[PATCH bpf-next v4 0/8] resolve_btfids: Support for BTF modifications

[PATCH bpf-next v4 0/8] resolve_btfids: Support for BTF modifications

[Ihor Solodrai]

This series changes resolve_btfids and kernel build scripts to enable
BTF transformations in resolve_btfids. Main motivation for enhancing
resolve_btfids is to reduce dependency of the kernel build on pahole
capabilities [1] and enable BTF features and optimizations [2][3]
particular to the kernel.

Patches #1-#4 in the series are non-functional changes in
resolve_btfids.

Patch #5 makes kernel build notice pahole version changes between
builds.

Patch #6 changes minimum version of pahole required for
CONFIG_DEBUG_INFO_BTF to v1.22

Patch #7 makes a small prep change in selftests/bpf build.

The last patch (#8) makes significant changes in resolve_btfids and
introduces scripts/gen-btf.sh. See implementation details in the patch
description.

Successful BPF CI run: https://github.com/kernel-patches/bpf/actions/runs/20321339588

[1] https://lore.kernel.org/dwarves/ba1650aa-fafd-49a8-bea4-bdddee7c38c9@linux.dev/
[2] https://lore.kernel.org/bpf/20251029190113.3323406-1-ihor.solodrai@linux.dev/
[3] https://lore.kernel.org/bpf/20251119031531.1817099-1-dolinux.peng@gmail.com/

---

v3->v4:
  - add patch #4: "resolve_btfids: Always build with -Wall -Werror"
  - add patch #5: "kbuild: Sync kconfig when PAHOLE_VERSION changes" (Alan)
  - fix clang cross-compilation (LKP)
    https://lore.kernel.org/bpf/cecb6351-ea9a-4f8a-863a-82c9ef02f012@linux.dev/
  - remove GEN_BTF env variable (Andrii)
  - nits and cleanup in resolve_btfids/main.c (Andrii, Eduard)
  - nits in a patch bumping minimum pahole version (Andrii, AI)

v3: https://lore.kernel.org/bpf/20251205223046.4155870-1-ihor.solodrai@linux.dev/

v2->v3:
  - add patch #4 bumping minimum pahole version (Andrii, Alan)
  - add patch #5 pre-fixing resolve_btfids test (Donglin)
  - add GEN_BTF var and assemble RESOLVE_BTFIDS_FLAGS in Makefile.btf (Alan)
  - implement --distill_base flag in resolve_btfids, set it depending
    on KBUILD_EXTMOD in Makefile.btf (Eduard)
  - various implementation nits, see the v2 thread for details (Andrii, Eduard)

v2: https://lore.kernel.org/bpf/20251127185242.3954132-1-ihor.solodrai@linux.dev/

v1->v2:
  - gen-btf.sh and other shell script fixes (Donglin)
  - update selftests build (Donglin)
  - generate .BTF.base only when KBUILD_EXTMOD is set (Alan)
  - proper endianness handling for cross-compilation
  - change elf_begin mode from ELF_C_RDWR_MMAP to ELF_C_READ_MMAP_PRIVATE
  - remove compressed_section_fix()
  - nit NULL check in patch #3 (suggested by AI)

v1: https://lore.kernel.org/bpf/20251126012656.3546071-1-ihor.solodrai@linux.dev/

Ihor Solodrai (8):
  resolve_btfids: Rename object btf field to btf_path
  resolve_btfids: Factor out load_btf()
  resolve_btfids: Introduce enum btf_id_kind
  resolve_btfids: Always build with -Wall -Werror
  kbuild: Sync kconfig when PAHOLE_VERSION changes
  lib/Kconfig.debug: Set the minimum required pahole version to v1.22
  selftests/bpf: Run resolve_btfids only for relevant .test.o objects
  resolve_btfids: Change in-place update with raw binary output

 Documentation/scheduler/sched-ext.rst         |   1 -
 MAINTAINERS                                   |   1 +
 Makefile                                      |   9 +-
 init/Kconfig                                  |   2 +-
 lib/Kconfig.debug                             |  13 +-
 scripts/Makefile.btf                          |  26 +-
 scripts/Makefile.modfinal                     |   5 +-
 scripts/Makefile.vmlinux                      |   2 +-
 scripts/gen-btf.sh                            | 157 ++++++++
 scripts/link-vmlinux.sh                       |  42 +--
 tools/bpf/resolve_btfids/Makefile             |   3 +-
 tools/bpf/resolve_btfids/main.c               | 356 ++++++++++++------
 tools/sched_ext/README.md                     |   1 -
 tools/testing/selftests/bpf/.gitignore        |   3 +
 tools/testing/selftests/bpf/Makefile          |  11 +-
 .../selftests/bpf/prog_tests/resolve_btfids.c |   4 +-
 16 files changed, 446 insertions(+), 190 deletions(-)
 create mode 100755 scripts/gen-btf.sh

-- 
2.52.0

[PATCH bpf-next v4 1/8] resolve_btfids: Rename object btf field to btf_path

[Ihor Solodrai]

Rename the member of `struct object` holding the path to BTF data if
provided via --btf arg. `btf_path` is less ambiguous.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/bpf/resolve_btfids/main.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index d47191c6e55e..164f0c941f04 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -113,7 +113,7 @@ struct btf_id {
 
 struct object {
 	const char *path;
-	const char *btf;
+	const char *btf_path;
 	const char *base_btf_path;
 
 	struct {
@@ -550,11 +550,11 @@ static int symbols_resolve(struct object *obj)
 		}
 	}
 
-	btf = btf__parse_split(obj->btf ?: obj->path, base_btf);
+	btf = btf__parse_split(obj->btf_path ?: obj->path, base_btf);
 	err = libbpf_get_error(btf);
 	if (err) {
 		pr_err("FAILED: load BTF from %s: %s\n",
-			obj->btf ?: obj->path, strerror(-err));
+			obj->btf_path ?: obj->path, strerror(-err));
 		goto out;
 	}
 
@@ -790,8 +790,8 @@ int main(int argc, const char **argv)
 	struct option btfid_options[] = {
 		OPT_INCR('v', "verbose", &verbose,
 			 "be more verbose (show errors, etc)"),
-		OPT_STRING(0, "btf", &obj.btf, "BTF data",
-			   "BTF data"),
+		OPT_STRING(0, "btf", &obj.btf_path, "file",
+			   "path to a file with input BTF data"),
 		OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
 			   "path of file providing base BTF"),
 		OPT_BOOLEAN(0, "fatal_warnings", &fatal_warnings,
-- 
2.52.0

[PATCH bpf-next v4 2/8] resolve_btfids: Factor out load_btf()

[Ihor Solodrai]

Increase the lifetime of parsed BTF in resolve_btfids by factoring
load_btf() routine out of symbols_resolve() and storing the base_btf
and btf pointers in the struct object.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/bpf/resolve_btfids/main.c | 47 ++++++++++++++++++++++++---------
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index 164f0c941f04..b4caae1170dd 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -116,6 +116,9 @@ struct object {
 	const char *btf_path;
 	const char *base_btf_path;
 
+	struct btf *btf;
+	struct btf *base_btf;
+
 	struct {
 		int		 fd;
 		Elf		*elf;
@@ -529,16 +532,10 @@ static int symbols_collect(struct object *obj)
 	return 0;
 }
 
-static int symbols_resolve(struct object *obj)
+static int load_btf(struct object *obj)
 {
-	int nr_typedefs = obj->nr_typedefs;
-	int nr_structs  = obj->nr_structs;
-	int nr_unions   = obj->nr_unions;
-	int nr_funcs    = obj->nr_funcs;
-	struct btf *base_btf = NULL;
-	int err, type_id;
-	struct btf *btf;
-	__u32 nr_types;
+	struct btf *base_btf = NULL, *btf = NULL;
+	int err;
 
 	if (obj->base_btf_path) {
 		base_btf = btf__parse(obj->base_btf_path, NULL);
@@ -546,7 +543,7 @@ static int symbols_resolve(struct object *obj)
 		if (err) {
 			pr_err("FAILED: load base BTF from %s: %s\n",
 			       obj->base_btf_path, strerror(-err));
-			return -1;
+			goto out_err;
 		}
 	}
 
@@ -555,9 +552,30 @@ static int symbols_resolve(struct object *obj)
 	if (err) {
 		pr_err("FAILED: load BTF from %s: %s\n",
 			obj->btf_path ?: obj->path, strerror(-err));
-		goto out;
+		goto out_err;
 	}
 
+	obj->base_btf = base_btf;
+	obj->btf = btf;
+
+	return 0;
+
+out_err:
+	btf__free(base_btf);
+	btf__free(btf);
+	return err;
+}
+
+static int symbols_resolve(struct object *obj)
+{
+	int nr_typedefs = obj->nr_typedefs;
+	int nr_structs  = obj->nr_structs;
+	int nr_unions   = obj->nr_unions;
+	int nr_funcs    = obj->nr_funcs;
+	struct btf *btf = obj->btf;
+	int err, type_id;
+	__u32 nr_types;
+
 	err = -1;
 	nr_types = btf__type_cnt(btf);
 
@@ -615,8 +633,6 @@ static int symbols_resolve(struct object *obj)
 
 	err = 0;
 out:
-	btf__free(base_btf);
-	btf__free(btf);
 	return err;
 }
 
@@ -824,6 +840,9 @@ int main(int argc, const char **argv)
 	if (symbols_collect(&obj))
 		goto out;
 
+	if (load_btf(&obj))
+		goto out;
+
 	if (symbols_resolve(&obj))
 		goto out;
 
@@ -833,6 +852,8 @@ int main(int argc, const char **argv)
 	if (!(fatal_warnings && warnings))
 		err = 0;
 out:
+	btf__free(obj.base_btf);
+	btf__free(obj.btf);
 	if (obj.efile.elf) {
 		elf_end(obj.efile.elf);
 		close(obj.efile.fd);
-- 
2.52.0

[PATCH bpf-next v4 3/8] resolve_btfids: Introduce enum btf_id_kind

[Ihor Solodrai]

Instead of using multiple flags, make struct btf_id tagged with an
enum value indicating its kind in the context of resolve_btfids.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/bpf/resolve_btfids/main.c | 83 ++++++++++++++++++++++++---------
 1 file changed, 60 insertions(+), 23 deletions(-)

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index b4caae1170dd..da8c7d127632 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -98,6 +98,13 @@
 # error "Unknown machine endianness!"
 #endif
 
+enum btf_id_kind {
+	BTF_ID_KIND_NONE,
+	BTF_ID_KIND_SYM,
+	BTF_ID_KIND_SET,
+	BTF_ID_KIND_SET8
+};
+
 struct btf_id {
 	struct rb_node	 rb_node;
 	char		*name;
@@ -105,9 +112,8 @@ struct btf_id {
 		int	 id;
 		int	 cnt;
 	};
+	enum btf_id_kind kind;
 	int		 addr_cnt;
-	bool		 is_set;
-	bool		 is_set8;
 	Elf64_Addr	 addr[ADDR_CNT];
 };
 
@@ -197,8 +203,10 @@ static struct btf_id *btf_id__find(struct rb_root *root, const char *name)
 	return NULL;
 }
 
-static struct btf_id *
-btf_id__add(struct rb_root *root, char *name, bool unique)
+static struct btf_id *__btf_id__add(struct rb_root *root,
+				    char *name,
+				    enum btf_id_kind kind,
+				    bool unique)
 {
 	struct rb_node **p = &root->rb_node;
 	struct rb_node *parent = NULL;
@@ -221,12 +229,23 @@ btf_id__add(struct rb_root *root, char *name, bool unique)
 	if (id) {
 		pr_debug("adding symbol %s\n", name);
 		id->name = name;
+		id->kind = kind;
 		rb_link_node(&id->rb_node, parent, p);
 		rb_insert_color(&id->rb_node, root);
 	}
 	return id;
 }
 
+static inline struct btf_id *btf_id__add(struct rb_root *root, char *name, enum btf_id_kind kind)
+{
+	return __btf_id__add(root, name, kind, false);
+}
+
+static inline struct btf_id *btf_id__add_unique(struct rb_root *root, char *name, enum btf_id_kind kind)
+{
+	return __btf_id__add(root, name, kind, true);
+}
+
 static char *get_id(const char *prefix_end)
 {
 	/*
@@ -260,22 +279,36 @@ static char *get_id(const char *prefix_end)
 	return id;
 }
 
-static struct btf_id *add_set(struct object *obj, char *name, bool is_set8)
+static struct btf_id *add_set(struct object *obj, char *name, enum btf_id_kind kind)
 {
+	int len = strlen(name);
+	int prefixlen;
+	char *id;
+
 	/*
 	 * __BTF_ID__set__name
 	 * name =    ^
 	 * id   =         ^
 	 */
-	char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
-	int len = strlen(name);
+	switch (kind) {
+	case BTF_ID_KIND_SET:
+		prefixlen = sizeof(BTF_SET "__") - 1;
+		break;
+	case BTF_ID_KIND_SET8:
+		prefixlen = sizeof(BTF_SET8 "__") - 1;
+		break;
+	default:
+		pr_err("Unexpected kind %d passed to %s() for symbol %s\n", kind, __func__, name);
+		return NULL;
+	}
 
+	id = name + prefixlen - 1;
 	if (id >= name + len) {
 		pr_err("FAILED to parse set name: %s\n", name);
 		return NULL;
 	}
 
-	return btf_id__add(&obj->sets, id, true);
+	return btf_id__add_unique(&obj->sets, id, kind);
 }
 
 static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
@@ -288,7 +321,7 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
 		return NULL;
 	}
 
-	return btf_id__add(root, id, false);
+	return btf_id__add(root, id, BTF_ID_KIND_SYM);
 }
 
 /* Older libelf.h and glibc elf.h might not yet define the ELF compression types. */
@@ -491,35 +524,31 @@ static int symbols_collect(struct object *obj)
 			id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1);
 		/* set8 */
 		} else if (!strncmp(prefix, BTF_SET8, sizeof(BTF_SET8) - 1)) {
-			id = add_set(obj, prefix, true);
+			id = add_set(obj, prefix, BTF_ID_KIND_SET8);
 			/*
 			 * SET8 objects store list's count, which is encoded
 			 * in symbol's size, together with 'cnt' field hence
 			 * that - 1.
 			 */
-			if (id) {
+			if (id)
 				id->cnt = sym.st_size / sizeof(uint64_t) - 1;
-				id->is_set8 = true;
-			}
 		/* set */
 		} else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) {
-			id = add_set(obj, prefix, false);
+			id = add_set(obj, prefix, BTF_ID_KIND_SET);
 			/*
 			 * SET objects store list's count, which is encoded
 			 * in symbol's size, together with 'cnt' field hence
 			 * that - 1.
 			 */
-			if (id) {
+			if (id)
 				id->cnt = sym.st_size / sizeof(int) - 1;
-				id->is_set = true;
-			}
 		} else {
 			pr_err("FAILED unsupported prefix %s\n", prefix);
 			return -1;
 		}
 
 		if (!id)
-			return -ENOMEM;
+			return -EINVAL;
 
 		if (id->addr_cnt >= ADDR_CNT) {
 			pr_err("FAILED symbol %s crossed the number of allowed lists\n",
@@ -643,7 +672,7 @@ static int id_patch(struct object *obj, struct btf_id *id)
 	int i;
 
 	/* For set, set8, id->id may be 0 */
-	if (!id->id && !id->is_set && !id->is_set8) {
+	if (!id->id && id->kind != BTF_ID_KIND_SET && id->kind != BTF_ID_KIND_SET8) {
 		pr_err("WARN: resolve_btfids: unresolved symbol %s\n", id->name);
 		warnings++;
 	}
@@ -696,6 +725,7 @@ static int sets_patch(struct object *obj)
 {
 	Elf_Data *data = obj->efile.idlist;
 	struct rb_node *next;
+	int cnt;
 
 	next = rb_first(&obj->sets);
 	while (next) {
@@ -715,11 +745,15 @@ static int sets_patch(struct object *obj)
 			return -1;
 		}
 
-		if (id->is_set) {
+		switch (id->kind) {
+		case BTF_ID_KIND_SET:
 			set = data->d_buf + off;
+			cnt = set->cnt;
 			qsort(set->ids, set->cnt, sizeof(set->ids[0]), cmp_id);
-		} else {
+			break;
+		case BTF_ID_KIND_SET8:
 			set8 = data->d_buf + off;
+			cnt = set8->cnt;
 			/*
 			 * Make sure id is at the beginning of the pairs
 			 * struct, otherwise the below qsort would not work.
@@ -744,10 +778,13 @@ static int sets_patch(struct object *obj)
 						bswap_32(set8->pairs[i].flags);
 				}
 			}
+			break;
+		default:
+			pr_err("Unexpected btf_id_kind %d for set '%s'\n", id->kind, id->name);
+			return -1;
 		}
 
-		pr_debug("sorting  addr %5lu: cnt %6d [%s]\n",
-			 off, id->is_set ? set->cnt : set8->cnt, id->name);
+		pr_debug("sorting  addr %5lu: cnt %6d [%s]\n", off, cnt, id->name);
 
 		next = rb_next(next);
 	}
-- 
2.52.0

Re: [PATCH bpf-next v4 3/8] resolve_btfids: Introduce enum btf_id_kind

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 1999 bytes --]

> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index b4caae1170dd..da8c7d127632 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c

[ ... ]

> @@ -260,22 +279,36 @@ static char *get_id(const char *prefix_end)
>  	return id;
>  }
>
> -static struct btf_id *add_set(struct object *obj, char *name, bool is_set8)
> +static struct btf_id *add_set(struct object *obj, char *name, enum btf_id_kind kind)
>  {
> +	int len = strlen(name);
> +	int prefixlen;
> +	char *id;
> +
>  	/*
>  	 * __BTF_ID__set__name
>  	 * name =    ^
>  	 * id   =         ^
>  	 */
> -	char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
> -	int len = strlen(name);
> +	switch (kind) {
> +	case BTF_ID_KIND_SET:
> +		prefixlen = sizeof(BTF_SET "__") - 1;
> +		break;
> +	case BTF_ID_KIND_SET8:
> +		prefixlen = sizeof(BTF_SET8 "__") - 1;
> +		break;
> +	default:
> +		pr_err("Unexpected kind %d passed to %s() for symbol %s\n", kind, __func__, name);
> +		return NULL;
> +	}
> +
> +	id = name + prefixlen - 1;

Is this off by one? The original code computed:

    id = name + sizeof(BTF_SET "__") - 1

For BTF_SET ("set"), this gives: name + sizeof("set__") - 1 = name + 6 - 1 = name + 5

The new code computes:

    prefixlen = sizeof(BTF_SET "__") - 1 = 6 - 1 = 5
    id = name + prefixlen - 1 = name + 5 - 1 = name + 4

The -1 appears to be applied twice now, once in the prefixlen assignment and
again when computing id. Should this line be:

    id = name + prefixlen;

>  	if (id >= name + len) {
>  		pr_err("FAILED to parse set name: %s\n", name);
>  		return NULL;
>  	}
>
> -	return btf_id__add(&obj->sets, id, true);
> +	return btf_id__add_unique(&obj->sets, id, kind);
>  }


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20321956014

Re: [PATCH bpf-next v4 3/8] resolve_btfids: Introduce enum btf_id_kind

[Ihor Solodrai]

On 12/17/25 4:47 PM, bot+bpf-ci@kernel.org wrote:
>> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
>> index b4caae1170dd..da8c7d127632 100644
>> --- a/tools/bpf/resolve_btfids/main.c
>> +++ b/tools/bpf/resolve_btfids/main.c
> 
> [ ... ]
> 
>> @@ -260,22 +279,36 @@ static char *get_id(const char *prefix_end)
>>  	return id;
>>  }
>>
>> -static struct btf_id *add_set(struct object *obj, char *name, bool is_set8)
>> +static struct btf_id *add_set(struct object *obj, char *name, enum btf_id_kind kind)
>>  {
>> +	int len = strlen(name);
>> +	int prefixlen;
>> +	char *id;
>> +
>>  	/*
>>  	 * __BTF_ID__set__name
>>  	 * name =    ^
>>  	 * id   =         ^
>>  	 */
>> -	char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
>> -	int len = strlen(name);
>> +	switch (kind) {
>> +	case BTF_ID_KIND_SET:
>> +		prefixlen = sizeof(BTF_SET "__") - 1;
>> +		break;
>> +	case BTF_ID_KIND_SET8:
>> +		prefixlen = sizeof(BTF_SET8 "__") - 1;
>> +		break;
>> +	default:
>> +		pr_err("Unexpected kind %d passed to %s() for symbol %s\n", kind, __func__, name);
>> +		return NULL;
>> +	}
>> +
>> +	id = name + prefixlen - 1;
> 
> Is this off by one? The original code computed:
> 
>     id = name + sizeof(BTF_SET "__") - 1
> 
> For BTF_SET ("set"), this gives: name + sizeof("set__") - 1 = name + 6 - 1 = name + 5
> 
> The new code computes:
> 
>     prefixlen = sizeof(BTF_SET "__") - 1 = 6 - 1 = 5
>     id = name + prefixlen - 1 = name + 5 - 1 = name + 4
> 
> The -1 appears to be applied twice now, once in the prefixlen assignment and
> again when computing id. Should this line be:
> 
>     id = name + prefixlen;

Yes, this is an off-by-one bug.

Good catch, Opus 4.5. Sonnet 4.5 missed this in v3.

This was "harmless", since the names stored in the trees don't affect
the output.  The comparison between the names still works, as they all
simply got a "_" prefix.  But this only makes the bug sneaky, which is
very bad.

The suggested fix is meh though, IMO a better one is:

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index 3e88dc862d87..ffc15c249ed4 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -295,10 +295,10 @@ static struct btf_id *add_set(struct object *obj, char *name, enum btf_id_kind k
         */
        switch (kind) {
        case BTF_ID_KIND_SET:
-               prefixlen = sizeof(BTF_SET "__") - 1;
+               prefixlen = sizeof(BTF_SET "__");
                break;
        case BTF_ID_KIND_SET8:
-               prefixlen = sizeof(BTF_SET8 "__") - 1;
+               prefixlen = sizeof(BTF_SET8 "__");
                break;
        default:
                pr_err("Unexpected kind %d passed to %s() for symbol %s\n", kind, __func__, name);

> 
>>  	if (id >= name + len) {
>>  		pr_err("FAILED to parse set name: %s\n", name);
>>  		return NULL;
>>  	}
>>
>> -	return btf_id__add(&obj->sets, id, true);
>> +	return btf_id__add_unique(&obj->sets, id, kind);
>>  }
> 
> 
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
> 
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20321956014

Re: [PATCH bpf-next v4 3/8] resolve_btfids: Introduce enum btf_id_kind

[Andrii Nakryiko]

On Thu, Dec 18, 2025 at 9:47 AM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>
> On 12/17/25 4:47 PM, bot+bpf-ci@kernel.org wrote:
> >> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> >> index b4caae1170dd..da8c7d127632 100644
> >> --- a/tools/bpf/resolve_btfids/main.c
> >> +++ b/tools/bpf/resolve_btfids/main.c
> >
> > [ ... ]
> >
> >> @@ -260,22 +279,36 @@ static char *get_id(const char *prefix_end)
> >>      return id;
> >>  }
> >>
> >> -static struct btf_id *add_set(struct object *obj, char *name, bool is_set8)
> >> +static struct btf_id *add_set(struct object *obj, char *name, enum btf_id_kind kind)
> >>  {
> >> +    int len = strlen(name);
> >> +    int prefixlen;
> >> +    char *id;
> >> +
> >>      /*
> >>       * __BTF_ID__set__name
> >>       * name =    ^
> >>       * id   =         ^
> >>       */
> >> -    char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
> >> -    int len = strlen(name);
> >> +    switch (kind) {
> >> +    case BTF_ID_KIND_SET:
> >> +            prefixlen = sizeof(BTF_SET "__") - 1;
> >> +            break;
> >> +    case BTF_ID_KIND_SET8:
> >> +            prefixlen = sizeof(BTF_SET8 "__") - 1;
> >> +            break;
> >> +    default:
> >> +            pr_err("Unexpected kind %d passed to %s() for symbol %s\n", kind, __func__, name);
> >> +            return NULL;
> >> +    }
> >> +
> >> +    id = name + prefixlen - 1;
> >
> > Is this off by one? The original code computed:
> >
> >     id = name + sizeof(BTF_SET "__") - 1
> >
> > For BTF_SET ("set"), this gives: name + sizeof("set__") - 1 = name + 6 - 1 = name + 5
> >
> > The new code computes:
> >
> >     prefixlen = sizeof(BTF_SET "__") - 1 = 6 - 1 = 5
> >     id = name + prefixlen - 1 = name + 5 - 1 = name + 4
> >
> > The -1 appears to be applied twice now, once in the prefixlen assignment and
> > again when computing id. Should this line be:
> >
> >     id = name + prefixlen;
>
> Yes, this is an off-by-one bug.
>
> Good catch, Opus 4.5. Sonnet 4.5 missed this in v3.
>
> This was "harmless", since the names stored in the trees don't affect
> the output.  The comparison between the names still works, as they all
> simply got a "_" prefix.  But this only makes the bug sneaky, which is
> very bad.
>
> The suggested fix is meh though, IMO a better one is:

the bug is not in determining prefix length, but in using it to find
where id starts in the string, so the fix should be

id = name + prefixlen;

prefixlen is calculated correctly, IMO

>
> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index 3e88dc862d87..ffc15c249ed4 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c
> @@ -295,10 +295,10 @@ static struct btf_id *add_set(struct object *obj, char *name, enum btf_id_kind k
>          */
>         switch (kind) {
>         case BTF_ID_KIND_SET:
> -               prefixlen = sizeof(BTF_SET "__") - 1;
> +               prefixlen = sizeof(BTF_SET "__");
>                 break;
>         case BTF_ID_KIND_SET8:
> -               prefixlen = sizeof(BTF_SET8 "__") - 1;
> +               prefixlen = sizeof(BTF_SET8 "__");
>                 break;
>         default:
>                 pr_err("Unexpected kind %d passed to %s() for symbol %s\n", kind, __func__, name);
>
> >
> >>      if (id >= name + len) {
> >>              pr_err("FAILED to parse set name: %s\n", name);
> >>              return NULL;
> >>      }
> >>
> >> -    return btf_id__add(&obj->sets, id, true);
> >> +    return btf_id__add_unique(&obj->sets, id, kind);
> >>  }
> >
> >
> > ---
> > AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> > See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
> >
> > CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20321956014
>

Re: [PATCH bpf-next v4 3/8] resolve_btfids: Introduce enum btf_id_kind

[Ihor Solodrai]

On 12/18/25 11:58 AM, Andrii Nakryiko wrote:
> On Thu, Dec 18, 2025 at 9:47 AM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>>
>> On 12/17/25 4:47 PM, bot+bpf-ci@kernel.org wrote:
>>>> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
>>>> index b4caae1170dd..da8c7d127632 100644
>>>> --- a/tools/bpf/resolve_btfids/main.c
>>>> +++ b/tools/bpf/resolve_btfids/main.c
>>>
>>> [ ... ]
>>>
>>>> @@ -260,22 +279,36 @@ static char *get_id(const char *prefix_end)
>>>>      return id;
>>>>  }
>>>>
>>>> -static struct btf_id *add_set(struct object *obj, char *name, bool is_set8)
>>>> +static struct btf_id *add_set(struct object *obj, char *name, enum btf_id_kind kind)
>>>>  {
>>>> +    int len = strlen(name);
>>>> +    int prefixlen;
>>>> +    char *id;
>>>> +
>>>>      /*
>>>>       * __BTF_ID__set__name
>>>>       * name =    ^
>>>>       * id   =         ^
>>>>       */
>>>> -    char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
>>>> -    int len = strlen(name);
>>>> +    switch (kind) {
>>>> +    case BTF_ID_KIND_SET:
>>>> +            prefixlen = sizeof(BTF_SET "__") - 1;
>>>> +            break;
>>>> +    case BTF_ID_KIND_SET8:
>>>> +            prefixlen = sizeof(BTF_SET8 "__") - 1;
>>>> +            break;
>>>> +    default:
>>>> +            pr_err("Unexpected kind %d passed to %s() for symbol %s\n", kind, __func__, name);
>>>> +            return NULL;
>>>> +    }
>>>> +
>>>> +    id = name + prefixlen - 1;
>>>
>>> Is this off by one? The original code computed:
>>>
>>>     id = name + sizeof(BTF_SET "__") - 1
>>>
>>> For BTF_SET ("set"), this gives: name + sizeof("set__") - 1 = name + 6 - 1 = name + 5
>>>
>>> The new code computes:
>>>
>>>     prefixlen = sizeof(BTF_SET "__") - 1 = 6 - 1 = 5
>>>     id = name + prefixlen - 1 = name + 5 - 1 = name + 4
>>>
>>> The -1 appears to be applied twice now, once in the prefixlen assignment and
>>> again when computing id. Should this line be:
>>>
>>>     id = name + prefixlen;
>>
>> Yes, this is an off-by-one bug.
>>
>> Good catch, Opus 4.5. Sonnet 4.5 missed this in v3.
>>
>> This was "harmless", since the names stored in the trees don't affect
>> the output.  The comparison between the names still works, as they all
>> simply got a "_" prefix.  But this only makes the bug sneaky, which is
>> very bad.
>>
>> The suggested fix is meh though, IMO a better one is:
> 
> the bug is not in determining prefix length, but in using it to find
> where id starts in the string, so the fix should be
> 
> id = name + prefixlen;
> 
> prefixlen is calculated correctly, IMO

Aaahh, because the null byte is counted by sizeof, right... I missed that.

> 
>>
>> [...]
>>

[PATCH bpf-next v4 4/8] resolve_btfids: Always build with -Wall -Werror

[Ihor Solodrai]

resolve_btfids builds without compiler warnings currently, so let's
enforce this for future changes with '-Wall -Werror' flags [1].

[1] https://lore.kernel.org/bpf/1957a60b-6c45-42a7-b525-a6e335a735ff@linux.dev/

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/bpf/resolve_btfids/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
index ce1b556dfa90..1733a6e93a07 100644
--- a/tools/bpf/resolve_btfids/Makefile
+++ b/tools/bpf/resolve_btfids/Makefile
@@ -70,7 +70,8 @@ HOSTCFLAGS_resolve_btfids += -g \
           -I$(srctree)/tools/include/uapi \
           -I$(LIBBPF_INCLUDE) \
           -I$(SUBCMD_INCLUDE) \
-          $(LIBELF_FLAGS)
+          $(LIBELF_FLAGS) \
+          -Wall -Werror
 
 LIBS = $(LIBELF_LIBS) -lz
 
-- 
2.52.0

[PATCH bpf-next v4 5/8] kbuild: Sync kconfig when PAHOLE_VERSION changes

[Ihor Solodrai]

This patch implements kconfig re-sync when the pahole version changes
between builds, similar to how it happens for compiler version change
via CC_VERSION_TEXT.

Define PAHOLE_VERSION in the top-level Makefile and export it for
config builds. Set CONFIG_PAHOLE_VERSION default to the exported
variable.

Kconfig records the PAHOLE_VERSION value in
include/config/auto.conf.cmd [1].

The Makefile includes auto.conf.cmd, so if PAHOLE_VERSION changes
between builds, make detects a dependency change and triggers
syncconfig to update the kconfig [2].

For external module builds, add a warning message in the prepare
target, similar to the existing compiler version mismatch warning.

Note that if pahole is not installed or available, PAHOLE_VERSION is
set to 0 by pahole-version.sh, so the (un)installation of pahole is
treated as a version change.

See previous discussions for context [3].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/kconfig/preprocess.c?h=v6.18#n91
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n815
[3] https://lore.kernel.org/bpf/8f946abf-dd88-4fac-8bb4-84fcd8d81cf0@oracle.com/

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 Makefile     | 9 ++++++++-
 init/Kconfig | 2 +-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index e404e4767944..9b90a2a2218e 100644
--- a/Makefile
+++ b/Makefile
@@ -713,6 +713,7 @@ endif
 # upgrade.
 CC_VERSION_TEXT = $(subst $(pound),,$(shell LC_ALL=C $(CC) --version 2>/dev/null | head -n 1))
 RUSTC_VERSION_TEXT = $(subst $(pound),,$(shell $(RUSTC) --version 2>/dev/null))
+PAHOLE_VERSION = $(shell $(srctree)/scripts/pahole-version.sh $(PAHOLE))
 
 ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
 include $(srctree)/scripts/Makefile.clang
@@ -733,7 +734,7 @@ ifdef config-build
 # KBUILD_DEFCONFIG may point out an alternative default configuration
 # used for 'make defconfig'
 include $(srctree)/arch/$(SRCARCH)/Makefile
-export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT RUSTC_VERSION_TEXT
+export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT RUSTC_VERSION_TEXT PAHOLE_VERSION
 
 config: outputmakefile scripts_basic FORCE
 	$(Q)$(MAKE) $(build)=scripts/kconfig $@
@@ -1921,12 +1922,18 @@ clean: private rm-files := Module.symvers modules.nsdeps compile_commands.json
 PHONY += prepare
 # now expand this into a simple variable to reduce the cost of shell evaluations
 prepare: CC_VERSION_TEXT := $(CC_VERSION_TEXT)
+prepare: PAHOLE_VERSION := $(PAHOLE_VERSION)
 prepare:
 	@if [ "$(CC_VERSION_TEXT)" != "$(CONFIG_CC_VERSION_TEXT)" ]; then \
 		echo >&2 "warning: the compiler differs from the one used to build the kernel"; \
 		echo >&2 "  The kernel was built by: $(CONFIG_CC_VERSION_TEXT)"; \
 		echo >&2 "  You are using:           $(CC_VERSION_TEXT)"; \
 	fi
+	@if [ "$(PAHOLE_VERSION)" != "$(CONFIG_PAHOLE_VERSION)" ]; then \
+		echo >&2 "warning: pahole version differs from the one used to build the kernel"; \
+		echo >&2 "  The kernel was built with: $(CONFIG_PAHOLE_VERSION)"; \
+		echo >&2 "  You are using:             $(PAHOLE_VERSION)"; \
+	fi
 
 PHONY += help
 help:
diff --git a/init/Kconfig b/init/Kconfig
index fa79feb8fe57..317f3c0b13ad 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -171,7 +171,7 @@ config RUSTC_HAS_FILE_AS_C_STR
 
 config PAHOLE_VERSION
 	int
-	default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
+	default "$(PAHOLE_VERSION)"
 
 config CONSTRUCTORS
 	bool
-- 
2.52.0

Re: [PATCH bpf-next v4 5/8] kbuild: Sync kconfig when PAHOLE_VERSION changes

[Eduard Zingerman]

On Wed, 2025-12-17 at 16:33 -0800, Ihor Solodrai wrote:
> This patch implements kconfig re-sync when the pahole version changes
> between builds, similar to how it happens for compiler version change
> via CC_VERSION_TEXT.
> 
> Define PAHOLE_VERSION in the top-level Makefile and export it for
> config builds. Set CONFIG_PAHOLE_VERSION default to the exported
> variable.
> 
> Kconfig records the PAHOLE_VERSION value in
> include/config/auto.conf.cmd [1].
> 
> The Makefile includes auto.conf.cmd, so if PAHOLE_VERSION changes
> between builds, make detects a dependency change and triggers
> syncconfig to update the kconfig [2].
> 
> For external module builds, add a warning message in the prepare
> target, similar to the existing compiler version mismatch warning.
> 
> Note that if pahole is not installed or available, PAHOLE_VERSION is
> set to 0 by pahole-version.sh, so the (un)installation of pahole is
> treated as a version change.
> 
> See previous discussions for context [3].
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/kconfig/preprocess.c?h=v6.18#n91
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n815
> [3] https://lore.kernel.org/bpf/8f946abf-dd88-4fac-8bb4-84fcd8d81cf0@oracle.com/
> 
> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
> ---

When building BPF selftest modules the pahole version change was
detected, but it seems that BTF rebuild was not triggered:

  $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
  make[1]: Entering directory '/home/ezingerman/bpf-next'
  make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
    CC [M]  bpf_testmod.o
    CC [M]  bpf_test_no_cfi.o
    CC [M]  bpf_test_modorder_x.o
    CC [M]  bpf_test_modorder_y.o
    CC [M]  bpf_test_rqspinlock.o
    MODPOST Module.symvers
    CC [M]  bpf_testmod.mod.o
    CC [M]  .module-common.o
    CC [M]  bpf_test_no_cfi.mod.o
    CC [M]  bpf_test_modorder_x.mod.o
    CC [M]  bpf_test_modorder_y.mod.o
    CC [M]  bpf_test_rqspinlock.mod.o
    LD [M]  bpf_test_modorder_x.ko
    LD [M]  bpf_testmod.ko
    LD [M]  bpf_test_modorder_y.ko
    LD [M]  bpf_test_no_cfi.ko
    BTF [M] bpf_test_modorder_x.ko
    LD [M]  bpf_test_rqspinlock.ko
    BTF     bpf_test_modorder_x.ko
    BTF [M] bpf_test_no_cfi.ko
    BTF [M] bpf_test_modorder_y.ko
    BTF [M] bpf_testmod.ko
    BTF     bpf_test_no_cfi.ko
    BTF     bpf_test_modorder_y.ko
    BTF [M] bpf_test_rqspinlock.ko
    BTF     bpf_testmod.ko
    BTF     bpf_test_rqspinlock.ko
    BTFIDS  bpf_test_modorder_x.ko
    BTFIDS  bpf_test_modorder_y.ko
    BTFIDS  bpf_test_no_cfi.ko
    BTFIDS  bpf_testmod.ko
    OBJCOPY bpf_test_modorder_x.ko.BTF
    BTFIDS  bpf_test_rqspinlock.ko
    OBJCOPY bpf_test_no_cfi.ko.BTF
    OBJCOPY bpf_test_modorder_y.ko.BTF
    OBJCOPY bpf_testmod.ko.BTF
    OBJCOPY bpf_test_rqspinlock.ko.BTF
  make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
  make[1]: Leaving directory '/home/ezingerman/bpf-next'
  [~/bpf-next]
  $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
  make[1]: Entering directory '/home/ezingerman/bpf-next'
  make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
  make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
  make[1]: Leaving directory '/home/ezingerman/bpf-next'

... update pahole from version 131 to 132 ...

  [~/bpf-next]
  $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
  make[1]: Entering directory '/home/ezingerman/bpf-next'
  make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
  warning: pahole version differs from the one used to build the kernel
    The kernel was built with: 131
    You are using:             132
  make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
  make[1]: Leaving directory '/home/ezingerman/bpf-next'

Is this an expected behavior?

Re: [PATCH bpf-next v4 5/8] kbuild: Sync kconfig when PAHOLE_VERSION changes

[Ihor Solodrai]

On 12/18/25 11:21 AM, Eduard Zingerman wrote:
> On Wed, 2025-12-17 at 16:33 -0800, Ihor Solodrai wrote:
>> This patch implements kconfig re-sync when the pahole version changes
>> between builds, similar to how it happens for compiler version change
>> via CC_VERSION_TEXT.
>>
>> Define PAHOLE_VERSION in the top-level Makefile and export it for
>> config builds. Set CONFIG_PAHOLE_VERSION default to the exported
>> variable.
>>
>> Kconfig records the PAHOLE_VERSION value in
>> include/config/auto.conf.cmd [1].
>>
>> The Makefile includes auto.conf.cmd, so if PAHOLE_VERSION changes
>> between builds, make detects a dependency change and triggers
>> syncconfig to update the kconfig [2].
>>
>> For external module builds, add a warning message in the prepare
>> target, similar to the existing compiler version mismatch warning.
>>
>> Note that if pahole is not installed or available, PAHOLE_VERSION is
>> set to 0 by pahole-version.sh, so the (un)installation of pahole is
>> treated as a version change.
>>
>> See previous discussions for context [3].
>>
>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/kconfig/preprocess.c?h=v6.18#n91
>> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n815
>> [3] https://lore.kernel.org/bpf/8f946abf-dd88-4fac-8bb4-84fcd8d81cf0@oracle.com/
>>
>> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
>> ---
> 
> When building BPF selftest modules the pahole version change was
> detected, but it seems that BTF rebuild was not triggered:
> 
>   $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
>   make[1]: Entering directory '/home/ezingerman/bpf-next'
>   make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
>     CC [M]  bpf_testmod.o
>     CC [M]  bpf_test_no_cfi.o
>     CC [M]  bpf_test_modorder_x.o
>     CC [M]  bpf_test_modorder_y.o
>     CC [M]  bpf_test_rqspinlock.o
>     MODPOST Module.symvers
>     CC [M]  bpf_testmod.mod.o
>     CC [M]  .module-common.o
>     CC [M]  bpf_test_no_cfi.mod.o
>     CC [M]  bpf_test_modorder_x.mod.o
>     CC [M]  bpf_test_modorder_y.mod.o
>     CC [M]  bpf_test_rqspinlock.mod.o
>     LD [M]  bpf_test_modorder_x.ko
>     LD [M]  bpf_testmod.ko
>     LD [M]  bpf_test_modorder_y.ko
>     LD [M]  bpf_test_no_cfi.ko
>     BTF [M] bpf_test_modorder_x.ko
>     LD [M]  bpf_test_rqspinlock.ko
>     BTF     bpf_test_modorder_x.ko
>     BTF [M] bpf_test_no_cfi.ko
>     BTF [M] bpf_test_modorder_y.ko
>     BTF [M] bpf_testmod.ko
>     BTF     bpf_test_no_cfi.ko
>     BTF     bpf_test_modorder_y.ko
>     BTF [M] bpf_test_rqspinlock.ko
>     BTF     bpf_testmod.ko
>     BTF     bpf_test_rqspinlock.ko
>     BTFIDS  bpf_test_modorder_x.ko
>     BTFIDS  bpf_test_modorder_y.ko
>     BTFIDS  bpf_test_no_cfi.ko
>     BTFIDS  bpf_testmod.ko
>     OBJCOPY bpf_test_modorder_x.ko.BTF
>     BTFIDS  bpf_test_rqspinlock.ko
>     OBJCOPY bpf_test_no_cfi.ko.BTF
>     OBJCOPY bpf_test_modorder_y.ko.BTF
>     OBJCOPY bpf_testmod.ko.BTF
>     OBJCOPY bpf_test_rqspinlock.ko.BTF
>   make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
>   make[1]: Leaving directory '/home/ezingerman/bpf-next'
>   [~/bpf-next]
>   $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
>   make[1]: Entering directory '/home/ezingerman/bpf-next'
>   make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
>   make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
>   make[1]: Leaving directory '/home/ezingerman/bpf-next'
> 
> ... update pahole from version 131 to 132 ...
> 
>   [~/bpf-next]
>   $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
>   make[1]: Entering directory '/home/ezingerman/bpf-next'
>   make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
>   warning: pahole version differs from the one used to build the kernel
>     The kernel was built with: 131
>     You are using:             132
>   make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
>   make[1]: Leaving directory '/home/ezingerman/bpf-next'
> 
> Is this an expected behavior?

Yes, it's expected.

I simply repeated the logic used for compiler version change: for
external modules only the warning is printed.

See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n1857

Re: [PATCH bpf-next v4 5/8] kbuild: Sync kconfig when PAHOLE_VERSION changes

[Eduard Zingerman]

On Thu, 2025-12-18 at 13:33 -0800, Ihor Solodrai wrote:
> On 12/18/25 11:21 AM, Eduard Zingerman wrote:
> > On Wed, 2025-12-17 at 16:33 -0800, Ihor Solodrai wrote:
> > > This patch implements kconfig re-sync when the pahole version changes
> > > between builds, similar to how it happens for compiler version change
> > > via CC_VERSION_TEXT.
> > > 
> > > Define PAHOLE_VERSION in the top-level Makefile and export it for
> > > config builds. Set CONFIG_PAHOLE_VERSION default to the exported
> > > variable.
> > > 
> > > Kconfig records the PAHOLE_VERSION value in
> > > include/config/auto.conf.cmd [1].
> > > 
> > > The Makefile includes auto.conf.cmd, so if PAHOLE_VERSION changes
> > > between builds, make detects a dependency change and triggers
> > > syncconfig to update the kconfig [2].
> > > 
> > > For external module builds, add a warning message in the prepare
> > > target, similar to the existing compiler version mismatch warning.
> > > 
> > > Note that if pahole is not installed or available, PAHOLE_VERSION is
> > > set to 0 by pahole-version.sh, so the (un)installation of pahole is
> > > treated as a version change.
> > > 
> > > See previous discussions for context [3].
> > > 
> > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/kconfig/preprocess.c?h=v6.18#n91
> > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n815
> > > [3] https://lore.kernel.org/bpf/8f946abf-dd88-4fac-8bb4-84fcd8d81cf0@oracle.com/
> > > 
> > > Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
> > > ---
> > 
> > When building BPF selftest modules the pahole version change was
> > detected, but it seems that BTF rebuild was not triggered:
> > 
> >   $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
> >   make[1]: Entering directory '/home/ezingerman/bpf-next'
> >   make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
> >     CC [M]  bpf_testmod.o
> >     CC [M]  bpf_test_no_cfi.o
> >     CC [M]  bpf_test_modorder_x.o
> >     CC [M]  bpf_test_modorder_y.o
> >     CC [M]  bpf_test_rqspinlock.o
> >     MODPOST Module.symvers
> >     CC [M]  bpf_testmod.mod.o
> >     CC [M]  .module-common.o
> >     CC [M]  bpf_test_no_cfi.mod.o
> >     CC [M]  bpf_test_modorder_x.mod.o
> >     CC [M]  bpf_test_modorder_y.mod.o
> >     CC [M]  bpf_test_rqspinlock.mod.o
> >     LD [M]  bpf_test_modorder_x.ko
> >     LD [M]  bpf_testmod.ko
> >     LD [M]  bpf_test_modorder_y.ko
> >     LD [M]  bpf_test_no_cfi.ko
> >     BTF [M] bpf_test_modorder_x.ko
> >     LD [M]  bpf_test_rqspinlock.ko
> >     BTF     bpf_test_modorder_x.ko
> >     BTF [M] bpf_test_no_cfi.ko
> >     BTF [M] bpf_test_modorder_y.ko
> >     BTF [M] bpf_testmod.ko
> >     BTF     bpf_test_no_cfi.ko
> >     BTF     bpf_test_modorder_y.ko
> >     BTF [M] bpf_test_rqspinlock.ko
> >     BTF     bpf_testmod.ko
> >     BTF     bpf_test_rqspinlock.ko
> >     BTFIDS  bpf_test_modorder_x.ko
> >     BTFIDS  bpf_test_modorder_y.ko
> >     BTFIDS  bpf_test_no_cfi.ko
> >     BTFIDS  bpf_testmod.ko
> >     OBJCOPY bpf_test_modorder_x.ko.BTF
> >     BTFIDS  bpf_test_rqspinlock.ko
> >     OBJCOPY bpf_test_no_cfi.ko.BTF
> >     OBJCOPY bpf_test_modorder_y.ko.BTF
> >     OBJCOPY bpf_testmod.ko.BTF
> >     OBJCOPY bpf_test_rqspinlock.ko.BTF
> >   make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
> >   make[1]: Leaving directory '/home/ezingerman/bpf-next'
> >   [~/bpf-next]
> >   $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
> >   make[1]: Entering directory '/home/ezingerman/bpf-next'
> >   make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
> >   make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
> >   make[1]: Leaving directory '/home/ezingerman/bpf-next'
> > 
> > ... update pahole from version 131 to 132 ...
> > 
> >   [~/bpf-next]
> >   $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
> >   make[1]: Entering directory '/home/ezingerman/bpf-next'
> >   make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
> >   warning: pahole version differs from the one used to build the kernel
> >     The kernel was built with: 131
> >     You are using:             132
> >   make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
> >   make[1]: Leaving directory '/home/ezingerman/bpf-next'
> > 
> > Is this an expected behavior?
> 
> Yes, it's expected.
> 
> I simply repeated the logic used for compiler version change: for
> external modules only the warning is printed.
> 
> See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n1857
> 

Ok, it does rebuild BTF for the kernel itself.

Tested-by: Eduard Zingerman <eddyz87@gmail.com>

Re: [PATCH bpf-next v4 5/8] kbuild: Sync kconfig when PAHOLE_VERSION changes

[Andrii Nakryiko]

On Wed, Dec 17, 2025 at 4:34 PM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>
> This patch implements kconfig re-sync when the pahole version changes
> between builds, similar to how it happens for compiler version change
> via CC_VERSION_TEXT.
>
> Define PAHOLE_VERSION in the top-level Makefile and export it for
> config builds. Set CONFIG_PAHOLE_VERSION default to the exported
> variable.
>
> Kconfig records the PAHOLE_VERSION value in
> include/config/auto.conf.cmd [1].
>
> The Makefile includes auto.conf.cmd, so if PAHOLE_VERSION changes
> between builds, make detects a dependency change and triggers
> syncconfig to update the kconfig [2].
>
> For external module builds, add a warning message in the prepare
> target, similar to the existing compiler version mismatch warning.
>
> Note that if pahole is not installed or available, PAHOLE_VERSION is
> set to 0 by pahole-version.sh, so the (un)installation of pahole is
> treated as a version change.
>
> See previous discussions for context [3].
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/kconfig/preprocess.c?h=v6.18#n91
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n815
> [3] https://lore.kernel.org/bpf/8f946abf-dd88-4fac-8bb4-84fcd8d81cf0@oracle.com/
>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
> ---
>  Makefile     | 9 ++++++++-
>  init/Kconfig | 2 +-
>  2 files changed, 9 insertions(+), 2 deletions(-)
>

This is great, we should have done that a long time ago :)

[...]

[PATCH bpf-next v4 6/8] lib/Kconfig.debug: Set the minimum required pahole version to v1.22

[Ihor Solodrai]

Subsequent patches in the series change vmlinux linking scripts to
unconditionally pass --btf_encode_detached to pahole, which was
introduced in v1.22 [1][2].

This change allows to remove PAHOLE_HAS_SPLIT_BTF Kconfig option and
other checks of older pahole versions.

[1] https://github.com/acmel/dwarves/releases/tag/v1.22
[2] https://lore.kernel.org/bpf/cbafbf4e-9073-4383-8ee6-1353f9e5869c@oracle.com/

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 Documentation/scheduler/sched-ext.rst |  1 -
 lib/Kconfig.debug                     | 13 ++++---------
 scripts/Makefile.btf                  |  9 +--------
 tools/sched_ext/README.md             |  1 -
 4 files changed, 5 insertions(+), 19 deletions(-)

diff --git a/Documentation/scheduler/sched-ext.rst b/Documentation/scheduler/sched-ext.rst
index 404fe6126a76..9e2882d937b4 100644
--- a/Documentation/scheduler/sched-ext.rst
+++ b/Documentation/scheduler/sched-ext.rst
@@ -43,7 +43,6 @@ options should be enabled to use sched_ext:
     CONFIG_DEBUG_INFO_BTF=y
     CONFIG_BPF_JIT_ALWAYS_ON=y
     CONFIG_BPF_JIT_DEFAULT_ON=y
-    CONFIG_PAHOLE_HAS_SPLIT_BTF=y
     CONFIG_PAHOLE_HAS_BTF_TAG=y
 
 sched_ext is used only when the BPF scheduler is loaded and running.
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ba36939fda79..60281c4f9e99 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -388,18 +388,13 @@ config DEBUG_INFO_BTF
 	depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
 	depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
 	depends on BPF_SYSCALL
-	depends on PAHOLE_VERSION >= 116
-	depends on DEBUG_INFO_DWARF4 || PAHOLE_VERSION >= 121
+	depends on PAHOLE_VERSION >= 122
 	# pahole uses elfutils, which does not have support for Hexagon relocations
 	depends on !HEXAGON
 	help
 	  Generate deduplicated BTF type information from DWARF debug info.
-	  Turning this on requires pahole v1.16 or later (v1.21 or later to
-	  support DWARF 5), which will convert DWARF type info into equivalent
-	  deduplicated BTF type info.
-
-config PAHOLE_HAS_SPLIT_BTF
-	def_bool PAHOLE_VERSION >= 119
+	  Turning this on requires pahole v1.22 or later, which will convert
+	  DWARF type info into equivalent deduplicated BTF type info.
 
 config PAHOLE_HAS_BTF_TAG
 	def_bool PAHOLE_VERSION >= 123
@@ -421,7 +416,7 @@ config PAHOLE_HAS_LANG_EXCLUDE
 config DEBUG_INFO_BTF_MODULES
 	bool "Generate BTF type information for kernel modules"
 	default y
-	depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
+	depends on DEBUG_INFO_BTF && MODULES
 	help
 	  Generate compact split BTF type information for kernel modules.
 
diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
index db76335dd917..840a55de42da 100644
--- a/scripts/Makefile.btf
+++ b/scripts/Makefile.btf
@@ -7,14 +7,7 @@ JOBS := $(patsubst -j%,%,$(filter -j%,$(MAKEFLAGS)))
 
 ifeq ($(call test-le, $(pahole-ver), 125),y)
 
-# pahole 1.18 through 1.21 can't handle zero-sized per-CPU vars
-ifeq ($(call test-le, $(pahole-ver), 121),y)
-pahole-flags-$(call test-ge, $(pahole-ver), 118)	+= --skip_encoding_btf_vars
-endif
-
-pahole-flags-$(call test-ge, $(pahole-ver), 121)	+= --btf_gen_floats
-
-pahole-flags-$(call test-ge, $(pahole-ver), 122)	+= -j$(JOBS)
+pahole-flags-y                                  	+= --btf_gen_floats -j$(JOBS)
 
 pahole-flags-$(call test-ge, $(pahole-ver), 125)	+= --skip_encoding_btf_inconsistent_proto --btf_gen_optimized
 
diff --git a/tools/sched_ext/README.md b/tools/sched_ext/README.md
index 16a42e4060f6..56a9d1557ac4 100644
--- a/tools/sched_ext/README.md
+++ b/tools/sched_ext/README.md
@@ -65,7 +65,6 @@ It's also recommended that you also include the following Kconfig options:
 ```
 CONFIG_BPF_JIT_ALWAYS_ON=y
 CONFIG_BPF_JIT_DEFAULT_ON=y
-CONFIG_PAHOLE_HAS_SPLIT_BTF=y
 CONFIG_PAHOLE_HAS_BTF_TAG=y
 ```
 
-- 
2.52.0

[PATCH bpf-next v4 7/8] selftests/bpf: Run resolve_btfids only for relevant .test.o objects

[Ihor Solodrai]

A selftest targeting resolve_btfids functionality relies on a resolved
.BTF_ids section to be available in the TRUNNER_BINARY. The underlying
BTF data is taken from a special BPF program (btf_data.c), and so
resolve_btfids is executed as a part of a TRUNNER_BINARY build recipe
on the final binary.

Subsequent patches in this series allow resolve_btfids to modify BTF
before resolving the symbols, which means that the test needs access
to that modified BTF [1]. Currently the test simply reads in
btf_data.bpf.o on the assumption that BTF hasn't changed.

Implement resolve_btfids call only for particular test objects (just
resolve_btfids.test.o for now). The test objects are linked into the
TRUNNER_BINARY, and so .BTF_ids section will be available there.

This will make it trivial for the resolve_btfids test to access BTF
modified by resolve_btfids.

[1] https://lore.kernel.org/bpf/CAErzpmvsgSDe-QcWH8SFFErL6y3p3zrqNri5-UHJ9iK2ChyiBw@mail.gmail.com/

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/testing/selftests/bpf/Makefile | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 4aa60e83ff19..ffd0a4c354c7 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -643,6 +643,9 @@ $(TRUNNER_TESTS_HDR): $(TRUNNER_TESTS_DIR)/*.c
 		 ) > $$@)
 endif
 
+$(TRUNNER_OUTPUT)/resolve_btfids.test.o: $(RESOLVE_BTFIDS) $(TRUNNER_OUTPUT)/btf_data.bpf.o
+$(TRUNNER_OUTPUT)/resolve_btfids.test.o: private TEST_NEEDS_BTFIDS = 1
+
 # compile individual test files
 # Note: we cd into output directory to ensure embedded BPF object is found
 $(TRUNNER_TEST_OBJS): $(TRUNNER_OUTPUT)/%.test.o:			\
@@ -650,6 +653,9 @@ $(TRUNNER_TEST_OBJS): $(TRUNNER_OUTPUT)/%.test.o:			\
 		      | $(TRUNNER_OUTPUT)/%.test.d
 	$$(call msg,TEST-OBJ,$(TRUNNER_BINARY),$$@)
 	$(Q)cd $$(@D) && $$(CC) -I. $$(CFLAGS) -MMD -MT $$@ -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F)
+	$$(if $$(TEST_NEEDS_BTFIDS),					\
+		$$(call msg,BTFIDS,$(TRUNNER_BINARY),$$@)		\
+		$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@)
 
 $(TRUNNER_TEST_OBJS:.o=.d): $(TRUNNER_OUTPUT)/%.test.d:			\
 			    $(TRUNNER_TESTS_DIR)/%.c			\
@@ -695,13 +701,11 @@ $(OUTPUT)/$(TRUNNER_BINARY): | $(TRUNNER_BPF_OBJS)
 $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS)			\
 			     $(TRUNNER_EXTRA_OBJS) $$(BPFOBJ)		\
 			     $(TRUNNER_LIB_OBJS)			\
-			     $(RESOLVE_BTFIDS)				\
 			     $(TRUNNER_BPFTOOL)				\
 			     $(OUTPUT)/veristat				\
 			     | $(TRUNNER_BINARY)-extras
 	$$(call msg,BINARY,,$$@)
 	$(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) $$(LLVM_LDLIBS) $$(LDFLAGS) $$(LLVM_LDFLAGS) -o $$@
-	$(Q)$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@
 	$(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/$(USE_BOOTSTRAP)bpftool \
 		   $(OUTPUT)/$(if $2,$2/)bpftool
 
-- 
2.52.0

Re: [PATCH bpf-next v4 7/8] selftests/bpf: Run resolve_btfids only for relevant .test.o objects

[Eduard Zingerman]

On Wed, 2025-12-17 at 16:33 -0800, Ihor Solodrai wrote:
> A selftest targeting resolve_btfids functionality relies on a resolved
> .BTF_ids section to be available in the TRUNNER_BINARY. The underlying
> BTF data is taken from a special BPF program (btf_data.c), and so
> resolve_btfids is executed as a part of a TRUNNER_BINARY build recipe
> on the final binary.
> 
> Subsequent patches in this series allow resolve_btfids to modify BTF
> before resolving the symbols, which means that the test needs access
> to that modified BTF [1]. Currently the test simply reads in
> btf_data.bpf.o on the assumption that BTF hasn't changed.
> 
> Implement resolve_btfids call only for particular test objects (just
> resolve_btfids.test.o for now). The test objects are linked into the
> TRUNNER_BINARY, and so .BTF_ids section will be available there.
> 
> This will make it trivial for the resolve_btfids test to access BTF
> modified by resolve_btfids.
> 
> [1] https://lore.kernel.org/bpf/CAErzpmvsgSDe-QcWH8SFFErL6y3p3zrqNri5-UHJ9iK2ChyiBw@mail.gmail.com/
> 
> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

[...]

[PATCH bpf-next v4 8/8] resolve_btfids: Change in-place update with raw binary output

[Ihor Solodrai]

Currently resolve_btfids updates .BTF_ids section of an ELF file
in-place, based on the contents of provided BTF, usually within the
same input file, and optionally a BTF base.

Change resolve_btfids behavior to enable BTF transformations as part
of its main operation. To achieve this, in-place ELF write in
resolve_btfids is replaced with generation of the following binaries:
  * ${1}.BTF with .BTF section data
  * ${1}.BTF_ids with .BTF_ids section data if it existed in ${1}
  * ${1}.BTF.base with .BTF.base section data for out-of-tree modules

The execution of resolve_btfids and consumption of its output is
orchestrated by scripts/gen-btf.sh introduced in this patch.

The motivation for emitting binary data is that it allows simplifying
resolve_btfids implementation by delegating ELF update to the $OBJCOPY
tool [1], which is already widely used across the codebase.

There are two distinct paths for BTF generation and resolve_btfids
application in the kernel build: for vmlinux and for kernel modules.

For the vmlinux binary a .BTF section is added in a roundabout way to
ensure correct linking. The patch doesn't change this approach, only
the implementation is a little different.

Before this patch it worked as follows:

  * pahole consumed .tmp_vmlinux1 [2] and added .BTF section with
    llvm-objcopy [3] to it
  * then everything except the .BTF section was stripped from .tmp_vmlinux1
    into a .tmp_vmlinux1.bpf.o object [2], later linked into vmlinux
  * resolve_btfids was executed later on vmlinux.unstripped [4],
    updating it in-place

After this patch gen-btf.sh implements the following:

  * pahole consumes .tmp_vmlinux1 and produces a *detached* file with
    raw BTF data
  * resolve_btfids consumes .tmp_vmlinux1 and detached BTF to produce
    (potentially modified) .BTF, and .BTF_ids sections data
  * a .tmp_vmlinux1.bpf.o object is then produced with objcopy copying
    BTF output of resolve_btfids
  * .BTF_ids data gets embedded into vmlinux.unstripped in
    link-vmlinux.sh by objcopy --update-section

For kernel modules, creating a special .bpf.o file is not necessary,
and so embedding of sections data produced by resolve_btfids is
straightforward with objcopy.

With this patch an ELF file becomes effectively read-only within
resolve_btfids, which allows deleting elf_update() call and satellite
code (like compressed_section_fix [5]).

Endianness handling of .BTF_ids data is also changed. Previously the
"flags" part of the section was bswapped in sets_patch() [6], and then
Elf_Type was modified before elf_update() to signal to libelf that
bswap may be necessary. With this patch we explicitly bswap entire
data buffer on load and on dump.

[1] https://lore.kernel.org/bpf/131b4190-9c49-4f79-a99d-c00fac97fa44@linux.dev/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/link-vmlinux.sh?h=v6.18#n110
[3] https://git.kernel.org/pub/scm/devel/pahole/pahole.git/tree/btf_encoder.c?h=v1.31#n1803
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/link-vmlinux.sh?h=v6.18#n284
[5] https://lore.kernel.org/bpf/20200819092342.259004-1-jolsa@kernel.org/
[6] https://lore.kernel.org/bpf/cover.1707223196.git.vmalik@redhat.com/

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 MAINTAINERS                                   |   1 +
 scripts/Makefile.btf                          |  17 +-
 scripts/Makefile.modfinal                     |   5 +-
 scripts/Makefile.vmlinux                      |   2 +-
 scripts/gen-btf.sh                            | 157 +++++++++++++
 scripts/link-vmlinux.sh                       |  42 +---
 tools/bpf/resolve_btfids/main.c               | 222 +++++++++++-------
 tools/testing/selftests/bpf/.gitignore        |   3 +
 tools/testing/selftests/bpf/Makefile          |   9 +-
 .../selftests/bpf/prog_tests/resolve_btfids.c |   4 +-
 10 files changed, 331 insertions(+), 131 deletions(-)
 create mode 100755 scripts/gen-btf.sh

diff --git a/MAINTAINERS b/MAINTAINERS
index 5b11839cba9d..cb1898a85b05 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4766,6 +4766,7 @@ F:	net/sched/act_bpf.c
 F:	net/sched/cls_bpf.c
 F:	samples/bpf/
 F:	scripts/bpf_doc.py
+F:	scripts/gen-btf.sh
 F:	scripts/Makefile.btf
 F:	scripts/pahole-version.sh
 F:	tools/bpf/
diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
index 840a55de42da..b8569d450ed9 100644
--- a/scripts/Makefile.btf
+++ b/scripts/Makefile.btf
@@ -1,5 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 
+gen-btf-y				=
+gen-btf-$(CONFIG_DEBUG_INFO_BTF)	= $(srctree)/scripts/gen-btf.sh
+
+export GEN_BTF := $(gen-btf-y)
+
 pahole-ver := $(CONFIG_PAHOLE_VERSION)
 pahole-flags-y :=
 
@@ -18,13 +23,15 @@ pahole-flags-$(call test-ge, $(pahole-ver), 126)  = -j$(JOBS) --btf_features=enc
 
 pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
 
-ifneq ($(KBUILD_EXTMOD),)
-module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
-endif
-
 endif
 
 pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE)		+= --lang_exclude=rust
 
 export PAHOLE_FLAGS := $(pahole-flags-y)
-export MODULE_PAHOLE_FLAGS := $(module-pahole-flags-y)
+
+resolve-btfids-flags-y :=
+resolve-btfids-flags-$(CONFIG_WERROR) += --fatal_warnings
+resolve-btfids-flags-$(if $(KBUILD_EXTMOD),y) += --distill_base
+resolve-btfids-flags-$(if $(KBUILD_VERBOSE),y) += --verbose
+
+export RESOLVE_BTFIDS_FLAGS := $(resolve-btfids-flags-y)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 149e12ff5700..422c56dc878e 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -42,9 +42,8 @@ quiet_cmd_btf_ko = BTF [M] $@
       cmd_btf_ko = 							\
 	if [ ! -f $(objtree)/vmlinux ]; then				\
 		printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
-	else								\
-		LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) $(MODULE_PAHOLE_FLAGS) --btf_base $(objtree)/vmlinux $@; \
-		$(RESOLVE_BTFIDS) -b $(objtree)/vmlinux $@;		\
+	else	\
+		$(srctree)/scripts/gen-btf.sh --btf_base $(objtree)/vmlinux $@; \
 	fi;
 
 # Same as newer-prereqs, but allows to exclude specified extra dependencies
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
index cd788cac9d91..20a988f4fe0c 100644
--- a/scripts/Makefile.vmlinux
+++ b/scripts/Makefile.vmlinux
@@ -71,7 +71,7 @@ targets += vmlinux.unstripped .vmlinux.export.o
 vmlinux.unstripped: scripts/link-vmlinux.sh vmlinux.o .vmlinux.export.o $(KBUILD_LDS) FORCE
 	+$(call if_changed_dep,link_vmlinux)
 ifdef CONFIG_DEBUG_INFO_BTF
-vmlinux.unstripped: $(RESOLVE_BTFIDS)
+vmlinux.unstripped: $(RESOLVE_BTFIDS) $(srctree)/scripts/gen-btf.sh
 endif
 
 ifdef CONFIG_BUILDTIME_TABLE_SORT
diff --git a/scripts/gen-btf.sh b/scripts/gen-btf.sh
new file mode 100755
index 000000000000..06c6d8becaa2
--- /dev/null
+++ b/scripts/gen-btf.sh
@@ -0,0 +1,157 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2025 Meta Platforms, Inc. and affiliates.
+#
+# This script generates BTF data for the provided ELF file.
+#
+# Kernel BTF generation involves these conceptual steps:
+#   1. pahole generates BTF from DWARF data
+#   2. resolve_btfids applies kernel-specific btf2btf
+#      transformations and computes data for .BTF_ids section
+#   3. the result gets linked/objcopied into the target binary
+#
+# How step (3) should be done differs between vmlinux, and
+# kernel modules, which is the primary reason for the existence
+# of this script.
+#
+# For modules the script expects vmlinux passed in as --btf_base.
+# Generated .BTF, .BTF.base and .BTF_ids sections become embedded
+# into the input ELF file with objcopy.
+#
+# For vmlinux the input file remains unchanged and two files are produced:
+#   - ${1}.btf.o ready for linking into vmlinux
+#   - ${1}.BTF_ids with .BTF_ids data blob
+# This output is consumed by scripts/link-vmlinux.sh
+
+set -e
+
+usage()
+{
+	echo "Usage: $0 [--btf_base <file>] <target ELF file>"
+	exit 1
+}
+
+BTF_BASE=""
+
+while [ $# -gt 0 ]; do
+	case "$1" in
+	--btf_base)
+		BTF_BASE="$2"
+		shift 2
+		;;
+	-*)
+		echo "Unknown option: $1" >&2
+		usage
+		;;
+	*)
+		break
+		;;
+	esac
+done
+
+if [ $# -ne 1 ]; then
+	usage
+fi
+
+ELF_FILE="$1"
+shift
+
+is_enabled() {
+	grep -q "^$1=y" ${objtree}/include/config/auto.conf
+}
+
+info()
+{
+	printf "  %-7s %s\n" "${1}" "${2}"
+}
+
+case "${KBUILD_VERBOSE}" in
+*1*)
+	set -x
+	;;
+esac
+
+
+gen_btf_data()
+{
+	info BTF "${ELF_FILE}"
+	btf1="${ELF_FILE}.BTF.1"
+	${PAHOLE} -J ${PAHOLE_FLAGS}			\
+		${BTF_BASE:+--btf_base ${BTF_BASE}}	\
+		--btf_encode_detached=${btf1}		\
+		"${ELF_FILE}"
+
+	info BTFIDS "${ELF_FILE}"
+	${RESOLVE_BTFIDS} ${RESOLVE_BTFIDS_FLAGS}	\
+		${BTF_BASE:+--btf_base ${BTF_BASE}}	\
+		--btf ${btf1} "${ELF_FILE}"
+}
+
+gen_btf_o()
+{
+	local btf_data=${ELF_FILE}.btf.o
+
+	# Create ${btf_data} which contains just .BTF section but no symbols. Add
+	# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
+	# deletes all symbols including __start_BTF and __stop_BTF, which will
+	# be redefined in the linker script.
+	info OBJCOPY "${btf_data}"
+	echo "" | ${CC} ${CLANG_FLAGS} -c -x c -o ${btf_data} -
+	${OBJCOPY} --add-section .BTF=${ELF_FILE}.BTF \
+		--set-section-flags .BTF=alloc,readonly ${btf_data}
+	${OBJCOPY} --only-section=.BTF --strip-all ${btf_data}
+
+	# Change e_type to ET_REL so that it can be used to link final vmlinux.
+	# GNU ld 2.35+ and lld do not allow an ET_EXEC input.
+	if is_enabled CONFIG_CPU_BIG_ENDIAN; then
+		et_rel='\0\1'
+	else
+		et_rel='\1\0'
+	fi
+	printf "${et_rel}" | dd of="${btf_data}" conv=notrunc bs=1 seek=16 status=none
+}
+
+embed_btf_data()
+{
+	info OBJCOPY "${ELF_FILE}.BTF"
+	${OBJCOPY} --add-section .BTF=${ELF_FILE}.BTF ${ELF_FILE}
+
+	# a module might not have a .BTF_ids or .BTF.base section
+	local btf_base="${ELF_FILE}.BTF.base"
+	if [ -f "${btf_base}" ]; then
+		${OBJCOPY} --add-section .BTF.base=${btf_base} ${ELF_FILE}
+	fi
+	local btf_ids="${ELF_FILE}.BTF_ids"
+	if [ -f "${btf_ids}" ]; then
+		${OBJCOPY} --update-section .BTF_ids=${btf_ids} ${ELF_FILE}
+	fi
+}
+
+cleanup()
+{
+	rm -f "${ELF_FILE}.BTF.1"
+	rm -f "${ELF_FILE}.BTF"
+	if [ "${BTFGEN_MODE}" = "module" ]; then
+		rm -f "${ELF_FILE}.BTF.base"
+		rm -f "${ELF_FILE}.BTF_ids"
+	fi
+}
+trap cleanup EXIT
+
+BTFGEN_MODE="vmlinux"
+if [ -n "${BTF_BASE}" ]; then
+	BTFGEN_MODE="module"
+fi
+
+gen_btf_data
+
+case "${BTFGEN_MODE}" in
+vmlinux)
+	gen_btf_o
+	;;
+module)
+	embed_btf_data
+	;;
+esac
+
+exit 0
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 4ab44c73da4d..e2207e612ac3 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -106,34 +106,6 @@ vmlinux_link()
 		${kallsymso} ${btf_vmlinux_bin_o} ${arch_vmlinux_o} ${ldlibs}
 }
 
-# generate .BTF typeinfo from DWARF debuginfo
-# ${1} - vmlinux image
-gen_btf()
-{
-	local btf_data=${1}.btf.o
-
-	info BTF "${btf_data}"
-	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
-
-	# Create ${btf_data} which contains just .BTF section but no symbols. Add
-	# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
-	# deletes all symbols including __start_BTF and __stop_BTF, which will
-	# be redefined in the linker script. Add 2>/dev/null to suppress GNU
-	# objcopy warnings: "empty loadable segment detected at ..."
-	${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
-		--strip-all ${1} "${btf_data}" 2>/dev/null
-	# Change e_type to ET_REL so that it can be used to link final vmlinux.
-	# GNU ld 2.35+ and lld do not allow an ET_EXEC input.
-	if is_enabled CONFIG_CPU_BIG_ENDIAN; then
-		et_rel='\0\1'
-	else
-		et_rel='\1\0'
-	fi
-	printf "${et_rel}" | dd of="${btf_data}" conv=notrunc bs=1 seek=16 status=none
-
-	btf_vmlinux_bin_o=${btf_data}
-}
-
 # Create ${2}.o file with all symbols from the ${1} object file
 kallsyms()
 {
@@ -205,6 +177,7 @@ if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
 fi
 
 btf_vmlinux_bin_o=
+btfids_vmlinux=
 kallsymso=
 strip_debug=
 generate_map=
@@ -232,11 +205,13 @@ if is_enabled CONFIG_KALLSYMS || is_enabled CONFIG_DEBUG_INFO_BTF; then
 fi
 
 if is_enabled CONFIG_DEBUG_INFO_BTF; then
-	if ! gen_btf .tmp_vmlinux1; then
+	if ! ${srctree}/scripts/gen-btf.sh .tmp_vmlinux1; then
 		echo >&2 "Failed to generate BTF for vmlinux"
 		echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
 		exit 1
 	fi
+	btf_vmlinux_bin_o=.tmp_vmlinux1.btf.o
+	btfids_vmlinux=.tmp_vmlinux1.BTF_ids
 fi
 
 if is_enabled CONFIG_KALLSYMS; then
@@ -289,14 +264,9 @@ fi
 
 vmlinux_link "${VMLINUX}"
 
-# fill in BTF IDs
 if is_enabled CONFIG_DEBUG_INFO_BTF; then
-	info BTFIDS "${VMLINUX}"
-	RESOLVE_BTFIDS_ARGS=""
-	if is_enabled CONFIG_WERROR; then
-		RESOLVE_BTFIDS_ARGS=" --fatal_warnings "
-	fi
-	${RESOLVE_BTFIDS} ${RESOLVE_BTFIDS_ARGS} "${VMLINUX}"
+	info OBJCOPY ${btfids_vmlinux}
+	${OBJCOPY} --update-section .BTF_ids=${btfids_vmlinux} ${VMLINUX}
 fi
 
 mksysmap "${VMLINUX}" System.map
diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index da8c7d127632..3e88dc862d87 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -71,9 +71,11 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <linux/btf_ids.h>
+#include <linux/kallsyms.h>
 #include <linux/rbtree.h>
 #include <linux/zalloc.h>
 #include <linux/err.h>
+#include <linux/limits.h>
 #include <bpf/btf.h>
 #include <bpf/libbpf.h>
 #include <subcmd/parse-options.h>
@@ -124,6 +126,7 @@ struct object {
 
 	struct btf *btf;
 	struct btf *base_btf;
+	bool distill_base;
 
 	struct {
 		int		 fd;
@@ -324,42 +327,16 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
 	return btf_id__add(root, id, BTF_ID_KIND_SYM);
 }
 
-/* Older libelf.h and glibc elf.h might not yet define the ELF compression types. */
-#ifndef SHF_COMPRESSED
-#define SHF_COMPRESSED (1 << 11) /* Section with compressed data. */
-#endif
-
-/*
- * The data of compressed section should be aligned to 4
- * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
- * sets sh_addralign to 1, which makes libelf fail with
- * misaligned section error during the update:
- *    FAILED elf_update(WRITE): invalid section alignment
- *
- * While waiting for ld fix, we fix the compressed sections
- * sh_addralign value manualy.
- */
-static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
+static void bswap_32_data(void *data, u32 nr_bytes)
 {
-	int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8;
-
-	if (!(sh->sh_flags & SHF_COMPRESSED))
-		return 0;
-
-	if (sh->sh_addralign == expected)
-		return 0;
+	u32 cnt, i;
+	u32 *ptr;
 
-	pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n",
-		  sh->sh_addralign, expected);
+	cnt = nr_bytes / sizeof(u32);
+	ptr = data;
 
-	sh->sh_addralign = expected;
-
-	if (gelf_update_shdr(scn, sh) == 0) {
-		pr_err("FAILED cannot update section header: %s\n",
-			elf_errmsg(-1));
-		return -1;
-	}
-	return 0;
+	for (i = 0; i < cnt; i++)
+		ptr[i] = bswap_32(ptr[i]);
 }
 
 static int elf_collect(struct object *obj)
@@ -380,7 +357,7 @@ static int elf_collect(struct object *obj)
 
 	elf_version(EV_CURRENT);
 
-	elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL);
+	elf = elf_begin(fd, ELF_C_READ_MMAP_PRIVATE, NULL);
 	if (!elf) {
 		close(fd);
 		pr_err("FAILED cannot create ELF descriptor: %s\n",
@@ -443,21 +420,20 @@ static int elf_collect(struct object *obj)
 			obj->efile.symbols_shndx = idx;
 			obj->efile.strtabidx     = sh.sh_link;
 		} else if (!strcmp(name, BTF_IDS_SECTION)) {
+			/*
+			 * If target endianness differs from host, we need to bswap32
+			 * the .BTF_ids section data on load, because .BTF_ids has
+			 * Elf_Type = ELF_T_BYTE, and so libelf returns data buffer in
+			 * the target endianness. We repeat this on dump.
+			 */
+			if (obj->efile.encoding != ELFDATANATIVE) {
+				pr_debug("bswap_32 .BTF_ids data from target to host endianness\n");
+				bswap_32_data(data->d_buf, data->d_size);
+			}
 			obj->efile.idlist       = data;
 			obj->efile.idlist_shndx = idx;
 			obj->efile.idlist_addr  = sh.sh_addr;
-		} else if (!strcmp(name, BTF_BASE_ELF_SEC)) {
-			/* If a .BTF.base section is found, do not resolve
-			 * BTF ids relative to vmlinux; resolve relative
-			 * to the .BTF.base section instead.  btf__parse_split()
-			 * will take care of this once the base BTF it is
-			 * passed is NULL.
-			 */
-			obj->base_btf_path = NULL;
 		}
-
-		if (compressed_section_fix(elf, scn, &sh))
-			return -1;
 	}
 
 	return 0;
@@ -587,6 +563,19 @@ static int load_btf(struct object *obj)
 	obj->base_btf = base_btf;
 	obj->btf = btf;
 
+	if (obj->base_btf && obj->distill_base) {
+		err = btf__distill_base(obj->btf, &base_btf, &btf);
+		if (err) {
+			pr_err("FAILED to distill base BTF: %s\n", strerror(errno));
+			goto out_err;
+		}
+
+		btf__free(obj->btf);
+		btf__free(obj->base_btf);
+		obj->btf = btf;
+		obj->base_btf = base_btf;
+	}
+
 	return 0;
 
 out_err:
@@ -760,24 +749,6 @@ static int sets_patch(struct object *obj)
 			 */
 			BUILD_BUG_ON((u32 *)set8->pairs != &set8->pairs[0].id);
 			qsort(set8->pairs, set8->cnt, sizeof(set8->pairs[0]), cmp_id);
-
-			/*
-			 * When ELF endianness does not match endianness of the
-			 * host, libelf will do the translation when updating
-			 * the ELF. This, however, corrupts SET8 flags which are
-			 * already in the target endianness. So, let's bswap
-			 * them to the host endianness and libelf will then
-			 * correctly translate everything.
-			 */
-			if (obj->efile.encoding != ELFDATANATIVE) {
-				int i;
-
-				set8->flags = bswap_32(set8->flags);
-				for (i = 0; i < set8->cnt; i++) {
-					set8->pairs[i].flags =
-						bswap_32(set8->pairs[i].flags);
-				}
-			}
 			break;
 		default:
 			pr_err("Unexpected btf_id_kind %d for set '%s'\n", id->kind, id->name);
@@ -793,8 +764,6 @@ static int sets_patch(struct object *obj)
 
 static int symbols_patch(struct object *obj)
 {
-	off_t err;
-
 	if (__symbols_patch(obj, &obj->structs)  ||
 	    __symbols_patch(obj, &obj->unions)   ||
 	    __symbols_patch(obj, &obj->typedefs) ||
@@ -805,20 +774,90 @@ static int symbols_patch(struct object *obj)
 	if (sets_patch(obj))
 		return -1;
 
-	/* Set type to ensure endian translation occurs. */
-	obj->efile.idlist->d_type = ELF_T_WORD;
+	return 0;
+}
 
-	elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY);
+static int dump_raw_data(const char *out_path, const void *data, u32 size)
+{
+	size_t written;
+	FILE *file;
 
-	err = elf_update(obj->efile.elf, ELF_C_WRITE);
-	if (err < 0) {
-		pr_err("FAILED elf_update(WRITE): %s\n",
-			elf_errmsg(-1));
+	file = fopen(out_path, "wb");
+	if (!file) {
+		pr_err("Couldn't open %s for writing\n", out_path);
+		return -1;
+	}
+
+	written = fwrite(data, 1, size, file);
+	if (written != size) {
+		pr_err("Failed to write data to %s\n", out_path);
+		fclose(file);
+		unlink(out_path);
+		return -1;
+	}
+
+	fclose(file);
+	pr_debug("Dumped %lu bytes of data to %s\n", size, out_path);
+
+	return 0;
+}
+
+static int dump_raw_btf_ids(struct object *obj, const char *out_path)
+{
+	Elf_Data *data = obj->efile.idlist;
+	int err;
+
+	if (!data || !data->d_buf) {
+		pr_debug("%s has no BTF_ids data to dump\n", obj->path);
+		return 0;
+	}
+
+	/*
+	 * If target endianness differs from host, we need to bswap32 the
+	 * .BTF_ids section data before dumping so that the output is in
+	 * target endianness.
+	 */
+	if (obj->efile.encoding != ELFDATANATIVE) {
+		pr_debug("bswap_32 .BTF_ids data from host to target endianness\n");
+		bswap_32_data(data->d_buf, data->d_size);
+	}
+
+	err = dump_raw_data(out_path, data->d_buf, data->d_size);
+	if (err)
+		return -1;
+
+	return 0;
+}
+
+static int dump_raw_btf(struct btf *btf, const char *out_path)
+{
+	const void *raw_btf_data;
+	u32 raw_btf_size;
+	int err;
+
+	raw_btf_data = btf__raw_data(btf, &raw_btf_size);
+	if (!raw_btf_data) {
+		pr_err("btf__raw_data() failed\n");
+		return -1;
 	}
 
-	pr_debug("update %s for %s\n",
-		 err >= 0 ? "ok" : "failed", obj->path);
-	return err < 0 ? -1 : 0;
+	err = dump_raw_data(out_path, raw_btf_data, raw_btf_size);
+	if (err)
+		return -1;
+
+	return 0;
+}
+
+static inline int make_out_path(char *buf, u32 buf_sz, const char *in_path, const char *suffix)
+{
+	int len = snprintf(buf, buf_sz, "%s%s", in_path, suffix);
+
+	if (len < 0 || len >= buf_sz) {
+		pr_err("Output path is too long: %s%s\n", in_path, suffix);
+		return -E2BIG;
+	}
+
+	return 0;
 }
 
 static const char * const resolve_btfids_usage[] = {
@@ -840,6 +879,8 @@ int main(int argc, const char **argv)
 		.sets     = RB_ROOT,
 	};
 	bool fatal_warnings = false;
+	char out_path[PATH_MAX];
+
 	struct option btfid_options[] = {
 		OPT_INCR('v', "verbose", &verbose,
 			 "be more verbose (show errors, etc)"),
@@ -849,6 +890,8 @@ int main(int argc, const char **argv)
 			   "path of file providing base BTF"),
 		OPT_BOOLEAN(0, "fatal_warnings", &fatal_warnings,
 			    "turn warnings into errors"),
+		OPT_BOOLEAN(0, "distill_base", &obj.distill_base,
+			    "distill --btf_base and emit .BTF.base section data"),
 		OPT_END()
 	};
 	int err = -1;
@@ -860,6 +903,9 @@ int main(int argc, const char **argv)
 
 	obj.path = argv[0];
 
+	if (load_btf(&obj))
+		goto out;
+
 	if (elf_collect(&obj))
 		goto out;
 
@@ -869,23 +915,37 @@ int main(int argc, const char **argv)
 	 */
 	if (obj.efile.idlist_shndx == -1 ||
 	    obj.efile.symbols_shndx == -1) {
-		pr_debug("Cannot find .BTF_ids or symbols sections, nothing to do\n");
-		err = 0;
-		goto out;
+		pr_debug("Cannot find .BTF_ids or symbols sections, skip symbols resolution\n");
+		goto dump_btf;
 	}
 
 	if (symbols_collect(&obj))
 		goto out;
 
-	if (load_btf(&obj))
-		goto out;
-
 	if (symbols_resolve(&obj))
 		goto out;
 
 	if (symbols_patch(&obj))
 		goto out;
 
+	err = make_out_path(out_path, sizeof(out_path), obj.path, BTF_IDS_SECTION);
+	err = err ?: dump_raw_btf_ids(&obj, out_path);
+	if (err)
+		goto out;
+
+dump_btf:
+	err = make_out_path(out_path, sizeof(out_path), obj.path, BTF_ELF_SEC);
+	err = err ?: dump_raw_btf(obj.btf, out_path);
+	if (err)
+		goto out;
+
+	if (obj.base_btf && obj.distill_base) {
+		err = make_out_path(out_path, sizeof(out_path), obj.path, BTF_BASE_ELF_SEC);
+		err = err ?: dump_raw_btf(obj.base_btf, out_path);
+		if (err)
+			goto out;
+	}
+
 	if (!(fatal_warnings && warnings))
 		err = 0;
 out:
diff --git a/tools/testing/selftests/bpf/.gitignore b/tools/testing/selftests/bpf/.gitignore
index 19c1638e312a..b8bf51b7a0b0 100644
--- a/tools/testing/selftests/bpf/.gitignore
+++ b/tools/testing/selftests/bpf/.gitignore
@@ -45,3 +45,6 @@ xdp_synproxy
 xdp_hw_metadata
 xdp_features
 verification_cert.h
+*.BTF
+*.BTF_ids
+*.BTF.base
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index ffd0a4c354c7..f28a32b16ff0 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -4,6 +4,7 @@ include ../../../scripts/Makefile.arch
 include ../../../scripts/Makefile.include
 
 CXX ?= $(CROSS_COMPILE)g++
+OBJCOPY ?= $(CROSS_COMPILE)objcopy
 
 CURDIR := $(abspath .)
 TOOLSDIR := $(abspath ../../..)
@@ -653,9 +654,10 @@ $(TRUNNER_TEST_OBJS): $(TRUNNER_OUTPUT)/%.test.o:			\
 		      | $(TRUNNER_OUTPUT)/%.test.d
 	$$(call msg,TEST-OBJ,$(TRUNNER_BINARY),$$@)
 	$(Q)cd $$(@D) && $$(CC) -I. $$(CFLAGS) -MMD -MT $$@ -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F)
-	$$(if $$(TEST_NEEDS_BTFIDS),					\
-		$$(call msg,BTFIDS,$(TRUNNER_BINARY),$$@)		\
-		$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@)
+	$$(if $$(TEST_NEEDS_BTFIDS),						\
+		$$(call msg,BTFIDS,$(TRUNNER_BINARY),$$@)			\
+		$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@;	\
+		$(OBJCOPY) --update-section .BTF_ids=$$@.BTF_ids $$@)
 
 $(TRUNNER_TEST_OBJS:.o=.d): $(TRUNNER_OUTPUT)/%.test.d:			\
 			    $(TRUNNER_TESTS_DIR)/%.c			\
@@ -894,6 +896,7 @@ EXTRA_CLEAN := $(SCRATCH_DIR) $(HOST_SCRATCH_DIR)			\
 	prog_tests/tests.h map_tests/tests.h verifier/tests.h		\
 	feature bpftool $(TEST_KMOD_TARGETS)				\
 	$(addprefix $(OUTPUT)/,*.o *.d *.skel.h *.lskel.h *.subskel.h	\
+			       *.BTF *.BTF_ids *.BTF.base		\
 			       no_alu32 cpuv4 bpf_gcc			\
 			       liburandom_read.so)			\
 	$(OUTPUT)/FEATURE-DUMP.selftests				\
diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
index 51544372f52e..41dfaaabb73f 100644
--- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
+++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
@@ -101,9 +101,9 @@ static int resolve_symbols(void)
 	int type_id;
 	__u32 nr;
 
-	btf = btf__parse_elf("btf_data.bpf.o", NULL);
+	btf = btf__parse_raw("resolve_btfids.test.o.BTF");
 	if (CHECK(libbpf_get_error(btf), "resolve",
-		  "Failed to load BTF from btf_data.bpf.o\n"))
+		  "Failed to load BTF from resolve_btfids.test.o.BTF\n"))
 		return -1;
 
 	nr = btf__type_cnt(btf);
-- 
2.52.0

Re: [PATCH bpf-next v4 8/8] resolve_btfids: Change in-place update with raw binary output

[Ihor Solodrai]

On 12/17/25 4:33 PM, Ihor Solodrai wrote:
> [...]
> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> index 840a55de42da..b8569d450ed9 100644
> --- a/scripts/Makefile.btf
> +++ b/scripts/Makefile.btf
> @@ -1,5 +1,10 @@
>  # SPDX-License-Identifier: GPL-2.0
>  
> +gen-btf-y				=
> +gen-btf-$(CONFIG_DEBUG_INFO_BTF)	= $(srctree)/scripts/gen-btf.sh
> +
> +export GEN_BTF := $(gen-btf-y)
> +

Ugh... GEN_BTF is not used anywhere in v4.
Looks like I forgot a `git add` at some point.

I'll wait a bit before sending a v5, in case there is more feedback.

>  pahole-ver := $(CONFIG_PAHOLE_VERSION)
>  pahole-flags-y :=
>  
> @@ -18,13 +23,15 @@ pahole-flags-$(call test-ge, $(pahole-ver), 126)  = -j$(JOBS) --btf_features=enc
>  
>  pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
>  
> -ifneq ($(KBUILD_EXTMOD),)
> -module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
> -endif
> -
>  endif
>  
>  [...]

Re: [PATCH bpf-next v4 8/8] resolve_btfids: Change in-place update with raw binary output

[Andrii Nakryiko]

On Thu, Dec 18, 2025 at 9:54 AM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>
> On 12/17/25 4:33 PM, Ihor Solodrai wrote:
> > [...]
> > diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> > index 840a55de42da..b8569d450ed9 100644
> > --- a/scripts/Makefile.btf
> > +++ b/scripts/Makefile.btf
> > @@ -1,5 +1,10 @@
> >  # SPDX-License-Identifier: GPL-2.0
> >
> > +gen-btf-y                            =
> > +gen-btf-$(CONFIG_DEBUG_INFO_BTF)     = $(srctree)/scripts/gen-btf.sh
> > +
> > +export GEN_BTF := $(gen-btf-y)
> > +
>
> Ugh... GEN_BTF is not used anywhere in v4.
> Looks like I forgot a `git add` at some point.
>
> I'll wait a bit before sending a v5, in case there is more feedback.

It all looks good to me, so don't wait for any more feedback from my
side. If Eduard doesn't find anything in patch #8, please send new
revision, thanks!

>
> >  pahole-ver := $(CONFIG_PAHOLE_VERSION)
> >  pahole-flags-y :=
> >
> > @@ -18,13 +23,15 @@ pahole-flags-$(call test-ge, $(pahole-ver), 126)  = -j$(JOBS) --btf_features=enc
> >
> >  pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
> >
> > -ifneq ($(KBUILD_EXTMOD),)
> > -module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
> > -endif
> > -
> >  endif
> >
> >  [...]
>

Re: [PATCH bpf-next v4 8/8] resolve_btfids: Change in-place update with raw binary output

[Eduard Zingerman]

On Thu, 2025-12-18 at 13:15 -0800, Andrii Nakryiko wrote:

[...]

> It all looks good to me, so don't wait for any more feedback from my
> side. If Eduard doesn't find anything in patch #8, please send new
> revision, thanks!

Lgtm, let's wrap this up.

[...]