linux-kernel - Re: [PATCH RFC bootconfig 0/2] Distinguish bootloader and embedded kernel parameters

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Date:   Fri, 28 Jul 2023 14:05:19 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     akpm@...ux-foundation.org, adobriyan@...il.com,
        mhiramat@...nel.org, arnd@...nel.org, ndesaulniers@...gle.com,
        sfr@...b.auug.org.au, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH RFC bootconfig 0/2] Distinguish bootloader and embedded
 kernel parameters

On Thu, Jul 27, 2023 at 09:25:06PM -0700, Randy Dunlap wrote:
> 
> 
> On 7/27/23 20:35, Paul E. McKenney wrote:
> > Hello!
> > 
> > This series provides /proc interfaces parallel to /proc/cmdline that
> > provide only those kernel boot parameters that were provided by the
> > bootloader (/proc/cmdline_load) and only those parameters that were
> > embedded in the kernel image (/proc/cmdline_image, in boot-config format).
> > This is especially important when these parameters are presented to the
> > boot loader by automation that might gather them from diverse sources,
> > and also when a kexec-based reboot process pulls the kernel boot
> > parameters from /proc.  If such a reboot process uses /proc/cmdline,
> > the kernel parameters from the image are replicated on every reboot,
> > which can be frustrating when the new kernel has different embedded
> > kernel boot parameters.
> > 
> > Why put these in /proc?  Because they is quite similar to /proc/cmdline,
> > so it makes sense to put it in the same place that /proc/cmdline is
> > located.
> > 
> > 1.	fs/proc: Add /proc/cmdline_load for boot loader arguments.
> > 
> > 2.	fs/proc: Add /proc/cmdline_image for embedded arguments.
> > 
> > 						Thanx, Paul
> > 
> 
> Hi Paul,
> 
> This series seems to be missing updates to
> Documentation/filesystems/proc.rst.
> 
> Please add them.

Good catch, thank you!

I will fold the diff below into the three respective commits on my next
rebase, but in the meantime, please let me know what you think.

							Thanx, Paul

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 7897a7dafcbc..98c43c5ef1ee 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -686,7 +686,10 @@ files are there, and which are missing.
  apm          Advanced power management info
  buddyinfo    Kernel memory allocator information (see text)	(2.5)
  bus          Directory containing bus specific information
- cmdline      Kernel command line
+ cmdline      Kernel command line, both from bootloader and embedded
+ 	      in the kernel image
+ cmdline_image Kernel command line obtained from boot loader	(6.6)
+ cmdline_load Kernel command line obtained from kernel image	(6.6)
  cpuinfo      Info about the CPU
  devices      Available devices (block and character)
  dma          Used DMS channels