[for-next][PATCH 12/21] bootconfig: Support embedding a bootconfig file in kernel

Steven Rostedt
2022-04-27T19:39:30Z

From: Masami Hiramatsu <mhiramat@kernel.org>

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>
---
MAINTAINERS | 1 +
include/linux/bootconfig.h | 10 ++++++++++
init/Kconfig | 21 ++++++++++++++++++++-
init/main.c | 22 ++++++++++++----------
lib/.gitignore | 1 +
lib/Makefile | 8 ++++++++
lib/bootconfig-data.S | 10 ++++++++++
lib/bootconfig.c | 13 +++++++++++++
8 files changed, 75 insertions(+), 11 deletions(-)
create mode 100644 lib/bootconfig-data.S

diff --git a/MAINTAINERS b/MAINTAINERS
index b90535d923a0..abc8e6fee21e 100644
--- 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 a4665c7ab07c..1611f9db878e 100644
--- 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 ddcbefe535e9..2462d4ae2dc8 100644
--- 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 266d61bc67b0..f7fe7cbb1df8 100644
--- 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 @@ static void * __init get_boot_config_from_initrd(u32 *_size)
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 e5e217b8307b..54596b634ecb 100644
--- 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 08053df16c7c..95268d6c75b7 100644
--- 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
index 000000000000..ef85ba1a82f4
--- /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 74f3201ab8e5..c59d26068a64 100644
--- 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
--
2.35.1