Re: [PATCH RFC bootconfig] 1/2] fs/proc: Add /proc/cmdline_load for boot loader arguments

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Mon, 14 Aug 2023 16:08:29 -0700
"Paul E. McKenney" <paulmck@kernel.org> wrote:

> On Sat, Aug 12, 2023 at 04:30:41PM -0700, Paul E. McKenney wrote:
> > On Sun, Aug 06, 2023 at 09:39:28PM -0700, Paul E. McKenney wrote:
> > > On Mon, Aug 07, 2023 at 11:44:55AM +0900, Masami Hiramatsu wrote:
> > > > On Fri, 4 Aug 2023 10:36:17 -0700
> > > > "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > > > 
> > > > > On Fri, Aug 04, 2023 at 08:23:20PM +0300, Alexey Dobriyan wrote:
> > > > > > On Thu, Jul 27, 2023 at 08:37:00PM -0700, Paul E. McKenney wrote:
> > > > > > > In kernels built with CONFIG_BOOT_CONFIG_FORCE=y, /proc/cmdline will
> > > > > > > show all kernel boot parameters, both those supplied by the boot loader
> > > > > > > and those embedded in the kernel image.  This works well for those who
> > > > > > > just want to see all of the kernel boot parameters, but is not helpful to
> > > > > > > those who need to see only those parameters supplied by the boot loader.
> > > > > > > This is especially important when these parameters are presented to the
> > > > > > > boot loader by automation that might gather them from diverse sources.
> > > > > > > 
> > > > > > > Therefore, provide a /proc/cmdline_load file that shows only those kernel
> > > > > > > boot parameters supplied by the boot loader.
> > > > > > 
> > > > > > > +static int cmdline_load_proc_show(struct seq_file *m, void *v)
> > > > > > > +{
> > > > > > > +	seq_puts(m, boot_command_line);
> > > > > > > +	seq_putc(m, '\n');
> > > > > > > +	return 0;
> > > > > > > +}
> > > > > > > +
> > > > > > >  static int __init proc_cmdline_init(void)
> > > > > > >  {
> > > > > > >  	struct proc_dir_entry *pde;
> > > > > > > @@ -19,6 +27,11 @@ static int __init proc_cmdline_init(void)
> > > > > > >  	pde = proc_create_single("cmdline", 0, NULL, cmdline_proc_show);
> > > > > > >  	pde_make_permanent(pde);
> > > > > > >  	pde->size = saved_command_line_len + 1;
> > > > > > > +	if (IS_ENABLED(CONFIG_BOOT_CONFIG_FORCE)) {
> > > > > > > +		pde = proc_create_single("cmdline_load", 0, NULL, cmdline_load_proc_show);
> > > > > > > +		pde_make_permanent(pde);
> > > > > > > +		pde->size = strnlen(boot_command_line, COMMAND_LINE_SIZE) + 1;
> > > > > > > +	}
> > > > > > 
> > > > > > Please add it as separate fs/proc/cmdline_load.c file so that name of
> > > > > > the file matches name of the /proc file.
> > > > > 
> > > > > Thank you, will do!
> > > > > 
> > > > > > The name "cmdline_load" is kind of non-descriptive. Mentioning "bootloader"
> > > > > > somewhere should improve things.
> > > > > 
> > > > > If we can all quickly come to agreement on a name, I can of course easily
> > > > > change it.
> > > > > 
> > > > > /proc/cmdline_bootloader?  Better than /proc/cmdline_from_bootloader,
> > > > > I suppose.  /proc/cmdline_bootldr?  /proc/bootloader by analogy with
> > > > > /proc/bootconfig?  Something else?
> > > > 
> > > > What about "/proc/raw_cmdline" ?
> > > 
> > > That would work of me!
> > > 
> > > Any objections to /proc/raw_cmdline?
> > > 
> > > Going once...
> > 
> > Going twice...
> > 
> > If I don't hear otherwise, /proc/raw_cmdline is is on Monday August 14 PDT.
> 
> And gone!
> 
> Please see below for the updated version.

OK, I'll pick this.

Thanks!

> 
> 								Thanx, Paul
> 
> ------------------------------------------------------------------------
> 
> commit 0fe10f0d1873a6f6e287c0c5b45e9203b0e33c83
> Author: Paul E. McKenney <paulmck@kernel.org>
> Date:   Fri Jul 21 16:05:38 2023 -0700
> 
>     fs/proc: Add /proc/raw_cmdline for boot loader arguments
>     
>     In kernels built with CONFIG_BOOT_CONFIG_FORCE=y, /proc/cmdline will
>     show all kernel boot parameters, both those supplied by the boot loader
>     and those embedded in the kernel image.  This works well for those who
>     just want to see all of the kernel boot parameters, but is not helpful to
>     those who need to see only those parameters supplied by the boot loader.
>     This is especially important when these parameters are presented to the
>     boot loader by automation that might gather them from diverse sources.
>     It is also useful when booting the next kernel via kexec(), in which
>     case it is necessary to supply only those kernel command-line arguments
>     from the boot loader, and most definitely not those that were embedded
>     into the current kernel.
>     
>     Therefore, provide a /proc/raw_cmdline file that shows only those kernel
>     boot parameters supplied by the boot loader.
>     
>     Why put this in /proc?  Because it is quite similar to /proc/cmdline,
>     and /proc/bootconfig, so it makes sense to put it in the same place that
>     those files are located.
>     
>     [ sfr: Apply kernel test robot feedback. ]
>     [ paulmck: Apply Randy Dunlap feedback. ]
>     [ paulmck: Apply naming feedback from Alexey Dobriyan and Masami Hiramatsu. ]
>     
>     Co-developed-by: Stephen Rothwell <sfr@canb.auug.org.au>
>     Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
>     Co-developed-by: Arnd Bergmann <arnd@kernel.org>
>     Signed-off-by: Arnd Bergmann <arnd@kernel.org>
>     Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
>     Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>     Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>     Cc: Andrew Morton <akpm@linux-foundation.org>
>     Cc: Alexey Dobriyan <adobriyan@gmail.com>
>     Cc: <linux-fsdevel@vger.kernel.org>
> 
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 75a8c899ebcc..61419270c38f 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -723,6 +723,7 @@ files are there, and which are missing.
>   partitions   Table of partitions known to the system
>   pci 	      Deprecated info of PCI bus (new way -> /proc/bus/pci/,
>                decoupled by lspci				(2.4)
> + raw_cmdline  Kernel command line obtained from kernel image	(6.6)
>   rtc          Real time clock
>   scsi         SCSI info (see text)
>   slabinfo     Slab pool info
> diff --git a/fs/proc/Makefile b/fs/proc/Makefile
> index bd08616ed8ba..6182296f3c6b 100644
> --- a/fs/proc/Makefile
> +++ b/fs/proc/Makefile
> @@ -34,3 +34,4 @@ proc-$(CONFIG_PROC_VMCORE)	+= vmcore.o
>  proc-$(CONFIG_PRINTK)	+= kmsg.o
>  proc-$(CONFIG_PROC_PAGE_MONITOR)	+= page.o
>  proc-$(CONFIG_BOOT_CONFIG)	+= bootconfig.o
> +proc-$(CONFIG_BOOT_CONFIG_FORCE)	+= raw_cmdline.o
> diff --git a/fs/proc/raw_cmdline.c b/fs/proc/raw_cmdline.c
> new file mode 100644
> index 000000000000..2e19eb89fc8e
> --- /dev/null
> +++ b/fs/proc/raw_cmdline.c
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/fs.h>
> +#include <linux/init.h>
> +#include <linux/proc_fs.h>
> +#include <linux/seq_file.h>
> +#include <asm/setup.h>
> +#include "internal.h"
> +
> +static int raw_cmdline_proc_show(struct seq_file *m, void *v)
> +{
> +	seq_puts(m, boot_command_line);
> +	seq_putc(m, '\n');
> +	return 0;
> +}
> +
> +static int __init proc_raw_cmdline_init(void)
> +{
> +	struct proc_dir_entry *pde;
> +
> +	pde = proc_create_single("raw_cmdline", 0, NULL, raw_cmdline_proc_show);
> +	pde_make_permanent(pde);
> +	pde->size = strnlen(boot_command_line, COMMAND_LINE_SIZE) + 1;
> +	return 0;
> +}
> +fs_initcall(proc_raw_cmdline_init);
> diff --git a/include/linux/init.h b/include/linux/init.h
> index 266c3e1640d4..29e75bbe7984 100644
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -112,6 +112,7 @@
>  #define __REFCONST       .section       ".ref.rodata", "a"
>  
>  #ifndef __ASSEMBLY__
> +
>  /*
>   * Used for initialization calls..
>   */
> @@ -143,7 +144,7 @@ struct file_system_type;
>  
>  /* Defined in init/main.c */
>  extern int do_one_initcall(initcall_t fn);
> -extern char __initdata boot_command_line[];
> +extern char boot_command_line[];
>  extern char *saved_command_line;
>  extern unsigned int saved_command_line_len;
>  extern unsigned int reset_devices;
> diff --git a/init/main.c b/init/main.c
> index ad920fac325c..2121685c479a 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -135,7 +135,7 @@ EXPORT_SYMBOL(system_state);
>  void (*__initdata late_time_init)(void);
>  
>  /* Untouched command line saved by arch-specific code. */
> -char __initdata boot_command_line[COMMAND_LINE_SIZE];
> +char boot_command_line[COMMAND_LINE_SIZE] __ro_after_init;
>  /* Untouched saved command line (eg. for /proc) */
>  char *saved_command_line __ro_after_init;
>  unsigned int saved_command_line_len __ro_after_init;


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>