bootconfig: Support embedding a bootconfig file in kernel

This allows kernel developer to embed a default bootconfig file in
the kernel instead of embedding it in the initrd. This will be good
for who are using the kernel without initrd, or who needs a default
bootconfigs.
This needs to set two kconfigs: CONFIG_BOOT_CONFIG_EMBED=y and set
the file path to CONFIG_BOOT_CONFIG_EMBED_FILE.

Note that you still need 'bootconfig' command line option to load the
embedded bootconfig. Also if you boot using an initrd with a different
bootconfig, the kernel will use the bootconfig in the initrd, instead
of the default bootconfig.

Link: https://lkml.kernel.org/r/164921227943.1090670.14035119557571329218.stgit@devnote2
Cc: Padmanabha Srinivasaiah <treasure4paddy@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/MAINTAINERS b/MAINTAINERS
index b90535d..abc8e6f 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7457,6 +7457,7 @@ S:        Maintained
 F:     Documentation/admin-guide/bootconfig.rst
 F:     fs/proc/bootconfig.c
 F:     include/linux/bootconfig.h
+F:     lib/bootconfig-data.S
 F:     lib/bootconfig.c
 F:     tools/bootconfig/*
 F:     tools/bootconfig/scripts/*

diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
index a4665c7..1611f9d 100644 (file)
--- a/include/linux/bootconfig.h
+++ b/include/linux/bootconfig.h
@@ -289,4 +289,14 @@ int __init xbc_get_info(int *node_size, size_t *data_size);
 /* XBC cleanup data structures */
 void __init xbc_exit(void);
 
+/* XBC embedded bootconfig data in kernel */
+#ifdef CONFIG_BOOT_CONFIG_EMBED
+const char * __init xbc_get_embedded_bootconfig(size_t *size);
+#else
+static inline const char *xbc_get_embedded_bootconfig(size_t *size)
+{
+       return NULL;
+}
+#endif
+
 #endif

diff --git a/init/Kconfig b/init/Kconfig
index ddcbefe..2462d4a 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1351,7 +1351,7 @@ endif
 
 config BOOT_CONFIG
        bool "Boot config support"
-       select BLK_DEV_INITRD
+       select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
        help
          Extra boot config allows system admin to pass a config file as
          complemental extension of kernel cmdline when booting.
@@ -1361,6 +1361,25 @@ config BOOT_CONFIG
 
          If unsure, say Y.
 
+config BOOT_CONFIG_EMBED
+       bool "Embed bootconfig file in the kernel"
+       depends on BOOT_CONFIG
+       help
+         Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
+         kernel. Usually, the bootconfig file is loaded with the initrd
+         image. But if the system doesn't support initrd, this option will
+         help you by embedding a bootconfig file while building the kernel.
+
+         If unsure, say N.
+
+config BOOT_CONFIG_EMBED_FILE
+       string "Embedded bootconfig file path"
+       depends on BOOT_CONFIG_EMBED
+       help
+         Specify a bootconfig file which will be embedded to the kernel.
+         This bootconfig will be used if there is no initrd or no other
+         bootconfig in the initrd.
+
 choice
        prompt "Compiler optimization level"
        default CC_OPTIMIZE_FOR_PERFORMANCE

diff --git a/init/main.c b/init/main.c
index 266d61b..f7fe7cb 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -266,7 +266,7 @@ static int __init loglevel(char *str)
 early_param("loglevel", loglevel);
 
 #ifdef CONFIG_BLK_DEV_INITRD
-static void * __init get_boot_config_from_initrd(u32 *_size)
+static void * __init get_boot_config_from_initrd(size_t *_size)
 {
        u32 size, csum;
        char *data;
@@ -313,7 +313,7 @@ found:
        return data;
 }
 #else
-static void * __init get_boot_config_from_initrd(u32 *_size)
+static void * __init get_boot_config_from_initrd(size_t *_size)
 {
        return NULL;
 }
@@ -410,14 +410,16 @@ static int __init warn_bootconfig(char *str)
 static void __init setup_boot_config(void)
 {
        static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
-       const char *msg;
-       int pos;
-       u32 size;
-       char *data, *err;
-       int ret;
+       const char *msg, *data;
+       int pos, ret;
+       size_t size;
+       char *err;
 
        /* Cut out the bootconfig data even if we have no bootconfig option */
        data = get_boot_config_from_initrd(&size);
+       /* If there is no bootconfig in initrd, try embedded one. */
+       if (!data)
+               data = xbc_get_embedded_bootconfig(&size);
 
        strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
        err = parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
@@ -436,8 +438,8 @@ static void __init setup_boot_config(void)
        }
 
        if (size >= XBC_DATA_MAX) {
-               pr_err("bootconfig size %d greater than max size %d\n",
-                       size, XBC_DATA_MAX);
+               pr_err("bootconfig size %ld greater than max size %d\n",
+                       (long)size, XBC_DATA_MAX);
                return;
        }
 
@@ -450,7 +452,7 @@ static void __init setup_boot_config(void)
                                msg, pos);
        } else {
                xbc_get_info(&ret, NULL);
-               pr_info("Load bootconfig: %d bytes %d nodes\n", size, ret);
+               pr_info("Load bootconfig: %ld bytes %d nodes\n", (long)size, ret);
                /* keys starting with "kernel." are passed via cmdline */
                extra_command_line = xbc_make_cmdline("kernel");
                /* Also, "init." keys are init arguments */

diff --git a/lib/.gitignore b/lib/.gitignore
index e5e217b..54596b6 100644 (file)
--- a/lib/.gitignore
+++ b/lib/.gitignore
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 /crc32table.h
 /crc64table.h
+/default.bconf
 /gen_crc32table
 /gen_crc64table
 /oid_registry_data.c

diff --git a/lib/Makefile b/lib/Makefile
index 08053df..95268d6 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -280,6 +280,14 @@ $(foreach file, $(libfdt_files), \
 lib-$(CONFIG_LIBFDT) += $(libfdt_files)
 
 obj-$(CONFIG_BOOT_CONFIG) += bootconfig.o
+obj-$(CONFIG_BOOT_CONFIG_EMBED) += bootconfig-data.o
+
+$(obj)/bootconfig-data.o: $(obj)/default.bconf
+
+targets += default.bconf
+filechk_defbconf = cat $(or $(real-prereqs), /dev/null)
+$(obj)/default.bconf: $(CONFIG_BOOT_CONFIG_EMBED_FILE) FORCE
+       $(call filechk,defbconf)
 
 obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o
 obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o

diff --git a/lib/bootconfig-data.S b/lib/bootconfig-data.S
new file mode 100644 (file)
index 0000000..ef85ba1
--- /dev/null
+++ b/lib/bootconfig-data.S
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Embed default bootconfig in the kernel.
+ */
+       .section .init.rodata, "aw"
+       .global embedded_bootconfig_data
+embedded_bootconfig_data:
+       .incbin "lib/default.bconf"
+       .global embedded_bootconfig_data_end
+embedded_bootconfig_data_end:

diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index 74f3201..c59d260 100644 (file)
--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -12,6 +12,19 @@
 #include <linux/kernel.h>
 #include <linux/memblock.h>
 #include <linux/string.h>
+
+#ifdef CONFIG_BOOT_CONFIG_EMBED
+/* embedded_bootconfig_data is defined in bootconfig-data.S */
+extern __visible const char embedded_bootconfig_data[];
+extern __visible const char embedded_bootconfig_data_end[];
+
+const char * __init xbc_get_embedded_bootconfig(size_t *size)
+{
+       *size = embedded_bootconfig_data_end - embedded_bootconfig_data;
+       return (*size) ? embedded_bootconfig_data : NULL;
+}
+#endif
+
 #else /* !__KERNEL__ */
 /*
  * NOTE: This is only for tools/bootconfig, because tools/bootconfig will