On Mon, 08 Jun 2026 09:23:57 -0700
Breno Leitao [off-list ref] wrote:
The userspace pieces (xbc_snprint_cmdline() in lib/, tools/bootconfig -C)
already landed; this series wires the rendered cmdline into the kernel.
Motivation: today the embedded bootconfig is parsed at runtime, after
parse_early_param() has already run, so early_param() handlers can't
see embedded values. Folding the kernel.* subtree into the cmdline at
build time gives a CONFIG_CMDLINE-equivalent for embedded-bootconfig
users without forcing them to maintain two cmdline sources.
Behaviorally, the "kernel" subtree is rendered to a flat string at
build time and stashed in .init.rodata. setup_arch() prepends it to
boot_command_line before parse_early_param() runs. Overflow is a soft
error: the helper logs and leaves boot_command_line untouched rather
than panicking, so an oversized embedded bconf cannot brick a boot.
Sashiko still leaves some comments.
https://sashiko.dev/#/patchset/20260608-bootconfig_using_tools-v3-0-4ddd079a0696%40debian.org
BTW, can you also update the document (Documentation/admin-guide/bootconfig.rst)
about what is the expected behavior of this feature (kconfigs, examples)?
Thank you,
Signed-off-by: Breno Leitao <leitao@debian.org>
---
Changes in v3:
- Patch 3: Move HOSTCC override to the kernel-side rule; tool keeps
$(CC) for standalone/cross builds.
- Patch 6: Drop the false fail-safe wording; document the
BOOT_CONFIG_FORCE=y default interaction.
- Link to v2:
https://lore.kernel.org/r/20260605-bootconfig_using_tools-v2-0-d309f544b5f7@debian.org (local)
Changes in v2 (addressing review of v1):
- Split out a standalone fix for the NULL-pointer arithmetic in
xbc_snprint_cmdline() so the build-time render cannot trip host
UBSan/FORTIFY_SOURCE.
- Rework the leaf-root handling: instead of returning early, skip @root
inside the loop so a root carrying both a value and subkeys
(kernel = x together with kernel.foo = bar) still renders its
descendant keys.
- Build tools/bootconfig with $(HOSTCC) so cross-compiled (ARCH=...)
builds render the cmdline on the build host instead of failing with
"Exec format error".
- Mark the embedded cmdline section read-only (drop the "w" flag from
.init.rodata).
- Add a make-clean hook so tools/bootconfig artifacts are removed by
make clean.
- Gate the x86 prepend on "bootconfig" being present on the command
line (or CONFIG_BOOT_CONFIG_FORCE), matching the init.* opt-in
semantics documented in bootconfig.rst and preserving fail-safe
recovery: dropping "bootconfig" from the bootloader cmdline now also
disables the embedded kernel.* keys.
- Link to v1: https://patch.msgid.link/20260527-bootconfig_using_tools-v1-0-b6906a86e7d5@debian.org (local)
---
Breno Leitao (6):
bootconfig: fix NULL-pointer arithmetic in xbc_snprint_cmdline()
bootconfig: render descendant keys when xbc_snprint_cmdline() root has a value
bootconfig: render embedded bootconfig as a kernel cmdline at build time
bootconfig: clean build-time tools/bootconfig from make clean
bootconfig: add xbc_prepend_embedded_cmdline() helper
x86/setup: prepend embedded bootconfig cmdline before parse_early_param
MAINTAINERS | 1 +
Makefile | 24 +++++++++-
arch/x86/Kconfig | 1 +
arch/x86/kernel/setup.c | 16 +++++++
include/linux/bootconfig.h | 9 ++++
init/Kconfig | 36 +++++++++++++++
init/main.c | 25 ++++++++--
lib/Makefile | 16 +++++++
lib/bootconfig.c | 112 ++++++++++++++++++++++++++++++++++++++++++---
lib/embedded-cmdline.S | 16 +++++++
tools/bootconfig/Makefile | 4 +-
11 files changed, 247 insertions(+), 13 deletions(-)
---
base-commit: e7e28506af98ce4e1059e5ec59334b335c00a246
change-id: 20260508-bootconfig_using_tools-cfa7aa9d6a5a
Best regards,
--
Breno Leitao [off-list ref]
--
Masami Hiramatsu (Google) [off-list ref]