From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BCBE6383C64; Tue, 9 Jun 2026 10:29:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781000942; cv=none; b=OmOoa4AIHvS3puquS73rU0xyLkyw0xd7Ra8D4lohYXHMzWZ61tfSIHdqhmDCkQRsquRBavKLvCSptABzLy4+cxKWh3L7ln+Myxc1BUui4ur4h2hgd0DqBn/qeRH7P8QFE2xuq+RqFqYLJaOeJHDRXHTUuEhVfmuFbHoPZGTd1FU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781000942; c=relaxed/simple; bh=1ISezvUOEgU2pm986SsP3ClobBmK+QblMQxp05eH3GA=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Esr7oN5o7ZZySAjTaUbKz2LrVeX4xSA2sGqcm/851l2Y4+iLe7MkN1aFa9ZAtSNXB71I4q4KzMj9iZUSSXTpJRBYlUC5E68C7fI2akDjHSjX9wPaEoC/go0XncbvH3ARf4POKK4Swa/+4uPMwHcRxb3+CZC00r8KLdKKd9fAcPc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org; spf=pass smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=FiSNxecz; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="FiSNxecz" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:Cc:To:In-Reply-To:References: Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description; bh=36MgmjwpSwvq2U+WRVOVhS75+Nlqig+N/ywyMKbbX24=; b=FiSNxeczkauNWO8maeu5IqIkEg 2A6MPPI5ZVP6etuPIzKRmpMh6b7jY2yst9ueYUORWHNbkbHuil1XlGjxWpjljcBhNd4p78jgENmJX wRJ3EzakGu6QoBKOuIEbT0/3/ZzvZO4DUQG5mRslim/p9IWSX2nIeBEohl68DaBmk/Q+EUSbHPYBL ofEuIyS3F1E93ZoFpGCj6GWwwB4KFikpIQ2ulC1BqT42+Ocoe+62KfeEtCO8jdDwXKoXpmXdS92Zq 1VqTGubpAzKziHP3Kt/2uNk83QCOwqH5LXYseS1toJtcRrakTpp540j0j1a820uQcajHaydCDIzDU PiDNYA2Q==; Received: from authenticated-user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1wWthV-008KsF-28; Tue, 09 Jun 2026 10:28:54 +0000 From: Breno Leitao Date: Tue, 09 Jun 2026 03:28:30 -0700 Subject: [PATCH v4 3/7] bootconfig: render embedded bootconfig as a kernel cmdline at build time Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260609-bootconfig_using_tools-v4-3-73c463f03a97@debian.org> References: <20260609-bootconfig_using_tools-v4-0-73c463f03a97@debian.org> In-Reply-To: <20260609-bootconfig_using_tools-v4-0-73c463f03a97@debian.org> To: Masami Hiramatsu , Andrew Morton , Nathan Chancellor , paulmck@kernel.org, Nicolas Schier Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, bpf@vger.kernel.org, Breno Leitao , kernel-team@meta.com X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=9520; i=leitao@debian.org; h=from:subject:message-id; bh=1ISezvUOEgU2pm986SsP3ClobBmK+QblMQxp05eH3GA=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBqJ+rRLXzVTZh5FrAsvuvUFhApYTSJN0nhpsOGq wqw6nkQkNmJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCaifq0QAKCRA1o5Of/Hh3 bb91EACXl0DlZWXrjvEGAbv9Lu5n2Qt+P1ghnoMaLdFstW/w3ORHX2hYNC32wbvhwm0fg8qzRFv HLY7GJYFm9RpKUeC7Q6Jhg/fivZ1ZO38RIkfjlmUb7saAIrGso9iMEH2VbIAO334foa8+bv8kjg NEzVjLVgN3GREkZSSBUau2SsUKR7JY5tEEv6C9d6pwSzOPIrNCD8LNG0SdcNeyAJBvswCqCWTdV KvMOpeJ5wy5hcDp/VHS55+l0yRi+9A1tvJT6WIeJeR4jhqJcsBzMp+H5d7epvg7+sV2xOpiVNaH sF5BcGfjKWmng4MJ3ri8d4D7j+i8J7Mwrxyzu35j6So8ckDWSv3kxYiOrM127eprLoilo1IMlST gDxu31d3XgUdRZkjpwu1g/JfTvWyXEQP/wL+Ga8VgbOK/PMxnxztLrJ4xzLVxLixJY7iZS6aPAT dZFRbWqMBZ4eRiTt5grURYImx/2yBu29M8Mj0iwChV0l8aVw6WBdYVTKOMSYKfue0jHvUt5emFm ktUHpQDU88LAaZqOl4i8gkGkFjy+OnsfN7/N10JmDPV3l2kY8n+z28oBHK/it750D/sDh2XAwMY GWLUOf3P+qxikpmQwsDbeHQpn4bPP/TYd4DSd+Z0Pwz5HK46CLQb1wlzv0q4OAUVtsao9v5kuYg T2H+8k5X/PXmUMw== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Debian-User: leitao Add the build-time pipeline that renders the "kernel" subtree of CONFIG_BOOT_CONFIG_EMBED_FILE into a flat cmdline string and stashes it in .init.rodata as embedded_kernel_cmdline[]. A follow-up patch adds the runtime helper that prepends this string to boot_command_line during early architecture setup so parse_early_param() sees the values. The build wires up: tools/bootconfig -C kernel - userspace tool already shared with lib/bootconfig.c, used here in -C mode to render a bootconfig file to a cmdline lib/embedded-cmdline.S - .incbin's the rendered text plus a NUL (listed under the EXTRA BOOT CONFIG MAINTAINERS entry) lib/Makefile rule - runs tools/bootconfig at build time Makefile prepare dep - ensures tools/bootconfig is built first, same pattern as tools/objtool and tools/bpf/resolve_btfids Drop the test target from tools/bootconfig/Makefile's default 'all' recipe so that hooking the binary into the kernel build does not run test-bootconfig.sh on every prepare. The tests stay available as 'make -C tools/bootconfig test', matching the convention of tools/objtool and tools/bpf/resolve_btfids whose 'all' targets only build the binary. Require BOOT_CONFIG_EMBED_FILE to be non-empty before the new option can be enabled, otherwise tools/bootconfig -C runs against an empty file and prints a parse error on every kernel build. The feature gates on CONFIG_ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG, a silent symbol arches select once they've wired the prepend call into setup_arch(). No arch selects it in this patch, so the user-visible CONFIG_BOOT_CONFIG_EMBED_CMDLINE is not yet enableable; when an arch later opts in, the runtime behavior is added by the follow-up patches. tools/bootconfig also installs on target systems, so its own Makefile keeps $(CC) and stays cross-buildable as a standalone tool. The kernel build, which runs the tool on the build host during prepare, instead forces CC=$(HOSTCC) from a dedicated tools/bootconfig rule and clears CROSS_COMPILE= in the sub-make. Without that clear, an LLVM=1 cross build would inherit CROSS_COMPILE and tools/scripts/Makefile.include would inject --target=/--sysroot= flags into the host clang invocation, producing a target binary that fails to exec ("Exec format error"). embedded-cmdline.S places the rendered string in its own .init.rodata subsection (.init.rodata.embed_cmdline) with the "a" (allocatable, read-only) flag and %progbits. lib/bootconfig-data.S already places the embedded bootconfig blob in .init.rodata with the "aw" flag (xbc_init() rewrites separators in place, so that data must be writable). Using a distinct subsection name avoids the ld.lld section- type mismatch that would otherwise arise from mixing "a" and "aw" under the same name; the linker's "*(.init.rodata .init.rodata.*)" glob still folds both into the init image and frees them after boot. A follow-up patch wires the build-time tools/bootconfig into the top-level clean target. Signed-off-by: Breno Leitao --- MAINTAINERS | 1 + Makefile | 15 +++++++++++++++ init/Kconfig | 36 ++++++++++++++++++++++++++++++++++++ lib/Makefile | 16 ++++++++++++++++ lib/embedded-cmdline.S | 16 ++++++++++++++++ tools/bootconfig/Makefile | 2 +- 6 files changed, 85 insertions(+), 1 deletion(-) diff --git a/MAINTAINERS b/MAINTAINERS index 57656ec0e9d5..953231df1911 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9844,6 +9844,7 @@ F: fs/proc/bootconfig.c F: include/linux/bootconfig.h F: lib/bootconfig-data.S F: lib/bootconfig.c +F: lib/embedded-cmdline.S F: tools/bootconfig/* F: tools/bootconfig/scripts/* diff --git a/Makefile b/Makefile index bf196c6df5b9..a7abb3f9a626 100644 --- a/Makefile +++ b/Makefile @@ -1545,6 +1545,21 @@ prepare: tools/bpf/resolve_btfids endif endif +# tools/bootconfig renders the embedded bootconfig into a cmdline at build time. +ifdef CONFIG_BOOT_CONFIG_EMBED_CMDLINE +prepare: tools/bootconfig +endif + +# tools/bootconfig is run on the build host during prepare, so force a host +# binary here; its own Makefile keeps $(CC) for standalone and cross builds. +# CROSS_COMPILE= is cleared so tools/scripts/Makefile.include does not inject +# the target's --target=/--sysroot= flags into the host clang invocation under +# LLVM=1 cross builds (which would produce a target binary that fails to exec). +tools/bootconfig: FORCE + $(Q)mkdir -p $(objtree)/tools + $(Q)$(MAKE) O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ \ + bootconfig CC=$(HOSTCC) CROSS_COMPILE= + # The tools build system is not a part of Kbuild and tends to introduce # its own unique issues. If you need to integrate a new tool into Kbuild, # please consider locating that tool outside the tools/ tree and using the diff --git a/init/Kconfig b/init/Kconfig index 5230d4879b1c..743f54397190 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1566,6 +1566,42 @@ config BOOT_CONFIG_EMBED_FILE This bootconfig will be used if there is no initrd or no other bootconfig in the initrd. +config ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG + bool + help + Silent symbol; no C code reads it directly. Architectures + select it once their setup_arch() calls + xbc_prepend_embedded_cmdline() before parse_early_param(). + Its only role is to gate the user-visible + BOOT_CONFIG_EMBED_CMDLINE option per-arch, the same + ARCH_SUPPORTS_* idiom used by ARCH_SUPPORTS_CFI, etc. + +config BOOT_CONFIG_EMBED_CMDLINE + bool "Render embedded bootconfig as kernel cmdline at build time" + depends on BOOT_CONFIG_EMBED + depends on BOOT_CONFIG_EMBED_FILE != "" + depends on ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG + default n + help + Render the "kernel" subtree of the embedded bootconfig file into a + flat cmdline string at kernel build time and prepend it to + boot_command_line during early architecture setup. This makes + early_param() handlers (e.g. mem=, earlycon=, loglevel=) see the + values supplied via the embedded bootconfig. + + The runtime bootconfig parser is unaffected, so tree-structured + consumers such as ftrace boot-time tracing keep working. + + Note: when an initrd also carries a bootconfig, its "kernel" + subtree is still parsed at runtime, but the embedded "kernel" + keys remain in boot_command_line for parse_early_param() and + end up later than the initrd keys in saved_command_line, so + parse_args() last-wins favors the embedded values. If you need + initrd to override embedded kernel.* keys, leave this option + off. + + If unsure, say N. + config CMDLINE_LOG_WRAP_IDEAL_LEN int "Length to try to wrap the cmdline when logged at boot" default 1021 diff --git a/lib/Makefile b/lib/Makefile index 7f75cc6edf94..4ace86a5cb6d 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -273,6 +273,22 @@ filechk_defbconf = cat $(or $(real-prereqs), /dev/null) $(obj)/default.bconf: $(CONFIG_BOOT_CONFIG_EMBED_FILE) FORCE $(call filechk,defbconf) +obj-$(CONFIG_BOOT_CONFIG_EMBED_CMDLINE) += embedded-cmdline.o +$(obj)/embedded-cmdline.o: $(obj)/embedded_cmdline.bin + +# Render the bootconfig "kernel" subtree to a flat cmdline string using +# the userspace tools/bootconfig parser (-C mode). The runtime prepend +# helper enforces COMMAND_LINE_SIZE at boot, so no build-time size +# check is performed here (COMMAND_LINE_SIZE is an arch header +# constant, not a Kconfig value). +quiet_cmd_render_cmdline = BCONF2C $@ + cmd_render_cmdline = \ + $(objtree)/tools/bootconfig/bootconfig -C $< > $@ + +targets += embedded_cmdline.bin +$(obj)/embedded_cmdline.bin: $(obj)/default.bconf $(objtree)/tools/bootconfig/bootconfig FORCE + $(call if_changed,render_cmdline) + obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o diff --git a/lib/embedded-cmdline.S b/lib/embedded-cmdline.S new file mode 100644 index 000000000000..bda81b4a42be --- /dev/null +++ b/lib/embedded-cmdline.S @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Embed the build-time-rendered bootconfig "kernel" subtree as a flat + * cmdline string. setup_arch() prepends this to boot_command_line on + * architectures that select ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG. + * + * Copyright (c) 2026 Meta Platforms, Inc. and affiliates + * Copyright (c) 2026 Breno Leitao + */ + .section .init.rodata.embed_cmdline, "a", %progbits + .global embedded_kernel_cmdline +embedded_kernel_cmdline: + .incbin "lib/embedded_cmdline.bin" + .byte 0 + .global embedded_kernel_cmdline_end +embedded_kernel_cmdline_end: diff --git a/tools/bootconfig/Makefile b/tools/bootconfig/Makefile index 90eb47c9d8de..4e82fd9553cd 100644 --- a/tools/bootconfig/Makefile +++ b/tools/bootconfig/Makefile @@ -15,7 +15,7 @@ override CFLAGS += -Wall -g -I$(CURDIR)/include ALL_TARGETS := bootconfig ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS)) -all: $(ALL_PROGRAMS) test +all: $(ALL_PROGRAMS) $(OUTPUT)bootconfig: main.c include/linux/bootconfig.h $(LIBSRC) $(CC) $(filter %.c,$^) $(CFLAGS) $(LDFLAGS) -o $@ -- 2.53.0-Meta