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authorMasahiro Yamada <masahiroy@kernel.org>2022-09-25 03:19:15 +0900
committerMasahiro Yamada <masahiroy@kernel.org>2022-10-02 18:06:03 +0900
commitce697ccee1a8661da4e23fbe5f3d45d8d6922c20 (patch)
tree3e4a66982f38b33d4c17b13a04161eb764bf6220 /Documentation/kbuild
parent3216484550610470013b7ce1c9ed272da0a74589 (diff)
downloadlinux-ce697ccee1a8661da4e23fbe5f3d45d8d6922c20.tar.bz2
kbuild: remove head-y syntax
Kbuild puts the objects listed in head-y at the head of vmlinux. Conventionally, we do this for head*.S, which contains the kernel entry point. A counter approach is to control the section order by the linker script. Actually, the code marked as __HEAD goes into the ".head.text" section, which is placed before the normal ".text" section. I do not know if both of them are needed. From the build system perspective, head-y is not mandatory. If you can achieve the proper code placement by the linker script only, it would be cleaner. I collected the current head-y objects into head-object-list.txt. It is a whitelist. My hope is it will be reduced in the long run. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Diffstat (limited to 'Documentation/kbuild')
-rw-r--r--Documentation/kbuild/makefiles.rst9
1 files changed, 5 insertions, 4 deletions
diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
index 5a6a8426cc97..60134ddf3db1 100644
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -1070,8 +1070,7 @@ When kbuild executes, the following steps are followed (roughly):
- The values of the above variables are expanded in arch/$(SRCARCH)/Makefile.
5) All object files are then linked and the resulting file vmlinux is
located at the root of the obj tree.
- The very first objects linked are listed in head-y, assigned by
- arch/$(SRCARCH)/Makefile.
+ The very first objects linked are listed in scripts/head-object-list.txt.
6) Finally, the architecture-specific part does any required post processing
and builds the final bootimage.
- This includes building boot records
@@ -1219,6 +1218,9 @@ When kbuild executes, the following steps are followed (roughly):
All object files for vmlinux. They are linked to vmlinux in the same
order as listed in KBUILD_VMLINUX_OBJS.
+ The objects listed in scripts/head-object-list.txt are exceptions;
+ they are placed before the other objects.
+
KBUILD_VMLINUX_LIBS
All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and
@@ -1262,8 +1264,7 @@ When kbuild executes, the following steps are followed (roughly):
machinery is all architecture-independent.
- head-y, core-y, libs-y, drivers-y
- $(head-y) lists objects to be linked first in vmlinux.
+ core-y, libs-y, drivers-y
$(libs-y) lists directories where a lib.a archive can be located.