On Mon, Apr 29, 2019 at 6:09 PM Alexey Gladkov <gladkov.alexey@xxxxxxxxx> wrote: > > Problem: > > When a kernel module is compiled as a separate module, some important > information about the kernel module is available via .modinfo section of > the module. In contrast, when the kernel module is compiled into the > kernel, that information is not available. > > Information about built-in modules is necessary in the following cases: > > 1. When it is necessary to find out what additional parameters can be > passed to the kernel at boot time. > > 2. When you need to know which module names and their aliases are in > the kernel. This is very useful for creating an initrd image. > > Proposal: > > The proposed patch does not remove .modinfo section with module > information from the vmlinux at the build time and saves it into a > separate file after kernel linking. So, the kernel does not increase in > size and no additional information remains in it. Information is stored > in the same format as in the separate modules (null-terminated string > array). Because the .modinfo section is already exported with a separate > modules, we are not creating a new API. > > It can be easily read in the userspace: > > $ tr '\0' '\n' < kernel.builtin > ext4.softdep=pre: crc32c > ext4.license=GPL > ext4.description=Fourth Extended Filesystem > ext4.author=Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others > ext4.alias=fs-ext4 > ext4.alias=ext3 > ext4.alias=fs-ext3 > ext4.alias=ext2 > ext4.alias=fs-ext2 > md_mod.alias=block-major-9-* > md_mod.alias=md > md_mod.description=MD RAID framework > md_mod.license=GPL > md_mod.parmtype=create_on_open:bool > md_mod.parmtype=start_dirty_degraded:int > ... > > v2: > * Extract modinfo from vmlinux.o as suggested by Masahiro Yamada; > * Rename output file to kernel.builtin; > * Add MODULE_VERSION to modinfo that is saved to the kernel.builtin; > * Fix build warnings on powerpc. > > v3: > * Rename output file to modules.builtin.modinfo as suggested by Masahiro Yamada; > * Update Documentation/dontdiff, Documentation/kbuild/kbuild.txt. > > Co-Developed-by: Gleb Fotengauer-Malinovskiy <glebfm@xxxxxxxxxxxx> > Signed-off-by: Gleb Fotengauer-Malinovskiy <glebfm@xxxxxxxxxxxx> > Signed-off-by: Alexey Gladkov <gladkov.alexey@xxxxxxxxx> > --- > .gitignore | 1 + > Documentation/dontdiff | 1 + > Documentation/kbuild/kbuild.txt | 5 +++++ > Makefile | 2 ++ > include/asm-generic/vmlinux.lds.h | 1 + > include/linux/module.h | 1 + > include/linux/moduleparam.h | 12 +++++------- > scripts/link-vmlinux.sh | 4 ++++ > 8 files changed, 20 insertions(+), 7 deletions(-) > > diff --git a/.gitignore b/.gitignore > index a20ac26aa2f5..8ef2c87703b3 100644 > --- a/.gitignore > +++ b/.gitignore > @@ -45,6 +45,7 @@ > *.xz > Module.symvers > modules.builtin > +modules.builtin.modinfo > > # > # Top-level generic files Let me repeat the same comments as in v2 (https://patchwork.kernel.org/patch/10888207/#22595563) as you ignored them. This file is generated only in the top of the tree. Please add '/' prefix and move it to the "# Top-level generic files" section. # # Top-level generic files # /tags /TAGS /linux /vmlinux /vmlinux.32 /vmlinux-gdb.py /vmlinuz /System.map /Module.markers /modules.builtin.modinfo > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh > index c8cf45362bd6..41ef7cb043c1 100755 > --- a/scripts/link-vmlinux.sh > +++ b/scripts/link-vmlinux.sh > @@ -226,6 +226,10 @@ modpost_link vmlinux.o > # modpost vmlinux.o to check for section mismatches > ${MAKE} -f "${srctree}/scripts/Makefile.modpost" vmlinux.o > > +info MODINFO modules.builtin.modinfo > +"${OBJCOPY}" -j .modinfo -O binary vmlinux.o modules.builtin.modinfo > +chmod 444 modules.builtin.modinfo Why is this 'chmod 444' necessary? > + > kallsymso="" > kallsyms_vmlinux="" > if [ -n "${CONFIG_KALLSYMS}" ]; then -- Best Regards Masahiro Yamada
