linux-kernel - Re: [PATCH bootconfig 2/3] fs/proc: Add boot loader arguments as comment to /proc/bootconfig

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Date:   Fri, 6 Oct 2023 20:42:34 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-doc@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Arnd Bergmann <arnd@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH bootconfig 2/3] fs/proc: Add boot loader arguments as
 comment to /proc/bootconfig

On Sat, Oct 07, 2023 at 10:42:09AM +0900, Masami Hiramatsu wrote:
> On Fri, 6 Oct 2023 09:52:30 -0700
> "Paul E. McKenney" <paulmck@...nel.org> wrote:
> 
> > On Fri, Oct 06, 2023 at 05:59:48PM +0900, Masami Hiramatsu wrote:
> > > On Thu,  5 Oct 2023 10:17:46 -0700
> > > "Paul E. McKenney" <paulmck@...nel.org> 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.
> > > > 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, add comments to /proc/bootconfig of the form:
> > > > 
> > > > 	# Parameters from bootloader:
> > > > 	# root=UUID=ac0f0548-a69d-43ca-a06b-7db01bcbd5ad ro quiet ...
> > > > 
> > > > The second added line shows only those kernel boot parameters supplied
> > > > by the boot loader.
> > > 
> > > Thanks for update it.
> > > 
> > > This looks good to me.
> > > 
> > > Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > > 
> > > Thank you!
> > 
> > And thank you!  I take this as meaning that I should push these three
> > commits for the upcoming v6.7 merge window.  Please let me know if I
> > should be doing something else.
> 
> I have my bootconfig branch, so I think I should pick this and push it
> to the next window. Does it work?

That works for me, and thank you!

(And thank you for taking and fixing my whitespace errors in the
other two patches!)

							Thanx, Paul

> > > > Link: https://lore.kernel.org/all/CAHk-=wjpVAW3iRq_bfKnVfs0ZtASh_aT67bQBG11b4W6niYVUw@mail.gmail.com/
> > > > Link: https://lore.kernel.org/all/20230731233130.424913-1-paulmck@kernel.org/
> > > > Co-developed-by: Masami Hiramatsu <mhiramat@...nel.org>
> > > > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > > > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > > > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > > > Cc: Stephen Rothwell <sfr@...b.auug.org.au>
> > > > Cc: Arnd Bergmann <arnd@...nel.org>
> > > > Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> > > > Cc: Alexey Dobriyan <adobriyan@...il.com>
> > > > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > > > Cc: Kees Cook <keescook@...omium.org>
> > > > Cc: <linux-trace-kernel@...r.kernel.org>
> > > > Cc: <linux-fsdevel@...r.kernel.org>
> > > > ---
> > > >  fs/proc/bootconfig.c | 6 ++++++
> > > >  1 file changed, 6 insertions(+)
> > > > 
> > > > diff --git a/fs/proc/bootconfig.c b/fs/proc/bootconfig.c
> > > > index 2e244ada1f97..902b326e1e56 100644
> > > > --- a/fs/proc/bootconfig.c
> > > > +++ b/fs/proc/bootconfig.c
> > > > @@ -62,6 +62,12 @@ static int __init copy_xbc_key_value_list(char *dst, size_t size)
> > > >  				break;
> > > >  			dst += ret;
> > > >  		}
> > > > +		if (ret >= 0 && boot_command_line[0]) {
> > > > +			ret = snprintf(dst, rest(dst, end), "# Parameters from bootloader:\n# %s\n",
> > > > +				       boot_command_line);
> > > > +			if (ret > 0)
> > > > +				dst += ret;
> > > > +		}
> > > >  	}
> > > >  out:
> > > >  	kfree(key);
> > > > -- 
> > > > 2.40.1
> > > > 
> > > 
> > > 
> > > -- 
> > > Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> 
> -- 
> Masami Hiramatsu (Google) <mhiramat@...nel.org>