From 951bb64621b8139c0cd99dcadc13e6510c08aa73 Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@kernel.org>
Date: Mon, 9 Nov 2020 17:19:28 -0800
Subject: [PATCH 1/5] bpf: Add in-kernel split BTF support

Adjust in-kernel BTF implementation to support a split BTF mode of operation.
Changes are mostly mirroring libbpf split BTF changes, with the exception of
start_id being 0 for in-kernel implementation due to simpler read-only mode.

Otherwise, for split BTF logic, most of the logic of jumping to base BTF,
where necessary, is encapsulated in few helper functions. Type numbering and
string offset in a split BTF are logically continuing where base BTF ends, so
most of the high-level logic is kept without changes.

Type verification and size resolution is only doing an added resolution of new
split BTF types and relies on already cached size and type resolution results
in the base BTF.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201110011932.3201430-2-andrii@kernel.org
---
 kernel/bpf/btf.c | 171 +++++++++++++++++++++++++++++++++--------------
 1 file changed, 119 insertions(+), 52 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 6324de8c59f79..727c1c27053fd 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -203,12 +203,17 @@ struct btf {
 	const char *strings;
 	void *nohdr_data;
 	struct btf_header hdr;
-	u32 nr_types;
+	u32 nr_types; /* includes VOID for base BTF */
 	u32 types_size;
 	u32 data_size;
 	refcount_t refcnt;
 	u32 id;
 	struct rcu_head rcu;
+
+	/* split BTF support */
+	struct btf *base_btf;
+	u32 start_id; /* first type ID in this BTF (0 for base BTF) */
+	u32 start_str_off; /* first string offset (0 for base BTF) */
 };
 
 enum verifier_phase {
@@ -449,14 +454,27 @@ static bool btf_type_is_datasec(const struct btf_type *t)
 	return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
 }
 
+static u32 btf_nr_types_total(const struct btf *btf)
+{
+	u32 total = 0;
+
+	while (btf) {
+		total += btf->nr_types;
+		btf = btf->base_btf;
+	}
+
+	return total;
+}
+
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind)
 {
 	const struct btf_type *t;
 	const char *tname;
-	u32 i;
+	u32 i, total;
 
-	for (i = 1; i <= btf->nr_types; i++) {
-		t = btf->types[i];
+	total = btf_nr_types_total(btf);
+	for (i = 1; i < total; i++) {
+		t = btf_type_by_id(btf, i);
 		if (BTF_INFO_KIND(t->info) != kind)
 			continue;
 
@@ -599,8 +617,14 @@ static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t)
 
 static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
 {
-	return BTF_STR_OFFSET_VALID(offset) &&
-		offset < btf->hdr.str_len;
+	if (!BTF_STR_OFFSET_VALID(offset))
+		return false;
+
+	while (offset < btf->start_str_off)
+		btf = btf->base_btf;
+
+	offset -= btf->start_str_off;
+	return offset < btf->hdr.str_len;
 }
 
 static bool __btf_name_char_ok(char c, bool first, bool dot_ok)
@@ -614,10 +638,22 @@ static bool __btf_name_char_ok(char c, bool first, bool dot_ok)
 	return true;
 }
 
+static const char *btf_str_by_offset(const struct btf *btf, u32 offset)
+{
+	while (offset < btf->start_str_off)
+		btf = btf->base_btf;
+
+	offset -= btf->start_str_off;
+	if (offset < btf->hdr.str_len)
+		return &btf->strings[offset];
+
+	return NULL;
+}
+
 static bool __btf_name_valid(const struct btf *btf, u32 offset, bool dot_ok)
 {
 	/* offset must be valid */
-	const char *src = &btf->strings[offset];
+	const char *src = btf_str_by_offset(btf, offset);
 	const char *src_limit;
 
 	if (!__btf_name_char_ok(*src, true, dot_ok))
@@ -650,27 +686,28 @@ static bool btf_name_valid_section(const struct btf *btf, u32 offset)
 
 static const char *__btf_name_by_offset(const struct btf *btf, u32 offset)
 {
+	const char *name;
+
 	if (!offset)
 		return "(anon)";
-	else if (offset < btf->hdr.str_len)
-		return &btf->strings[offset];
-	else
-		return "(invalid-name-offset)";
+
+	name = btf_str_by_offset(btf, offset);
+	return name ?: "(invalid-name-offset)";
 }
 
 const char *btf_name_by_offset(const struct btf *btf, u32 offset)
 {
-	if (offset < btf->hdr.str_len)
-		return &btf->strings[offset];
-
-	return NULL;
+	return btf_str_by_offset(btf, offset);
 }
 
 const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
 {
-	if (type_id > btf->nr_types)
-		return NULL;
+	while (type_id < btf->start_id)
+		btf = btf->base_btf;
 
+	type_id -= btf->start_id;
+	if (type_id >= btf->nr_types)
+		return NULL;
 	return btf->types[type_id];
 }
 
@@ -1390,17 +1427,13 @@ static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
 {
 	struct btf *btf = env->btf;
 
-	/* < 2 because +1 for btf_void which is always in btf->types[0].
-	 * btf_void is not accounted in btf->nr_types because btf_void
-	 * does not come from the BTF file.
-	 */
-	if (btf->types_size - btf->nr_types < 2) {
+	if (btf->types_size == btf->nr_types) {
 		/* Expand 'types' array */
 
 		struct btf_type **new_types;
 		u32 expand_by, new_size;
 
-		if (btf->types_size == BTF_MAX_TYPE) {
+		if (btf->start_id + btf->types_size == BTF_MAX_TYPE) {
 			btf_verifier_log(env, "Exceeded max num of types");
 			return -E2BIG;
 		}
@@ -1414,18 +1447,23 @@ static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
 		if (!new_types)
 			return -ENOMEM;
 
-		if (btf->nr_types == 0)
-			new_types[0] = &btf_void;
-		else
+		if (btf->nr_types == 0) {
+			if (!btf->base_btf) {
+				/* lazily init VOID type */
+				new_types[0] = &btf_void;
+				btf->nr_types++;
+			}
+		} else {
 			memcpy(new_types, btf->types,
-			       sizeof(*btf->types) * (btf->nr_types + 1));
+			       sizeof(*btf->types) * btf->nr_types);
+		}
 
 		kvfree(btf->types);
 		btf->types = new_types;
 		btf->types_size = new_size;
 	}
 
-	btf->types[++(btf->nr_types)] = t;
+	btf->types[btf->nr_types++] = t;
 
 	return 0;
 }
@@ -1498,18 +1536,17 @@ static int env_resolve_init(struct btf_verifier_env *env)
 	u32 *resolved_ids = NULL;
 	u8 *visit_states = NULL;
 
-	/* +1 for btf_void */
-	resolved_sizes = kvcalloc(nr_types + 1, sizeof(*resolved_sizes),
+	resolved_sizes = kvcalloc(nr_types, sizeof(*resolved_sizes),
 				  GFP_KERNEL | __GFP_NOWARN);
 	if (!resolved_sizes)
 		goto nomem;
 
-	resolved_ids = kvcalloc(nr_types + 1, sizeof(*resolved_ids),
+	resolved_ids = kvcalloc(nr_types, sizeof(*resolved_ids),
 				GFP_KERNEL | __GFP_NOWARN);
 	if (!resolved_ids)
 		goto nomem;
 
-	visit_states = kvcalloc(nr_types + 1, sizeof(*visit_states),
+	visit_states = kvcalloc(nr_types, sizeof(*visit_states),
 				GFP_KERNEL | __GFP_NOWARN);
 	if (!visit_states)
 		goto nomem;
@@ -1561,21 +1598,27 @@ static bool env_type_is_resolve_sink(const struct btf_verifier_env *env,
 static bool env_type_is_resolved(const struct btf_verifier_env *env,
 				 u32 type_id)
 {
-	return env->visit_states[type_id] == RESOLVED;
+	/* base BTF types should be resolved by now */
+	if (type_id < env->btf->start_id)
+		return true;
+
+	return env->visit_states[type_id - env->btf->start_id] == RESOLVED;
 }
 
 static int env_stack_push(struct btf_verifier_env *env,
 			  const struct btf_type *t, u32 type_id)
 {
+	const struct btf *btf = env->btf;
 	struct resolve_vertex *v;
 
 	if (env->top_stack == MAX_RESOLVE_DEPTH)
 		return -E2BIG;
 
-	if (env->visit_states[type_id] != NOT_VISITED)
+	if (type_id < btf->start_id
+	    || env->visit_states[type_id - btf->start_id] != NOT_VISITED)
 		return -EEXIST;
 
-	env->visit_states[type_id] = VISITED;
+	env->visit_states[type_id - btf->start_id] = VISITED;
 
 	v = &env->stack[env->top_stack++];
 	v->t = t;
@@ -1605,6 +1648,7 @@ static void env_stack_pop_resolved(struct btf_verifier_env *env,
 	u32 type_id = env->stack[--(env->top_stack)].type_id;
 	struct btf *btf = env->btf;
 
+	type_id -= btf->start_id; /* adjust to local type id */
 	btf->resolved_sizes[type_id] = resolved_size;
 	btf->resolved_ids[type_id] = resolved_type_id;
 	env->visit_states[type_id] = RESOLVED;
@@ -1709,14 +1753,30 @@ btf_resolve_size(const struct btf *btf, const struct btf_type *type,
 	return __btf_resolve_size(btf, type, type_size, NULL, NULL, NULL, NULL);
 }
 
+static u32 btf_resolved_type_id(const struct btf *btf, u32 type_id)
+{
+	while (type_id < btf->start_id)
+		btf = btf->base_btf;
+
+	return btf->resolved_ids[type_id - btf->start_id];
+}
+
 /* The input param "type_id" must point to a needs_resolve type */
 static const struct btf_type *btf_type_id_resolve(const struct btf *btf,
 						  u32 *type_id)
 {
-	*type_id = btf->resolved_ids[*type_id];
+	*type_id = btf_resolved_type_id(btf, *type_id);
 	return btf_type_by_id(btf, *type_id);
 }
 
+static u32 btf_resolved_type_size(const struct btf *btf, u32 type_id)
+{
+	while (type_id < btf->start_id)
+		btf = btf->base_btf;
+
+	return btf->resolved_sizes[type_id - btf->start_id];
+}
+
 const struct btf_type *btf_type_id_size(const struct btf *btf,
 					u32 *type_id, u32 *ret_size)
 {
@@ -1731,7 +1791,7 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,
 	if (btf_type_has_size(size_type)) {
 		size = size_type->size;
 	} else if (btf_type_is_array(size_type)) {
-		size = btf->resolved_sizes[size_type_id];
+		size = btf_resolved_type_size(btf, size_type_id);
 	} else if (btf_type_is_ptr(size_type)) {
 		size = sizeof(void *);
 	} else {
@@ -1739,14 +1799,14 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,
 				 !btf_type_is_var(size_type)))
 			return NULL;
 
-		size_type_id = btf->resolved_ids[size_type_id];
+		size_type_id = btf_resolved_type_id(btf, size_type_id);
 		size_type = btf_type_by_id(btf, size_type_id);
 		if (btf_type_nosize_or_null(size_type))
 			return NULL;
 		else if (btf_type_has_size(size_type))
 			size = size_type->size;
 		else if (btf_type_is_array(size_type))
-			size = btf->resolved_sizes[size_type_id];
+			size = btf_resolved_type_size(btf, size_type_id);
 		else if (btf_type_is_ptr(size_type))
 			size = sizeof(void *);
 		else
@@ -3798,7 +3858,7 @@ static int btf_check_all_metas(struct btf_verifier_env *env)
 	cur = btf->nohdr_data + hdr->type_off;
 	end = cur + hdr->type_len;
 
-	env->log_type_id = 1;
+	env->log_type_id = btf->base_btf ? btf->start_id : 1;
 	while (cur < end) {
 		struct btf_type *t = cur;
 		s32 meta_size;
@@ -3825,8 +3885,8 @@ static bool btf_resolve_valid(struct btf_verifier_env *env,
 		return false;
 
 	if (btf_type_is_struct(t) || btf_type_is_datasec(t))
-		return !btf->resolved_ids[type_id] &&
-		       !btf->resolved_sizes[type_id];
+		return !btf_resolved_type_id(btf, type_id) &&
+		       !btf_resolved_type_size(btf, type_id);
 
 	if (btf_type_is_modifier(t) || btf_type_is_ptr(t) ||
 	    btf_type_is_var(t)) {
@@ -3846,7 +3906,7 @@ static bool btf_resolve_valid(struct btf_verifier_env *env,
 		elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
 		return elem_type && !btf_type_is_modifier(elem_type) &&
 			(array->nelems * elem_size ==
-			 btf->resolved_sizes[type_id]);
+			 btf_resolved_type_size(btf, type_id));
 	}
 
 	return false;
@@ -3888,7 +3948,8 @@ static int btf_resolve(struct btf_verifier_env *env,
 static int btf_check_all_types(struct btf_verifier_env *env)
 {
 	struct btf *btf = env->btf;
-	u32 type_id;
+	const struct btf_type *t;
+	u32 type_id, i;
 	int err;
 
 	err = env_resolve_init(env);
@@ -3896,8 +3957,9 @@ static int btf_check_all_types(struct btf_verifier_env *env)
 		return err;
 
 	env->phase++;
-	for (type_id = 1; type_id <= btf->nr_types; type_id++) {
-		const struct btf_type *t = btf_type_by_id(btf, type_id);
+	for (i = btf->base_btf ? 0 : 1; i < btf->nr_types; i++) {
+		type_id = btf->start_id + i;
+		t = btf_type_by_id(btf, type_id);
 
 		env->log_type_id = type_id;
 		if (btf_type_needs_resolve(t) &&
@@ -3934,7 +3996,7 @@ static int btf_parse_type_sec(struct btf_verifier_env *env)
 		return -EINVAL;
 	}
 
-	if (!hdr->type_len) {
+	if (!env->btf->base_btf && !hdr->type_len) {
 		btf_verifier_log(env, "No type found");
 		return -EINVAL;
 	}
@@ -3961,13 +4023,18 @@ static int btf_parse_str_sec(struct btf_verifier_env *env)
 		return -EINVAL;
 	}
 
-	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||
-	    start[0] || end[-1]) {
+	btf->strings = start;
+
+	if (btf->base_btf && !hdr->str_len)
+		return 0;
+	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET || end[-1]) {
+		btf_verifier_log(env, "Invalid string section");
+		return -EINVAL;
+	}
+	if (!btf->base_btf && start[0]) {
 		btf_verifier_log(env, "Invalid string section");
 		return -EINVAL;
 	}
-
-	btf->strings = start;
 
 	return 0;
 }
@@ -4908,7 +4975,7 @@ static int __get_type_size(struct btf *btf, u32 btf_id,
 	while (t && btf_type_is_modifier(t))
 		t = btf_type_by_id(btf, t->type);
 	if (!t) {
-		*bad_type = btf->types[0];
+		*bad_type = btf_type_by_id(btf, 0);
 		return -EINVAL;
 	}
 	if (btf_type_is_ptr(t))

From 5329722057d41aebc31e391907a501feaa42f7d9 Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@kernel.org>
Date: Mon, 9 Nov 2020 17:19:29 -0800
Subject: [PATCH 2/5] bpf: Assign ID to vmlinux BTF and return extra info for
 BTF in GET_OBJ_INFO

Allocate ID for vmlinux BTF. This makes it visible when iterating over all BTF
objects in the system. To allow distinguishing vmlinux BTF (and later kernel
module BTF) from user-provided BTFs, expose extra kernel_btf flag, as well as
BTF name ("vmlinux" for vmlinux BTF, will equal to module's name for module
BTF).  We might want to later allow specifying BTF name for user-provided BTFs
as well, if that makes sense. But currently this is reserved only for
in-kernel BTFs.

Having in-kernel BTFs exposed IDs will allow to extend BPF APIs that require
in-kernel BTF type with ability to specify BTF types from kernel modules, not
just vmlinux BTF. This will be implemented in a follow up patch set for
fentry/fexit/fmod_ret/lsm/etc.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201110011932.3201430-3-andrii@kernel.org
---
 include/uapi/linux/bpf.h       |  3 +++
 kernel/bpf/btf.c               | 43 +++++++++++++++++++++++++++++++---
 tools/include/uapi/linux/bpf.h |  3 +++
 3 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9879d6793e904..162999b127901 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4466,6 +4466,9 @@ struct bpf_btf_info {
 	__aligned_u64 btf;
 	__u32 btf_size;
 	__u32 id;
+	__aligned_u64 name;
+	__u32 name_len;
+	__u32 kernel_btf;
 } __attribute__((aligned(8)));
 
 struct bpf_link_info {
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 727c1c27053fd..856585db7aa72 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -214,6 +214,8 @@ struct btf {
 	struct btf *base_btf;
 	u32 start_id; /* first type ID in this BTF (0 for base BTF) */
 	u32 start_str_off; /* first string offset (0 for base BTF) */
+	char name[MODULE_NAME_LEN];
+	bool kernel_btf;
 };
 
 enum verifier_phase {
@@ -4429,6 +4431,8 @@ struct btf *btf_parse_vmlinux(void)
 
 	btf->data = __start_BTF;
 	btf->data_size = __stop_BTF - __start_BTF;
+	btf->kernel_btf = true;
+	snprintf(btf->name, sizeof(btf->name), "vmlinux");
 
 	err = btf_parse_hdr(env);
 	if (err)
@@ -4454,8 +4458,13 @@ struct btf *btf_parse_vmlinux(void)
 
 	bpf_struct_ops_init(btf, log);
 
-	btf_verifier_env_free(env);
 	refcount_set(&btf->refcnt, 1);
+
+	err = btf_alloc_id(btf);
+	if (err)
+		goto errout;
+
+	btf_verifier_env_free(env);
 	return btf;
 
 errout:
@@ -5553,7 +5562,9 @@ int btf_get_info_by_fd(const struct btf *btf,
 	struct bpf_btf_info info;
 	u32 info_copy, btf_copy;
 	void __user *ubtf;
-	u32 uinfo_len;
+	char __user *uname;
+	u32 uinfo_len, uname_len, name_len;
+	int ret = 0;
 
 	uinfo = u64_to_user_ptr(attr->info.info);
 	uinfo_len = attr->info.info_len;
@@ -5570,11 +5581,37 @@ int btf_get_info_by_fd(const struct btf *btf,
 		return -EFAULT;
 	info.btf_size = btf->data_size;
 
+	info.kernel_btf = btf->kernel_btf;
+
+	uname = u64_to_user_ptr(info.name);
+	uname_len = info.name_len;
+	if (!uname ^ !uname_len)
+		return -EINVAL;
+
+	name_len = strlen(btf->name);
+	info.name_len = name_len;
+
+	if (uname) {
+		if (uname_len >= name_len + 1) {
+			if (copy_to_user(uname, btf->name, name_len + 1))
+				return -EFAULT;
+		} else {
+			char zero = '\0';
+
+			if (copy_to_user(uname, btf->name, uname_len - 1))
+				return -EFAULT;
+			if (put_user(zero, uname + uname_len - 1))
+				return -EFAULT;
+			/* let user-space know about too short buffer */
+			ret = -ENOSPC;
+		}
+	}
+
 	if (copy_to_user(uinfo, &info, info_copy) ||
 	    put_user(info_copy, &uattr->info.info_len))
 		return -EFAULT;
 
-	return 0;
+	return ret;
 }
 
 int btf_get_fd_by_id(u32 id)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 9879d6793e904..162999b127901 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4466,6 +4466,9 @@ struct bpf_btf_info {
 	__aligned_u64 btf;
 	__u32 btf_size;
 	__u32 id;
+	__aligned_u64 name;
+	__u32 name_len;
+	__u32 kernel_btf;
 } __attribute__((aligned(8)));
 
 struct bpf_link_info {

From 5f9ae91f7c0dbbc4195e2a6c8eedcaeb5b9e4cbb Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@kernel.org>
Date: Mon, 9 Nov 2020 17:19:30 -0800
Subject: [PATCH 3/5] kbuild: Build kernel module BTFs if BTF is enabled and
 pahole supports it

Detect if pahole supports split BTF generation, and generate BTF for each
selected kernel module, if it does. This is exposed to Makefiles and C code as
CONFIG_DEBUG_INFO_BTF_MODULES flag.

Kernel module BTF has to be re-generated if either vmlinux's BTF changes or
module's .ko changes. To achieve that, I needed a helper similar to
if_changed, but that would allow to filter out vmlinux from the list of
updated dependencies for .ko building. I've put it next to the only place that
uses and needs it, but it might be a better idea to just add it along the
other if_changed variants into scripts/Kbuild.include.

Each kernel module's BTF deduplication is pretty fast, as it does only
incremental BTF deduplication on top of already deduplicated vmlinux BTF. To
show the added build time, I've first ran make only just built kernel (to
establish the baseline) and then forced only BTF re-generation, without
regenerating .ko files. The build was performed with -j60 parallelization on
56-core machine. The final time also includes bzImage building, so it's not
a pure BTF overhead.

$ time make -j60
...
make -j60  27.65s user 10.96s system 782% cpu 4.933 total
$ touch ~/linux-build/default/vmlinux && time make -j60
...
make -j60  123.69s user 27.85s system 1566% cpu 9.675 total

So 4.6 seconds real time, with noticeable part spent in compressed vmlinux and
bzImage building.

To show size savings, I've built my kernel configuration with about 700 kernel
modules with full BTF per each kernel module (without deduplicating against
vmlinux) and with split BTF against deduplicated vmlinux (approach in this
patch). Below are top 10 modules with biggest BTF sizes. And total size of BTF
data across all kernel modules.

It shows that split BTF "compresses" 115MB down to 5MB total. And the biggest
kernel modules get a downsize from 500-570KB down to 200-300KB.

FULL BTF
========

$ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }'
115710691

$ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10
./drivers/gpu/drm/i915/i915.ko 570570
./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 520240
./drivers/gpu/drm/radeon/radeon.ko 503849
./drivers/infiniband/hw/mlx5/mlx5_ib.ko 491777
./fs/xfs/xfs.ko 411544
./drivers/net/ethernet/intel/i40e/i40e.ko 403904
./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 398754
./drivers/infiniband/core/ib_core.ko 397224
./fs/cifs/cifs.ko 386249
./fs/nfsd/nfsd.ko 379738

SPLIT BTF
=========

$ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }'
5194047

$ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10
./drivers/gpu/drm/i915/i915.ko 293206
./drivers/gpu/drm/radeon/radeon.ko 282103
./fs/xfs/xfs.ko 222150
./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 198503
./drivers/infiniband/hw/mlx5/mlx5_ib.ko 198356
./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 113444
./fs/cifs/cifs.ko 109379
./arch/x86/kvm/kvm.ko 100225
./drivers/gpu/drm/drm.ko 94827
./drivers/infiniband/core/ib_core.ko 91188

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201110011932.3201430-4-andrii@kernel.org
---
 lib/Kconfig.debug         |  9 +++++++++
 scripts/Makefile.modfinal | 20 ++++++++++++++++++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d7a7bc3b60982..1e78faaf20a50 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -274,6 +274,15 @@ config DEBUG_INFO_BTF
 	  Turning this on expects presence of pahole tool, which will convert
 	  DWARF type info into equivalent deduplicated BTF type info.
 
+config PAHOLE_HAS_SPLIT_BTF
+	def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")
+
+config DEBUG_INFO_BTF_MODULES
+	def_bool y
+	depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
+	help
+	  Generate compact split BTF type information for kernel modules.
+
 config GDB_SCRIPTS
 	bool "Provide GDB scripts for kernel debugging"
 	help
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index ae01baf96f4e8..02b892421f7a2 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -6,6 +6,7 @@
 PHONY := __modfinal
 __modfinal:
 
+include include/config/auto.conf
 include $(srctree)/scripts/Kbuild.include
 
 # for c_flags
@@ -36,8 +37,23 @@ quiet_cmd_ld_ko_o = LD [M]  $@
 		-T scripts/module.lds -o $@ $(filter %.o, $^);		\
 	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
 
-$(modules): %.ko: %.o %.mod.o scripts/module.lds FORCE
-	+$(call if_changed,ld_ko_o)
+quiet_cmd_btf_ko = BTF [M] $@
+      cmd_btf_ko = LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@
+
+# Same as newer-prereqs, but allows to exclude specified extra dependencies
+newer_prereqs_except = $(filter-out $(PHONY) $(1),$?)
+
+# Same as if_changed, but allows to exclude specified extra dependencies
+if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check),      \
+	$(cmd);                                                              \
+	printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
+
+# Re-generate module BTFs if either module's .ko or vmlinux changed
+$(modules): %.ko: %.o %.mod.o scripts/module.lds vmlinux FORCE
+	+$(call if_changed_except,ld_ko_o,vmlinux)
+ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+	+$(if $(newer-prereqs),$(call cmd,btf_ko))
+endif
 
 targets += $(modules) $(modules:.ko=.mod.o)
 

From 36e68442d1afd4f720704ee1ea8486331507e834 Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@kernel.org>
Date: Mon, 9 Nov 2020 17:19:31 -0800
Subject: [PATCH 4/5] bpf: Load and verify kernel module BTFs

Add kernel module listener that will load/validate and unload module BTF.
Module BTFs gets ID generated for them, which makes it possible to iterate
them with existing BTF iteration API. They are given their respective module's
names, which will get reported through GET_OBJ_INFO API. They are also marked
as in-kernel BTFs for tooling to distinguish them from user-provided BTFs.

Also, similarly to vmlinux BTF, kernel module BTFs are exposed through
sysfs as /sys/kernel/btf/<module-name>. This is convenient for user-space
tools to inspect module BTF contents and dump their types with existing tools:

[vmuser@archvm bpf]$ ls -la /sys/kernel/btf
total 0
drwxr-xr-x  2 root root       0 Nov  4 19:46 .
drwxr-xr-x 13 root root       0 Nov  4 19:46 ..

...

-r--r--r--  1 root root     888 Nov  4 19:46 irqbypass
-r--r--r--  1 root root  100225 Nov  4 19:46 kvm
-r--r--r--  1 root root   35401 Nov  4 19:46 kvm_intel
-r--r--r--  1 root root     120 Nov  4 19:46 pcspkr
-r--r--r--  1 root root     399 Nov  4 19:46 serio_raw
-r--r--r--  1 root root 4094095 Nov  4 19:46 vmlinux

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/bpf/20201110011932.3201430-5-andrii@kernel.org
---
 Documentation/ABI/testing/sysfs-kernel-btf |   8 +
 include/linux/bpf.h                        |   2 +
 include/linux/module.h                     |   4 +
 kernel/bpf/btf.c                           | 194 +++++++++++++++++++++
 kernel/bpf/sysfs_btf.c                     |   2 +-
 kernel/module.c                            |  32 ++++
 6 files changed, 241 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-kernel-btf b/Documentation/ABI/testing/sysfs-kernel-btf
index 2c9744b2cd59f..fe96efdc9b6c2 100644
--- a/Documentation/ABI/testing/sysfs-kernel-btf
+++ b/Documentation/ABI/testing/sysfs-kernel-btf
@@ -15,3 +15,11 @@ Description:
 		information with description of all internal kernel types. See
 		Documentation/bpf/btf.rst for detailed description of format
 		itself.
+
+What:		/sys/kernel/btf/<module-name>
+Date:		Nov 2020
+KernelVersion:	5.11
+Contact:	bpf@vger.kernel.org
+Description:
+		Read-only binary attribute exposing kernel module's BTF type
+		information as an add-on to the kernel's BTF (/sys/kernel/btf/vmlinux).
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 73d5381a5d5c4..581b2a2e78eb7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -36,9 +36,11 @@ struct seq_operations;
 struct bpf_iter_aux_info;
 struct bpf_local_storage;
 struct bpf_local_storage_map;
+struct kobject;
 
 extern struct idr btf_idr;
 extern spinlock_t btf_idr_lock;
+extern struct kobject *btf_kobj;
 
 typedef int (*bpf_iter_init_seq_priv_t)(void *private_data,
 					struct bpf_iter_aux_info *aux);
diff --git a/include/linux/module.h b/include/linux/module.h
index a29187f7c360e..20fce258ffba0 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -475,6 +475,10 @@ struct module {
 	unsigned int num_bpf_raw_events;
 	struct bpf_raw_event_map *bpf_raw_events;
 #endif
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+	unsigned int btf_data_size;
+	void *btf_data;
+#endif
 #ifdef CONFIG_JUMP_LABEL
 	struct jump_entry *jump_entries;
 	unsigned int num_jump_entries;
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 856585db7aa72..0f1fd2669d697 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -22,6 +22,8 @@
 #include <linux/skmsg.h>
 #include <linux/perf_event.h>
 #include <linux/bsearch.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
 #include <net/sock.h>
 
 /* BTF (BPF Type Format) is the meta data format which describes
@@ -4476,6 +4478,75 @@ struct btf *btf_parse_vmlinux(void)
 	return ERR_PTR(err);
 }
 
+static struct btf *btf_parse_module(const char *module_name, const void *data, unsigned int data_size)
+{
+	struct btf_verifier_env *env = NULL;
+	struct bpf_verifier_log *log;
+	struct btf *btf = NULL, *base_btf;
+	int err;
+
+	base_btf = bpf_get_btf_vmlinux();
+	if (IS_ERR(base_btf))
+		return base_btf;
+	if (!base_btf)
+		return ERR_PTR(-EINVAL);
+
+	env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
+	if (!env)
+		return ERR_PTR(-ENOMEM);
+
+	log = &env->log;
+	log->level = BPF_LOG_KERNEL;
+
+	btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
+	if (!btf) {
+		err = -ENOMEM;
+		goto errout;
+	}
+	env->btf = btf;
+
+	btf->base_btf = base_btf;
+	btf->start_id = base_btf->nr_types;
+	btf->start_str_off = base_btf->hdr.str_len;
+	btf->kernel_btf = true;
+	snprintf(btf->name, sizeof(btf->name), "%s", module_name);
+
+	btf->data = kvmalloc(data_size, GFP_KERNEL | __GFP_NOWARN);
+	if (!btf->data) {
+		err = -ENOMEM;
+		goto errout;
+	}
+	memcpy(btf->data, data, data_size);
+	btf->data_size = data_size;
+
+	err = btf_parse_hdr(env);
+	if (err)
+		goto errout;
+
+	btf->nohdr_data = btf->data + btf->hdr.hdr_len;
+
+	err = btf_parse_str_sec(env);
+	if (err)
+		goto errout;
+
+	err = btf_check_all_metas(env);
+	if (err)
+		goto errout;
+
+	btf_verifier_env_free(env);
+	refcount_set(&btf->refcnt, 1);
+	return btf;
+
+errout:
+	btf_verifier_env_free(env);
+	if (btf) {
+		kvfree(btf->data);
+		kvfree(btf->types);
+		kfree(btf);
+	}
+	return ERR_PTR(err);
+}
+
 struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog)
 {
 	struct bpf_prog *tgt_prog = prog->aux->dst_prog;
@@ -5651,3 +5722,126 @@ bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
 {
 	return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
 }
+
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+struct btf_module {
+	struct list_head list;
+	struct module *module;
+	struct btf *btf;
+	struct bin_attribute *sysfs_attr;
+};
+
+static LIST_HEAD(btf_modules);
+static DEFINE_MUTEX(btf_module_mutex);
+
+static ssize_t
+btf_module_read(struct file *file, struct kobject *kobj,
+		struct bin_attribute *bin_attr,
+		char *buf, loff_t off, size_t len)
+{
+	const struct btf *btf = bin_attr->private;
+
+	memcpy(buf, btf->data + off, len);
+	return len;
+}
+
+static int btf_module_notify(struct notifier_block *nb, unsigned long op,
+			     void *module)
+{
+	struct btf_module *btf_mod, *tmp;
+	struct module *mod = module;
+	struct btf *btf;
+	int err = 0;
+
+	if (mod->btf_data_size == 0 ||
+	    (op != MODULE_STATE_COMING && op != MODULE_STATE_GOING))
+		goto out;
+
+	switch (op) {
+	case MODULE_STATE_COMING:
+		btf_mod = kzalloc(sizeof(*btf_mod), GFP_KERNEL);
+		if (!btf_mod) {
+			err = -ENOMEM;
+			goto out;
+		}
+		btf = btf_parse_module(mod->name, mod->btf_data, mod->btf_data_size);
+		if (IS_ERR(btf)) {
+			pr_warn("failed to validate module [%s] BTF: %ld\n",
+				mod->name, PTR_ERR(btf));
+			kfree(btf_mod);
+			err = PTR_ERR(btf);
+			goto out;
+		}
+		err = btf_alloc_id(btf);
+		if (err) {
+			btf_free(btf);
+			kfree(btf_mod);
+			goto out;
+		}
+
+		mutex_lock(&btf_module_mutex);
+		btf_mod->module = module;
+		btf_mod->btf = btf;
+		list_add(&btf_mod->list, &btf_modules);
+		mutex_unlock(&btf_module_mutex);
+
+		if (IS_ENABLED(CONFIG_SYSFS)) {
+			struct bin_attribute *attr;
+
+			attr = kzalloc(sizeof(*attr), GFP_KERNEL);
+			if (!attr)
+				goto out;
+
+			sysfs_bin_attr_init(attr);
+			attr->attr.name = btf->name;
+			attr->attr.mode = 0444;
+			attr->size = btf->data_size;
+			attr->private = btf;
+			attr->read = btf_module_read;
+
+			err = sysfs_create_bin_file(btf_kobj, attr);
+			if (err) {
+				pr_warn("failed to register module [%s] BTF in sysfs: %d\n",
+					mod->name, err);
+				kfree(attr);
+				err = 0;
+				goto out;
+			}
+
+			btf_mod->sysfs_attr = attr;
+		}
+
+		break;
+	case MODULE_STATE_GOING:
+		mutex_lock(&btf_module_mutex);
+		list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) {
+			if (btf_mod->module != module)
+				continue;
+
+			list_del(&btf_mod->list);
+			if (btf_mod->sysfs_attr)
+				sysfs_remove_bin_file(btf_kobj, btf_mod->sysfs_attr);
+			btf_put(btf_mod->btf);
+			kfree(btf_mod->sysfs_attr);
+			kfree(btf_mod);
+			break;
+		}
+		mutex_unlock(&btf_module_mutex);
+		break;
+	}
+out:
+	return notifier_from_errno(err);
+}
+
+static struct notifier_block btf_module_nb = {
+	.notifier_call = btf_module_notify,
+};
+
+static int __init btf_module_init(void)
+{
+	register_module_notifier(&btf_module_nb);
+	return 0;
+}
+
+fs_initcall(btf_module_init);
+#endif /* CONFIG_DEBUG_INFO_BTF_MODULES */
diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c
index 11b3380887fa0..ef6911aee3bbb 100644
--- a/kernel/bpf/sysfs_btf.c
+++ b/kernel/bpf/sysfs_btf.c
@@ -26,7 +26,7 @@ static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
 	.read = btf_vmlinux_read,
 };
 
-static struct kobject *btf_kobj;
+struct kobject *btf_kobj;
 
 static int __init btf_vmlinux_init(void)
 {
diff --git a/kernel/module.c b/kernel/module.c
index a4fa44a652a75..f2996b02ab2e4 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -380,6 +380,35 @@ static void *section_objs(const struct load_info *info,
 	return (void *)info->sechdrs[sec].sh_addr;
 }
 
+/* Find a module section: 0 means not found. Ignores SHF_ALLOC flag. */
+static unsigned int find_any_sec(const struct load_info *info, const char *name)
+{
+	unsigned int i;
+
+	for (i = 1; i < info->hdr->e_shnum; i++) {
+		Elf_Shdr *shdr = &info->sechdrs[i];
+		if (strcmp(info->secstrings + shdr->sh_name, name) == 0)
+			return i;
+	}
+	return 0;
+}
+
+/*
+ * Find a module section, or NULL. Fill in number of "objects" in section.
+ * Ignores SHF_ALLOC flag.
+ */
+static __maybe_unused void *any_section_objs(const struct load_info *info,
+					     const char *name,
+					     size_t object_size,
+					     unsigned int *num)
+{
+	unsigned int sec = find_any_sec(info, name);
+
+	/* Section 0 has sh_addr 0 and sh_size 0. */
+	*num = info->sechdrs[sec].sh_size / object_size;
+	return (void *)info->sechdrs[sec].sh_addr;
+}
+
 /* Provided by the linker */
 extern const struct kernel_symbol __start___ksymtab[];
 extern const struct kernel_symbol __stop___ksymtab[];
@@ -3250,6 +3279,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 					   sizeof(*mod->bpf_raw_events),
 					   &mod->num_bpf_raw_events);
 #endif
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+	mod->btf_data = any_section_objs(info, ".BTF", 1, &mod->btf_data_size);
+#endif
 #ifdef CONFIG_JUMP_LABEL
 	mod->jump_entries = section_objs(info, "__jump_table",
 					sizeof(*mod->jump_entries),

From cecaf4a0f2dcbd7e76156f6d63748b84c176b95b Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@kernel.org>
Date: Mon, 9 Nov 2020 17:19:32 -0800
Subject: [PATCH 5/5] tools/bpftool: Add support for in-kernel and named BTF in
 `btf show`

Display vmlinux BTF name and kernel module names when listing available BTFs
on the system.

In human-readable output mode, module BTFs are reported with "name
[module-name]", while vmlinux BTF will be reported as "name [vmlinux]".
Square brackets are added by bpftool and follow kernel convention when
displaying modules in human-readable text outputs.

[vmuser@archvm bpf]$ sudo ../../../bpf/bpftool/bpftool btf s
1: name [vmlinux]  size 4082281B
6: size 2365B  prog_ids 8,6  map_ids 3
7: name [button]  size 46895B
8: name [pcspkr]  size 42328B
9: name [serio_raw]  size 39375B
10: name [floppy]  size 57185B
11: name [i2c_core]  size 76186B
12: name [crc32c_intel]  size 16036B
13: name [i2c_piix4]  size 50497B
14: name [irqbypass]  size 14124B
15: name [kvm]  size 197985B
16: name [kvm_intel]  size 123564B
17: name [cryptd]  size 42466B
18: name [crypto_simd]  size 17187B
19: name [glue_helper]  size 39205B
20: name [aesni_intel]  size 41034B
25: size 36150B
        pids bpftool(2519)

In JSON mode, two fields (boolean "kernel" and string "name") are reported for
each BTF object. vmlinux BTF is reported with name "vmlinux" (kernel itself
returns and empty name for vmlinux BTF).

[vmuser@archvm bpf]$ sudo ../../../bpf/bpftool/bpftool btf s -jp
[{
        "id": 1,
        "size": 4082281,
        "prog_ids": [],
        "map_ids": [],
        "kernel": true,
        "name": "vmlinux"
    },{
        "id": 6,
        "size": 2365,
        "prog_ids": [8,6
        ],
        "map_ids": [3
        ],
        "kernel": false
    },{
        "id": 7,
        "size": 46895,
        "prog_ids": [],
        "map_ids": [],
        "kernel": true,
        "name": "button"
    },{

...

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/bpf/20201110011932.3201430-6-andrii@kernel.org
---
 tools/bpf/bpftool/btf.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index c96b56e8e3a42..ed5e971572414 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -742,9 +742,14 @@ show_btf_plain(struct bpf_btf_info *info, int fd,
 	       struct btf_attach_table *btf_map_table)
 {
 	struct btf_attach_point *obj;
+	const char *name = u64_to_ptr(info->name);
 	int n;
 
 	printf("%u: ", info->id);
+	if (info->kernel_btf)
+		printf("name [%s]  ", name);
+	else if (name && name[0])
+		printf("name %s  ", name);
 	printf("size %uB", info->btf_size);
 
 	n = 0;
@@ -771,6 +776,7 @@ show_btf_json(struct bpf_btf_info *info, int fd,
 	      struct btf_attach_table *btf_map_table)
 {
 	struct btf_attach_point *obj;
+	const char *name = u64_to_ptr(info->name);
 
 	jsonw_start_object(json_wtr);	/* btf object */
 	jsonw_uint_field(json_wtr, "id", info->id);
@@ -796,6 +802,11 @@ show_btf_json(struct bpf_btf_info *info, int fd,
 
 	emit_obj_refs_json(&refs_table, info->id, json_wtr); /* pids */
 
+	jsonw_bool_field(json_wtr, "kernel", info->kernel_btf);
+
+	if (name && name[0])
+		jsonw_string_field(json_wtr, "name", name);
+
 	jsonw_end_object(json_wtr);	/* btf object */
 }
 
@@ -803,15 +814,30 @@ static int
 show_btf(int fd, struct btf_attach_table *btf_prog_table,
 	 struct btf_attach_table *btf_map_table)
 {
-	struct bpf_btf_info info = {};
+	struct bpf_btf_info info;
 	__u32 len = sizeof(info);
+	char name[64];
 	int err;
 
+	memset(&info, 0, sizeof(info));
 	err = bpf_obj_get_info_by_fd(fd, &info, &len);
 	if (err) {
 		p_err("can't get BTF object info: %s", strerror(errno));
 		return -1;
 	}
+	/* if kernel support emitting BTF object name, pass name pointer */
+	if (info.name_len) {
+		memset(&info, 0, sizeof(info));
+		info.name_len = sizeof(name);
+		info.name = ptr_to_u64(name);
+		len = sizeof(info);
+
+		err = bpf_obj_get_info_by_fd(fd, &info, &len);
+		if (err) {
+			p_err("can't get BTF object info: %s", strerror(errno));
+			return -1;
+		}
+	}
 
 	if (json_output)
 		show_btf_json(&info, fd, btf_prog_table, btf_map_table);