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Date: Mon, 28 Mar 2022 20:16:22 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Padmanabha Srinivasaiah <treasure4paddy@...il.com>,
LKML <linux-kernel@...r.kernel.org>,
Jonathan Corbet <corbet@....net>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
Randy Dunlap <rdunlap@...radead.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Sami Tolvanen <samitolvanen@...gle.com>,
Nathan Chancellor <nathan@...nel.org>, llvm@...ts.linux.dev,
Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v4 2/3] bootconfig: Support embedding a bootconfig file
in kernel
On Mon, 28 Mar 2022 15:27:43 +0900
Masahiro Yamada <masahiroy@...nel.org> wrote:
> On Sun, Mar 27, 2022 at 8:53 AM Masami Hiramatsu <mhiramat@...nel.org> wrote:
> >
> > 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_EMBED_BOOT_CONFIG=y and set
> > the file path to CONFIG_EMBED_BOOT_CONFIG_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.
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > ---
> > Changes in v3:
> > - Avoid updating the default.bconf if the file is not changed.
> > ---
> > include/linux/bootconfig.h | 10 ++++++++++
> > init/Kconfig | 21 +++++++++++++++++++++
> > init/main.c | 13 ++++++++-----
> > lib/.gitignore | 1 +
> > lib/Makefile | 10 ++++++++++
> > lib/bootconfig.c | 23 +++++++++++++++++++++++
> > 6 files changed, 73 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
> > index a4665c7ab07c..5dbda5e3e9bb 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_EMBED_BOOT_CONFIG
> > +char * __init xbc_get_embedded_bootconfig(size_t *size);
> > +#else
> > +static inline char *xbc_get_embedded_bootconfig(size_t *size)
> > +{
> > + return NULL;
> > +}
> > +#endif
> > +
> > #endif
> > diff --git a/init/Kconfig b/init/Kconfig
> > index beb5b866c318..bff308a782f8 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1357,6 +1357,27 @@ config BOOT_CONFIG
> >
> > If unsure, say Y.
> >
> > +config EMBED_BOOT_CONFIG
> > + bool "Embed bootconfig file in the kernel"
> > + depends on BOOT_CONFIG
> > + default n
> > + help
> > + Embed a bootconfig file given by EMBED_BOOT_CONFIG_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 EMBED_BOOT_CONFIG_FILE
> > + string "Embedded bootconfig file path"
> > + default ""
> > + depends on EMBED_BOOT_CONFIG
> > + 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 4f3ba3b84e34..180511324c95 100644
> > --- a/init/main.c
> > +++ b/init/main.c
> > @@ -265,7 +265,7 @@ 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;
> > @@ -411,12 +411,15 @@ static void __init setup_boot_config(void)
> > static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
> > const char *msg;
> > int pos;
> > - u32 size;
> > + size_t size;
> > char *data, *err;
> > int ret;
> >
> > /* 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,
> > @@ -435,8 +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;
> > }
> >
> > @@ -449,7 +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..30a2a5db7033 100644
> > --- a/lib/.gitignore
> > +++ b/lib/.gitignore
> > @@ -6,3 +6,4 @@
> > /oid_registry_data.c
> > /test_fortify.log
> > /test_fortify/*.log
> > +/default.bconf
>
>
> I think lib/.gitignore is alphabetically sorted.
>
> Please insert the new one
> to the proper line.
Ah, OK. Let me fix that.
> > diff --git a/lib/Makefile b/lib/Makefile
> > index 353bc09ce38d..dd9f3ebb62ca 100644
> > --- a/lib/Makefile
> > +++ b/lib/Makefile
> > @@ -276,6 +276,16 @@ $(foreach file, $(libfdt_files), \
> > $(eval CFLAGS_$(file) = -I $(srctree)/scripts/dtc/libfdt))
> > lib-$(CONFIG_LIBFDT) += $(libfdt_files)
> >
> > +ifeq ($(CONFIG_EMBED_BOOT_CONFIG),y)
> > +$(obj)/bootconfig.o: $(obj)/default.bconf
> > +
> > +targets += default.bconf
>
>
> I did not test this patch, but presumably
> "make clean" will miss to clean up default.bconf
>
> The 'targets' must exist outside the ifeq-block.
> Move the 'endif' up.
>
>
> ifeq ($(CONFIG_EMBED_BOOT_CONFIG),y)
> $(obj)/bootconfig.o: $(obj)/default.bconf
> endif
>
> targets += default.bconf
>
> ...
You're right! I didn't know this behavior. Thanks for the notice.
I misunderstood that the files in targets always be built...
After moving the 'targets' out of ifeq-block, I confirmed that the
default.bconf was not generated when CONFIG_EMBED_BOOT_CONFIG is not
set, and it is cleaned up when CONFIG_EMBED_BOOT_CONFIG=y.
Thanks!
>
> > +filechk_defbconf = cat /dev/null $(CONFIG_EMBED_BOOT_CONFIG_FILE)
> > +$(obj)/default.bconf: FORCE
> > + $(call filechk,defbconf)
>
>
> This will work, but users will be confused when they
> try to build out-of-tree with the O= option.
>
> If CONFIG_EMBED_BOOT_CONFIG_FILE is a relative path,
> it is actually relative to the object tree, not the source tree.
Yes, that's right. I would like to fix this issue.
> I am not sure if that is the expected behavior, but it is not documented
> anywhere.
>
>
> If you want to search both in the objtree and srctree,
> you can write like follows: [UNTESTED]
>
>
> filechk_defbconf = cat $(or $(real-prereqs), /dev/null)
> $(obj)/default.bconf: $(CONFIG_EMBED_BOOT_CONFIG_FILE) FORCE
> $(call filechk,defbconf)
Great! let me check it works.
Thank you,
>
>
>
>
> > +
> > +endif
> > +
> > lib-$(CONFIG_BOOT_CONFIG) += bootconfig.o
> >
> > obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o
> > diff --git a/lib/bootconfig.c b/lib/bootconfig.c
> > index 74f3201ab8e5..3a3bf3a208e3 100644
> > --- a/lib/bootconfig.c
> > +++ b/lib/bootconfig.c
> > @@ -12,6 +12,29 @@
> > #include <linux/kernel.h>
> > #include <linux/memblock.h>
> > #include <linux/string.h>
> > +
> > +#ifdef CONFIG_EMBED_BOOT_CONFIG
> > +asm (
> > +" .pushsection .init.data, \"aw\" \n"
> > +" .global embedded_bootconfig_data \n"
> > +"embedded_bootconfig_data: \n"
> > +" .incbin \"lib/default.bconf\" \n"
> > +" .global embedded_bootconfig_data_end \n"
> > +"embedded_bootconfig_data_end: \n"
> > +" .popsection \n"
> > +);
> > +
> > +extern __visible char embedded_bootconfig_data[];
> > +extern __visible char embedded_bootconfig_data_end[];
> > +
> > +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
> >
>
>
> --
> Best Regards
> Masahiro Yamada
--
Masami Hiramatsu <mhiramat@...nel.org>
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