tools/bpf/bpftool/Documentation/bpftool-prog.rst | 8 +++++++- tools/bpf/bpftool/bash-completion/bpftool | 4 ++-- tools/bpf/bpftool/prog.c | 12 +++++++++++- 3 files changed, 20 insertions(+), 4 deletions(-)
This patch exposes the btf_custom_path feature to bpftool, allowing users
to specify a custom BTF file when loading BPF programs using prog load or
prog loadall commands.
The argument 'btf_custom_path' in libbpf is used for those kernels that
don't have CONFIG_DEBUG_INFO_BTF enabled but still want to perform CO-RE
relocations.
Suggested-by: Quentin Monnet <qmo@kernel.org>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
V2 -> V3: Optimized document grammar and some prompts
https://lore.kernel.org/bpf/20250515065018.240188-1-jiayuan.chen@linux.dev/
V1 -> V2: Added bash completion and documentation
https://lore.kernel.org/bpf/20250513035853.75820-1-jiayuan.chen@linux.dev/
---
tools/bpf/bpftool/Documentation/bpftool-prog.rst | 8 +++++++-
tools/bpf/bpftool/bash-completion/bpftool | 4 ++--
tools/bpf/bpftool/prog.c | 12 +++++++++++-
3 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
index d6304e01afe0..4dce43e8e8a3 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
@@ -127,7 +127,7 @@ bpftool prog pin *PROG* *FILE*
Note: *FILE* must be located in *bpffs* mount. It must not contain a dot
character ('.'), which is reserved for future extensions of *bpffs*.
-bpftool prog { load | loadall } *OBJ* *PATH* [type *TYPE*] [map { idx *IDX* | name *NAME* } *MAP*] [{ offload_dev | xdpmeta_dev } *NAME*] [pinmaps *MAP_DIR*] [autoattach]
+bpftool prog { load | loadall } *OBJ* *PATH* [type *TYPE*] [map { idx *IDX* | name *NAME* } *MAP*] [{ offload_dev | xdpmeta_dev } *NAME*] [pinmaps *MAP_DIR*] [autoattach] [kernel_btf *BTF_FILE*]
Load bpf program(s) from binary *OBJ* and pin as *PATH*. **bpftool prog
load** pins only the first program from the *OBJ* as *PATH*. **bpftool prog
loadall** pins all programs from the *OBJ* under *PATH* directory. **type**
@@ -153,6 +153,12 @@ bpftool prog { load | loadall } *OBJ* *PATH* [type *TYPE*] [map { idx *IDX* | na
program does not support autoattach, bpftool falls back to regular pinning
for that program instead.
+ The **kernel_btf** option allows specifying an external BTF file to replace
+ the system's own vmlinux BTF file for CO-RE relocations. Note that any
+ other feature relying on BTF (such as fentry/fexit programs, struct_ops)
+ requires the BTF file for the actual kernel running on the host, often
+ exposed at /sys/kernel/btf/vmlinux.
+
Note: *PATH* must be located in *bpffs* mount. It must not contain a dot
character ('.'), which is reserved for future extensions of *bpffs*.
diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index 1ce409a6cbd9..27512feb5c70 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -505,13 +505,13 @@ _bpftool()
_bpftool_get_map_names
return 0
;;
- pinned|pinmaps)
+ pinned|pinmaps|kernel_btf)
_filedir
return 0
;;
*)
COMPREPLY=( $( compgen -W "map" -- "$cur" ) )
- _bpftool_once_attr 'type pinmaps autoattach'
+ _bpftool_once_attr 'type pinmaps autoattach kernel_btf'
_bpftool_one_of_list 'offload_dev xdpmeta_dev'
return 0
;;
diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index f010295350be..96eea8a67225 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -1681,8 +1681,17 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
} else if (is_prefix(*argv, "autoattach")) {
auto_attach = true;
NEXT_ARG();
+ } else if (is_prefix(*argv, "kernel_btf")) {
+ NEXT_ARG();
+
+ if (!REQ_ARGS(1))
+ goto err_free_reuse_maps;
+
+ open_opts.btf_custom_path = GET_ARG();
} else {
- p_err("expected no more arguments, 'type', 'map' or 'dev', got: '%s'?",
+ p_err("expected no more arguments, "
+ "'type', 'map', 'offload_dev', 'xdpmeta_dev', 'pinmaps', "
+ "'autoattach', or 'kernel_btf', got: '%s'?",
*argv);
goto err_free_reuse_maps;
}
@@ -2474,6 +2483,7 @@ static int do_help(int argc, char **argv)
" [map { idx IDX | name NAME } MAP]\\\n"
" [pinmaps MAP_DIR]\n"
" [autoattach]\n"
+ " [kernel_btf BTF_FILE]\n"
" %1$s %2$s attach PROG ATTACH_TYPE [MAP]\n"
" %1$s %2$s detach PROG ATTACH_TYPE [MAP]\n"
" %1$s %2$s run PROG \\\n"
--
2.47.12025-05-16 11:23 UTC+0800 ~ Jiayuan Chen <jiayuan.chen@linux.dev>
> This patch exposes the btf_custom_path feature to bpftool, allowing users
> to specify a custom BTF file when loading BPF programs using prog load or
> prog loadall commands.
>
> The argument 'btf_custom_path' in libbpf is used for those kernels that
> don't have CONFIG_DEBUG_INFO_BTF enabled but still want to perform CO-RE
> relocations.
>
> Suggested-by: Quentin Monnet <qmo@kernel.org>
> Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
>
> ---
> V2 -> V3: Optimized document grammar and some prompts
> https://lore.kernel.org/bpf/20250515065018.240188-1-jiayuan.chen@linux.dev/
> V1 -> V2: Added bash completion and documentation
> https://lore.kernel.org/bpf/20250513035853.75820-1-jiayuan.chen@linux.dev/
> ---
> tools/bpf/bpftool/Documentation/bpftool-prog.rst | 8 +++++++-
> tools/bpf/bpftool/bash-completion/bpftool | 4 ++--
> tools/bpf/bpftool/prog.c | 12 +++++++++++-
> 3 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> index d6304e01afe0..4dce43e8e8a3 100644
> --- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> +++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> @@ -127,7 +127,7 @@ bpftool prog pin *PROG* *FILE*
> Note: *FILE* must be located in *bpffs* mount. It must not contain a dot
> character ('.'), which is reserved for future extensions of *bpffs*.
>
> -bpftool prog { load | loadall } *OBJ* *PATH* [type *TYPE*] [map { idx *IDX* | name *NAME* } *MAP*] [{ offload_dev | xdpmeta_dev } *NAME*] [pinmaps *MAP_DIR*] [autoattach]
> +bpftool prog { load | loadall } *OBJ* *PATH* [type *TYPE*] [map { idx *IDX* | name *NAME* } *MAP*] [{ offload_dev | xdpmeta_dev } *NAME*] [pinmaps *MAP_DIR*] [autoattach] [kernel_btf *BTF_FILE*]
Woops, I just realised we also need to add kernel_btf to the command
summary at the top of the document (line 34), sorry for missing it
during the previous pass. Please add it, and mark v4 as:
Reviewed-by: Quentin Monnet <qmo@kernel.org>
Thanks!
May 16, 2025 at 18:18, "Quentin Monnet" <qmo@kernel.org> wrote:
>
> 2025-05-16 11:23 UTC+0800 ~ Jiayuan Chen <jiayuan.chen@linux.dev>
>
> >
> > This patch exposes the btf_custom_path feature to bpftool, allowing users
> >
> > to specify a custom BTF file when loading BPF programs using prog load or
> >
> > prog loadall commands.
> >
> >
> >
> > The argument 'btf_custom_path' in libbpf is used for those kernels that
> >
> > don't have CONFIG_DEBUG_INFO_BTF enabled but still want to perform CO-RE
> >
> > relocations.
> >
> >
> >
> > Suggested-by: Quentin Monnet <qmo@kernel.org>
> >
> > Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
> >
> >
> >
> > ---
> >
> > V2 -> V3: Optimized document grammar and some prompts
> >
> > https://lore.kernel.org/bpf/20250515065018.240188-1-jiayuan.chen@linux.dev/
> >
> > V1 -> V2: Added bash completion and documentation
> >
> > https://lore.kernel.org/bpf/20250513035853.75820-1-jiayuan.chen@linux.dev/
> >
> > ---
> >
> > tools/bpf/bpftool/Documentation/bpftool-prog.rst | 8 +++++++-
> >
> > tools/bpf/bpftool/bash-completion/bpftool | 4 ++--
> >
> > tools/bpf/bpftool/prog.c | 12 +++++++++++-
> >
> > 3 files changed, 20 insertions(+), 4 deletions(-)
> >
> >
> >
> > diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> >
> > index d6304e01afe0..4dce43e8e8a3 100644
> >
> > --- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> >
> > +++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> >
> > @@ -127,7 +127,7 @@ bpftool prog pin *PROG* *FILE*
> >
> > Note: *FILE* must be located in *bpffs* mount. It must not contain a dot
> >
> > character ('.'), which is reserved for future extensions of *bpffs*.
> >
> >
> >
> > -bpftool prog { load | loadall } *OBJ* *PATH* [type *TYPE*] [map { idx *IDX* | name *NAME* } *MAP*] [{ offload_dev | xdpmeta_dev } *NAME*] [pinmaps *MAP_DIR*] [autoattach]
> >
> > +bpftool prog { load | loadall } *OBJ* *PATH* [type *TYPE*] [map { idx *IDX* | name *NAME* } *MAP*] [{ offload_dev | xdpmeta_dev } *NAME*] [pinmaps *MAP_DIR*] [autoattach] [kernel_btf *BTF_FILE*]
> >
>
> Woops, I just realised we also need to add kernel_btf to the command
>
> summary at the top of the document (line 34), sorry for missing it
It was my mistake to miss that part. I'll prepare an updated version soon. :)
Thanks.
> during the previous pass. Please add it, and mark v4 as:
>
> Reviewed-by: Quentin Monnet <qmo@kernel.org>
>
> Thanks!
>
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