed for exceptional exits.
+				 */
+				if (exception_exit)
+					goto process_bpf_exit;
+
 				if (state->curframe) {
 					/* exit from nested function */
 					err = prepare_func_exit(env, &env->insn_idx);
@@ -16819,7 +17068,7 @@ static int do_check(struct bpf_verifier_env *env)
 					continue;
 				}
 
-				err = check_return_code(env);
+				err = check_return_code(env, BPF_REG_0);
 				if (err)
 					return err;
 process_bpf_exit:
@@ -18112,6 +18361,9 @@ static int jit_subprogs(struct bpf_verifier_env *env)
 		}
 		func[i]->aux->num_exentries = num_exentries;
 		func[i]->aux->tail_call_reachable = env->subprog_info[i].tail_call_reachable;
+		func[i]->aux->exception_cb = env->subprog_info[i].is_exception_cb;
+		if (!i)
+			func[i]->aux->exception_boundary = env->seen_exception;
 		func[i] = bpf_int_jit_compile(func[i]);
 		if (!func[i]->jited) {
 			err = -ENOTSUPP;
@@ -18151,7 +18403,8 @@ static int jit_subprogs(struct bpf_verifier_env *env)
 		 * the call instruction, as an index for this list
 		 */
 		func[i]->aux->func = func;
-		func[i]->aux->func_cnt = env->subprog_cnt;
+		func[i]->aux->func_cnt = env->subprog_cnt - env->hidden_subprog_cnt;
+		func[i]->aux->real_func_cnt = env->subprog_cnt;
 	}
 	for (i = 0; i < env->subprog_cnt; i++) {
 		old_bpf_func = func[i]->bpf_func;
@@ -18197,7 +18450,10 @@ static int jit_subprogs(struct bpf_verifier_env *env)
 	prog->aux->extable = func[0]->aux->extable;
 	prog->aux->num_exentries = func[0]->aux->num_exentries;
 	prog->aux->func = func;
-	prog->aux->func_cnt = env->subprog_cnt;
+	prog->aux->func_cnt = env->subprog_cnt - env->hidden_subprog_cnt;
+	prog->aux->real_func_cnt = env->subprog_cnt;
+	prog->aux->bpf_exception_cb = (void *)func[env->exception_callback_subprog]->bpf_func;
+	prog->aux->exception_boundary = func[0]->aux->exception_boundary;
 	bpf_prog_jit_attempt_done(prog);
 	return 0;
 out_free:
@@ -18433,6 +18689,33 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	return 0;
 }
 
+/* The function requires that first instruction in 'patch' is insnsi[prog->len - 1] */
+static int add_hidden_subprog(struct bpf_verifier_env *env, struct bpf_insn *patch, int len)
+{
+	struct bpf_subprog_info *info = env->subprog_info;
+	int cnt = env->subprog_cnt;
+	struct bpf_prog *prog;
+
+	/* We only reserve one slot for hidden subprogs in subprog_info. */
+	if (env->hidden_subprog_cnt) {
+		verbose(env, "verifier internal error: only one hidden subprog supported\n");
+		return -EFAULT;
+	}
+	/* We're not patching any existing instruction, just appending the new
+	 * ones for the hidden subprog. Hence all of the adjustment operations
+	 * in bpf_patch_insn_data are no-ops.
+	 */
+	prog = bpf_patch_insn_data(env, env->prog->len - 1, patch, len);
+	if (!prog)
+		return -ENOMEM;
+	env->prog = prog;
+	info[cnt + 1].start = info[cnt].start;
+	info[cnt].start = prog->len - len + 1;
+	env->subprog_cnt++;
+	env->hidden_subprog_cnt++;
+	return 0;
+}
+
 /* Do various post-verification rewrites in a single program pass.
  * These rewrites simplify JIT and interpreter implementations.
  */
@@ -18451,6 +18734,26 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 	struct bpf_map *map_ptr;
 	int i, ret, cnt, delta = 0;
 
+	if (env->seen_exception && !env->exception_callback_subprog) {
+		struct bpf_insn patch[] = {
+			env->prog->insnsi[insn_cnt - 1],
+			BPF_MOV64_REG(BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		};
+
+		ret = add_hidden_subprog(env, patch, ARRAY_SIZE(patch));
+		if (ret < 0)
+			return ret;
+		prog = env->prog;
+		insn = prog->insnsi;
+
+		env->exception_callback_subprog = env->subprog_cnt - 1;
+		/* Don't update insn_cnt, as add_hidden_subprog always appends insns */
+		env->subprog_info[env->exception_callback_subprog].is_cb = true;
+		env->subprog_info[env->exception_callback_subprog].is_async_cb = true;
+		env->subprog_info[env->exception_callback_subprog].is_exception_cb = true;
+	}
+
 	for (i = 0; i < insn_cnt; i++, insn++) {
 		/* Make divide-by-zero exceptions impossible. */
 		if (insn->code == (BPF_ALU64 | BPF_MOD | BPF_X) ||
@@ -19148,7 +19451,7 @@ static void free_states(struct bpf_verifier_env *env)
 	}
 }
 
-static int do_check_common(struct bpf_verifier_env *env, int subprog)
+static int do_check_common(struct bpf_verifier_env *env, int subprog, bool is_ex_cb)
 {
 	bool pop_log = !(env->log.level & BPF_LOG_LEVEL2);
 	struct bpf_verifier_state *state;
@@ -19179,7 +19482,7 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog)
 
 	regs = state->frame[state->curframe]->regs;
 	if (subprog || env->prog->type == BPF_PROG_TYPE_EXT) {
-		ret = btf_prepare_func_args(env, subprog, regs);
+		ret = btf_prepare_func_args(env, subprog, regs, is_ex_cb);
 		if (ret)
 			goto out;
 		for (i = BPF_REG_1; i <= BPF_REG_5; i++) {
@@ -19195,6 +19498,12 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog)
 				regs[i].id = ++env->id_gen;
 			}
 		}
+		if (is_ex_cb) {
+			state->frame[0]->in_exception_callback_fn = true;
+			env->subprog_info[subprog].is_cb = true;
+			env->subprog_info[subprog].is_async_cb = true;
+			env->subprog_info[subprog].is_exception_cb = true;
+		}
 	} else {
 		/* 1st arg to a function */
 		regs[BPF_REG_1].type = PTR_TO_CTX;
@@ -19259,7 +19568,7 @@ static int do_check_subprogs(struct bpf_verifier_env *env)
 			continue;
 		env->insn_idx = env->subprog_info[i].start;
 		WARN_ON_ONCE(env->insn_idx == 0);
-		ret = do_check_common(env, i);
+		ret = do_check_common(env, i, env->exception_callback_subprog == i);
 		if (ret) {
 			return ret;
 		} else if (env->log.level & BPF_LOG_LEVEL) {
@@ -19276,7 +19585,7 @@ static int do_check_main(struct bpf_verifier_env *env)
 	int ret;
 
 	env->insn_idx = 0;
-	ret = do_check_common(env, 0);
+	ret = do_check_common(env, 0, false);
 	if (!ret)
 		env->prog->aux->stack_depth = env->subprog_info[0].stack_depth;
 	return ret;
@@ -19445,6 +19754,12 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 			bpf_log(log, "Subprog %s doesn't exist\n", tname);
 			return -EINVAL;
 		}
+		if (aux->func && aux->func[subprog]->aux->exception_cb) {
+			bpf_log(log,
+				"%s programs cannot attach to exception callback\n",
+				prog_extension ? "Extension" : "FENTRY/FEXIT");
+			return -EINVAL;
+		}
 		conservative = aux->func_info_aux[subprog].unreliable;
 		if (prog_extension) {
 			if (conservative) {
@@ -19872,6 +20187,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	if (!env->explored_states)
 		goto skip_full_check;
 
+	ret = check_btf_info_early(env, attr, uattr);
+	if (ret < 0)
+		goto skip_full_check;
+
 	ret = add_subprog_and_kfunc(env);
 	if (ret < 0)
 		goto skip_full_check;