[PATCH 00/62] initrd: remove classic initrd support

[PATCH 00/62] initrd: remove classic initrd support

[Askar Safin]

Intro
====
This patchset removes classic initrd (initial RAM disk) support,
which was deprecated in 2020.
Initramfs still stays, and RAM disk itself (brd) still stays, too.
init/do_mounts* and init/*initramfs* are listed in VFS entry in
MAINTAINERS, so I think this patchset should go through VFS tree.
This patchset touchs every subdirectory in arch/, so I tested it
on 8 (!!!) archs in Qemu (see details below).
Warning: this patchset renames CONFIG_BLK_DEV_INITRD (!!!) to CONFIG_INITRAMFS
and CONFIG_RD_* to CONFIG_INITRAMFS_DECOMPRESS_* (for example,
CONFIG_RD_GZIP to CONFIG_INITRAMFS_DECOMPRESS_GZIP).
If you still use initrd, see below for workaround.

Details
====
I not only removed initrd, I also removed a lot of code, which
became dead, including a lot of code in arch/.

Still I think the only two architectures I touched in non-trivial
way are sh and 32-bit arm.

Also I renamed some files, functions and variables (which became misnomers) to proper names,
moved some code around, removed a lot of mentions of initrd
in code and comments. Also I cleaned up some docs.

For example, I renamed the following global variables:

__initramfs_start
__initramfs_size
phys_initrd_start
phys_initrd_size
initrd_start
initrd_end

to:

__builtin_initramfs_start
__builtin_initramfs_size
phys_external_initramfs_start
phys_external_initramfs_size
virt_external_initramfs_start
virt_external_initramfs_end

New names precisely capture meaning of these variables.

Also I renamed CONFIG_BLK_DEV_INITRD (which became total misnomer)
to CONFIG_INITRAMFS. And CONFIG_RD_* to CONFIG_INITRAMFS_DECOMPRESS_*.
This will break all configs out there (update your configs!).
Still I think this is okay,
because config names never were part of stable API.
Still, I don't have strong opinion here, so I can drop these renamings
if needed.

Other user-visible changes:

- Removed kernel command line parameters "load_ramdisk" and
"prompt_ramdisk", which did nothing and were deprecated
- Removed kernel command line parameter "ramdisk_start",
which was used for initrd only (not for initramfs)
- Removed kernel command line parameter "noinitrd",
which was inconsistent: it controlled initrd only
(not initramfs), except for EFI boot, where it
controlled both initramfs and initrd. EFI users
still can disable initramfs simply by not passing it
- Removed kernel command line parameter "ramdisk_size",
which used for controlling ramdisk (brd), but only
in non-modular mode. Use brd.rd_size instead, it
always works
- Removed /proc/sys/kernel/real-root-dev . It was used
for initrd only

This patchset is based on v6.17-rc5.

Testing
====
I tested my patchset on many architectures in Qemu using my Rust
program, heavily based on mkroot [1].

I used the following cross-compilers:

aarch64-linux-musleabi
armv4l-linux-musleabihf
armv5l-linux-musleabihf
armv7l-linux-musleabihf
i486-linux-musl
i686-linux-musl
mips-linux-musl
mips64-linux-musl
mipsel-linux-musl
powerpc-linux-musl
powerpc64-linux-musl
powerpc64le-linux-musl
riscv32-linux-musl
riscv64-linux-musl
s390x-linux-musl
sh4-linux-musl
sh4eb-linux-musl
x86_64-linux-musl

taken from this directory [2].

So, as you can see, there are 18 triplets, which correspond to 8 subdirs in arch/.

And note that this list contains two archs (arm and sh) touched in non-trivial way.

For every triplet I tested that:
- Initramfs still works (both builtin and external)
- Direct boot from disk still works

Workaround
====
If "retain_initrd" is passed to kernel, then initramfs/initrd,
passed by bootloader, is retained and becomes available after boot
as read-only magic file /sys/firmware/initrd [3].

No copies are involved. I. e. /sys/firmware/initrd is simply
a reference to original blob passed by bootloader.

This works even if initrd/initramfs is not recognized by kernel
in any way, i. e. even if it is not valid cpio archive, nor
a fs image supported by classic initrd.

This works both with my patchset and without it.

This means that you can emulate classic initrd so:
link builtin initramfs to kernel. In /init in this initramfs
copy /sys/firmware/initrd to some file in / and loop-mount it.

This is even better than classic initrd, because:
- You can use fs not supported by classic initrd, for example erofs
- One copy is involved (from /sys/firmware/initrd to some file in /)
as opposed to two when using classic initrd

Still, I don't recommend using this workaround, because
I want everyone to migrate to proper modern initramfs.
But still you can use this workaround if you want.

Also: it is not possible to directly loop-mount
/sys/firmware/initrd . Theoretically kernel can be changed
to allow this (and/or to make it writable), but I think nobody needs this.
And I don't want to implement this.


[1] https://github.com/landley/toybox/tree/master/mkroot
[2] https://landley.net/toybox/downloads/binaries/toolchains/latest
[3] https://lore.kernel.org/all/20231207235654.16622-1-graf@amazon.com/


Askar Safin (62):
  init: remove deprecated "load_ramdisk" command line parameter, which
    does nothing
  init: remove deprecated "prompt_ramdisk" command line parameter, which
    does nothing
  init: sh, sparc, x86: remove unused constants RAMDISK_PROMPT_FLAG and
    RAMDISK_LOAD_FLAG
  init: x86, arm, sh, sparc: remove variable rd_image_start, which
    controls starting block number of initrd
  init: remove "ramdisk_start" command line parameter, which controls
    starting block number of initrd
  arm: init: remove special logic for setting brd.rd_size
  arm: init: remove ATAG_RAMDISK
  arm: init: remove FLAG_RDLOAD and FLAG_RDPROMPT
  arm: init: document rd_start (in param_struct) as obsolete
  initrd: remove initrd (initial RAM disk) support
  init, efi: remove "noinitrd" command line parameter
  init: remove /proc/sys/kernel/real-root-dev
  ext2: remove ext2_image_size and associated code
  init: m68k, mips, powerpc, s390, sh: remove Root_RAM0
  doc: modernize Documentation/admin-guide/blockdev/ramdisk.rst
  brd: remove "ramdisk_size" command line parameter
  doc: modernize Documentation/filesystems/ramfs-rootfs-initramfs.rst
  doc: modernize
    Documentation/driver-api/early-userspace/early_userspace_support.rst
  init: remove mentions of "ramdisk=" command line parameter
  doc: remove Documentation/power/swsusp-dmcrypt.rst
  init: remove all mentions of root=/dev/ram*
  doc: remove obsolete mentions of pivot_root
  init: rename __initramfs_{start,size} to
    __builtin_initramfs_{start,size}
  init: remove wrong comment
  init: rename phys_initrd_{start,size} to
    phys_external_initramfs_{start,size}
  init: move phys_external_initramfs_{start,size} to init/initramfs.c
  init: alpha: remove "extern unsigned long initrd_start, initrd_end"
  init: alpha, arc, arm, arm64, csky, m68k, microblaze, mips, nios2,
    openrisc, parisc, powerpc, s390, sh, sparc, um, x86, xtensa: rename
    initrd_{start,end} to virt_external_initramfs_{start,end}
  init: move virt_external_initramfs_{start,end} to init/initramfs.c
  doc: remove documentation for block device 4 0
  init: rename initrd_below_start_ok to initramfs_below_start_ok
  init: move initramfs_below_start_ok to init/initramfs.c
  init: remove init/do_mounts_initrd.c
  init: inline create_dev into the only caller
  init: make mount_root_generic static
  init: make mount_root static
  init: remove root_mountflags from init/do_mounts.h
  init: remove most headers from init/do_mounts.h
  init: make console_on_rootfs static
  init: rename free_initrd_mem to free_initramfs_mem
  init: rename reserve_initrd_mem to reserve_initramfs_mem
  init: rename <linux/initrd.h> to <linux/initramfs.h>
  setsid: inline ksys_setsid into the only caller
  doc: kernel-parameters: remove [RAM] from reserve_mem=
  doc: kernel-parameters: replace [RAM] with [INITRAMFS]
  init: edit docs for initramfs-related configs
  init: fix typo: virtul => virtual
  init: fix comment
  init: rename ramdisk_execute_command to initramfs_execute_command
  init: rename ramdisk_command_access to initramfs_command_access
  init: rename get_boot_config_from_initrd to
    get_boot_config_from_initramfs
  init: rename do_retain_initrd to retain_initramfs
  init: rename kexec_free_initrd to kexec_free_initramfs
  init: arm, x86: deal with some references to initrd
  init: rename CONFIG_BLK_DEV_INITRD to CONFIG_INITRAMFS
  init: rename CONFIG_RD_GZIP to CONFIG_INITRAMFS_DECOMPRESS_GZIP
  init: rename CONFIG_RD_BZIP2 to CONFIG_INITRAMFS_DECOMPRESS_BZIP2
  init: rename CONFIG_RD_LZMA to CONFIG_INITRAMFS_DECOMPRESS_LZMA
  init: rename CONFIG_RD_XZ to CONFIG_INITRAMFS_DECOMPRESS_XZ
  init: rename CONFIG_RD_LZO to CONFIG_INITRAMFS_DECOMPRESS_LZO
  init: rename CONFIG_RD_LZ4 to CONFIG_INITRAMFS_DECOMPRESS_LZ4
  init: rename CONFIG_RD_ZSTD to CONFIG_INITRAMFS_DECOMPRESS_ZSTD

 .../admin-guide/blockdev/ramdisk.rst          | 104 +----
 .../admin-guide/device-mapper/dm-init.rst     |   4 +-
 Documentation/admin-guide/devices.txt         |  12 -
 Documentation/admin-guide/index.rst           |   1 -
 Documentation/admin-guide/initrd.rst          | 383 ------------------
 .../admin-guide/kernel-parameters.rst         |   4 +-
 .../admin-guide/kernel-parameters.txt         |  38 +-
 Documentation/admin-guide/nfs/nfsroot.rst     |   4 +-
 Documentation/admin-guide/sysctl/kernel.rst   |   6 -
 Documentation/arch/arm/ixp4xx.rst             |   4 +-
 Documentation/arch/arm/setup.rst              |   6 +-
 Documentation/arch/m68k/kernel-options.rst    |  29 +-
 Documentation/arch/x86/boot.rst               |   4 +-
 .../early_userspace_support.rst               |  18 +-
 .../filesystems/ramfs-rootfs-initramfs.rst    |  20 +-
 Documentation/power/index.rst                 |   1 -
 Documentation/power/swsusp-dmcrypt.rst        | 140 -------
 Documentation/security/ipe.rst                |   2 +-
 .../translations/zh_CN/power/index.rst        |   1 -
 arch/alpha/kernel/core_irongate.c             |  12 +-
 arch/alpha/kernel/proto.h                     |   2 +-
 arch/alpha/kernel/setup.c                     |  32 +-
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 arch/arc/configs/nsimosci_hs_smp_defconfig    |   2 +-
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 arch/arc/configs/vdk_hs38_defconfig           |   2 +-
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 arch/arc/mm/init.c                            |  14 +-
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 arch/arm/boot/dts/arm/integratorap.dts        |   2 +-
 arch/arm/boot/dts/arm/integratorcp.dts        |   2 +-
 .../dts/aspeed/aspeed-bmc-facebook-cmm.dts    |   2 +-
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 arch/arm/configs/sunxi_defconfig              |   2 +-
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 arch/arm/configs/wpcm450_defconfig            |   2 +-
 arch/arm/include/uapi/asm/setup.h             |  10 -
 arch/arm/kernel/atags_compat.c                |  10 -
 arch/arm/kernel/atags_parse.c                 |  16 +-
 arch/arm/kernel/setup.c                       |   2 +-
 arch/arm/mm/init.c                            |  24 +-
 arch/arm64/configs/defconfig                  |   2 +-
 arch/arm64/kernel/setup.c                     |   2 +-
 arch/arm64/mm/init.c                          |  17 +-
 arch/csky/kernel/setup.c                      |  24 +-
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 arch/m68k/kernel/setup_mm.c                   |  12 +-
 arch/m68k/kernel/setup_no.c                   |  12 +-
 arch/m68k/kernel/uboot.c                      |  17 +-
 arch/microblaze/kernel/cpu/mb.c               |   2 +-
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 arch/mips/kernel/setup.c                      |  53 ++-
 arch/mips/mm/init.c                           |   2 +-
 arch/mips/sibyte/common/cfe.c                 |  36 +-
 arch/mips/sibyte/swarm/setup.c                |   2 +-
 arch/nios2/kernel/setup.c                     |  20 +-
 arch/openrisc/configs/or1klitex_defconfig     |   2 +-
 arch/openrisc/configs/or1ksim_defconfig       |   4 +-
 arch/openrisc/configs/simple_smp_defconfig    |  14 +-
 arch/openrisc/configs/virt_defconfig          |   2 +-
 arch/openrisc/kernel/setup.c                  |  24 +-
 arch/openrisc/kernel/vmlinux.h                |   2 +-
 arch/parisc/boot/compressed/misc.c            |   2 +-
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 arch/parisc/kernel/pdt.c                      |   6 +-
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 arch/powerpc/configs/85xx/socrates_defconfig  |   2 +-
 arch/powerpc/configs/85xx/stx_gp3_defconfig   |   2 +-
 arch/powerpc/configs/85xx/tqm8540_defconfig   |   2 +-
 arch/powerpc/configs/85xx/tqm8541_defconfig   |   2 +-
 arch/powerpc/configs/85xx/tqm8548_defconfig   |   2 +-
 arch/powerpc/configs/85xx/tqm8555_defconfig   |   2 +-
 arch/powerpc/configs/85xx/tqm8560_defconfig   |   2 +-
 .../configs/85xx/xes_mpc85xx_defconfig        |   2 +-
 arch/powerpc/configs/amigaone_defconfig       |   2 +-
 arch/powerpc/configs/cell_defconfig           |   2 +-
 arch/powerpc/configs/chrp32_defconfig         |   2 +-
 arch/powerpc/configs/fsl-emb-nonhw.config     |   2 +-
 arch/powerpc/configs/g5_defconfig             |   2 +-
 arch/powerpc/configs/gamecube_defconfig       |   2 +-
 arch/powerpc/configs/holly_defconfig          |   2 +-
 arch/powerpc/configs/linkstation_defconfig    |   2 +-
 arch/powerpc/configs/mgcoge_defconfig         |   4 +-
 arch/powerpc/configs/microwatt_defconfig      |   2 +-
 arch/powerpc/configs/mpc512x_defconfig        |   2 +-
 arch/powerpc/configs/mpc5200_defconfig        |   2 +-
 arch/powerpc/configs/mpc83xx_defconfig        |   2 +-
 arch/powerpc/configs/pasemi_defconfig         |   2 +-
 arch/powerpc/configs/pmac32_defconfig         |   2 +-
 arch/powerpc/configs/powernv_defconfig        |   2 +-
 arch/powerpc/configs/ppc44x_defconfig         |   2 +-
 arch/powerpc/configs/ppc64_defconfig          |   2 +-
 arch/powerpc/configs/ppc64e_defconfig         |   2 +-
 arch/powerpc/configs/ppc6xx_defconfig         |   2 +-
 arch/powerpc/configs/ps3_defconfig            |   2 +-
 arch/powerpc/configs/skiroot_defconfig        |  12 +-
 arch/powerpc/configs/wii_defconfig            |   2 +-
 arch/powerpc/kernel/prom.c                    |  22 +-
 arch/powerpc/kernel/prom_init.c               |   6 +-
 arch/powerpc/kernel/setup-common.c            |  25 +-
 arch/powerpc/kernel/setup_32.c                |   2 +-
 arch/powerpc/kernel/setup_64.c                |   2 +-
 arch/powerpc/mm/init_32.c                     |   2 +-
 arch/powerpc/platforms/52xx/lite5200.c        |   2 +-
 arch/powerpc/platforms/83xx/km83xx.c          |   2 +-
 arch/powerpc/platforms/85xx/mpc85xx_mds.c     |   2 +-
 arch/powerpc/platforms/chrp/setup.c           |   2 +-
 .../platforms/embedded6xx/linkstation.c       |   2 +-
 .../platforms/embedded6xx/storcenter.c        |   2 +-
 arch/powerpc/platforms/powermac/setup.c       |   8 +-
 arch/riscv/configs/defconfig                  |   2 +-
 arch/riscv/configs/nommu_k210_defconfig       |  16 +-
 arch/riscv/configs/nommu_virt_defconfig       |  12 +-
 arch/riscv/mm/init.c                          |   4 +-
 arch/s390/boot/ipl_parm.c                     |   2 +-
 arch/s390/boot/startup.c                      |   4 +-
 arch/s390/configs/zfcpdump_defconfig          |   2 +-
 arch/s390/kernel/setup.c                      |  10 +-
 arch/s390/mm/init.c                           |   2 +-
 arch/sh/configs/apsh4a3a_defconfig            |   2 +-
 arch/sh/configs/apsh4ad0a_defconfig           |   2 +-
 arch/sh/configs/ecovec24-romimage_defconfig   |   2 +-
 arch/sh/configs/edosk7760_defconfig           |   2 +-
 arch/sh/configs/kfr2r09-romimage_defconfig    |   2 +-
 arch/sh/configs/kfr2r09_defconfig             |   2 +-
 arch/sh/configs/magicpanelr2_defconfig        |   2 +-
 arch/sh/configs/migor_defconfig               |   2 +-
 arch/sh/configs/rsk7201_defconfig             |   2 +-
 arch/sh/configs/rsk7203_defconfig             |   2 +-
 arch/sh/configs/sdk7786_defconfig             |   8 +-
 arch/sh/configs/se7206_defconfig              |   2 +-
 arch/sh/configs/se7705_defconfig              |   2 +-
 arch/sh/configs/se7722_defconfig              |   2 +-
 arch/sh/configs/se7751_defconfig              |   2 +-
 arch/sh/configs/secureedge5410_defconfig      |   2 +-
 arch/sh/configs/sh03_defconfig                |   2 +-
 arch/sh/configs/sh7757lcr_defconfig           |   2 +-
 arch/sh/configs/titan_defconfig               |   2 +-
 arch/sh/configs/ul2_defconfig                 |   2 +-
 arch/sh/configs/urquell_defconfig             |   2 +-
 arch/sh/include/asm/setup.h                   |   1 -
 arch/sh/kernel/head_32.S                      |   2 +-
 arch/sh/kernel/setup.c                        |  27 +-
 arch/sparc/boot/piggyback.c                   |   4 +-
 arch/sparc/configs/sparc32_defconfig          |   2 +-
 arch/sparc/configs/sparc64_defconfig          |   2 +-
 arch/sparc/kernel/head_32.S                   |   4 +-
 arch/sparc/kernel/head_64.S                   |   6 +-
 arch/sparc/kernel/setup_32.c                  |   9 +-
 arch/sparc/kernel/setup_64.c                  |   9 +-
 arch/sparc/mm/init_32.c                       |  22 +-
 arch/sparc/mm/init_64.c                       |  20 +-
 arch/um/kernel/Makefile                       |   2 +-
 arch/um/kernel/initrd.c                       |   6 +-
 arch/x86/Kconfig                              |   2 +-
 arch/x86/boot/header.S                        |   2 +-
 arch/x86/boot/startup/sme.c                   |   2 +-
 arch/x86/configs/i386_defconfig               |   2 +-
 arch/x86/configs/x86_64_defconfig             |   2 +-
 arch/x86/include/uapi/asm/bootparam.h         |   7 +-
 arch/x86/kernel/cpu/microcode/amd.c           |   2 +-
 arch/x86/kernel/cpu/microcode/core.c          |  12 +-
 arch/x86/kernel/cpu/microcode/intel.c         |   2 +-
 arch/x86/kernel/cpu/microcode/internal.h      |   2 +-
 arch/x86/kernel/devicetree.c                  |   2 +-
 arch/x86/kernel/setup.c                       |  39 +-
 arch/x86/mm/init.c                            |   8 +-
 arch/x86/mm/init_32.c                         |   2 +-
 arch/x86/mm/init_64.c                         |   2 +-
 arch/x86/tools/relocs.c                       |   2 +-
 arch/xtensa/Kconfig                           |   2 +-
 arch/xtensa/boot/dts/csp.dts                  |   2 +-
 arch/xtensa/configs/audio_kc705_defconfig     |   2 +-
 arch/xtensa/configs/cadence_csp_defconfig     |  12 +-
 arch/xtensa/configs/generic_kc705_defconfig   |   2 +-
 arch/xtensa/configs/nommu_kc705_defconfig     |  12 +-
 arch/xtensa/configs/smp_lx200_defconfig       |   2 +-
 arch/xtensa/configs/virt_defconfig            |   2 +-
 arch/xtensa/configs/xip_kc705_defconfig       |   2 +-
 arch/xtensa/kernel/setup.c                    |  26 +-
 drivers/acpi/Kconfig                          |   2 +-
 drivers/acpi/tables.c                         |  10 +-
 drivers/base/firmware_loader/main.c           |   2 +-
 drivers/block/Kconfig                         |   8 +-
 drivers/block/brd.c                           |  20 +-
 drivers/firmware/efi/efi.c                    |  10 +-
 .../firmware/efi/libstub/efi-stub-helper.c    |   5 +-
 drivers/gpu/drm/ci/arm.config                 |   2 +-
 drivers/gpu/drm/ci/arm64.config               |   2 +-
 drivers/gpu/drm/ci/x86_64.config              |   2 +-
 drivers/of/fdt.c                              |  18 +-
 fs/ext2/ext2.h                                |   9 -
 fs/init.c                                     |  14 -
 include/asm-generic/vmlinux.lds.h             |   8 +-
 include/linux/ext2_fs.h                       |  13 -
 include/linux/init_syscalls.h                 |   1 -
 include/linux/initramfs.h                     |  26 ++
 include/linux/initrd.h                        |  37 --
 include/linux/root_dev.h                      |   1 -
 include/linux/syscalls.h                      |   1 -
 include/uapi/linux/sysctl.h                   |   1 -
 init/.kunitconfig                             |   2 +-
 init/Kconfig                                  |  28 +-
 init/Makefile                                 |   6 +-
 init/do_mounts.c                              |  28 +-
 init/do_mounts.h                              |  42 --
 init/do_mounts_initrd.c                       | 154 -------
 init/do_mounts_rd.c                           | 334 ---------------
 init/initramfs.c                              | 152 ++++---
 init/main.c                                   |  66 +--
 kernel/sys.c                                  |   7 +-
 kernel/sysctl.c                               |   2 +-
 kernel/umh.c                                  |   2 +-
 scripts/package/builddeb                      |   2 +-
 .../ktest/examples/bootconfigs/tracing.bconf  |   3 -
 tools/testing/selftests/bpf/config.aarch64    |   2 +-
 tools/testing/selftests/bpf/config.ppc64el    |   2 +-
 tools/testing/selftests/bpf/config.riscv64    |   2 +-
 tools/testing/selftests/bpf/config.s390x      |   2 +-
 tools/testing/selftests/kho/vmtest.sh         |   2 +-
 .../testing/selftests/nolibc/Makefile.nolibc  |   4 +-
 tools/testing/selftests/vsock/config          |   2 +-
 .../selftests/wireguard/qemu/kernel.config    |   2 +-
 usr/Kconfig                                   |  70 ++--
 usr/Makefile                                  |   2 +-
 usr/initramfs_data.S                          |   4 +-
 385 files changed, 969 insertions(+), 2346 deletions(-)
 delete mode 100644 Documentation/admin-guide/initrd.rst
 delete mode 100644 Documentation/power/swsusp-dmcrypt.rst
 create mode 100644 include/linux/initramfs.h
 delete mode 100644 include/linux/initrd.h
 delete mode 100644 init/do_mounts_initrd.c
 delete mode 100644 init/do_mounts_rd.c


base-commit: 76eeb9b8de9880ca38696b2fb56ac45ac0a25c6c
-- 
2.47.2

[PATCH 01/62] init: remove deprecated "load_ramdisk" command line parameter, which does nothing

[Askar Safin]

This is preparation for initrd removal

Signed-off-by: Askar Safin <safinaskar@zohomail.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 2 --
 arch/arm/configs/neponset_defconfig             | 2 +-
 init/do_mounts.c                                | 7 -------
 3 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 747a55abf494..d3b05ce249ff 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3275,8 +3275,6 @@
 			If there are multiple matching configurations changing
 			the same attribute, the last one is used.
 
-	load_ramdisk=	[RAM] [Deprecated]
-
 	lockd.nlm_grace_period=P  [NFS] Assign grace period.
 			Format: <integer>
 
diff --git a/arch/arm/configs/neponset_defconfig b/arch/arm/configs/neponset_defconfig
index 2227f86100ad..16f7300239da 100644
--- a/arch/arm/configs/neponset_defconfig
+++ b/arch/arm/configs/neponset_defconfig
@@ -9,7 +9,7 @@ CONFIG_ASSABET_NEPONSET=y
 CONFIG_ZBOOT_ROM_TEXT=0x80000
 CONFIG_ZBOOT_ROM_BSS=0xc1000000
 CONFIG_ZBOOT_ROM=y
-CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) load_ramdisk=1 prompt_ramdisk=0 mem=32M noinitrd initrd=0xc0800000,3M"
+CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) prompt_ramdisk=0 mem=32M noinitrd initrd=0xc0800000,3M"
 CONFIG_FPE_NWFPE=y
 CONFIG_PM=y
 CONFIG_MODULES=y
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 6af29da8889e..0f2f44e6250c 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -34,13 +34,6 @@ static int root_wait;
 
 dev_t ROOT_DEV;
 
-static int __init load_ramdisk(char *str)
-{
-	pr_warn("ignoring the deprecated load_ramdisk= option\n");
-	return 1;
-}
-__setup("load_ramdisk=", load_ramdisk);
-
 static int __init readonly(char *str)
 {
 	if (*str)
-- 
2.47.2

[PATCH 02/62] init: remove deprecated "prompt_ramdisk" command line parameter, which does nothing

[Askar Safin]

This is preparation for initrd removal

Signed-off-by: Askar Safin <safinaskar@zohomail.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 2 --
 arch/arm/configs/neponset_defconfig             | 2 +-
 init/do_mounts_rd.c                             | 7 -------
 3 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d3b05ce249ff..f940c1184912 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5229,8 +5229,6 @@
 			Param: <number> - step/bucket size as a power of 2 for
 				statistical time based profiling.
 
-	prompt_ramdisk=	[RAM] [Deprecated]
-
 	prot_virt=	[S390] enable hosting protected virtual machines
 			isolated from the hypervisor (if hardware supports
 			that). If enabled, the default kernel base address
diff --git a/arch/arm/configs/neponset_defconfig b/arch/arm/configs/neponset_defconfig
index 16f7300239da..4d720001c12e 100644
--- a/arch/arm/configs/neponset_defconfig
+++ b/arch/arm/configs/neponset_defconfig
@@ -9,7 +9,7 @@ CONFIG_ASSABET_NEPONSET=y
 CONFIG_ZBOOT_ROM_TEXT=0x80000
 CONFIG_ZBOOT_ROM_BSS=0xc1000000
 CONFIG_ZBOOT_ROM=y
-CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) prompt_ramdisk=0 mem=32M noinitrd initrd=0xc0800000,3M"
+CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) mem=32M noinitrd initrd=0xc0800000,3M"
 CONFIG_FPE_NWFPE=y
 CONFIG_PM=y
 CONFIG_MODULES=y
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index ac021ae6e6fa..f7d53bc21e41 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -17,13 +17,6 @@
 static struct file *in_file, *out_file;
 static loff_t in_pos, out_pos;
 
-static int __init prompt_ramdisk(char *str)
-{
-	pr_warn("ignoring the deprecated prompt_ramdisk= option\n");
-	return 1;
-}
-__setup("prompt_ramdisk=", prompt_ramdisk);
-
 int __initdata rd_image_start;		/* starting block # of image */
 
 static int __init ramdisk_start_setup(char *str)
-- 
2.47.2

[PATCH 03/62] init: sh, sparc, x86: remove unused constants RAMDISK_PROMPT_FLAG and RAMDISK_LOAD_FLAG

[Askar Safin]

They were used for initrd before c8376994c86.

c8376994c86c made them unused and forgot to remove them

Fixes: c8376994c86c ("initrd: remove support for multiple floppies")
Cc: <stable+noautosel@kernel.org> # because changes uapi headers
Signed-off-by: Askar Safin <safinaskar@zohomail.com>
---
 arch/sh/kernel/setup.c                | 2 --
 arch/sparc/kernel/setup_32.c          | 2 --
 arch/sparc/kernel/setup_64.c          | 2 --
 arch/x86/include/uapi/asm/bootparam.h | 2 --
 arch/x86/kernel/setup.c               | 2 --
 5 files changed, 10 deletions(-)

diff --git a/arch/sh/kernel/setup.c b/arch/sh/kernel/setup.c
index 039a51291002..d66f098e9e9f 100644
--- a/arch/sh/kernel/setup.c
+++ b/arch/sh/kernel/setup.c
@@ -71,8 +71,6 @@ EXPORT_SYMBOL(sh_mv);
 extern int root_mountflags;
 
 #define RAMDISK_IMAGE_START_MASK	0x07FF
-#define RAMDISK_PROMPT_FLAG		0x8000
-#define RAMDISK_LOAD_FLAG		0x4000
 
 static char __initdata command_line[COMMAND_LINE_SIZE] = { 0, };
 
diff --git a/arch/sparc/kernel/setup_32.c b/arch/sparc/kernel/setup_32.c
index 704375c061e7..eb60be31127f 100644
--- a/arch/sparc/kernel/setup_32.c
+++ b/arch/sparc/kernel/setup_32.c
@@ -172,8 +172,6 @@ extern unsigned short root_flags;
 extern unsigned short root_dev;
 extern unsigned short ram_flags;
 #define RAMDISK_IMAGE_START_MASK	0x07FF
-#define RAMDISK_PROMPT_FLAG		0x8000
-#define RAMDISK_LOAD_FLAG		0x4000
 
 extern int root_mountflags;
 
diff --git a/arch/sparc/kernel/setup_64.c b/arch/sparc/kernel/setup_64.c
index 63615f5c99b4..f728f1b00aca 100644
--- a/arch/sparc/kernel/setup_64.c
+++ b/arch/sparc/kernel/setup_64.c
@@ -145,8 +145,6 @@ extern unsigned short root_flags;
 extern unsigned short root_dev;
 extern unsigned short ram_flags;
 #define RAMDISK_IMAGE_START_MASK	0x07FF
-#define RAMDISK_PROMPT_FLAG		0x8000
-#define RAMDISK_LOAD_FLAG		0x4000
 
 extern int root_mountflags;
 
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index dafbf581c515..f53dd3f319ba 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -6,8 +6,6 @@
 
 /* ram_size flags */
 #define RAMDISK_IMAGE_START_MASK	0x07FF
-#define RAMDISK_PROMPT_FLAG		0x8000
-#define RAMDISK_LOAD_FLAG		0x4000
 
 /* loadflags */
 #define LOADED_HIGH	(1<<0)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 1b2edd07a3e1..6409e766fb17 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -223,8 +223,6 @@ extern int root_mountflags;
 unsigned long saved_video_mode;
 
 #define RAMDISK_IMAGE_START_MASK	0x07FF
-#define RAMDISK_PROMPT_FLAG		0x8000
-#define RAMDISK_LOAD_FLAG		0x4000
 
 static char __initdata command_line[COMMAND_LINE_SIZE];
 #ifdef CONFIG_CMDLINE_BOOL
-- 
2.47.2

Re: [PATCH 00/62] initrd: remove classic initrd support

[Rob Landley]

On 9/12/25 17:38, Askar Safin wrote:
> Intro
> ====
> This patchset removes classic initrd (initial RAM disk) support,
> which was deprecated in 2020.

Still useful for embedded systems that can memory map flash, but it's 
getting harder to find embedded developers who consider new kernels an 
improvement over older ones...

> Initramfs still stays, and RAM disk itself (brd) still stays, too.

While you're at it, could you fix static/builtin initramfs so PID 1 has 
a valid stdin/stdout/stderr?

A static initramfs won't create /dev/console if the embedded initramfs 
image doesn't contain it, which a non-root build can't mknod, so the 
kernel plumbing won't see it dev in the directory we point it at unless 
we build with root access. This means the open("/dev/console") fails, so 
init starts with no error reporting and we have to get far enough to 
mount our own devtmpfs or similar and open our own stdout/stderr before 
we can see any error output from init, which is kinda brittle.

I posted various patches to make CONFIG_DEVTMPFS_MOUNT work for initmpfs 
repeatedly since 2017, which also addressed it, but the kernel 
community's been hermetically sealed against outside intrusion for a 
while now...

https://lkml.iu.edu/hypermail/linux/kernel/2005.1/09399.html

https://lkml.iu.edu/2302.2/05597.html

> init/do_mounts* and init/*initramfs* are listed in VFS entry in
> MAINTAINERS, so I think this patchset should go through VFS tree.
> This patchset touchs every subdirectory in arch/, so I tested it
> on 8 (!!!) archs in Qemu (see details below).

Oh hey, somebody using mkroot. Cool. :)

My current "passes basic automated smoketests" list for 6.16 is:

aarch64 armv4l armv5l armv7l i486 i686 m68k mips64 mipsel mips powerpc 
powerpc64le powerpc64 riscv32 riscv64 s390x sh4 x86_64

I'm assuming that's your 8: arm, x86, m68k, mips, ppc, riscv, s390x, 
superh. (The variants are mostly 32/64 bit and bit/little endian, couple 
architecture generations in there. The old ones go out of patent first, 
you can always tell patents are about to expire and get generic clones 
when corporate shills start insisting that support for something REALLY 
NEEDS TO GO AWAY RIGHT NOW...)

The or1k, microblaze, and sh4eb targets mostly work: sh4eb has broken 
eithernet (never tracked down whether it's kernel or qemu that's wrong I 
just know they disagree), or1k doesn't know how to exit ala 
https://lists.gnu.org/archive/html/qemu-devel/2024-11/msg04522.html and 
microblaze never wired up -hda to their hard drive emulation 
https://lists.nongnu.org/archive/html/qemu-devel/2025-01/msg01149.html
but I haven't had the spoons to argue with IBM Hat developers about 
procedure compliance auditing.

I need to track down a decent qemu emulation for armv7m, last time I 
tried with vanilla was https://landley.net/notes-2023.html#23-02-2023 
which was not promising, I downloaded a pic32 qemu fork last week, but 
haven't had the spoons to follow up on that either. Or to ship a new 
toybox/mkroot release: I've had 6.16 kernel patches since the week it 
came out, unbreaking powerpc and adding fdpic support to sh4-mmu, but 
hobbyist friendly this community ain't. Sigh, I should get back on the 
(beating a dead) horse...

I had hexagon userspace working for a while ("qemu-hexagon ls -l") but 
no kernel for it: Taylor Simpson said he was going to post a 
qemu-system-hexagon patchset with a comet board emulation, but that 
architecture has no gcc support (there was a gcc fork on code aurora but 
they abandoned it when the FSF went gplv3) so it needs an llvm-only 
toolchain build with a non-vanilla musl libc fork... Honestly the 
problem is compiler-rt sucks rocks: I should cycle back around to 
https://landley.net/notes-2021.html#28-07-2021 but just haven't.

(Although part of the "Just haven't" is that I posted a patch to lkml 
making generic $CROSS_COMPILE prefixes automatically work whether your 
toolchain was gcc or llvm, and the response was literally "we decided to 
manually specify LLVM= on the command line so you must always do that 
and we're refusing your two line fix to NOT need to do that". No really: 
https://lkml.iu.edu/2302.2/08170.html

> Warning: this patchset renames CONFIG_BLK_DEV_INITRD (!!!) to CONFIG_INITRAMFS
> and CONFIG_RD_* to CONFIG_INITRAMFS_DECOMPRESS_* (for example,
> CONFIG_RD_GZIP to CONFIG_INITRAMFS_DECOMPRESS_GZIP).
> If you still use initrd, see below for workaround.

Which will break existing configs for what benefit?

I'm not convinced the churn improves matters. Presumably the kernel 
command line paremeter is still rdinit= and grub still uses the "initrd" 
command to load an external cpio.gz.

But I bisect to find breakage like that every release so I assume the 
other embedded linux developers... are mostly shipping 10+ year old 
kernels that use half the memory of today's.

> Details
> ====
> I not only removed initrd, I also removed a lot of code, which
> became dead, including a lot of code in arch/.
> 
> Still I think the only two architectures I touched in non-trivial
> way are sh and 32-bit arm.
> 
> Also I renamed some files, functions and variables (which became misnomers) to proper names,
> moved some code around, removed a lot of mentions of initrd
> in code and comments. Also I cleaned up some docs.

Now that lkml.iu.edu is back up (yay!) all the links in 
ramfs-rootfs-initramfs.txt can theoretically be fixed just by switching 
the domain name.

> For example, I renamed the following global variables:
> 
> __initramfs_start
> __initramfs_size

That already said initramfs, and you renamed it.

> phys_initrd_start
> phys_initrd_size
> initrd_start
> initrd_end

Which is data delivered through grub's "initrd" command. Here's how I've 
been explaining it to people for years:

1) initrd is the external blob from the bootloader's initrd= option.

2) initramfs is the extractor plumbing, _init code that gets discarded.

3) rootfs is (for some reason) the name of the mounted filesystem in 
/proc/mounts (because letting it say "ramfs" or "tmpfs" like normal in 
/proc/mounts would be consistent and immediately understandable, so they 
couldn't have that).

(No I don't know why it's called rootfs. Having things like df not show 
overmounted filesystems isn't special case logic, why...? The argument 
to special case this because you can't unmount it is like saying PID 1 
shouldn't have a number because it can't exit. I would happily call the 
whole thing initramfs... but it's already not.)

> to:
> 
> __builtin_initramfs_start
> __builtin_initramfs_size
> phys_external_initramfs_start
> phys_external_initramfs_size
> virt_external_initramfs_start
> virt_external_initramfs_end

Do you believe people will understand what the slightly longer names are 
without looking them up?

I'm all for removing obsolete code, but a partial cleanup that still 
leaves various sharp edges around isn't necessarily a net improvement. 
Did you remove the NFS mount code from init/do_mounts.c? Part of the 
initramfs justification back in 2005 was "you can have a tiny initramfs 
set up our root filesystem so most of the init special casing can go"... 
and then they added CONFIG_DEVTMPFS_MOUNT but made it ONLY apply to the 
fallback root after the system has decided NOT to stay on rootfs, and 
ignored my patches to at least make it consistent.

The one config symbol that really seems to bite people in this area is 
BLK_DEV_INITRD because a common thing people running from initramfs want 
to do is yank the block layer entirely (CONFIG_BLOCK=n) and use 
initramfs instead, and needing to enable CONFIG_BLK_DEV_INITRD while

And the INSANE part is they generally want a static initrd to do it so 
they're not using the external loader, but Kconfig has INITRAMFS_SOURCE 
under CONFIG_BLK_DEV_INITRD and it's a mess. Renaming THAT symbol would 
be good.

But then, CONFIG_BLOCK is hidden under CONFIG_EXPERT which selects 
DEBUG_KERNEL (INCREASING KERNEL SIZE!!!) and thus everybody who does 
this patches the kconfig plumbing to be less stupid anyway. So the 
problem isn't JUST renaming the symbol...

(Oh CONFIG_EXPERT is SO STUPID. It's got a menu under it, but 
CONFIG_BLOCK isn't in that menu, it's at the top of menuconfig between 
loadable module support and executable file formats, just invisible 
unless you go down into a menu and switch on a setting and then back out 
to go find it. WHY WOULD YOU DO THAT?)

> New names precisely capture meaning of these variables.

To you. I'm not entirely sure what virt_external means. (Yes I could go 
read the code. No I don't want to. I EXPECT to need context and 
refreshing stuff, but having it change out from under me since the LAST 
time I did that is annoying when it's "same thing, new name, because".)

It makes more sense to YOU because you changed it to smell like you. 
Meanwhile 35 years of installed base expertise in other people's heads 
has been discarded and developed version skew for anyone maintaining an 
existing system. (That's not a "never do this", that's a "be aware 
humans consistently have the wrong weightings in our heads for this".)

Personally I usually have to look it up either way. And am spending more 
and more of my time poking at older kernels rather because newer stuff 
has either removed support for things I need or grown dependencies. (And 
because there's 20 years of installed base still in various stages of 
use, I'm personally likely to spend more time looking at the old names 
than the new ones.)

> This will break all configs out there (update your configs!).
> Still I think this is okay,

Because you don't have to clean up after it.

> because config names never were part of stable API.

I can forward everyone who asks me questions to you, or just agree when 
they tell me it's yet another reason not to upgrade.

> Other user-visible changes:
> 
> - Removed kernel command line parameters "load_ramdisk" and
> "prompt_ramdisk", which did nothing and were deprecated

Sure.

> - Removed kernel command line parameter "ramdisk_start",
> which was used for initrd only (not for initramfs)

Some bootloaders appended that to the kernel command line to specify 
where in memory they've loaded the initrd image, which could be a 
cpio.gz once upon a time. No idea what regressions happened since though.

(Last new bootloader I was involved with that had to make it work used 
some horrible hack editing a dtb at a fixed offset, like the old "rdev" 
trick but more brittle. Because "device tree better" than human readable 
textual mechanism. Fixing ramdisk_start to work right sounded like a 
more sane approach to me, but...)

> I tested my patchset on many architectures in Qemu using my Rust
> program, heavily based on mkroot [1].

You rewrote a 400 line bash script in rust.

Yeah, that's a rust developer. (And it smells like you now...)

> I used the following cross-compilers:
> 
> aarch64-linux-musleabi
> armv4l-linux-musleabihf
> armv5l-linux-musleabihf
> armv7l-linux-musleabihf
> i486-linux-musl
> i686-linux-musl
> mips-linux-musl
> mips64-linux-musl
> mipsel-linux-musl
> powerpc-linux-musl
> powerpc64-linux-musl
> powerpc64le-linux-musl
> riscv32-linux-musl
> riscv64-linux-musl
> s390x-linux-musl
> sh4-linux-musl
> sh4eb-linux-musl
> x86_64-linux-musl

or1k and microblaze work, they just don't pass the full smoketest for 
reasons that shouldn't affect initramfs testing.

I'm still waiting for Rich to ship the next musl release to do new 
toolchains...

https://www.openwall.com/lists/musl/2025/08/04/1

> Workaround
> ====
> If "retain_initrd" is passed to kernel, then initramfs/initrd,
> passed by bootloader, is retained and becomes available after boot
> as read-only magic file /sys/firmware/initrd [3].

Common use case for eg romfs is memory mapped flash or rom, so the 
address range in question isn't actually ram anyway. Mostly on mmu 
systems you just don't want the mapping to go away, so the kernel can 
still reach out and read it.

> This is even better than classic initrd, because:
> - You can use fs not supported by classic initrd, for example erofs

Network block device was the most recent one I saw used, but it had a 
tiny initramfs to set up and switch_root into it...

(Network block device != network filesystem. I have a todo item to 
integrate nbd-server into mkroot/testroot.sh but "-hda works" is one of 
the things it's testing...)

> - One copy is involved (from /sys/firmware/initrd to some file in /)
> as opposed to two when using classic initrd

Embedded developers have always been reaching out and using mappable 
flash directly. Vitaly Wool's ELC talk in 2015 (about running Linux in 
256k of sram, yes one quarter of one megabyte) described the process:

https://elinux.org/images/9/90/Linux_for_Microcontrollers-_From_Marginal_to_Mainstream.pdf

Rob

Re: [PATCH 00/62] initrd: remove classic initrd support

[Dave Young]

Hi,

On Sat, 13 Sept 2025 at 06:42, Askar Safin <safinaskar@zohomail.com> wrote:
>
> Intro
> ====
> This patchset removes classic initrd (initial RAM disk) support,
> which was deprecated in 2020.
> Initramfs still stays, and RAM disk itself (brd) still stays, too.

There is one initrd use case in my mind, it can be extended to co-work
with overlayfs as a kernel built-in solution for initrd(compressed fs
image)+overlayfs.   Currently we can use compressed fs images
(squashfs or erofs) within initramfs,  and kernel loop mount together
with overlayfs, this works fine but extra pre-mount phase is needed.

Thanks
Dave

Re: [PATCH 00/62] initrd: remove classic initrd support

[Andy Lutomirski]

On Mon, Sep 15, 2025 at 10:09 AM Rob Landley <rob@landley.net> wrote:

> While you're at it, could you fix static/builtin initramfs so PID 1 has
> a valid stdin/stdout/stderr?
>
> A static initramfs won't create /dev/console if the embedded initramfs
> image doesn't contain it, which a non-root build can't mknod, so the
> kernel plumbing won't see it dev in the directory we point it at unless
> we build with root access.

I have no current insight as to whether there's a kernel issue here,
but why are you trying to put actual device nodes in an actual
filesystem as part of a build process?  It's extremely straightforward
to emit devices nodes in cpio format, and IMO it's far *more*
straightforward to do that than to make a whole directory, try to get
all the modes right, and cpio it up.

I wrote an absolutely trivial tool for this several years ago:

https://github.com/amluto/virtme/blob/master/virtme/cpiowriter.py

it would be barely more complicated to strip the trailer off an cpio
file from some other source, add some device nodes, and stick the
trailer back on.  But it's also really, really, really easy to emit an
entire, functioning cpio-formatted initramfs from plain user code with
no filesystem manipulation at all.  This also makes that portion of
the build reproducible, which is worth quite a bit IMO.

--Andy