Various subsystems embed non-code build artifacts into the kernel, for example the initramfs, /proc/config.gz, vDSO image, etc. Currently each user has their own implementation for that.
Add a common "blob" framework to provide this functionality. It provides standard kbuild and C APIs to embed and later access non-code build artifacts into the kernel image or modules.
Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de
--- Due to its closeness to kbuild this is currently added to its MAINTAINER entry. But I can also maintain it on its own. --- Documentation/kbuild/makefiles.rst | 23 +++++++++++++++++++++-- MAINTAINERS | 2 ++ include/linux/blob.h | 32 ++++++++++++++++++++++++++++++++ scripts/Makefile.blobs | 19 +++++++++++++++++++ scripts/Makefile.build | 6 ++++++ scripts/Makefile.clean | 2 +- scripts/blob-wrap.c | 27 +++++++++++++++++++++++++++ 7 files changed, 108 insertions(+), 3 deletions(-)
diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst index d5cd73820e406276ee2e3721e265e3ed3cc299c9..c3a165fcb1ab0bbc090fd61c38ebd78317c7aa85 100644 --- a/Documentation/kbuild/makefiles.rst +++ b/Documentation/kbuild/makefiles.rst @@ -521,8 +521,8 @@ otherwise the command line check will fail, and the target will always be built.
If the target is already listed in the recognized syntax such as -obj-y/m, lib-y/m, extra-y/m, always-y/m, hostprogs, userprogs, Kbuild -automatically adds it to $(targets). Otherwise, the target must be +obj-y/m, lib-y/m, extra-y/m, always-y/m, hostprogs, userprogs, blobs, +Kbuild automatically adds it to $(targets). Otherwise, the target must be explicitly added to $(targets).
Assignments to $(targets) are without $(obj)/ prefix. if_changed may be @@ -1014,6 +1014,25 @@ There are two ways to do this. This will tell Kbuild to build binderfs_example when it visits this Makefile.
+.. _kbuild_blobs: + +Blob framework +============== + +Kbuild supports wrapping source or generated files into object files which are linked +into the kernel and then accessed at runtime through ``include/linux/blob.h``. + +Example:: + + obj-m := some-module.o + userprogs := some-userprog + blobs := some-userprog.blob.o + some-userprog.blob-symbol := some_userprog + some-module-y += some-userprog.blob.o + +Kbuild will build the :ref:`userprog <kbuild_userprogs>` ``some-userprog`` and +link it into ``some-module`` from where it can be accessed as ``BLOB(some_userprog)``. + Kbuild clean infrastructure ===========================
diff --git a/MAINTAINERS b/MAINTAINERS index 96b82704950184bd71623ff41fc4df31e4c7fe87..d61e28e289c7027c026a872cd166342a4761b2a4 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -12847,11 +12847,13 @@ Q: https://patchwork.kernel.org/project/linux-kbuild/list/ T: git git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git F: Documentation/kbuild/ F: Makefile +F: include/linux/blob.h F: scripts/*vmlinux* F: scripts/Kbuild* F: scripts/Makefile* F: scripts/bash-completion/ F: scripts/basic/ +F: scripts/blob-wrap.c F: scripts/clang-tools/ F: scripts/dummy-tools/ F: scripts/include/ diff --git a/include/linux/blob.h b/include/linux/blob.h new file mode 100644 index 0000000000000000000000000000000000000000..de76cdb76cbab388b62f574b80fb13a4c84d1d2d --- /dev/null +++ b/include/linux/blob.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Linkable blob API. + * + * Copyright (C) 2025, Linutronix GmbH. + * Author: Thomas Weißschuh thomas.weissschuh@linutronix.de + */ + +#ifndef _LINUX_BLOB_H +#define _LINUX_BLOB_H + +#include <linux/args.h> +#include <linux/compiler_types.h> +#include <linux/types.h> + +struct blob { + const char *const path; + const u8 *data; + const u8 __private *end; +}; + +#define BLOB(_symbol) ({ \ + extern const struct blob CONCATENATE(__blob_, _symbol); \ + &CONCATENATE(__blob_, _symbol); \ +}) + +static inline size_t blob_size(const struct blob *blob) +{ + return ACCESS_PRIVATE(blob, end) - blob->data; +} + +#endif /* _LINUX_BLOB_H */ diff --git a/scripts/Makefile.blobs b/scripts/Makefile.blobs new file mode 100644 index 0000000000000000000000000000000000000000..fd20ebb41c1d6509750debf7896a08a143d28759 --- /dev/null +++ b/scripts/Makefile.blobs @@ -0,0 +1,19 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +# Build linkable blobs +# + +blobs := $(addprefix $(obj)/, $(blobs)) + +blob-stem = $(subst -,_,$(subst .blob,,$(basename $(patsubst $(obj)/%,%,$@)))) +blob-symbol = $(or $($(target-stem)-symbol),$(blob-stem)) + +blob-flags = -DBLOB_SYMBOL="$(blob-symbol)" -DBLOB_INPUT=$< + +quiet_cmd_blob = BLOB $@ + cmd_blob = $(CC) $(c_flags) $(blob-flags) -c -o $@ $(srctree)/scripts/blob-wrap.c + +$(blobs): $(obj)/%.blob.o: $(obj)/% $(srctree)/scripts/blob-wrap.c FORCE + $(call if_changed_dep,blob) + +targets += $(blobs) diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 13dcd86e74ca830ce3fb2587df7f200105490881..c2965ee4002d239bf4e18115e026e7bcd5abb197 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -436,6 +436,12 @@ ifneq ($(need-dtbslist)$(dtb-y)$(dtb-)$(filter %.dtb %.dtb.o %.dtbo.o,$(targets) include $(srctree)/scripts/Makefile.dtbs endif
+# $(sort ...) is used here to remove duplicated words and excessive spaces. +blobs := $(sort $(blobs)) +ifneq ($(blobs),) +include $(srctree)/scripts/Makefile.blobs +endif + # Build # ---------------------------------------------------------------------------
diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean index 6ead00ec7313b3e4330a8de5f1342f2da1d6eb84..536972b0a528d117e17296da9936825c3903af6e 100644 --- a/scripts/Makefile.clean +++ b/scripts/Makefile.clean @@ -25,7 +25,7 @@ subdir-ymn := $(addprefix $(obj)/,$(subdir-ymn)) # directory
__clean-files := \ - $(clean-files) $(targets) $(hostprogs) $(userprogs) \ + $(clean-files) $(targets) $(hostprogs) $(userprogs) $(blobs) \ $(extra-y) $(extra-m) $(extra-) \ $(always-y) $(always-m) $(always-) \ $(hostprogs-always-y) $(hostprogs-always-m) $(hostprogs-always-) \ diff --git a/scripts/blob-wrap.c b/scripts/blob-wrap.c new file mode 100644 index 0000000000000000000000000000000000000000..82ab3bc641bd69ec35029c2f4a9dd6d6c6720a02 --- /dev/null +++ b/scripts/blob-wrap.c @@ -0,0 +1,27 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/args.h> +#include <linux/blob.h> +#include <linux/stringify.h> + +#define BLOB_SYMBOL_DATA CONCATENATE(__blob_data_, BLOB_SYMBOL) +#define BLOB_SYMBOL_END CONCATENATE(__blob_end_, BLOB_SYMBOL) + +asm ( +" .pushsection .rodata, "a"\n" +" .global " __stringify(BLOB_SYMBOL_DATA) "\n" +__stringify(BLOB_SYMBOL_DATA) ":\n" +" .incbin "" __stringify(BLOB_INPUT) ""\n" +" .global " __stringify(BLOB_SYMBOL_END) "\n" +__stringify(BLOB_SYMBOL_END) ":\n" +" .popsection\n" +); + +extern const u8 BLOB_SYMBOL_DATA; +extern const u8 BLOB_SYMBOL_END; + +const struct blob CONCATENATE(__blob_, BLOB_SYMBOL) = { + .path = __stringify(BLOB_INPUT), + .data = &BLOB_SYMBOL_DATA, + .end = &BLOB_SYMBOL_END, +};