Call xbc_prepend_embedded_cmdline() in setup_arch() right after the
CONFIG_CMDLINE merge and before strscpy(command_line, ...) so the
build-time-rendered embedded bootconfig "kernel" subtree is part of
boot_command_line by the time parse_early_param() runs. early_param()
handlers (mem=, earlycon=, loglevel=, ...) now see values supplied via
CONFIG_BOOT_CONFIG_EMBED_FILE without parsing bootconfig at runtime.

Gate the prepend on the same opt-in the runtime parser uses: prepend
when "bootconfig" is present on the command line, or when
CONFIG_BOOT_CONFIG_FORCE is set. Detect it with parse_args(), exactly
as setup_boot_config() does, so both agree on what counts as opt-in:
any "bootconfig" key regardless of value (bare, =0, =1, ...), and only
before the "--" that separates init arguments. Sharing the parser keeps
the early and late paths from diverging -- e.g. "bootconfig=0" or a
"-- bootconfig" meant for init must not apply the embedded keys early
while the runtime parser skips them.

The prepend necessarily runs before setup_boot_config() detects an
initrd bootconfig, so an initrd cannot override the embedded "kernel"
keys for early_param(). This is intentional: the embedded cmdline acts
like a build-time CONFIG_CMDLINE. An initrd bootconfig's "kernel" keys
never reached early_param() anyway (they apply late via
extra_command_line), so nothing is lost -- the initrd keys still apply
late, with last-wins keeping the embedded values in effect.

Signed-off-by: Breno Leitao <[email protected]>
---
 arch/x86/Kconfig        |  1 +
 arch/x86/kernel/setup.c | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0de23e6471973..8ab11199c16d5 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -127,6 +127,7 @@ config X86
        select ARCH_SUPPORTS_NUMA_BALANCING     if X86_64
        select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP       if NR_CPUS <= 4096
        select ARCH_SUPPORTS_CFI                if X86_64
+       select ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG
        select ARCH_USES_CFI_TRAPS              if X86_64 && CFI
        select ARCH_SUPPORTS_LTO_CLANG
        select ARCH_SUPPORTS_LTO_CLANG_THIN
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 46882ce79c3a4..88b055a46591e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -6,6 +6,7 @@
  * parts of early kernel initialization.
  */
 #include <linux/acpi.h>
+#include <linux/bootconfig.h>
 #include <linux/console.h>
 #include <linux/cpu.h>
 #include <linux/crash_dump.h>
@@ -880,7 +881,6 @@ static void __init x86_report_nx(void)
  *
  * Note: On x86_64, fixmaps are ready for use even before this is called.
  */
-
 void __init setup_arch(char **cmdline_p)
 {
 #ifdef CONFIG_X86_32
@@ -924,6 +924,18 @@ void __init setup_arch(char **cmdline_p)
        builtin_cmdline_added = true;
 #endif
 
+#ifdef CONFIG_CMDLINE_FROM_BOOTCONFIG
+       /*
+        * Prepend the build-time-rendered embedded "kernel" keys here so
+        * parse_early_param() below sees them, using the same opt-in as the
+        * runtime parser, plus the build-time CONFIG_BOOT_CONFIG_FORCE.
+        */
+       if (bootconfig_cmdline_requested(boot_command_line, NULL) ||
+           IS_ENABLED(CONFIG_BOOT_CONFIG_FORCE))
+               xbc_prepend_embedded_cmdline(boot_command_line,
+                                            COMMAND_LINE_SIZE);
+#endif
+
        strscpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
        *cmdline_p = command_line;
 

-- 
2.53.0-Meta


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