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SubjectRe: [PATCH] initramfs: Fix disabling of initramfs (and its compression)
On Thu, 7 Sep 2017 05:50:30 -0700
Florian Fainelli <f.fainelli@gmail.com> wrote:

> On 08/28/2017 08:09 PM, Nicholas Piggin wrote:
> > On Mon, 28 Aug 2017 13:03:31 -0700
> > Florian Fainelli <f.fainelli@gmail.com> wrote:
> >
> >> On 05/21/2017 07:46 PM, Nicholas Piggin wrote:
> >>> On Sat, 20 May 2017 20:33:35 -0700
> >>> Florian Fainelli <f.fainelli@gmail.com> wrote:
> >>>
> >>>> Commit db2aa7fd15e8 ("initramfs: allow again choice of the embedded
> >>>> initram compression algorithm") introduced the possibility to select the
> >>>> initramfs compression algorithm from Kconfig and while this is a nice
> >>>> feature it broke the use case described below.
> >>>>
> >>>> Here is what my build system does:
> >>>>
> >>>> - kernel is initially configured not to have an initramfs included
> >>>> - build the user space root file system
> >>>> - re-configure the kernel to have an initramfs included
> >>>> (CONFIG_INITRAMFS_SOURCE="/path/to/romfs") and set relevant
> >>>> CONFIG_INITRAMFS options, in my case, no compression option
> >>>> (CONFIG_INITRAMFS_COMPRESSION_NONE)
> >>>> - kernel is re-built with these options -> kernel+initramfs image is
> >>>> copied
> >>>> - kernel is re-built again without these options -> kernel image is
> >>>> copied
> >>>>
> >>>> Building a kernel without an initramfs means setting this option:
> >>>>
> >>>> CONFIG_INITRAMFS_SOURCE="" (and this one only)
> >>>>
> >>>> whereas building a kernel with an initramfs means setting these options:
> >>>>
> >>>> CONFIG_INITRAMFS_SOURCE="/home/fainelli/work/uclinux-rootfs/romfs
> >>>> /home/fainelli/work/uclinux-rootfs/misc/initramfs.dev"
> >>>> CONFIG_INITRAMFS_ROOT_UID=1000
> >>>> CONFIG_INITRAMFS_ROOT_GID=1000
> >>>> CONFIG_INITRAMFS_COMPRESSION_NONE=y
> >>>> CONFIG_INITRAMFS_COMPRESSION=""
> >>>>
> >>>> Commit db2aa7fd15e857891cefbada8348c8d938c7a2bc ("initramfs: allow again
> >>>> choice of the embedded initram compression algorithm") is problematic
> >>>> because CONFIG_INITRAMFS_COMPRESSION which is used to determine the
> >>>> initramfs_data.cpio extension/compression is a string, and due to how
> >>>> Kconfig works it will evaluate in order, how to assign it.
> >>>>
> >>>> Setting CONFIG_INITRAMFS_COMPRESSION_NONE with
> >>>> CONFIG_INITRAMFS_SOURCE="" cannot possibly work (because of the depends
> >>>> on INITRAMFS_SOURCE!="" imposed on CONFIG_INITRAMFS_COMPRESSION ) yet we
> >>>> still get CONFIG_INITRAMFS_COMPRESSION assigned to ".gz" because
> >>>> CONFIG_RD_GZIP=y is set in my kernel, even when there is no initramfs
> >>>> being built.
> >>>>
> >>>> So we basically end-up generating two initramfs_data.cpio* files, one
> >>>> without extension, and one with .gz. This causes usr/Makefile to track
> >>>> usr/initramfs_data.cpio.gz, and not usr/initramfs_data.cpio anymore,
> >>>> that is also largely problematic after
> >>>> 9e3596b0c6539e28546ff7c72a06576627068353 ("kbuild: initramfs cleanup,
> >>>> set target from Kconfig") because we used to track all possible
> >>>> initramfs_data files in the $(targets) variable before that commit.
> >>>>
> >>>> The end result is that the kernel with an initramfs clearly does not
> >>>> contain what we expect it to, it has a stale initramfs_data.cpio file
> >>>> built into it, and we keep re-generating an initramfs_data.cpio.gz file
> >>>> which is not the one that we want to include in the kernel image proper.
> >>>>
> >>>> The fix consists in hiding CONFIG_INITRAMFS_COMPRESSION when
> >>>> CONFIG_INITRAMFS_SOURCE="". This puts us back in a state to the pre-4.10
> >>>> behavior where we can properly disable and re-enable initramfs within
> >>>> the same kernel .config file, and be in control of what
> >>>> CONFIG_INITRAMFS_COMPRESSION is set to.
> >>>>
> >>>> Fixes: db2aa7fd15e8 ("initramfs: allow again choice of the embedded initram compression algorithm")
> >>>> Fixes: 9e3596b0c653 ("kbuild: initramfs cleanup, set target from Kconfig")
> >>>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> >>>
> >>> This is very thorough, thank you for tracking it down and fixing it.
> >>>
> >>> I can't say I've worked through the problem in the code, but your
> >>> changelog and the proposed fix seem reasonable to me. So for what
> >>> it's worth:
> >>>
> >>> Acked-by: Nicholas Piggin <npiggin@gmail.com>
> >>
> >> Well, I am looking at this again, and it's still broken, the same test
> >> case is involved, except this time, I am switching beween no-initramfs
> >> and initramfs with gzip compression (the key thing is using a
> >> compression of some sort). The end result is the following:
> >>
> >> - change stuff in the rootfs
> >> - build the kernel with initramfs, CONFIG_INITRAMFS_COMPRESSION_GZIP=y,
> >> usr/initramfs_data.cpio.gz gets generated correctly the first time
> >> - build the kernel without initramfs,
> >> CONFIG_INITRAMFS_COMPRESSION_NONE=y, usr/initramfs_data.cpio gets generated
> >>
> >> Now back to step 1 add some files, and we can see that
> >> usr/initramfs_data.cpio.gz is now stale from before...
> >>
> >> So while my earlier fix switched the initramfs w/o compression to no
> >> initramfs rebuild, now this does not work because we still have two
> >> files left to be tracked:
> >>
> >> usr/initramfs_data.cpio (no compression, or when initramfs is disabled)
> >> and usr/initramfs_data.cpio.$(suffix_y)
> >>
> >> How would you go about solving this?
> >
> > I don't see the problem. When I change back to .gz, modify the source
> > directory, and rebuild, it rebuilds a new initramfs_data.cpio.gz here.
>
> This is really puzzling me, so here is what is going on my side:
>
> First time build w/ initramfs enabled:
>
> grep INITRAMFS .config
> CONFIG_INITRAMFS_SOURCE="/home/fainelli/work/uclinux-rootfs/romfs
> /home/fainelli/work/uclinux-rootfs/misc/initramfs.dev"
> CONFIG_INITRAMFS_ROOT_UID=1000
> CONFIG_INITRAMFS_ROOT_GID=1000
> # CONFIG_INITRAMFS_COMPRESSION_NONE is not set
> CONFIG_INITRAMFS_COMPRESSION_GZIP=y
> # CONFIG_INITRAMFS_COMPRESSION_BZIP2 is not set
> # CONFIG_INITRAMFS_COMPRESSION_LZMA is not set
> # CONFIG_INITRAMFS_COMPRESSION_XZ is not set
> # CONFIG_INITRAMFS_COMPRESSION_LZO is not set
> # CONFIG_INITRAMFS_COMPRESSION_LZ4 is not set
> CONFIG_INITRAMFS_COMPRESSION=".gz"
>
> fainelli@fainelli-laptop:[~/../linux]$ ls -la usr
> total 6.8M
> drwxrwxr-x 2 fainelli fainelli 4.0K Sep 7 05:37 ./
> drwxrwxr-x 27 fainelli fainelli 16K Sep 7 05:38 ../
> -rw-rw-r-- 1 fainelli fainelli 146 Sep 7 05:37 built-in.o
> -rw-rw-r-- 1 fainelli fainelli 112 Sep 7 05:37 .built-in.o.cmd
> -rwxrwxr-x 1 fainelli fainelli 23K Sep 7 05:36 gen_init_cpio*
> -rw-rw-r-- 1 fainelli fainelli 13K Oct 13 2016 gen_init_cpio.c
> -rw-rw-r-- 1 fainelli fainelli 3.3K Sep 7 05:36 .gen_init_cpio.cmd
> -rw-rw-r-- 1 fainelli fainelli 151 Aug 28 2016 .gitignore
> -rw-rw-r-- 1 fainelli fainelli 9.6K Sep 7 05:36 .initramfs_data.cpio.d
> -rw-rw-r-- 1 fainelli fainelli 3.3M Sep 7 05:37 initramfs_data.cpio.gz
> -rw-rw-r-- 1 fainelli fainelli 220 Sep 7 05:37
> .initramfs_data.cpio.gz.cmd
> -rw-rw-r-- 1 fainelli fainelli 3.3M Sep 7 05:37 initramfs_data.o
> -rw-rw-r-- 1 fainelli fainelli 2.7K Sep 7 05:37 .initramfs_data.o.cmd
> -rw-rw-r-- 1 fainelli fainelli 1.3K Aug 28 2016 initramfs_data.S
> -rw-rw-r-- 1 fainelli fainelli 7.8K Aug 18 19:25 Kconfig
> -rw-rw-r-- 1 fainelli fainelli 2.0K Aug 31 20:46 Makefile
> -rw-rw-r-- 1 fainelli fainelli 0 Sep 7 05:34 modules.builtin
> -rw-rw-r-- 1 fainelli fainelli 0 Sep 7 05:35 modules.order
>
> Now let's reconfigure this kernel w/o initramfs and rebuild:
>
> grep INITRAMFS .config
> CONFIG_INITRAMFS_SOURCE=""
>
> fainelli@fainelli-laptop:[~/../linux]$ ls -la usr
> total 3.6M
> drwxrwxr-x 2 fainelli fainelli 4.0K Sep 7 05:44 ./
> drwxrwxr-x 27 fainelli fainelli 16K Sep 7 05:44 ../
> -rw-rw-r-- 1 fainelli fainelli 146 Sep 7 05:44 built-in.o
> -rw-rw-r-- 1 fainelli fainelli 112 Sep 7 05:44 .built-in.o.cmd
> -rwxrwxr-x 1 fainelli fainelli 23K Sep 7 05:36 gen_init_cpio*
> -rw-rw-r-- 1 fainelli fainelli 13K Oct 13 2016 gen_init_cpio.c
> -rw-rw-r-- 1 fainelli fainelli 3.3K Sep 7 05:36 .gen_init_cpio.cmd
> -rw-rw-r-- 1 fainelli fainelli 151 Aug 28 2016 .gitignore
> -rw-rw-r-- 1 fainelli fainelli 512 Sep 7 05:44 initramfs_data.cpio
> -rw-rw-r-- 1 fainelli fainelli 105 Sep 7 05:44 .initramfs_data.cpio.cmd
> -rw-rw-r-- 1 fainelli fainelli 52 Sep 7 05:44 .initramfs_data.cpio.d
> -rw-rw-r-- 1 fainelli fainelli 3.3M Sep 7 05:37 initramfs_data.cpio.gz
> -rw-rw-r-- 1 fainelli fainelli 220 Sep 7 05:37
> .initramfs_data.cpio.gz.cmd
> -rw-rw-r-- 1 fainelli fainelli 1.3K Sep 7 05:44 initramfs_data.o
> -rw-rw-r-- 1 fainelli fainelli 2.7K Sep 7 05:44 .initramfs_data.o.cmd
> -rw-rw-r-- 1 fainelli fainelli 1.3K Aug 28 2016 initramfs_data.S
> -rw-rw-r-- 1 fainelli fainelli 7.8K Aug 18 19:25 Kconfig
> -rw-rw-r-- 1 fainelli fainelli 2.0K Aug 31 20:46 Makefile
> -rw-rw-r-- 1 fainelli fainelli 0 Sep 7 05:34 modules.builtin
> -rw-rw-r-- 1 fainelli fainelli 0 Sep 7 05:35 modules.order
>
> Now let's rebuild with a new application added to the root filesystem:
>
> grep INITRAMFS .config
> CONFIG_INITRAMFS_SOURCE="/home/fainelli/work/uclinux-rootfs/romfs
> /home/fainelli/work/uclinux-rootfs/misc/initramfs.dev"
> CONFIG_INITRAMFS_ROOT_UID=1000
> CONFIG_INITRAMFS_ROOT_GID=1000
> # CONFIG_INITRAMFS_COMPRESSION_NONE is not set
> CONFIG_INITRAMFS_COMPRESSION_GZIP=y
> # CONFIG_INITRAMFS_COMPRESSION_BZIP2 is not set
> # CONFIG_INITRAMFS_COMPRESSION_LZMA is not set
> # CONFIG_INITRAMFS_COMPRESSION_XZ is not set
> # CONFIG_INITRAMFS_COMPRESSION_LZO is not set
> # CONFIG_INITRAMFS_COMPRESSION_LZ4 is not set
> CONFIG_INITRAMFS_COMPRESSION=".gz"
>
> We are not fine here:
> scripts/kconfig/conf --silentoldconfig Kconfig
> #
> # configuration written to .config
> #
> CHK include/config/kernel.release
> CHK include/generated/uapi/linux/version.h
> CHK scripts/mod/devicetable-offsets.h
> CHK include/generated/utsrelease.h
> CHK include/generated/timeconst.h
> CHK include/generated/bounds.h
> CHK include/generated/asm-offsets.h
> CALL scripts/checksyscalls.sh
> CHK include/generated/compile.h
> AS usr/initramfs_data.o
>
> ^===== we should have called gzip to re-generate the initramfs, we did not
>
> AR usr/built-in.o
> GEN .version
> CHK include/generated/compile.h
> UPD include/generated/compile.h
> CC init/version.o
> AR init/built-in.o
> AR built-in.o
> LD vmlinux.o
> MODPOST vmlinux.o
>
> And the timestamps here confirm that:
>
> fainelli@fainelli-laptop:[~/../linux]$ ls -la usr
> total 6.9M
> drwxrwxr-x 2 fainelli fainelli 4.0K Sep 7 05:46 ./
> drwxrwxr-x 27 fainelli fainelli 16K Sep 7 05:46 ../
> -rw-rw-r-- 1 fainelli fainelli 146 Sep 7 05:46 built-in.o
> -rw-rw-r-- 1 fainelli fainelli 112 Sep 7 05:46 .built-in.o.cmd
> -rwxrwxr-x 1 fainelli fainelli 23K Sep 7 05:36 gen_init_cpio*
> -rw-rw-r-- 1 fainelli fainelli 13K Oct 13 2016 gen_init_cpio.c
> -rw-rw-r-- 1 fainelli fainelli 3.3K Sep 7 05:36 .gen_init_cpio.cmd
> -rw-rw-r-- 1 fainelli fainelli 151 Aug 28 2016 .gitignore
> -rw-rw-r-- 1 fainelli fainelli 512 Sep 7 05:44 initramfs_data.cpio
> -rw-rw-r-- 1 fainelli fainelli 105 Sep 7 05:44 .initramfs_data.cpio.cmd
> -rw-rw-r-- 1 fainelli fainelli 11K Sep 7 05:46 .initramfs_data.cpio.d
> -rw-rw-r-- 1 fainelli fainelli 3.3M Sep 7 05:37 initramfs_data.cpio.gz
> -rw-rw-r-- 1 fainelli fainelli 220 Sep 7 05:37
> .initramfs_data.cpio.gz.cmd
> -rw-rw-r-- 1 fainelli fainelli 3.3M Sep 7 05:46 initramfs_data.o
> -rw-rw-r-- 1 fainelli fainelli 2.7K Sep 7 05:46 .initramfs_data.o.cmd
> -rw-rw-r-- 1 fainelli fainelli 1.3K Aug 28 2016 initramfs_data.S
> -rw-rw-r-- 1 fainelli fainelli 7.8K Aug 18 19:25 Kconfig
> -rw-rw-r-- 1 fainelli fainelli 2.0K Aug 31 20:46 Makefile
> -rw-rw-r-- 1 fainelli fainelli 0 Sep 7 05:46 modules.builtin
> -rw-rw-r-- 1 fainelli fainelli 0 Sep 7 05:46 modules.order
>
> Worse yet, usr/.initramfs_data.cpio.d does list the binary that was just
> added, but for some reason, this did not trigger a rebuild of
> initramfs_data.cpio.gz do you see any reasons why?

This rule

$(obj)/$(datafile_y): $(obj)/gen_init_cpio $(deps_initramfs) klibcdirs
$(Q)$(initramfs) -l $(ramfs-input) > $(obj)/.initramfs_data.cpio.d
$(call if_changed,initfs)

does not have FORCE on the end, so I guess is not picking up the dependency
properly, perhaps?

Thanks,
Nick

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