From: Donglin Peng <pengdonglin@xiaomi.com>
This patch introduces a new --btf_sort option that leverages libbpf's
btf__permute interface to reorganize BTF layout. The implementation
sorts BTF types by name in ascending order, placing anonymous types at
the end to enable efficient binary search lookup.
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Song Liu <song@kernel.org>
Cc: Xiaoqin Zhang <zhangxiaoqin@xiaomi.com>
Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
---
scripts/Makefile.btf | 2 +
scripts/Makefile.modfinal | 1 +
scripts/link-vmlinux.sh | 1 +
tools/bpf/resolve_btfids/main.c | 200 ++++++++++++++++++++++++++++++++
4 files changed, 204 insertions(+)
diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
index db76335dd917..d5eb4ee70e88 100644
--- a/scripts/Makefile.btf
+++ b/scripts/Makefile.btf
@@ -27,6 +27,7 @@ pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
ifneq ($(KBUILD_EXTMOD),)
module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
+module-resolve_btfid-flags-y = --distilled_base
endif
endif
@@ -35,3 +36,4 @@ pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE) += --lang_exclude=rust
export PAHOLE_FLAGS := $(pahole-flags-y)
export MODULE_PAHOLE_FLAGS := $(module-pahole-flags-y)
+export MODULE_RESOLVE_BTFID_FLAGS := $(module-resolve_btfid-flags-y)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 542ba462ed3e..4481dda2f485 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -40,6 +40,7 @@ quiet_cmd_btf_ko = BTF [M] $@
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 $(MODULE_RESOLVE_BTFID_FLAGS) --btf_sort $@; \
$(RESOLVE_BTFIDS) -b $(objtree)/vmlinux $@; \
fi;
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 433849ff7529..f21f6300815b 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -288,6 +288,7 @@ if is_enabled CONFIG_DEBUG_INFO_BTF; then
if is_enabled CONFIG_WERROR; then
RESOLVE_BTFIDS_ARGS=" --fatal_warnings "
fi
+ ${RESOLVE_BTFIDS} ${RESOLVE_BTFIDS_ARGS} --btf_sort "${VMLINUX}"
${RESOLVE_BTFIDS} ${RESOLVE_BTFIDS_ARGS} "${VMLINUX}"
fi
diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index d47191c6e55e..dc0badd6f375 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -768,6 +768,195 @@ static int symbols_patch(struct object *obj)
return err < 0 ? -1 : 0;
}
+/* Anonymous types (with empty names) are considered greater than named types
+ * and are sorted after them. Two anonymous types are considered equal. Named
+ * types are compared lexicographically.
+ */
+static int cmp_type_names(const void *a, const void *b, void *priv)
+{
+ struct btf *btf = (struct btf *)priv;
+ const struct btf_type *ta = btf__type_by_id(btf, *(__u32 *)a);
+ const struct btf_type *tb = btf__type_by_id(btf, *(__u32 *)b);
+ const char *na, *nb;
+
+ if (!ta->name_off && tb->name_off)
+ return 1;
+ if (ta->name_off && !tb->name_off)
+ return -1;
+ if (!ta->name_off && !tb->name_off)
+ return 0;
+
+ na = btf__str_by_offset(btf, ta->name_off);
+ nb = btf__str_by_offset(btf, tb->name_off);
+ return strcmp(na, nb);
+}
+
+static int update_btf_section(const char *path, const struct btf *btf,
+ const char *btf_secname)
+{
+ GElf_Shdr shdr_mem, *shdr;
+ Elf_Data *btf_data = NULL;
+ Elf_Scn *scn = NULL;
+ Elf *elf = NULL;
+ const void *raw_btf_data;
+ uint32_t raw_btf_size;
+ int fd, err = -1;
+ size_t strndx;
+
+ fd = open(path, O_RDWR);
+ if (fd < 0) {
+ pr_err("FAILED to open %s\n", path);
+ return -1;
+ }
+
+ if (elf_version(EV_CURRENT) == EV_NONE) {
+ pr_err("FAILED to set libelf version");
+ goto out;
+ }
+
+ elf = elf_begin(fd, ELF_C_RDWR, NULL);
+ if (elf == NULL) {
+ pr_err("FAILED to update ELF file");
+ goto out;
+ }
+
+ elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
+
+ elf_getshdrstrndx(elf, &strndx);
+ while ((scn = elf_nextscn(elf, scn)) != NULL) {
+ char *secname;
+
+ shdr = gelf_getshdr(scn, &shdr_mem);
+ if (shdr == NULL)
+ continue;
+ secname = elf_strptr(elf, strndx, shdr->sh_name);
+ if (strcmp(secname, btf_secname) == 0) {
+ btf_data = elf_getdata(scn, btf_data);
+ break;
+ }
+ }
+
+ raw_btf_data = btf__raw_data(btf, &raw_btf_size);
+
+ if (btf_data) {
+ if (raw_btf_size != btf_data->d_size) {
+ pr_err("FAILED: size mismatch");
+ goto out;
+ }
+
+ btf_data->d_buf = (void *)raw_btf_data;
+ btf_data->d_type = ELF_T_WORD;
+ elf_flagdata(btf_data, ELF_C_SET, ELF_F_DIRTY);
+
+ if (elf_update(elf, ELF_C_WRITE) >= 0)
+ err = 0;
+ }
+
+out:
+ if (fd != -1)
+ close(fd);
+ if (elf)
+ elf_end(elf);
+ return err;
+}
+
+static int sort_update_btf(struct object *obj, bool distilled_base)
+{
+ struct btf *base_btf = NULL;
+ struct btf *btf = NULL;
+ int start_id = 1, nr_types, id;
+ int err = 0, i;
+ __u32 *permute_ids = NULL, *id_map = NULL, btf_size;
+ const void *btf_data;
+ int fd;
+
+ if (obj->base_btf_path) {
+ base_btf = btf__parse(obj->base_btf_path, NULL);
+ err = libbpf_get_error(base_btf);
+ if (err) {
+ pr_err("FAILED: load base BTF from %s: %s\n",
+ obj->base_btf_path, strerror(-err));
+ return -1;
+ }
+ }
+
+ btf = btf__parse_elf_split(obj->path, base_btf);
+ err = libbpf_get_error(btf);
+ if (err) {
+ pr_err("FAILED: load BTF from %s: %s\n", obj->path, strerror(-err));
+ goto out;
+ }
+
+ if (base_btf)
+ start_id = btf__type_cnt(base_btf);
+ nr_types = btf__type_cnt(btf) - start_id;
+ if (nr_types < 2)
+ goto out;
+
+ permute_ids = calloc(nr_types, sizeof(*permute_ids));
+ if (!permute_ids) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ id_map = calloc(nr_types, sizeof(*id_map));
+ if (!id_map) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ for (i = 0, id = start_id; i < nr_types; i++, id++)
+ permute_ids[i] = id;
+
+ qsort_r(permute_ids, nr_types, sizeof(*permute_ids), cmp_type_names, btf);
+
+ for (i = 0; i < nr_types; i++) {
+ id = permute_ids[i] - start_id;
+ id_map[id] = i + start_id;
+ }
+
+ err = btf__permute(btf, id_map, nr_types, NULL);
+ if (err) {
+ pr_err("FAILED: btf permute: %s\n", strerror(-err));
+ goto out;
+ }
+
+ if (distilled_base) {
+ struct btf *new_btf = NULL, *distilled_base = NULL;
+
+ if (btf__distill_base(btf, &distilled_base, &new_btf) < 0) {
+ pr_err("FAILED to generate distilled base BTF: %s\n",
+ strerror(errno));
+ goto out;
+ }
+
+ err = update_btf_section(obj->path, new_btf, BTF_ELF_SEC);
+ if (!err) {
+ err = update_btf_section(obj->path, distilled_base, BTF_BASE_ELF_SEC);
+ if (err < 0)
+ pr_err("FAILED to update '%s'\n", BTF_BASE_ELF_SEC);
+ } else {
+ pr_err("FAILED to update '%s'\n", BTF_ELF_SEC);
+ }
+
+ btf__free(new_btf);
+ btf__free(distilled_base);
+ } else {
+ err = update_btf_section(obj->path, btf, BTF_ELF_SEC);
+ if (err < 0) {
+ pr_err("FAILED to update '%s'\n", BTF_ELF_SEC);
+ goto out;
+ }
+ }
+
+out:
+ free(permute_ids);
+ free(id_map);
+ btf__free(base_btf);
+ btf__free(btf);
+ return err;
+}
+
static const char * const resolve_btfids_usage[] = {
"resolve_btfids [<options>] <ELF object>",
NULL
@@ -787,6 +976,8 @@ int main(int argc, const char **argv)
.sets = RB_ROOT,
};
bool fatal_warnings = false;
+ bool btf_sort = false;
+ bool distilled_base = false;
struct option btfid_options[] = {
OPT_INCR('v', "verbose", &verbose,
"be more verbose (show errors, etc)"),
@@ -796,6 +987,10 @@ 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, "btf_sort", &btf_sort,
+ "sort BTF by name in ascending order"),
+ OPT_BOOLEAN(0, "distilled_base", &distilled_base,
+ "distill base"),
OPT_END()
};
int err = -1;
@@ -807,6 +1002,11 @@ int main(int argc, const char **argv)
obj.path = argv[0];
+ if (btf_sort) {
+ err = sort_update_btf(&obj, distilled_base);
+ goto out;
+ }
+
if (elf_collect(&obj))
goto out;
--
2.34.1On Wed, 2025-11-19 at 11:15 +0800, Donglin Peng wrote:
[...]
> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> index db76335dd917..d5eb4ee70e88 100644
> --- a/scripts/Makefile.btf
> +++ b/scripts/Makefile.btf
> @@ -27,6 +27,7 @@ pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
>
> ifneq ($(KBUILD_EXTMOD),)
> module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
> +module-resolve_btfid-flags-y = --distilled_base
^^^^^^^^^^^^^^^^
This flag should be guarded by pahole version as well. However, I'd
suggest not adding this flag at all, but instead modify resolve_btfids
to check for BTF_BASE_ELF_SEC section existence and acting accordingly.
> endif
>
> endif
> @@ -35,3 +36,4 @@ pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE) += --lang_exclude=rust
>
> export PAHOLE_FLAGS := $(pahole-flags-y)
> export MODULE_PAHOLE_FLAGS := $(module-pahole-flags-y)
> +export MODULE_RESOLVE_BTFID_FLAGS := $(module-resolve_btfid-flags-y)
> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> index 542ba462ed3e..4481dda2f485 100644
> --- a/scripts/Makefile.modfinal
> +++ b/scripts/Makefile.modfinal
> @@ -40,6 +40,7 @@ quiet_cmd_btf_ko = BTF [M] $@
> 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 $(MODULE_RESOLVE_BTFID_FLAGS) --btf_sort $@; \
^^^^^^^^^^
Agree with Ihor (and off-list discussion with Alexei),
this flag appears redundant. Are there situations when
one would like to avoid sorting kernel/module BTF?
> $(RESOLVE_BTFIDS) -b $(objtree)/vmlinux $@; \
> fi;
[...]
> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index d47191c6e55e..dc0badd6f375 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c
[...]
> +static int update_btf_section(const char *path, const struct btf *btf,
> + const char *btf_secname)
> +{
> + GElf_Shdr shdr_mem, *shdr;
> + Elf_Data *btf_data = NULL;
> + Elf_Scn *scn = NULL;
> + Elf *elf = NULL;
> + const void *raw_btf_data;
> + uint32_t raw_btf_size;
> + int fd, err = -1;
> + size_t strndx;
> +
> + fd = open(path, O_RDWR);
> + if (fd < 0) {
> + pr_err("FAILED to open %s\n", path);
> + return -1;
> + }
> +
> + if (elf_version(EV_CURRENT) == EV_NONE) {
> + pr_err("FAILED to set libelf version");
> + goto out;
> + }
> +
> + elf = elf_begin(fd, ELF_C_RDWR, NULL);
> + if (elf == NULL) {
> + pr_err("FAILED to update ELF file");
> + goto out;
> + }
> +
> + elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
> +
> + elf_getshdrstrndx(elf, &strndx);
> + while ((scn = elf_nextscn(elf, scn)) != NULL) {
> + char *secname;
> +
> + shdr = gelf_getshdr(scn, &shdr_mem);
> + if (shdr == NULL)
> + continue;
> + secname = elf_strptr(elf, strndx, shdr->sh_name);
> + if (strcmp(secname, btf_secname) == 0) {
> + btf_data = elf_getdata(scn, btf_data);
> + break;
> + }
> + }
> +
> + raw_btf_data = btf__raw_data(btf, &raw_btf_size);
`btf__raw_data()` can return NULL.
> +
> + if (btf_data) {
> + if (raw_btf_size != btf_data->d_size) {
> + pr_err("FAILED: size mismatch");
> + goto out;
> + }
> +
> + btf_data->d_buf = (void *)raw_btf_data;
> + btf_data->d_type = ELF_T_WORD;
> + elf_flagdata(btf_data, ELF_C_SET, ELF_F_DIRTY);
> +
> + if (elf_update(elf, ELF_C_WRITE) >= 0)
> + err = 0;
> + }
> +
> +out:
> + if (fd != -1)
> + close(fd);
> + if (elf)
> + elf_end(elf);
> + return err;
> +}
[...]
On Fri, Nov 21, 2025 at 8:18 AM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> On Wed, 2025-11-19 at 11:15 +0800, Donglin Peng wrote:
>
> [...]
>
> > diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> > index db76335dd917..d5eb4ee70e88 100644
> > --- a/scripts/Makefile.btf
> > +++ b/scripts/Makefile.btf
> > @@ -27,6 +27,7 @@ pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
> >
> > ifneq ($(KBUILD_EXTMOD),)
> > module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
> > +module-resolve_btfid-flags-y = --distilled_base
> ^^^^^^^^^^^^^^^^
> This flag should be guarded by pahole version as well. However, I'd
> suggest not adding this flag at all, but instead modify resolve_btfids
> to check for BTF_BASE_ELF_SEC section existence and acting accordingly.
Thanks, I will remove it in the next version.
>
> > endif
> >
> > endif
> > @@ -35,3 +36,4 @@ pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE) += --lang_exclude=rust
> >
> > export PAHOLE_FLAGS := $(pahole-flags-y)
> > export MODULE_PAHOLE_FLAGS := $(module-pahole-flags-y)
> > +export MODULE_RESOLVE_BTFID_FLAGS := $(module-resolve_btfid-flags-y)
> > diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> > index 542ba462ed3e..4481dda2f485 100644
> > --- a/scripts/Makefile.modfinal
> > +++ b/scripts/Makefile.modfinal
> > @@ -40,6 +40,7 @@ quiet_cmd_btf_ko = BTF [M] $@
> > 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 $(MODULE_RESOLVE_BTFID_FLAGS) --btf_sort $@; \
> ^^^^^^^^^^
> Agree with Ihor (and off-list discussion with Alexei),
> this flag appears redundant. Are there situations when
> one would like to avoid sorting kernel/module BTF?
Thanks, I will make sorting unconditional.
>
> > $(RESOLVE_BTFIDS) -b $(objtree)/vmlinux $@; \
> > fi;
>
> [...]
>
> > diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> > index d47191c6e55e..dc0badd6f375 100644
> > --- a/tools/bpf/resolve_btfids/main.c
> > +++ b/tools/bpf/resolve_btfids/main.c
>
> [...]
>
> > +static int update_btf_section(const char *path, const struct btf *btf,
> > + const char *btf_secname)
> > +{
> > + GElf_Shdr shdr_mem, *shdr;
> > + Elf_Data *btf_data = NULL;
> > + Elf_Scn *scn = NULL;
> > + Elf *elf = NULL;
> > + const void *raw_btf_data;
> > + uint32_t raw_btf_size;
> > + int fd, err = -1;
> > + size_t strndx;
> > +
> > + fd = open(path, O_RDWR);
> > + if (fd < 0) {
> > + pr_err("FAILED to open %s\n", path);
> > + return -1;
> > + }
> > +
> > + if (elf_version(EV_CURRENT) == EV_NONE) {
> > + pr_err("FAILED to set libelf version");
> > + goto out;
> > + }
> > +
> > + elf = elf_begin(fd, ELF_C_RDWR, NULL);
> > + if (elf == NULL) {
> > + pr_err("FAILED to update ELF file");
> > + goto out;
> > + }
> > +
> > + elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
> > +
> > + elf_getshdrstrndx(elf, &strndx);
> > + while ((scn = elf_nextscn(elf, scn)) != NULL) {
> > + char *secname;
> > +
> > + shdr = gelf_getshdr(scn, &shdr_mem);
> > + if (shdr == NULL)
> > + continue;
> > + secname = elf_strptr(elf, strndx, shdr->sh_name);
> > + if (strcmp(secname, btf_secname) == 0) {
> > + btf_data = elf_getdata(scn, btf_data);
> > + break;
> > + }
> > + }
> > +
> > + raw_btf_data = btf__raw_data(btf, &raw_btf_size);
>
> `btf__raw_data()` can return NULL.
Thanks, I will fix it.
>
> > +
> > + if (btf_data) {
> > + if (raw_btf_size != btf_data->d_size) {
> > + pr_err("FAILED: size mismatch");
> > + goto out;
> > + }
> > +
> > + btf_data->d_buf = (void *)raw_btf_data;
> > + btf_data->d_type = ELF_T_WORD;
> > + elf_flagdata(btf_data, ELF_C_SET, ELF_F_DIRTY);
> > +
> > + if (elf_update(elf, ELF_C_WRITE) >= 0)
> > + err = 0;
> > + }
> > +
> > +out:
> > + if (fd != -1)
> > + close(fd);
> > + if (elf)
> > + elf_end(elf);
> > + return err;
> > +}
>
> [...]
On 11/18/25 7:15 PM, Donglin Peng wrote:
> From: Donglin Peng <pengdonglin@xiaomi.com>
>
> This patch introduces a new --btf_sort option that leverages libbpf's
> btf__permute interface to reorganize BTF layout. The implementation
> sorts BTF types by name in ascending order, placing anonymous types at
> the end to enable efficient binary search lookup.
>
> Cc: Eduard Zingerman <eddyz87@gmail.com>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Cc: Alan Maguire <alan.maguire@oracle.com>
> Cc: Song Liu <song@kernel.org>
> Cc: Xiaoqin Zhang <zhangxiaoqin@xiaomi.com>
> Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
> ---
> scripts/Makefile.btf | 2 +
> scripts/Makefile.modfinal | 1 +
> scripts/link-vmlinux.sh | 1 +
> tools/bpf/resolve_btfids/main.c | 200 ++++++++++++++++++++++++++++++++
> 4 files changed, 204 insertions(+)
>
> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> index db76335dd917..d5eb4ee70e88 100644
> --- a/scripts/Makefile.btf
> +++ b/scripts/Makefile.btf
> @@ -27,6 +27,7 @@ pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
>
> ifneq ($(KBUILD_EXTMOD),)
> module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
> +module-resolve_btfid-flags-y = --distilled_base
> endif
>
> endif
> @@ -35,3 +36,4 @@ pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE) += --lang_exclude=rust
>
> export PAHOLE_FLAGS := $(pahole-flags-y)
> export MODULE_PAHOLE_FLAGS := $(module-pahole-flags-y)
> +export MODULE_RESOLVE_BTFID_FLAGS := $(module-resolve_btfid-flags-y)
> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> index 542ba462ed3e..4481dda2f485 100644
> --- a/scripts/Makefile.modfinal
> +++ b/scripts/Makefile.modfinal
> @@ -40,6 +40,7 @@ quiet_cmd_btf_ko = BTF [M] $@
> 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 $(MODULE_RESOLVE_BTFID_FLAGS) --btf_sort $@; \
> $(RESOLVE_BTFIDS) -b $(objtree)/vmlinux $@; \
> fi;
>
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index 433849ff7529..f21f6300815b 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -288,6 +288,7 @@ if is_enabled CONFIG_DEBUG_INFO_BTF; then
> if is_enabled CONFIG_WERROR; then
> RESOLVE_BTFIDS_ARGS=" --fatal_warnings "
> fi
> + ${RESOLVE_BTFIDS} ${RESOLVE_BTFIDS_ARGS} --btf_sort "${VMLINUX}"
> ${RESOLVE_BTFIDS} ${RESOLVE_BTFIDS_ARGS} "${VMLINUX}"
> fi
>
> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index d47191c6e55e..dc0badd6f375 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c
> @@ -768,6 +768,195 @@ static int symbols_patch(struct object *obj)
> return err < 0 ? -1 : 0;
> }
>
> +/* Anonymous types (with empty names) are considered greater than named types
> + * and are sorted after them. Two anonymous types are considered equal. Named
> + * types are compared lexicographically.
> + */
> +static int cmp_type_names(const void *a, const void *b, void *priv)
> +{
> + struct btf *btf = (struct btf *)priv;
> + const struct btf_type *ta = btf__type_by_id(btf, *(__u32 *)a);
> + const struct btf_type *tb = btf__type_by_id(btf, *(__u32 *)b);
> + const char *na, *nb;
> +
> + if (!ta->name_off && tb->name_off)
> + return 1;
> + if (ta->name_off && !tb->name_off)
> + return -1;
> + if (!ta->name_off && !tb->name_off)
> + return 0;
> +
> + na = btf__str_by_offset(btf, ta->name_off);
> + nb = btf__str_by_offset(btf, tb->name_off);
> + return strcmp(na, nb);
> +}
> +
> +static int update_btf_section(const char *path, const struct btf *btf,
Hi Dongling.
Thanks for working on this, it's a great optimization. Just want to
give you a heads up that I am preparing a patchset changing
resolve_btfids behavior.
In particular, instead of updating the .BTF_ids section (and now with
your and upcoming changes the .BTF section) *in-place*, resolve_btfids
will only emit the data for the sections. And then it'll be integrated
into vmlinux with objcopy and linker. We already do a similar thing
with .BTF for vmlinux [1].
For your patchset it means that the parts handling ELF update will be
unnecessary.
Also I think the --btf_sort flag is unnecessary. We probably want
kernel BTF to always be sorted in this way. And if resolve_btfids will
be handling more btf2btf transformation, we should avoid adding a
flags for every one of them.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/scripts/link-vmlinux.sh#n110
> + const char *btf_secname)
> +{
> + GElf_Shdr shdr_mem, *shdr;
> + Elf_Data *btf_data = NULL;
> + Elf_Scn *scn = NULL;
> + Elf *elf = NULL;
> + const void *raw_btf_data;
> + uint32_t raw_btf_size;
> + int fd, err = -1;
> + size_t strndx;
> +
> + fd = open(path, O_RDWR);
> + if (fd < 0) {
> + pr_err("FAILED to open %s\n", path);
> + return -1;
> + }
> +
> + if (elf_version(EV_CURRENT) == EV_NONE) {
> + pr_err("FAILED to set libelf version");
> + goto out;
> + }
> +
> + elf = elf_begin(fd, ELF_C_RDWR, NULL);
> + if (elf == NULL) {
> + pr_err("FAILED to update ELF file");
> + goto out;
> + }
> +
> + elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
> +
> + elf_getshdrstrndx(elf, &strndx);
> + while ((scn = elf_nextscn(elf, scn)) != NULL) {
> + char *secname;
> +
> + shdr = gelf_getshdr(scn, &shdr_mem);
> + if (shdr == NULL)
> + continue;
> + secname = elf_strptr(elf, strndx, shdr->sh_name);
> + if (strcmp(secname, btf_secname) == 0) {
> + btf_data = elf_getdata(scn, btf_data);
> + break;
> + }
> + }
> +
> + raw_btf_data = btf__raw_data(btf, &raw_btf_size);
> +
> + if (btf_data) {
> + if (raw_btf_size != btf_data->d_size) {
> + pr_err("FAILED: size mismatch");
> + goto out;
> + }
> +
> + btf_data->d_buf = (void *)raw_btf_data;
> + btf_data->d_type = ELF_T_WORD;
> + elf_flagdata(btf_data, ELF_C_SET, ELF_F_DIRTY);
> +
> + if (elf_update(elf, ELF_C_WRITE) >= 0)
> + err = 0;
> + }
> +
> +out:
> + if (fd != -1)
> + close(fd);
> + if (elf)
> + elf_end(elf);
> + return err;
> +}
> +
> +static int sort_update_btf(struct object *obj, bool distilled_base)
> +{
> + struct btf *base_btf = NULL;
> + struct btf *btf = NULL;
> + int start_id = 1, nr_types, id;
> + int err = 0, i;
> + __u32 *permute_ids = NULL, *id_map = NULL, btf_size;
> + const void *btf_data;
> + int fd;
> +
> + if (obj->base_btf_path) {
> + base_btf = btf__parse(obj->base_btf_path, NULL);
> + err = libbpf_get_error(base_btf);
> + if (err) {
> + pr_err("FAILED: load base BTF from %s: %s\n",
> + obj->base_btf_path, strerror(-err));
> + return -1;
> + }
> + }
> +
> + btf = btf__parse_elf_split(obj->path, base_btf);
> + err = libbpf_get_error(btf);
> + if (err) {
> + pr_err("FAILED: load BTF from %s: %s\n", obj->path, strerror(-err));
> + goto out;
> + }
> +
> + if (base_btf)
> + start_id = btf__type_cnt(base_btf);
> + nr_types = btf__type_cnt(btf) - start_id;
> + if (nr_types < 2)
> + goto out;
> +
> + permute_ids = calloc(nr_types, sizeof(*permute_ids));
> + if (!permute_ids) {
> + err = -ENOMEM;
> + goto out;
> + }
> +
> + id_map = calloc(nr_types, sizeof(*id_map));
> + if (!id_map) {
> + err = -ENOMEM;
> + goto out;
> + }
> +
> + for (i = 0, id = start_id; i < nr_types; i++, id++)
> + permute_ids[i] = id;
> +
> + qsort_r(permute_ids, nr_types, sizeof(*permute_ids), cmp_type_names, btf);
> +
> + for (i = 0; i < nr_types; i++) {
> + id = permute_ids[i] - start_id;
> + id_map[id] = i + start_id;
> + }
> +
> + err = btf__permute(btf, id_map, nr_types, NULL);
> + if (err) {
> + pr_err("FAILED: btf permute: %s\n", strerror(-err));
> + goto out;
> + }
> +
> + if (distilled_base) {
> + struct btf *new_btf = NULL, *distilled_base = NULL;
> +
> + if (btf__distill_base(btf, &distilled_base, &new_btf) < 0) {
> + pr_err("FAILED to generate distilled base BTF: %s\n",
> + strerror(errno));
> + goto out;
> + }
> +
> + err = update_btf_section(obj->path, new_btf, BTF_ELF_SEC);
> + if (!err) {
> + err = update_btf_section(obj->path, distilled_base, BTF_BASE_ELF_SEC);
> + if (err < 0)
> + pr_err("FAILED to update '%s'\n", BTF_BASE_ELF_SEC);
> + } else {
> + pr_err("FAILED to update '%s'\n", BTF_ELF_SEC);
> + }
> +
> + btf__free(new_btf);
> + btf__free(distilled_base);
> + } else {
> + err = update_btf_section(obj->path, btf, BTF_ELF_SEC);
> + if (err < 0) {
> + pr_err("FAILED to update '%s'\n", BTF_ELF_SEC);
> + goto out;
> + }
> + }
> +
> +out:
> + free(permute_ids);
> + free(id_map);
> + btf__free(base_btf);
> + btf__free(btf);
> + return err;
> +}
> +
> static const char * const resolve_btfids_usage[] = {
> "resolve_btfids [<options>] <ELF object>",
> NULL
> @@ -787,6 +976,8 @@ int main(int argc, const char **argv)
> .sets = RB_ROOT,
> };
> bool fatal_warnings = false;
> + bool btf_sort = false;
> + bool distilled_base = false;
> struct option btfid_options[] = {
> OPT_INCR('v', "verbose", &verbose,
> "be more verbose (show errors, etc)"),
> @@ -796,6 +987,10 @@ 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, "btf_sort", &btf_sort,
> + "sort BTF by name in ascending order"),
> + OPT_BOOLEAN(0, "distilled_base", &distilled_base,
> + "distill base"),
> OPT_END()
> };
> int err = -1;
> @@ -807,6 +1002,11 @@ int main(int argc, const char **argv)
>
> obj.path = argv[0];
>
> + if (btf_sort) {
> + err = sort_update_btf(&obj, distilled_base);
> + goto out;
> + }
> +
> if (elf_collect(&obj))
> goto out;
>
On Fri, Nov 21, 2025 at 5:34 AM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>
> On 11/18/25 7:15 PM, Donglin Peng wrote:
> > From: Donglin Peng <pengdonglin@xiaomi.com>
> >
> > This patch introduces a new --btf_sort option that leverages libbpf's
> > btf__permute interface to reorganize BTF layout. The implementation
> > sorts BTF types by name in ascending order, placing anonymous types at
> > the end to enable efficient binary search lookup.
> >
> > Cc: Eduard Zingerman <eddyz87@gmail.com>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> > Cc: Alan Maguire <alan.maguire@oracle.com>
> > Cc: Song Liu <song@kernel.org>
> > Cc: Xiaoqin Zhang <zhangxiaoqin@xiaomi.com>
> > Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
> > ---
> > scripts/Makefile.btf | 2 +
> > scripts/Makefile.modfinal | 1 +
> > scripts/link-vmlinux.sh | 1 +
> > tools/bpf/resolve_btfids/main.c | 200 ++++++++++++++++++++++++++++++++
> > 4 files changed, 204 insertions(+)
> >
> > diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> > index db76335dd917..d5eb4ee70e88 100644
> > --- a/scripts/Makefile.btf
> > +++ b/scripts/Makefile.btf
> > @@ -27,6 +27,7 @@ pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
> >
> > ifneq ($(KBUILD_EXTMOD),)
> > module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
> > +module-resolve_btfid-flags-y = --distilled_base
> > endif
> >
> > endif
> > @@ -35,3 +36,4 @@ pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE) += --lang_exclude=rust
> >
> > export PAHOLE_FLAGS := $(pahole-flags-y)
> > export MODULE_PAHOLE_FLAGS := $(module-pahole-flags-y)
> > +export MODULE_RESOLVE_BTFID_FLAGS := $(module-resolve_btfid-flags-y)
> > diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> > index 542ba462ed3e..4481dda2f485 100644
> > --- a/scripts/Makefile.modfinal
> > +++ b/scripts/Makefile.modfinal
> > @@ -40,6 +40,7 @@ quiet_cmd_btf_ko = BTF [M] $@
> > 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 $(MODULE_RESOLVE_BTFID_FLAGS) --btf_sort $@; \
> > $(RESOLVE_BTFIDS) -b $(objtree)/vmlinux $@; \
> > fi;
> >
> > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > index 433849ff7529..f21f6300815b 100755
> > --- a/scripts/link-vmlinux.sh
> > +++ b/scripts/link-vmlinux.sh
> > @@ -288,6 +288,7 @@ if is_enabled CONFIG_DEBUG_INFO_BTF; then
> > if is_enabled CONFIG_WERROR; then
> > RESOLVE_BTFIDS_ARGS=" --fatal_warnings "
> > fi
> > + ${RESOLVE_BTFIDS} ${RESOLVE_BTFIDS_ARGS} --btf_sort "${VMLINUX}"
> > ${RESOLVE_BTFIDS} ${RESOLVE_BTFIDS_ARGS} "${VMLINUX}"
> > fi
> >
> > diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> > index d47191c6e55e..dc0badd6f375 100644
> > --- a/tools/bpf/resolve_btfids/main.c
> > +++ b/tools/bpf/resolve_btfids/main.c
> > @@ -768,6 +768,195 @@ static int symbols_patch(struct object *obj)
> > return err < 0 ? -1 : 0;
> > }
> >
> > +/* Anonymous types (with empty names) are considered greater than named types
> > + * and are sorted after them. Two anonymous types are considered equal. Named
> > + * types are compared lexicographically.
> > + */
> > +static int cmp_type_names(const void *a, const void *b, void *priv)
> > +{
> > + struct btf *btf = (struct btf *)priv;
> > + const struct btf_type *ta = btf__type_by_id(btf, *(__u32 *)a);
> > + const struct btf_type *tb = btf__type_by_id(btf, *(__u32 *)b);
> > + const char *na, *nb;
> > +
> > + if (!ta->name_off && tb->name_off)
> > + return 1;
> > + if (ta->name_off && !tb->name_off)
> > + return -1;
> > + if (!ta->name_off && !tb->name_off)
> > + return 0;
> > +
> > + na = btf__str_by_offset(btf, ta->name_off);
> > + nb = btf__str_by_offset(btf, tb->name_off);
> > + return strcmp(na, nb);
> > +}
> > +
> > +static int update_btf_section(const char *path, const struct btf *btf,
>
> Hi Dongling.
>
> Thanks for working on this, it's a great optimization. Just want to
> give you a heads up that I am preparing a patchset changing
> resolve_btfids behavior.
Thanks. I'm curious about the new behavior of resolve_btfids. Does it
replace pahole and generate the sorted .BTF data directly from the
DWARF data? Also, does its sorting method differ from the cmp_type_names
approach mentioned above — specifically, does it place named types
before all anonymous types? I'm asking because the search method
needs to be compatible with this sorting approach.
>
> In particular, instead of updating the .BTF_ids section (and now with
> your and upcoming changes the .BTF section) *in-place*, resolve_btfids
> will only emit the data for the sections. And then it'll be integrated
> into vmlinux with objcopy and linker. We already do a similar thing
> with .BTF for vmlinux [1].
>
> For your patchset it means that the parts handling ELF update will be
> unnecessary.
>
> Also I think the --btf_sort flag is unnecessary. We probably want
> kernel BTF to always be sorted in this way. And if resolve_btfids will
> be handling more btf2btf transformation, we should avoid adding a
> flags for every one of them.
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/scripts/link-vmlinux.sh#n110
>
>
> > + const char *btf_secname)
> > +{
> > + GElf_Shdr shdr_mem, *shdr;
> > + Elf_Data *btf_data = NULL;
> > + Elf_Scn *scn = NULL;
> > + Elf *elf = NULL;
> > + const void *raw_btf_data;
> > + uint32_t raw_btf_size;
> > + int fd, err = -1;
> > + size_t strndx;
> > +
> > + fd = open(path, O_RDWR);
> > + if (fd < 0) {
> > + pr_err("FAILED to open %s\n", path);
> > + return -1;
> > + }
> > +
> > + if (elf_version(EV_CURRENT) == EV_NONE) {
> > + pr_err("FAILED to set libelf version");
> > + goto out;
> > + }
> > +
> > + elf = elf_begin(fd, ELF_C_RDWR, NULL);
> > + if (elf == NULL) {
> > + pr_err("FAILED to update ELF file");
> > + goto out;
> > + }
> > +
> > + elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
> > +
> > + elf_getshdrstrndx(elf, &strndx);
> > + while ((scn = elf_nextscn(elf, scn)) != NULL) {
> > + char *secname;
> > +
> > + shdr = gelf_getshdr(scn, &shdr_mem);
> > + if (shdr == NULL)
> > + continue;
> > + secname = elf_strptr(elf, strndx, shdr->sh_name);
> > + if (strcmp(secname, btf_secname) == 0) {
> > + btf_data = elf_getdata(scn, btf_data);
> > + break;
> > + }
> > + }
> > +
> > + raw_btf_data = btf__raw_data(btf, &raw_btf_size);
> > +
> > + if (btf_data) {
> > + if (raw_btf_size != btf_data->d_size) {
> > + pr_err("FAILED: size mismatch");
> > + goto out;
> > + }
> > +
> > + btf_data->d_buf = (void *)raw_btf_data;
> > + btf_data->d_type = ELF_T_WORD;
> > + elf_flagdata(btf_data, ELF_C_SET, ELF_F_DIRTY);
> > +
> > + if (elf_update(elf, ELF_C_WRITE) >= 0)
> > + err = 0;
> > + }
> > +
> > +out:
> > + if (fd != -1)
> > + close(fd);
> > + if (elf)
> > + elf_end(elf);
> > + return err;
> > +}
> > +
> > +static int sort_update_btf(struct object *obj, bool distilled_base)
> > +{
> > + struct btf *base_btf = NULL;
> > + struct btf *btf = NULL;
> > + int start_id = 1, nr_types, id;
> > + int err = 0, i;
> > + __u32 *permute_ids = NULL, *id_map = NULL, btf_size;
> > + const void *btf_data;
> > + int fd;
> > +
> > + if (obj->base_btf_path) {
> > + base_btf = btf__parse(obj->base_btf_path, NULL);
> > + err = libbpf_get_error(base_btf);
> > + if (err) {
> > + pr_err("FAILED: load base BTF from %s: %s\n",
> > + obj->base_btf_path, strerror(-err));
> > + return -1;
> > + }
> > + }
> > +
> > + btf = btf__parse_elf_split(obj->path, base_btf);
> > + err = libbpf_get_error(btf);
> > + if (err) {
> > + pr_err("FAILED: load BTF from %s: %s\n", obj->path, strerror(-err));
> > + goto out;
> > + }
> > +
> > + if (base_btf)
> > + start_id = btf__type_cnt(base_btf);
> > + nr_types = btf__type_cnt(btf) - start_id;
> > + if (nr_types < 2)
> > + goto out;
> > +
> > + permute_ids = calloc(nr_types, sizeof(*permute_ids));
> > + if (!permute_ids) {
> > + err = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + id_map = calloc(nr_types, sizeof(*id_map));
> > + if (!id_map) {
> > + err = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + for (i = 0, id = start_id; i < nr_types; i++, id++)
> > + permute_ids[i] = id;
> > +
> > + qsort_r(permute_ids, nr_types, sizeof(*permute_ids), cmp_type_names, btf);
> > +
> > + for (i = 0; i < nr_types; i++) {
> > + id = permute_ids[i] - start_id;
> > + id_map[id] = i + start_id;
> > + }
> > +
> > + err = btf__permute(btf, id_map, nr_types, NULL);
> > + if (err) {
> > + pr_err("FAILED: btf permute: %s\n", strerror(-err));
> > + goto out;
> > + }
> > +
> > + if (distilled_base) {
> > + struct btf *new_btf = NULL, *distilled_base = NULL;
> > +
> > + if (btf__distill_base(btf, &distilled_base, &new_btf) < 0) {
> > + pr_err("FAILED to generate distilled base BTF: %s\n",
> > + strerror(errno));
> > + goto out;
> > + }
> > +
> > + err = update_btf_section(obj->path, new_btf, BTF_ELF_SEC);
> > + if (!err) {
> > + err = update_btf_section(obj->path, distilled_base, BTF_BASE_ELF_SEC);
> > + if (err < 0)
> > + pr_err("FAILED to update '%s'\n", BTF_BASE_ELF_SEC);
> > + } else {
> > + pr_err("FAILED to update '%s'\n", BTF_ELF_SEC);
> > + }
> > +
> > + btf__free(new_btf);
> > + btf__free(distilled_base);
> > + } else {
> > + err = update_btf_section(obj->path, btf, BTF_ELF_SEC);
> > + if (err < 0) {
> > + pr_err("FAILED to update '%s'\n", BTF_ELF_SEC);
> > + goto out;
> > + }
> > + }
> > +
> > +out:
> > + free(permute_ids);
> > + free(id_map);
> > + btf__free(base_btf);
> > + btf__free(btf);
> > + return err;
> > +}
> > +
> > static const char * const resolve_btfids_usage[] = {
> > "resolve_btfids [<options>] <ELF object>",
> > NULL
> > @@ -787,6 +976,8 @@ int main(int argc, const char **argv)
> > .sets = RB_ROOT,
> > };
> > bool fatal_warnings = false;
> > + bool btf_sort = false;
> > + bool distilled_base = false;
> > struct option btfid_options[] = {
> > OPT_INCR('v', "verbose", &verbose,
> > "be more verbose (show errors, etc)"),
> > @@ -796,6 +987,10 @@ 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, "btf_sort", &btf_sort,
> > + "sort BTF by name in ascending order"),
> > + OPT_BOOLEAN(0, "distilled_base", &distilled_base,
> > + "distill base"),
> > OPT_END()
> > };
> > int err = -1;
> > @@ -807,6 +1002,11 @@ int main(int argc, const char **argv)
> >
> > obj.path = argv[0];
> >
> > + if (btf_sort) {
> > + err = sort_update_btf(&obj, distilled_base);
> > + goto out;
> > + }
> > +
> > if (elf_collect(&obj))
> > goto out;
> >
>
On 11/21/25 7:36 AM, Donglin Peng wrote: > On Fri, Nov 21, 2025 at 5:34 AM Ihor Solodrai <ihor.solodrai@linux.dev> wrote: >> >> On 11/18/25 7:15 PM, Donglin Peng wrote: >>> From: Donglin Peng <pengdonglin@xiaomi.com> >>> >>> This patch introduces a new --btf_sort option that leverages libbpf's >>> btf__permute interface to reorganize BTF layout. The implementation >>> sorts BTF types by name in ascending order, placing anonymous types at >>> the end to enable efficient binary search lookup. >> >> [...] >> >> Hi Dongling. >> >> Thanks for working on this, it's a great optimization. Just want to >> give you a heads up that I am preparing a patchset changing >> resolve_btfids behavior. > > Thanks. I'm curious about the new behavior of resolve_btfids. Does it > replace pahole and generate the sorted .BTF data directly from the > DWARF data? Also, does its sorting method differ from the cmp_type_names > approach mentioned above — specifically, does it place named types > before all anonymous types? I'm asking because the search method > needs to be compatible with this sorting approach. No, replacing pahole entirely isn't really feasible, and unnecessary. TL;DR is that resolve_btfids will also do kernel-specific btf2btf transformations. The sorting feature is independent, it's relevant only in that it is also a btf2btf transformation and will be included in the pipeline. I described the approach here: https://lore.kernel.org/dwarves/ba1650aa-fafd-49a8-bea4-bdddee7c38c9@linux.dev/ > >> >> In particular, instead of updating the .BTF_ids section (and now with >> your and upcoming changes the .BTF section) *in-place*, resolve_btfids >> will only emit the data for the sections. And then it'll be integrated >> into vmlinux with objcopy and linker. We already do a similar thing >> with .BTF for vmlinux [1]. >> >> For your patchset it means that the parts handling ELF update will be >> unnecessary. >> >> Also I think the --btf_sort flag is unnecessary. We probably want >> kernel BTF to always be sorted in this way. And if resolve_btfids will >> be handling more btf2btf transformation, we should avoid adding a >> flags for every one of them. >> >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/scripts/link-vmlinux.sh#n110 >>
On Tue, Nov 25, 2025 at 3:35 AM Ihor Solodrai <ihor.solodrai@linux.dev> wrote: > > On 11/21/25 7:36 AM, Donglin Peng wrote: > > On Fri, Nov 21, 2025 at 5:34 AM Ihor Solodrai <ihor.solodrai@linux.dev> wrote: > >> > >> On 11/18/25 7:15 PM, Donglin Peng wrote: > >>> From: Donglin Peng <pengdonglin@xiaomi.com> > >>> > >>> This patch introduces a new --btf_sort option that leverages libbpf's > >>> btf__permute interface to reorganize BTF layout. The implementation > >>> sorts BTF types by name in ascending order, placing anonymous types at > >>> the end to enable efficient binary search lookup. > >> > >> [...] > >> > >> Hi Dongling. > >> > >> Thanks for working on this, it's a great optimization. Just want to > >> give you a heads up that I am preparing a patchset changing > >> resolve_btfids behavior. > > > > Thanks. I'm curious about the new behavior of resolve_btfids. Does it > > replace pahole and generate the sorted .BTF data directly from the > > DWARF data? Also, does its sorting method differ from the cmp_type_names > > approach mentioned above — specifically, does it place named types > > before all anonymous types? I'm asking because the search method > > needs to be compatible with this sorting approach. > > No, replacing pahole entirely isn't really feasible, and unnecessary. > > TL;DR is that resolve_btfids will also do kernel-specific btf2btf > transformations. The sorting feature is independent, it's relevant > only in that it is also a btf2btf transformation and will be included > in the pipeline. > > I described the approach here: > https://lore.kernel.org/dwarves/ba1650aa-fafd-49a8-bea4-bdddee7c38c9@linux.dev/ Thanks for the explanation. > > > > > >> > >> In particular, instead of updating the .BTF_ids section (and now with > >> your and upcoming changes the .BTF section) *in-place*, resolve_btfids > >> will only emit the data for the sections. And then it'll be integrated > >> into vmlinux with objcopy and linker. We already do a similar thing > >> with .BTF for vmlinux [1]. > >> > >> For your patchset it means that the parts handling ELF update will be > >> unnecessary. > >> > >> Also I think the --btf_sort flag is unnecessary. We probably want > >> kernel BTF to always be sorted in this way. And if resolve_btfids will > >> be handling more btf2btf transformation, we should avoid adding a > >> flags for every one of them. > >> > >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/scripts/link-vmlinux.sh#n110 > >>
On 11/20/25 1:34 PM, Ihor Solodrai wrote: > On 11/18/25 7:15 PM, Donglin Peng wrote: >> From: Donglin Peng <pengdonglin@xiaomi.com> >> >> This patch introduces a new --btf_sort option that leverages libbpf's >> btf__permute interface to reorganize BTF layout. The implementation >> sorts BTF types by name in ascending order, placing anonymous types at >> the end to enable efficient binary search lookup. >> >> [...] >> >> +} >> + >> +static int update_btf_section(const char *path, const struct btf *btf, > > Hi Dongling. > > Thanks for working on this, it's a great optimization. Just want to > give you a heads up that I am preparing a patchset changing > resolve_btfids behavior. > > In particular, instead of updating the .BTF_ids section (and now with > your and upcoming changes the .BTF section) *in-place*, resolve_btfids > will only emit the data for the sections. And then it'll be integrated > into vmlinux with objcopy and linker. We already do a similar thing > with .BTF for vmlinux [1]. > > For your patchset it means that the parts handling ELF update will be > unnecessary. > > Also I think the --btf_sort flag is unnecessary. We probably want > kernel BTF to always be sorted in this way. And if resolve_btfids will > be handling more btf2btf transformation, we should avoid adding a > flags for every one of them. The same applies to --distilled_base. AFAIU we always want to do it, so there is not need for the flag. Unless there is a strong use case for generating module BTF *without* the distilled base that I am not aware of. Maybe an explicit "--kmodule" flag would be appropriate?.. For resolve_btfids, is it reasonable to assume it's a module if --base is passed in? Andrii, Eduard, wdyt? > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/scripts/link-vmlinux.sh#n110 > >
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