Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Daniel Borkmann says:

====================
pull-request: bpf-next 2020-11-14

1) Add BTF generation for kernel modules and extend BTF infra in kernel
   e.g. support for split BTF loading and validation, from Andrii Nakryiko.

2) Support for pointers beyond pkt_end to recognize LLVM generated patterns
   on inlined branch conditions, from Alexei Starovoitov.

3) Implements bpf_local_storage for task_struct for BPF LSM, from KP Singh.

4) Enable FENTRY/FEXIT/RAW_TP tracing program to use the bpf_sk_storage
   infra, from Martin KaFai Lau.

5) Add XDP bulk APIs that introduce a defer/flush mechanism to optimize the
   XDP_REDIRECT path, from Lorenzo Bianconi.

6) Fix a potential (although rather theoretical) deadlock of hashtab in NMI
   context, from Song Liu.

7) Fixes for cross and out-of-tree build of bpftool and runqslower allowing build
   for different target archs on same source tree, from Jean-Philippe Brucker.

8) Fix error path in htab_map_alloc() triggered from syzbot, from Eric Dumazet.

9) Move functionality from test_tcpbpf_user into the test_progs framework so it
   can run in BPF CI, from Alexander Duyck.

10) Lift hashtab key_size limit to be larger than MAX_BPF_STACK, from Florian Lehner.

Note that for the fix from Song we have seen a sparse report on context
imbalance which requires changes in sparse itself for proper annotation
detection where this is currently being discussed on linux-sparse among
developers [0]. Once we have more clarification/guidance after their fix,
Song will follow-up.

  [0] https://lore.kernel.org/linux-sparse/CAHk-=wh4bx8A8dHnX612MsDO13st6uzAz1mJ1PaHHVevJx_ZCw@mail.gmail.com/T/
      https://lore.kernel.org/linux-sparse/20201109221345.uklbp3lzgq6g42zb@ltop.local/T/

* git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (66 commits)
  net: mlx5: Add xdp tx return bulking support
  net: mvpp2: Add xdp tx return bulking support
  net: mvneta: Add xdp tx return bulking support
  net: page_pool: Add bulk support for ptr_ring
  net: xdp: Introduce bulking for xdp tx return path
  bpf: Expose bpf_d_path helper to sleepable LSM hooks
  bpf: Augment the set of sleepable LSM hooks
  bpf: selftest: Use bpf_sk_storage in FENTRY/FEXIT/RAW_TP
  bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP
  bpf: Rename some functions in bpf_sk_storage
  bpf: Folding omem_charge() into sk_storage_charge()
  selftests/bpf: Add asm tests for pkt vs pkt_end comparison.
  selftests/bpf: Add skb_pkt_end test
  bpf: Support for pointers beyond pkt_end.
  tools/bpf: Always run the *-clean recipes
  tools/bpf: Add bootstrap/ to .gitignore
  bpf: Fix NULL dereference in bpf_task_storage
  tools/bpftool: Fix build slowdown
  tools/runqslower: Build bpftool using HOSTCC
  tools/runqslower: Enable out-of-tree build
  ...
====================

Link: https://lore.kernel.org/r/20201114020819.29584-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 490 insertions, 335 deletions

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 231b07203e3d..2d0d064c6d31 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -78,10 +78,32 @@ struct btf {
 	void *types_data;
 	size_t types_data_cap; /* used size stored in hdr->type_len */
 
-	/* type ID to `struct btf_type *` lookup index */
+	/* type ID to `struct btf_type *` lookup index
+	 * type_offs[0] corresponds to the first non-VOID type:
+	 *   - for base BTF it's type [1];
+	 *   - for split BTF it's the first non-base BTF type.
+	 */
 	__u32 *type_offs;
 	size_t type_offs_cap;
+	/* number of types in this BTF instance:
+	 *   - doesn't include special [0] void type;
+	 *   - for split BTF counts number of types added on top of base BTF.
+	 */
 	__u32 nr_types;
+	/* if not NULL, points to the base BTF on top of which the current
+	 * split BTF is based
+	 */
+	struct btf *base_btf;
+	/* BTF type ID of the first type in this BTF instance:
+	 *   - for base BTF it's equal to 1;
+	 *   - for split BTF it's equal to biggest type ID of base BTF plus 1.
+	 */
+	int start_id;
+	/* logical string offset of this BTF instance:
+	 *   - for base BTF it's equal to 0;
+	 *   - for split BTF it's equal to total size of base BTF's string section size.
+	 */
+	int start_str_off;
 
 	void *strs_data;
 	size_t strs_data_cap; /* used size stored in hdr->str_len */
@@ -90,6 +112,14 @@ struct btf {
 	struct hashmap *strs_hash;
 	/* whether strings are already deduplicated */
 	bool strs_deduped;
+	/* extra indirection layer to make strings hashmap work with stable
+	 * string offsets and ability to transparently choose between
+	 * btf->strs_data or btf_dedup->strs_data as a source of strings.
+	 * This is used for BTF strings dedup to transfer deduplicated strings
+	 * data back to struct btf without re-building strings index.
+	 */
+	void **strs_data_ptr;
+
 	/* BTF object FD, if loaded into kernel */
 	int fd;
 
@@ -168,7 +198,7 @@ static int btf_add_type_idx_entry(struct btf *btf, __u32 type_off)
 	__u32 *p;
 
 	p = btf_add_mem((void **)&btf->type_offs, &btf->type_offs_cap, sizeof(__u32),
-			btf->nr_types + 1, BTF_MAX_NR_TYPES, 1);
+			btf->nr_types, BTF_MAX_NR_TYPES, 1);
 	if (!p)
 		return -ENOMEM;
 
@@ -215,22 +245,18 @@ static int btf_parse_hdr(struct btf *btf)
 		return -EINVAL;
 	}
 
-	if (meta_left < hdr->type_off) {
-		pr_debug("Invalid BTF type section offset:%u\n", hdr->type_off);
-		return -EINVAL;
-	}
-
-	if (meta_left < hdr->str_off) {
-		pr_debug("Invalid BTF string section offset:%u\n", hdr->str_off);
+	if (meta_left < hdr->str_off + hdr->str_len) {
+		pr_debug("Invalid BTF total size:%u\n", btf->raw_size);
 		return -EINVAL;
 	}
 
-	if (hdr->type_off >= hdr->str_off) {
-		pr_debug("BTF type section offset >= string section offset. No type?\n");
+	if (hdr->type_off + hdr->type_len > hdr->str_off) {
+		pr_debug("Invalid BTF data sections layout: type data at %u + %u, strings data at %u + %u\n",
+			 hdr->type_off, hdr->type_len, hdr->str_off, hdr->str_len);
 		return -EINVAL;
 	}
 
-	if (hdr->type_off & 0x02) {
+	if (hdr->type_off % 4) {
 		pr_debug("BTF type section is not aligned to 4 bytes\n");
 		return -EINVAL;
 	}
@@ -244,12 +270,16 @@ static int btf_parse_str_sec(struct btf *btf)
 	const char *start = btf->strs_data;
 	const char *end = start + btf->hdr->str_len;
 
-	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_STR_OFFSET ||
-	    start[0] || end[-1]) {
+	if (btf->base_btf && hdr->str_len == 0)
+		return 0;
+	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_STR_OFFSET || end[-1]) {
+		pr_debug("Invalid BTF string section\n");
+		return -EINVAL;
+	}
+	if (!btf->base_btf && start[0]) {
 		pr_debug("Invalid BTF string section\n");
 		return -EINVAL;
 	}
-
 	return 0;
 }
 
@@ -364,19 +394,9 @@ static int btf_parse_type_sec(struct btf *btf)
 	struct btf_header *hdr = btf->hdr;
 	void *next_type = btf->types_data;
 	void *end_type = next_type + hdr->type_len;
-	int err, i = 0, type_size;
-
-	/* VOID (type_id == 0) is specially handled by btf__get_type_by_id(),
-	 * so ensure we can never properly use its offset from index by
-	 * setting it to a large value
-	 */
-	err = btf_add_type_idx_entry(btf, UINT_MAX);
-	if (err)
-		return err;
+	int err, type_size;
 
 	while (next_type + sizeof(struct btf_type) <= end_type) {
-		i++;
-
 		if (btf->swapped_endian)
 			btf_bswap_type_base(next_type);
 
@@ -384,7 +404,7 @@ static int btf_parse_type_sec(struct btf *btf)
 		if (type_size < 0)
 			return type_size;
 		if (next_type + type_size > end_type) {
-			pr_warn("BTF type [%d] is malformed\n", i);
+			pr_warn("BTF type [%d] is malformed\n", btf->start_id + btf->nr_types);
 			return -EINVAL;
 		}
 
@@ -409,7 +429,7 @@ static int btf_parse_type_sec(struct btf *btf)
 
 __u32 btf__get_nr_types(const struct btf *btf)
 {
-	return btf->nr_types;
+	return btf->start_id + btf->nr_types - 1;
 }
 
 /* internal helper returning non-const pointer to a type */
@@ -417,13 +437,14 @@ static struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id)
 {
 	if (type_id == 0)
 		return &btf_void;
-
-	return btf->types_data + btf->type_offs[type_id];
+	if (type_id < btf->start_id)
+		return btf_type_by_id(btf->base_btf, type_id);
+	return btf->types_data + btf->type_offs[type_id - btf->start_id];
 }
 
 const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id)
 {
-	if (type_id > btf->nr_types)
+	if (type_id >= btf->start_id + btf->nr_types)
 		return NULL;
 	return btf_type_by_id((struct btf *)btf, type_id);
 }
@@ -432,9 +453,13 @@ static int determine_ptr_size(const struct btf *btf)
 {
 	const struct btf_type *t;
 	const char *name;
-	int i;
+	int i, n;
 
-	for (i = 1; i <= btf->nr_types; i++) {
+	if (btf->base_btf && btf->base_btf->ptr_sz > 0)
+		return btf->base_btf->ptr_sz;
+
+	n = btf__get_nr_types(btf);
+	for (i = 1; i <= n; i++) {
 		t = btf__type_by_id(btf, i);
 		if (!btf_is_int(t))
 			continue;
@@ -717,7 +742,7 @@ void btf__free(struct btf *btf)
 	free(btf);
 }
 
-struct btf *btf__new_empty(void)
+static struct btf *btf_new_empty(struct btf *base_btf)
 {
 	struct btf *btf;
 
@@ -725,12 +750,21 @@ struct btf *btf__new_empty(void)
 	if (!btf)
 		return ERR_PTR(-ENOMEM);
 
+	btf->nr_types = 0;
+	btf->start_id = 1;
+	btf->start_str_off = 0;
 	btf->fd = -1;
 	btf->ptr_sz = sizeof(void *);
 	btf->swapped_endian = false;
 
+	if (base_btf) {
+		btf->base_btf = base_btf;
+		btf->start_id = btf__get_nr_types(base_btf) + 1;
+		btf->start_str_off = base_btf->hdr->str_len;
+	}
+
 	/* +1 for empty string at offset 0 */
-	btf->raw_size = sizeof(struct btf_header) + 1;
+	btf->raw_size = sizeof(struct btf_header) + (base_btf ? 0 : 1);
 	btf->raw_data = calloc(1, btf->raw_size);
 	if (!btf->raw_data) {
 		free(btf);
@@ -744,12 +778,22 @@ struct btf *btf__new_empty(void)
 
 	btf->types_data = btf->raw_data + btf->hdr->hdr_len;
 	btf->strs_data = btf->raw_data + btf->hdr->hdr_len;
-	btf->hdr->str_len = 1; /* empty string at offset 0 */
+	btf->hdr->str_len = base_btf ? 0 : 1; /* empty string at offset 0 */
 
 	return btf;
 }
 
-struct btf *btf__new(const void *data, __u32 size)
+struct btf *btf__new_empty(void)
+{
+	return btf_new_empty(NULL);
+}
+
+struct btf *btf__new_empty_split(struct btf *base_btf)
+{
+	return btf_new_empty(base_btf);
+}
+
+static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf)
 {
 	struct btf *btf;
 	int err;
@@ -758,6 +802,16 @@ struct btf *btf__new(const void *data, __u32 size)
 	if (!btf)
 		return ERR_PTR(-ENOMEM);
 
+	btf->nr_types = 0;
+	btf->start_id = 1;
+	btf->start_str_off = 0;
+
+	if (base_btf) {
+		btf->base_btf = base_btf;
+		btf->start_id = btf__get_nr_types(base_btf) + 1;
+		btf->start_str_off = base_btf->hdr->str_len;
+	}
+
 	btf->raw_data = malloc(size);
 	if (!btf->raw_data) {
 		err = -ENOMEM;
@@ -790,7 +844,13 @@ done:
 	return btf;
 }
 
-struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
+struct btf *btf__new(const void *data, __u32 size)
+{
+	return btf_new(data, size, NULL);
+}
+
+static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
+				 struct btf_ext **btf_ext)
 {
 	Elf_Data *btf_data = NULL, *btf_ext_data = NULL;
 	int err = 0, fd = -1, idx = 0;
@@ -868,7 +928,7 @@ struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
 		err = -ENOENT;
 		goto done;
 	}
-	btf = btf__new(btf_data->d_buf, btf_data->d_size);
+	btf = btf_new(btf_data->d_buf, btf_data->d_size, base_btf);
 	if (IS_ERR(btf))
 		goto done;
 
@@ -913,7 +973,17 @@ done:
 	return btf;
 }
 
-struct btf *btf__parse_raw(const char *path)
+struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
+{
+	return btf_parse_elf(path, NULL, btf_ext);
+}
+
+struct btf *btf__parse_elf_split(const char *path, struct btf *base_btf)
+{
+	return btf_parse_elf(path, base_btf, NULL);
+}
+
+static struct btf *btf_parse_raw(const char *path, struct btf *base_btf)
 {
 	struct btf *btf = NULL;
 	void *data = NULL;
@@ -967,7 +1037,7 @@ struct btf *btf__parse_raw(const char *path)
 	}
 
 	/* finally parse BTF data */
-	btf = btf__new(data, sz);
+	btf = btf_new(data, sz, base_btf);
 
 err_out:
 	free(data);
@@ -976,18 +1046,38 @@ err_out:
 	return err ? ERR_PTR(err) : btf;
 }
 
-struct btf *btf__parse(const char *path, struct btf_ext **btf_ext)
+struct btf *btf__parse_raw(const char *path)
+{
+	return btf_parse_raw(path, NULL);
+}
+
+struct btf *btf__parse_raw_split(const char *path, struct btf *base_btf)
+{
+	return btf_parse_raw(path, base_btf);
+}
+
+static struct btf *btf_parse(const char *path, struct btf *base_btf, struct btf_ext **btf_ext)
 {
 	struct btf *btf;
 
 	if (btf_ext)
 		*btf_ext = NULL;
 
-	btf = btf__parse_raw(path);
+	btf = btf_parse_raw(path, base_btf);
 	if (!IS_ERR(btf) || PTR_ERR(btf) != -EPROTO)
 		return btf;
 
-	return btf__parse_elf(path, btf_ext);
+	return btf_parse_elf(path, base_btf, btf_ext);
+}
+
+struct btf *btf__parse(const char *path, struct btf_ext **btf_ext)
+{
+	return btf_parse(path, NULL, btf_ext);
+}
+
+struct btf *btf__parse_split(const char *path, struct btf *base_btf)
+{
+	return btf_parse(path, base_btf, NULL);
 }
 
 static int compare_vsi_off(const void *_a, const void *_b)
@@ -1171,8 +1261,8 @@ static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endi
 
 	memcpy(p, btf->types_data, hdr->type_len);
 	if (swap_endian) {
-		for (i = 1; i <= btf->nr_types; i++) {
-			t = p  + btf->type_offs[i];
+		for (i = 0; i < btf->nr_types; i++) {
+			t = p + btf->type_offs[i];
 			/* btf_bswap_type_rest() relies on native t->info, so
 			 * we swap base type info after we swapped all the
 			 * additional information
@@ -1215,8 +1305,10 @@ const void *btf__get_raw_data(const struct btf *btf_ro, __u32 *size)
 
 const char *btf__str_by_offset(const struct btf *btf, __u32 offset)
 {
-	if (offset < btf->hdr->str_len)
-		return btf->strs_data + offset;
+	if (offset < btf->start_str_off)
+		return btf__str_by_offset(btf->base_btf, offset);
+	else if (offset - btf->start_str_off < btf->hdr->str_len)
+		return btf->strs_data + (offset - btf->start_str_off);
 	else
 		return NULL;
 }
@@ -1363,17 +1455,19 @@ int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
 
 static size_t strs_hash_fn(const void *key, void *ctx)
 {
-	struct btf *btf = ctx;
-	const char *str = btf->strs_data + (long)key;
+	const struct btf *btf = ctx;
+	const char *strs = *btf->strs_data_ptr;
+	const char *str = strs + (long)key;
 
 	return str_hash(str);
 }
 
 static bool strs_hash_equal_fn(const void *key1, const void *key2, void *ctx)
 {
-	struct btf *btf = ctx;
-	const char *str1 = btf->strs_data + (long)key1;
-	const char *str2 = btf->strs_data + (long)key2;
+	const struct btf *btf = ctx;
+	const char *strs = *btf->strs_data_ptr;
+	const char *str1 = strs + (long)key1;
+	const char *str2 = strs + (long)key2;
 
 	return strcmp(str1, str2) == 0;
 }
@@ -1418,6 +1512,9 @@ static int btf_ensure_modifiable(struct btf *btf)
 	memcpy(types, btf->types_data, btf->hdr->type_len);
 	memcpy(strs, btf->strs_data, btf->hdr->str_len);
 
+	/* make hashmap below use btf->strs_data as a source of strings */
+	btf->strs_data_ptr = &btf->strs_data;
+
 	/* build lookup index for all strings */
 	hash = hashmap__new(strs_hash_fn, strs_hash_equal_fn, btf);
 	if (IS_ERR(hash)) {
@@ -1448,7 +1545,10 @@ static int btf_ensure_modifiable(struct btf *btf)
 	/* if BTF was created from scratch, all strings are guaranteed to be
 	 * unique and deduplicated
 	 */
-	btf->strs_deduped = btf->hdr->str_len <= 1;
+	if (btf->hdr->str_len == 0)
+		btf->strs_deduped = true;
+	if (!btf->base_btf && btf->hdr->str_len == 1)
+		btf->strs_deduped = true;
 
 	/* invalidate raw_data representation */
 	btf_invalidate_raw_data(btf);
@@ -1480,6 +1580,14 @@ int btf__find_str(struct btf *btf, const char *s)
 	long old_off, new_off, len;
 	void *p;
 
+	if (btf->base_btf) {
+		int ret;
+
+		ret = btf__find_str(btf->base_btf, s);
+		if (ret != -ENOENT)
+			return ret;
+	}
+
 	/* BTF needs to be in a modifiable state to build string lookup index */
 	if (btf_ensure_modifiable(btf))
 		return -ENOMEM;
@@ -1494,7 +1602,7 @@ int btf__find_str(struct btf *btf, const char *s)
 	memcpy(p, s, len);
 
 	if (hashmap__find(btf->strs_hash, (void *)new_off, (void **)&old_off))
-		return old_off;
+		return btf->start_str_off + old_off;
 
 	return -ENOENT;
 }
@@ -1510,6 +1618,14 @@ int btf__add_str(struct btf *btf, const char *s)
 	void *p;
 	int err;
 
+	if (btf->base_btf) {
+		int ret;
+
+		ret = btf__find_str(btf->base_btf, s);
+		if (ret != -ENOENT)
+			return ret;
+	}
+
 	if (btf_ensure_modifiable(btf))
 		return -ENOMEM;
 
@@ -1536,12 +1652,12 @@ int btf__add_str(struct btf *btf, const char *s)
 	err = hashmap__insert(btf->strs_hash, (void *)new_off, (void *)new_off,
 			      HASHMAP_ADD, (const void **)&old_off, NULL);
 	if (err == -EEXIST)
-		return old_off; /* duplicated string, return existing offset */
+		return btf->start_str_off + old_off; /* duplicated string, return existing offset */
 	if (err)
 		return err;
 
 	btf->hdr->str_len += len; /* new unique string, adjust data length */
-	return new_off;
+	return btf->start_str_off + new_off;
 }
 
 static void *btf_add_type_mem(struct btf *btf, size_t add_sz)
@@ -1560,6 +1676,20 @@ static void btf_type_inc_vlen(struct btf_type *t)
 	t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, btf_kflag(t));
 }
 
+static int btf_commit_type(struct btf *btf, int data_sz)
+{
+	int err;
+
+	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
+	if (err)
+		return err;
+
+	btf->hdr->type_len += data_sz;
+	btf->hdr->str_off += data_sz;
+	btf->nr_types++;
+	return btf->start_id + btf->nr_types - 1;
+}
+
 /*
  * Append new BTF_KIND_INT type with:
  *   - *name* - non-empty, non-NULL type name;
@@ -1572,7 +1702,7 @@ static void btf_type_inc_vlen(struct btf_type *t)
 int btf__add_int(struct btf *btf, const char *name, size_t byte_sz, int encoding)
 {
 	struct btf_type *t;
-	int sz, err, name_off;
+	int sz, name_off;
 
 	/* non-empty name */
 	if (!name || !name[0])
@@ -1606,14 +1736,7 @@ int btf__add_int(struct btf *btf, const char *name, size_t byte_sz, int encoding
 	/* set INT info, we don't allow setting legacy bit offset/size */
 	*(__u32 *)(t + 1) = (encoding << 24) | (byte_sz * 8);
 
-	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
-	if (err)
-		return err;
-
-	btf->hdr->type_len += sz;
-	btf->hdr->str_off += sz;
-	btf->nr_types++;
-	return btf->nr_types;
+	return btf_commit_type(btf, sz);
 }
 
 /* it's completely legal to append BTF types with type IDs pointing forward to
@@ -1631,7 +1754,7 @@ static int validate_type_id(int id)
 static int btf_add_ref_kind(struct btf *btf, int kind, const char *name, int ref_type_id)
 {
 	struct btf_type *t;
-	int sz, name_off = 0, err;
+	int sz, name_off = 0;
 
 	if (validate_type_id(ref_type_id))
 		return -EINVAL;
@@ -1654,14 +1777,7 @@ static int btf_add_ref_kind(struct btf *btf, int kind, const char *name, int ref
 	t->info = btf_type_info(kind, 0, 0);
 	t->type = ref_type_id;
 
-	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
-	if (err)
-		return err;
-
-	btf->hdr->type_len += sz;
-	btf->hdr->str_off += sz;
-	btf->nr_types++;
-	return btf->nr_types;
+	return btf_commit_type(btf, sz);
 }
 
 /*
@@ -1689,7 +1805,7 @@ int btf__add_array(struct btf *btf, int index_type_id, int elem_type_id, __u32 n
 {
 	struct btf_type *t;
 	struct btf_array *a;
-	int sz, err;
+	int sz;
 
 	if (validate_type_id(index_type_id) || validate_type_id(elem_type_id))
 		return -EINVAL;
@@ -1711,21 +1827,14 @@ int btf__add_array(struct btf *btf, int index_type_id, int elem_type_id, __u32 n
 	a->index_type = index_type_id;
 	a->nelems = nr_elems;
 
-	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
-	if (err)
-		return err;
-
-	btf->hdr->type_len += sz;
-	btf->hdr->str_off += sz;
-	btf->nr_types++;
-	return btf->nr_types;
+	return btf_commit_type(btf, sz);
 }
 
 /* generic STRUCT/UNION append function */
 static int btf_add_composite(struct btf *btf, int kind, const char *name, __u32 bytes_sz)
 {
 	struct btf_type *t;
-	int sz, err, name_off = 0;
+	int sz, name_off = 0;
 
 	if (btf_ensure_modifiable(btf))
 		return -ENOMEM;
@@ -1748,14 +1857,7 @@ static int btf_add_composite(struct btf *btf, int kind, const char *name, __u32
 	t->info = btf_type_info(kind, 0, 0);
 	t->size = bytes_sz;
 
-	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
-	if (err)
-		return err;
-
-	btf->hdr->type_len += sz;
-	btf->hdr->str_off += sz;
-	btf->nr_types++;
-	return btf->nr_types;
+	return btf_commit_type(btf, sz);
 }
 
 /*
@@ -1793,6 +1895,11 @@ int btf__add_union(struct btf *btf, const char *name, __u32 byte_sz)
 	return btf_add_composite(btf, BTF_KIND_UNION, name, byte_sz);
 }
 
+static struct btf_type *btf_last_type(struct btf *btf)
+{
+	return btf_type_by_id(btf, btf__get_nr_types(btf));
+}
+
 /*
  * Append new field for the current STRUCT/UNION type with:
  *   - *name* - name of the field, can be NULL or empty for anonymous field;
@@ -1814,7 +1921,7 @@ int btf__add_field(struct btf *btf, const char *name, int type_id,
 	/* last type should be union/struct */
 	if (btf->nr_types == 0)
 		return -EINVAL;
-	t = btf_type_by_id(btf, btf->nr_types);
+	t = btf_last_type(btf);
 	if (!btf_is_composite(t))
 		return -EINVAL;
 
@@ -1849,7 +1956,7 @@ int btf__add_field(struct btf *btf, const char *name, int type_id,
 	m->offset = bit_offset | (bit_size << 24);
 
 	/* btf_add_type_mem can invalidate t pointer */
-	t = btf_type_by_id(btf, btf->nr_types);
+	t = btf_last_type(btf);
 	/* update parent type's vlen and kflag */
 	t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, is_bitfield || btf_kflag(t));
 
@@ -1874,7 +1981,7 @@ int btf__add_field(struct btf *btf, const char *name, int type_id,
 int btf__add_enum(struct btf *btf, const char *name, __u32 byte_sz)
 {
 	struct btf_type *t;
-	int sz, err, name_off = 0;
+	int sz, name_off = 0;
 
 	/* byte_sz must be power of 2 */
 	if (!byte_sz || (byte_sz & (byte_sz - 1)) || byte_sz > 8)
@@ -1899,14 +2006,7 @@ int btf__add_enum(struct btf *btf, const char *name, __u32 byte_sz)
 	t->info = btf_type_info(BTF_KIND_ENUM, 0, 0);
 	t->size = byte_sz;
 
-	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
-	if (err)
-		return err;
-
-	btf->hdr->type_len += sz;
-	btf->hdr->str_off += sz;
-	btf->nr_types++;
-	return btf->nr_types;
+	return btf_commit_type(btf, sz);
 }
 
 /*
@@ -1926,7 +2026,7 @@ int btf__add_enum_value(struct btf *btf, const char *name, __s64 value)
 	/* last type should be BTF_KIND_ENUM */
 	if (btf->nr_types == 0)
 		return -EINVAL;
-	t = btf_type_by_id(btf, btf->nr_types);
+	t = btf_last_type(btf);
 	if (!btf_is_enum(t))
 		return -EINVAL;
 
@@ -1953,7 +2053,7 @@ int btf__add_enum_value(struct btf *btf, const char *name, __s64 value)
 	v->val = value;
 
 	/* update parent type's vlen */
-	t = btf_type_by_id(btf, btf->nr_types);
+	t = btf_last_type(btf);
 	btf_type_inc_vlen(t);
 
 	btf->hdr->type_len += sz;
@@ -2093,7 +2193,7 @@ int btf__add_func(struct btf *btf, const char *name,
 int btf__add_func_proto(struct btf *btf, int ret_type_id)
 {
 	struct btf_type *t;
-	int sz, err;
+	int sz;
 
 	if (validate_type_id(ret_type_id))
 		return -EINVAL;
@@ -2113,14 +2213,7 @@ int btf__add_func_proto(struct btf *btf, int ret_type_id)
 	t->info = btf_type_info(BTF_KIND_FUNC_PROTO, 0, 0);
 	t->type = ret_type_id;
 
-	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
-	if (err)
-		return err;
-
-	btf->hdr->type_len += sz;
-	btf->hdr->str_off += sz;
-	btf->nr_types++;
-	return btf->nr_types;
+	return btf_commit_type(btf, sz);
 }
 
 /*
@@ -2143,7 +2236,7 @@ int btf__add_func_param(struct btf *btf, const char *name, int type_id)
 	/* last type should be BTF_KIND_FUNC_PROTO */
 	if (btf->nr_types == 0)
 		return -EINVAL;
-	t = btf_type_by_id(btf, btf->nr_types);
+	t = btf_last_type(btf);
 	if (!btf_is_func_proto(t))
 		return -EINVAL;
 
@@ -2166,7 +2259,7 @@ int btf__add_func_param(struct btf *btf, const char *name, int type_id)
 	p->type = type_id;
 
 	/* update parent type's vlen */
-	t = btf_type_by_id(btf, btf->nr_types);
+	t = btf_last_type(btf);
 	btf_type_inc_vlen(t);
 
 	btf->hdr->type_len += sz;
@@ -2188,7 +2281,7 @@ int btf__add_var(struct btf *btf, const char *name, int linkage, int type_id)
 {
 	struct btf_type *t;
 	struct btf_var *v;
-	int sz, err, name_off;
+	int sz, name_off;
 
 	/* non-empty name */
 	if (!name || !name[0])
@@ -2219,14 +2312,7 @@ int btf__add_var(struct btf *btf, const char *name, int linkage, int type_id)
 	v = btf_var(t);
 	v->linkage = linkage;
 
-	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
-	if (err)
-		return err;
-
-	btf->hdr->type_len += sz;
-	btf->hdr->str_off += sz;
-	btf->nr_types++;
-	return btf->nr_types;
+	return btf_commit_type(btf, sz);
 }
 
 /*
@@ -2244,7 +2330,7 @@ int btf__add_var(struct btf *btf, const char *name, int linkage, int type_id)
 int btf__add_datasec(struct btf *btf, const char *name, __u32 byte_sz)
 {
 	struct btf_type *t;
-	int sz, err, name_off;
+	int sz, name_off;
 
 	/* non-empty name */
 	if (!name || !name[0])
@@ -2267,14 +2353,7 @@ int btf__add_datasec(struct btf *btf, const char *name, __u32 byte_sz)
 	t->info = btf_type_info(BTF_KIND_DATASEC, 0, 0);
 	t->size = byte_sz;
 
-	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
-	if (err)
-		return err;
-
-	btf->hdr->type_len += sz;
-	btf->hdr->str_off += sz;
-	btf->nr_types++;
-	return btf->nr_types;
+	return btf_commit_type(btf, sz);
 }
 
 /*
@@ -2296,7 +2375,7 @@ int btf__add_datasec_var_info(struct btf *btf, int var_type_id, __u32 offset, __
 	/* last type should be BTF_KIND_DATASEC */
 	if (btf->nr_types == 0)
 		return -EINVAL;
-	t = btf_type_by_id(btf, btf->nr_types);
+	t = btf_last_type(btf);
 	if (!btf_is_datasec(t))
 		return -EINVAL;
 
@@ -2317,7 +2396,7 @@ int btf__add_datasec_var_info(struct btf *btf, int var_type_id, __u32 offset, __
 	v->size = byte_sz;
 
 	/* update parent type's vlen */
-	t = btf_type_by_id(btf, btf->nr_types);
+	t = btf_last_type(btf);
 	btf_type_inc_vlen(t);
 
 	btf->hdr->type_len += sz;
@@ -2639,6 +2718,7 @@ struct btf_dedup;
 static struct btf_dedup *btf_dedup_new(struct btf *btf, struct btf_ext *btf_ext,
 				       const struct btf_dedup_opts *opts);
 static void btf_dedup_free(struct btf_dedup *d);
+static int btf_dedup_prep(struct btf_dedup *d);
 static int btf_dedup_strings(struct btf_dedup *d);
 static int btf_dedup_prim_types(struct btf_dedup *d);
 static int btf_dedup_struct_types(struct btf_dedup *d);
@@ -2797,6 +2877,11 @@ int btf__dedup(struct btf *btf, struct btf_ext *btf_ext,
 	if (btf_ensure_modifiable(btf))
 		return -ENOMEM;
 
+	err = btf_dedup_prep(d);
+	if (err) {
+		pr_debug("btf_dedup_prep failed:%d\n", err);
+		goto done;
+	}
 	err = btf_dedup_strings(d);
 	if (err < 0) {
 		pr_debug("btf_dedup_strings failed:%d\n", err);
@@ -2859,21 +2944,20 @@ struct btf_dedup {
 	__u32 *hypot_list;
 	size_t hypot_cnt;
 	size_t hypot_cap;
+	/* Whether hypothetical mapping, if successful, would need to adjust
+	 * already canonicalized types (due to a new forward declaration to
+	 * concrete type resolution). In such case, during split BTF dedup
+	 * candidate type would still be considered as different, because base
+	 * BTF is considered to be immutable.
+	 */
+	bool hypot_adjust_canon;
 	/* Various option modifying behavior of algorithm */
 	struct btf_dedup_opts opts;
-};
-
-struct btf_str_ptr {
-	const char *str;
-	__u32 new_off;
-	bool used;
-};
-
-struct btf_str_ptrs {
-	struct btf_str_ptr *ptrs;
-	const char *data;
-	__u32 cnt;
-	__u32 cap;
+	/* temporary strings deduplication state */
+	void *strs_data;
+	size_t strs_cap;
+	size_t strs_len;
+	struct hashmap* strs_hash;
 };
 
 static long hash_combine(long h, long value)
@@ -2914,6 +2998,7 @@ static void btf_dedup_clear_hypot_map(struct btf_dedup *d)
 	for (i = 0; i < d->hypot_cnt; i++)
 		d->hypot_map[d->hypot_list[i]] = BTF_UNPROCESSED_ID;
 	d->hypot_cnt = 0;
+	d->hypot_adjust_canon = false;
 }
 
 static void btf_dedup_free(struct btf_dedup *d)
@@ -2953,7 +3038,7 @@ static struct btf_dedup *btf_dedup_new(struct btf *btf, struct btf_ext *btf_ext,
 {
 	struct btf_dedup *d = calloc(1, sizeof(struct btf_dedup));
 	hashmap_hash_fn hash_fn = btf_dedup_identity_hash_fn;
-	int i, err = 0;
+	int i, err = 0, type_cnt;
 
 	if (!d)
 		return ERR_PTR(-ENOMEM);
@@ -2973,14 +3058,15 @@ static struct btf_dedup *btf_dedup_new(struct btf *btf, struct btf_ext *btf_ext,
 		goto done;
 	}
 
-	d->map = malloc(sizeof(__u32) * (1 + btf->nr_types));
+	type_cnt = btf__get_nr_types(btf) + 1;
+	d->map = malloc(sizeof(__u32) * type_cnt);
 	if (!d->map) {
 		err = -ENOMEM;
 		goto done;
 	}
 	/* special BTF "void" type is made canonical immediately */
 	d->map[0] = 0;
-	for (i = 1; i <= btf->nr_types; i++) {
+	for (i = 1; i < type_cnt; i++) {
 		struct btf_type *t = btf_type_by_id(d->btf, i);
 
 		/* VAR and DATASEC are never deduped and are self-canonical */
@@ -2990,12 +3076,12 @@ static struct btf_dedup *btf_dedup_new(struct btf *btf, struct btf_ext *btf_ext,
 			d->map[i] = BTF_UNPROCESSED_ID;
 	}
 
-	d->hypot_map = malloc(sizeof(__u32) * (1 + btf->nr_types));
+	d->hypot_map = malloc(sizeof(__u32) * type_cnt);
 	if (!d->hypot_map) {
 		err = -ENOMEM;
 		goto done;
 	}
-	for (i = 0; i <= btf->nr_types; i++)
+	for (i = 0; i < type_cnt; i++)
 		d->hypot_map[i] = BTF_UNPROCESSED_ID;
 
 done:
@@ -3019,8 +3105,8 @@ static int btf_for_each_str_off(struct btf_dedup *d, str_off_fn_t fn, void *ctx)
 	int i, j, r, rec_size;
 	struct btf_type *t;
 
-	for (i = 1; i <= d->btf->nr_types; i++) {
-		t = btf_type_by_id(d->btf, i);
+	for (i = 0; i < d->btf->nr_types; i++) {
+		t = btf_type_by_id(d->btf, d->btf->start_id + i);
 		r = fn(&t->name_off, ctx);
 		if (r)
 			return r;
@@ -3100,64 +3186,53 @@ static int btf_for_each_str_off(struct btf_dedup *d, str_off_fn_t fn, void *ctx)
 	return 0;
 }
 
-static int str_sort_by_content(const void *a1, const void *a2)
+static int strs_dedup_remap_str_off(__u32 *str_off_ptr, void *ctx)
 {
-	const struct btf_str_ptr *p1 = a1;
-	const struct btf_str_ptr *p2 = a2;
-
-	return strcmp(p1->str, p2->str);
-}
-
-static int str_sort_by_offset(const void *a1, const void *a2)
-{
-	const struct btf_str_ptr *p1 = a1;
-	const struct btf_str_ptr *p2 = a2;
-
-	if (p1->str != p2->str)
-		return p1->str < p2->str ? -1 : 1;
-	return 0;
-}
-
-static int btf_dedup_str_ptr_cmp(const void *str_ptr, const void *pelem)
-{
-	const struct btf_str_ptr *p = pelem;
-
-	if (str_ptr != p->str)
-		return (const char *)str_ptr < p->str ? -1 : 1;
-	return 0;
-}
-
-static int btf_str_mark_as_used(__u32 *str_off_ptr, void *ctx)
-{
-	struct btf_str_ptrs *strs;
-	struct btf_str_ptr *s;
+	struct btf_dedup *d = ctx;
+	__u32 str_off = *str_off_ptr;
+	long old_off, new_off, len;
+	const char *s;
+	void *p;
+	int err;
 
-	if (*str_off_ptr == 0)
+	/* don't touch empty string or string in main BTF */
+	if (str_off == 0 || str_off < d->btf->start_str_off)
 		return 0;
 
-	strs = ctx;
-	s = bsearch(strs->data + *str_off_ptr, strs->ptrs, strs->cnt,
-		    sizeof(struct btf_str_ptr), btf_dedup_str_ptr_cmp);
-	if (!s)
-		return -EINVAL;
-	s->used = true;
-	return 0;
-}
+	s = btf__str_by_offset(d->btf, str_off);
+	if (d->btf->base_btf) {
+		err = btf__find_str(d->btf->base_btf, s);
+		if (err >= 0) {
+			*str_off_ptr = err;
+			return 0;
+		}
+		if (err != -ENOENT)
+			return err;
+	}
 
-static int btf_str_remap_offset(__u32 *str_off_ptr, void *ctx)
-{
-	struct btf_str_ptrs *strs;
-	struct btf_str_ptr *s;
+	len = strlen(s) + 1;
 
-	if (*str_off_ptr == 0)
-		return 0;
+	new_off = d->strs_len;
+	p = btf_add_mem(&d->strs_data, &d->strs_cap, 1, new_off, BTF_MAX_STR_OFFSET, len);
+	if (!p)
+		return -ENOMEM;
 
-	strs = ctx;
-	s = bsearch(strs->data + *str_off_ptr, strs->ptrs, strs->cnt,
-		    sizeof(struct btf_str_ptr), btf_dedup_str_ptr_cmp);
-	if (!s)
-		return -EINVAL;
-	*str_off_ptr = s->new_off;
+	memcpy(p, s, len);
+
+	/* Now attempt to add the string, but only if the string with the same
+	 * contents doesn't exist already (HASHMAP_ADD strategy). If such
+	 * string exists, we'll get its offset in old_off (that's old_key).
+	 */
+	err = hashmap__insert(d->strs_hash, (void *)new_off, (void *)new_off,
+			      HASHMAP_ADD, (const void **)&old_off, NULL);
+	if (err == -EEXIST) {
+		*str_off_ptr = d->btf->start_str_off + old_off;
+	} else if (err) {
+		return err;
+	} else {
+		*str_off_ptr = d->btf->start_str_off + new_off;
+		d->strs_len += len;
+	}
 	return 0;
 }
 
@@ -3174,118 +3249,71 @@ static int btf_str_remap_offset(__u32 *str_off_ptr, void *ctx)
  */
 static int btf_dedup_strings(struct btf_dedup *d)
 {
-	char *start = d->btf->strs_data;
-	char *end = start + d->btf->hdr->str_len;
-	char *p = start, *tmp_strs = NULL;
-	struct btf_str_ptrs strs = {
-		.cnt = 0,
-		.cap = 0,
-		.ptrs = NULL,
-		.data = start,
-	};
-	int i, j, err = 0, grp_idx;
-	bool grp_used;
+	char *s;
+	int err;
 
 	if (d->btf->strs_deduped)
 		return 0;
 
-	/* build index of all strings */
-	while (p < end) {
-		if (strs.cnt + 1 > strs.cap) {
-			struct btf_str_ptr *new_ptrs;
-
-			strs.cap += max(strs.cnt / 2, 16U);
-			new_ptrs = libbpf_reallocarray(strs.ptrs, strs.cap, sizeof(strs.ptrs[0]));
-			if (!new_ptrs) {
-				err = -ENOMEM;
-				goto done;
-			}
-			strs.ptrs = new_ptrs;
-		}
-
-		strs.ptrs[strs.cnt].str = p;
-		strs.ptrs[strs.cnt].used = false;
-
-		p += strlen(p) + 1;
-		strs.cnt++;
-	}
+	/* temporarily switch to use btf_dedup's strs_data for strings for hash
+	 * functions; later we'll just transfer hashmap to struct btf as is,
+	 * along the strs_data
+	 */
+	d->btf->strs_data_ptr = &d->strs_data;
 
-	/* temporary storage for deduplicated strings */
-	tmp_strs = malloc(d->btf->hdr->str_len);
-	if (!tmp_strs) {
-		err = -ENOMEM;
-		goto done;
+	d->strs_hash = hashmap__new(strs_hash_fn, strs_hash_equal_fn, d->btf);
+	if (IS_ERR(d->strs_hash)) {
+		err = PTR_ERR(d->strs_hash);
+		d->strs_hash = NULL;
+		goto err_out;
 	}
 
-	/* mark all used strings */
-	strs.ptrs[0].used = true;
-	err = btf_for_each_str_off(d, btf_str_mark_as_used, &strs);
-	if (err)
-		goto done;
-
-	/* sort strings by context, so that we can identify duplicates */
-	qsort(strs.ptrs, strs.cnt, sizeof(strs.ptrs[0]), str_sort_by_content);
-
-	/*
-	 * iterate groups of equal strings and if any instance in a group was
-	 * referenced, emit single instance and remember new offset
-	 */
-	p = tmp_strs;
-	grp_idx = 0;
-	grp_used = strs.ptrs[0].used;
-	/* iterate past end to avoid code duplication after loop */
-	for (i = 1; i <= strs.cnt; i++) {
-		/*
-		 * when i == strs.cnt, we want to skip string comparison and go
-		 * straight to handling last group of strings (otherwise we'd
-		 * need to handle last group after the loop w/ duplicated code)
-		 */
-		if (i < strs.cnt &&
-		    !strcmp(strs.ptrs[i].str, strs.ptrs[grp_idx].str)) {
-			grp_used = grp_used || strs.ptrs[i].used;
-			continue;
-		}
+	if (!d->btf->base_btf) {
+		s = btf_add_mem(&d->strs_data, &d->strs_cap, 1, d->strs_len, BTF_MAX_STR_OFFSET, 1);
+		if (!s)
+			return -ENOMEM;
+		/* initial empty string */
+		s[0] = 0;
+		d->strs_len = 1;
 
-		/*
-		 * this check would have been required after the loop to handle
-		 * last group of strings, but due to <= condition in a loop
-		 * we avoid that duplication
+		/* insert empty string; we won't be looking it up during strings
+		 * dedup, but it's good to have it for generic BTF string lookups
 		 */
-		if (grp_used) {
-			int new_off = p - tmp_strs;
-			__u32 len = strlen(strs.ptrs[grp_idx].str);
-
-			memmove(p, strs.ptrs[grp_idx].str, len + 1);
-			for (j = grp_idx; j < i; j++)
-				strs.ptrs[j].new_off = new_off;
-			p += len + 1;
-		}
-
-		if (i < strs.cnt) {
-			grp_idx = i;
-			grp_used = strs.ptrs[i].used;
-		}
+		err = hashmap__insert(d->strs_hash, (void *)0, (void *)0,
+				      HASHMAP_ADD, NULL, NULL);
+		if (err)
+			goto err_out;
 	}
 
-	/* replace original strings with deduped ones */
-	d->btf->hdr->str_len = p - tmp_strs;
-	memmove(start, tmp_strs, d->btf->hdr->str_len);
-	end = start + d->btf->hdr->str_len;
-
-	/* restore original order for further binary search lookups */
-	qsort(strs.ptrs, strs.cnt, sizeof(strs.ptrs[0]), str_sort_by_offset);
-
 	/* remap string offsets */
-	err = btf_for_each_str_off(d, btf_str_remap_offset, &strs);
+	err = btf_for_each_str_off(d, strs_dedup_remap_str_off, d);
 	if (err)
-		goto done;
+		goto err_out;
 
-	d->btf->hdr->str_len = end - start;
+	/* replace BTF string data and hash with deduped ones */
+	free(d->btf->strs_data);
+	hashmap__free(d->btf->strs_hash);
+	d->btf->strs_data = d->strs_data;
+	d->btf->strs_data_cap = d->strs_cap;
+	d->btf->hdr->str_len = d->strs_len;
+	d->btf->strs_hash = d->strs_hash;
+	/* now point strs_data_ptr back to btf->strs_data */
+	d->btf->strs_data_ptr = &d->btf->strs_data;
+
+	d->strs_data = d->strs_hash = NULL;
+	d->strs_len = d->strs_cap = 0;
 	d->btf->strs_deduped = true;
+	return 0;
+
+err_out:
+	free(d->strs_data);
+	hashmap__free(d->strs_hash);
+	d->strs_data = d->strs_hash = NULL;
+	d->strs_len = d->strs_cap = 0;
+
+	/* restore strings pointer for existing d->btf->strs_hash back */
+	d->btf->strs_data_ptr = &d->strs_data;
 
-done:
-	free(tmp_strs);
-	free(strs.ptrs);
 	return err;
 }
 
@@ -3550,6 +3578,66 @@ static bool btf_compat_fnproto(struct btf_type *t1, struct btf_type *t2)
 	return true;
 }
 
+/* Prepare split BTF for deduplication by calculating hashes of base BTF's
+ * types and initializing the rest of the state (canonical type mapping) for
+ * the fixed base BTF part.
+ */
+static int btf_dedup_prep(struct btf_dedup *d)
+{
+	struct btf_type *t;
+	int type_id;
+	long h;
+
+	if (!d->btf->base_btf)
+		return 0;
+
+	for (type_id = 1; type_id < d->btf->start_id; type_id++) {
+		t = btf_type_by_id(d->btf, type_id);
+
+		/* all base BTF types are self-canonical by definition */
+		d->map[type_id] = type_id;
+
+		switch (btf_kind(t)) {
+		case BTF_KIND_VAR:
+		case BTF_KIND_DATASEC:
+			/* VAR and DATASEC are never hash/deduplicated */
+			continue;
+		case BTF_KIND_CONST:
+		case BTF_KIND_VOLATILE:
+		case BTF_KIND_RESTRICT:
+		case BTF_KIND_PTR:
+		case BTF_KIND_FWD:
+		case BTF_KIND_TYPEDEF:
+		case BTF_KIND_FUNC:
+			h = btf_hash_common(t);
+			break;
+		case BTF_KIND_INT:
+			h = btf_hash_int(t);
+			break;
+		case BTF_KIND_ENUM:
+			h = btf_hash_enum(t);
+			break;
+		case BTF_KIND_STRUCT:
+		case BTF_KIND_UNION:
+			h = btf_hash_struct(t);
+			break;
+		case BTF_KIND_ARRAY:
+			h = btf_hash_array(t);
+			break;
+		case BTF_KIND_FUNC_PROTO:
+			h = btf_hash_fnproto(t);
+			break;
+		default:
+			pr_debug("unknown kind %d for type [%d]\n", btf_kind(t), type_id);
+			return -EINVAL;
+		}
+		if (btf_dedup_table_add(d, h, type_id))
+			return -ENOMEM;
+	}
+
+	return 0;
+}
+
 /*
  * Deduplicate primitive types, that can't reference other types, by calculating
  * their type signature hash and comparing them with any possible canonical
@@ -3643,8 +3731,8 @@ static int btf_dedup_prim_types(struct btf_dedup *d)
 {
 	int i, err;
 
-	for (i = 1; i <= d->btf->nr_types; i++) {
-		err = btf_dedup_prim_type(d, i);
+	for (i = 0; i < d->btf->nr_types; i++) {
+		err = btf_dedup_prim_type(d, d->btf->start_id + i);
 		if (err)
 			return err;
 	}
@@ -3697,6 +3785,19 @@ static inline __u16 btf_fwd_kind(struct btf_type *t)
 	return btf_kflag(t) ? BTF_KIND_UNION : BTF_KIND_STRUCT;
 }
 
+/* Check if given two types are identical ARRAY definitions */
+static int btf_dedup_identical_arrays(struct btf_dedup *d, __u32 id1, __u32 id2)
+{
+	struct btf_type *t1, *t2;
+
+	t1 = btf_type_by_id(d->btf, id1);
+	t2 = btf_type_by_id(d->btf, id2);
+	if (!btf_is_array(t1) || !btf_is_array(t2))
+		return 0;
+
+	return btf_equal_array(t1, t2);
+}
+
 /*
  * Check equivalence of BTF type graph formed by candidate struct/union (we'll
  * call it "candidate graph" in this description for brevity) to a type graph
@@ -3807,8 +3908,18 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
 	canon_id = resolve_fwd_id(d, canon_id);
 
 	hypot_type_id = d->hypot_map[canon_id];
-	if (hypot_type_id <= BTF_MAX_NR_TYPES)
-		return hypot_type_id == cand_id;
+	if (hypot_type_id <= BTF_MAX_NR_TYPES) {
+		/* In some cases compiler will generate different DWARF types
+		 * for *identical* array type definitions and use them for
+		 * different fields within the *same* struct. This breaks type
+		 * equivalence check, which makes an assumption that candidate
+		 * types sub-graph has a consistent and deduped-by-compiler
+		 * types within a single CU. So work around that by explicitly
+		 * allowing identical array types here.
+		 */
+		return hypot_type_id == cand_id ||
+		       btf_dedup_identical_arrays(d, hypot_type_id, cand_id);
+	}
 
 	if (btf_dedup_hypot_map_add(d, canon_id, cand_id))
 		return -ENOMEM;
@@ -3834,6 +3945,9 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
 		} else {
 			real_kind = cand_kind;
 			fwd_kind = btf_fwd_kind(canon_type);
+			/* we'd need to resolve base FWD to STRUCT/UNION */
+			if (fwd_kind == real_kind && canon_id < d->btf->start_id)
+				d->hypot_adjust_canon = true;
 		}
 		return fwd_kind == real_kind;
 	}
@@ -3871,8 +3985,7 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
 			return 0;
 		cand_arr = btf_array(cand_type);
 		canon_arr = btf_array(canon_type);
-		eq = btf_dedup_is_equiv(d,
-			cand_arr->index_type, canon_arr->index_type);
+		eq = btf_dedup_is_equiv(d, cand_arr->index_type, canon_arr->index_type);
 		if (eq <= 0)
 			return eq;
 		return btf_dedup_is_equiv(d, cand_arr->type, canon_arr->type);
@@ -3955,16 +4068,16 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
  */
 static void btf_dedup_merge_hypot_map(struct btf_dedup *d)
 {
-	__u32 cand_type_id, targ_type_id;
+	__u32 canon_type_id, targ_type_id;
 	__u16 t_kind, c_kind;
 	__u32 t_id, c_id;
 	int i;
 
 	for (i = 0; i < d->hypot_cnt; i++) {
-		cand_type_id = d->hypot_list[i];
-		targ_type_id = d->hypot_map[cand_type_id];
+		canon_type_id = d->hypot_list[i];
+		targ_type_id = d->hypot_map[canon_type_id];
 		t_id = resolve_type_id(d, targ_type_id);
-		c_id = resolve_type_id(d, cand_type_id);
+		c_id = resolve_type_id(d, canon_type_id);
 		t_kind = btf_kind(btf__type_by_id(d->btf, t_id));
 		c_kind = btf_kind(btf__type_by_id(d->btf, c_id));
 		/*
@@ -3979,9 +4092,26 @@ static void btf_dedup_merge_hypot_map(struct btf_dedup *d)
 		 * stability is not a requirement for STRUCT/UNION equivalence
 		 * checks, though.
 		 */
+
+		/* if it's the split BTF case, we still need to point base FWD
+		 * to STRUCT/UNION in a split BTF, because FWDs from split BTF
+		 * will be resolved against base FWD. If we don't point base
+		 * canonical FWD to the resolved STRUCT/UNION, then all the
+		 * FWDs in split BTF won't be correctly resolved to a proper
+		 * STRUCT/UNION.
+		 */
 		if (t_kind != BTF_KIND_FWD && c_kind == BTF_KIND_FWD)
 			d->map[c_id] = t_id;
-		else if (t_kind == BTF_KIND_FWD && c_kind != BTF_KIND_FWD)
+
+		/* if graph equivalence determined that we'd need to adjust
+		 * base canonical types, then we need to only point base FWDs
+		 * to STRUCTs/UNIONs and do no more modifications. For all
+		 * other purposes the type graphs were not equivalent.
+		 */
+		if (d->hypot_adjust_canon)
+			continue;
+		
+		if (t_kind == BTF_KIND_FWD && c_kind != BTF_KIND_FWD)
 			d->map[t_id] = c_id;
 
 		if ((t_kind == BTF_KIND_STRUCT || t_kind == BTF_KIND_UNION) &&
@@ -4065,8 +4195,10 @@ static int btf_dedup_struct_type(struct btf_dedup *d, __u32 type_id)
 			return eq;
 		if (!eq)
 			continue;
-		new_id = cand_id;
 		btf_dedup_merge_hypot_map(d);
+		if (d->hypot_adjust_canon) /* not really equivalent */
+			continue;
+		new_id = cand_id;
 		break;
 	}
 
@@ -4081,8 +4213,8 @@ static int btf_dedup_struct_types(struct btf_dedup *d)
 {
 	int i, err;
 
-	for (i = 1; i <= d->btf->nr_types; i++) {
-		err = btf_dedup_struct_type(d, i);
+	for (i = 0; i < d->btf->nr_types; i++) {
+		err = btf_dedup_struct_type(d, d->btf->start_id + i);
 		if (err)
 			return err;
 	}
@@ -4225,8 +4357,8 @@ static int btf_dedup_ref_types(struct btf_dedup *d)
 {
 	int i, err;
 
-	for (i = 1; i <= d->btf->nr_types; i++) {
-		err = btf_dedup_ref_type(d, i);
+	for (i = 0; i < d->btf->nr_types; i++) {
+		err = btf_dedup_ref_type(d, d->btf->start_id + i);
 		if (err < 0)
 			return err;
 	}
@@ -4250,39 +4382,44 @@ static int btf_dedup_ref_types(struct btf_dedup *d)
 static int btf_dedup_compact_types(struct btf_dedup *d)
 {
 	__u32 *new_offs;
-	__u32 next_type_id = 1;
+	__u32 next_type_id = d->btf->start_id;
+	const struct btf_type *t;
 	void *p;
-	int i, len;
+	int i, id, len;
 
 	/* we are going to reuse hypot_map to store compaction remapping */
 	d->hypot_map[0] = 0;
-	for (i = 1; i <= d->btf->nr_types; i++)
-		d->hypot_map[i] = BTF_UNPROCESSED_ID;
+	/* base BTF types are not renumbered */
+	for (id = 1; id < d->btf->start_id; id++)
+		d->hypot_map[id] = id;
+	for (i = 0, id = d->btf->start_id; i < d->btf->nr_types; i++, id++)
+		d->hypot_map[id] = BTF_UNPROCESSED_ID;
 
 	p = d->btf->types_data;
 
-	for (i = 1; i <= d->btf->nr_types; i++) {
-		if (d->map[i] != i)
+	for (i = 0, id = d->btf->start_id; i < d->btf->nr_types; i++, id++) {
+		if (d->map[id] != id)
 			continue;
 
-		len = btf_type_size(btf__type_by_id(d->btf, i));
+		t = btf__type_by_id(d->btf, id);
+		len = btf_type_size(t);
 		if (len < 0)
 			return len;
 
-		memmove(p, btf__type_by_id(d->btf, i), len);
-		d->hypot_map[i] = next_type_id;
-		d->btf->type_offs[next_type_id] = p - d->btf->types_data;
+		memmove(p, t, len);
+		d->hypot_map[id] = next_type_id;
+		d->btf->type_offs[next_type_id - d->btf->start_id] = p - d->btf->types_data;
 		p += len;
 		next_type_id++;
 	}
 
 	/* shrink struct btf's internal types index and update btf_header */
-	d->btf->nr_types = next_type_id - 1;
-	d->btf->type_offs_cap = d->btf->nr_types + 1;
+	d->btf->nr_types = next_type_id - d->btf->start_id;
+	d->btf->type_offs_cap = d->btf->nr_types;
 	d->btf->hdr->type_len = p - d->btf->types_data;
 	new_offs = libbpf_reallocarray(d->btf->type_offs, d->btf->type_offs_cap,
 				       sizeof(*new_offs));
-	if (!new_offs)
+	if (d->btf->type_offs_cap && !new_offs)
 		return -ENOMEM;
 	d->btf->type_offs = new_offs;
 	d->btf->hdr->str_off = d->btf->hdr->type_len;
@@ -4414,8 +4551,8 @@ static int btf_dedup_remap_types(struct btf_dedup *d)
 {
 	int i, r;
 
-	for (i = 1; i <= d->btf->nr_types; i++) {
-		r = btf_dedup_remap_type(d, i);
+	for (i = 0; i < d->btf->nr_types; i++) {
+		r = btf_dedup_remap_type(d, d->btf->start_id + i);
 		if (r < 0)
 			return r;
 	}
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 57247240a20a..1093f6fe6800 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -31,11 +31,19 @@ enum btf_endianness {
 };
 
 LIBBPF_API void btf__free(struct btf *btf);
+
 LIBBPF_API struct btf *btf__new(const void *data, __u32 size);
+LIBBPF_API struct btf *btf__new_split(const void *data, __u32 size, struct btf *base_btf);
 LIBBPF_API struct btf *btf__new_empty(void);
+LIBBPF_API struct btf *btf__new_empty_split(struct btf *base_btf);
+
 LIBBPF_API struct btf *btf__parse(const char *path, struct btf_ext **btf_ext);
+LIBBPF_API struct btf *btf__parse_split(const char *path, struct btf *base_btf);
 LIBBPF_API struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext);
+LIBBPF_API struct btf *btf__parse_elf_split(const char *path, struct btf *base_btf);
 LIBBPF_API struct btf *btf__parse_raw(const char *path);
+LIBBPF_API struct btf *btf__parse_raw_split(const char *path, struct btf *base_btf);
+
 LIBBPF_API int btf__finalize_data(struct bpf_object *obj, struct btf *btf);
 LIBBPF_API int btf__load(struct btf *btf);
 LIBBPF_API __s32 btf__find_by_name(const struct btf *btf,
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 4ebfadf45b47..29ff4807b909 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -337,3 +337,12 @@ LIBBPF_0.2.0 {
 		perf_buffer__consume_buffer;
 		xsk_socket__create_shared;
 } LIBBPF_0.1.0;
+
+LIBBPF_0.3.0 {
+	global:
+		btf__parse_elf_split;
+		btf__parse_raw_split;
+		btf__parse_split;
+		btf__new_empty_split;
+		btf__new_split;
+} LIBBPF_0.2.0;
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 5482a9b7ae2d..ecaae2927ab8 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -230,6 +230,7 @@ bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex)
 		break;
 	case BPF_MAP_TYPE_SK_STORAGE:
 	case BPF_MAP_TYPE_INODE_STORAGE:
+	case BPF_MAP_TYPE_TASK_STORAGE:
 		btf_key_type_id = 1;
 		btf_value_type_id = 3;
 		value_size = 8;