linux-kernel - Re: [PATCH 6/8] drivers: firmware: efi: libstub: enable generic commandline

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Date:   Wed, 31 Mar 2021 11:21:45 -0700
From:   Daniel Walker <danielwa@...co.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Will Deacon <will@...nel.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        ob Herring <robh@...nel.org>,
        Daniel Gimpelevich <daniel@...pelevich.san-francisco.ca.us>,
        Andrew Morton <akpm@...ux-foundation.org>,
        X86 ML <x86@...nel.org>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@...ts.ozlabs.org>, xe-linux-external@...co.com,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/8] drivers: firmware: efi: libstub: enable generic
 commandline

On Wed, Mar 31, 2021 at 06:10:08PM +0200, Ard Biesheuvel wrote:
> (+ Arvind)
> 
> On Tue, 30 Mar 2021 at 19:57, Daniel Walker <danielwa@...co.com> wrote:
> >
> > This adds code to handle the generic command line changes.
> > The efi code appears that it doesn't benefit as much from this design
> > as it could.
> >
> > For example, if you had a prepend command line with "nokaslr" then
> > you might be helpful to re-enable it in the boot loader or dts,
> > but there appears to be no way to re-enable kaslr or some of the
> > other options.
> >
> > Cc: xe-linux-external@...co.com
> > Signed-off-by: Daniel Walker <danielwa@...co.com>
> > ---
> >  .../firmware/efi/libstub/efi-stub-helper.c    | 35 +++++++++++++++++++
> >  drivers/firmware/efi/libstub/efi-stub.c       |  7 ++++
> >  drivers/firmware/efi/libstub/efistub.h        |  1 +
> >  drivers/firmware/efi/libstub/x86-stub.c       | 13 +++++--
> >  4 files changed, 54 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
> > index aa8da0a49829..c155837cedc9 100644
> > --- a/drivers/firmware/efi/libstub/efi-stub-helper.c
> > +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
> > @@ -13,6 +13,7 @@
> >  #include <linux/efi.h>
> >  #include <linux/kernel.h>
> >  #include <linux/printk.h> /* For CONSOLE_LOGLEVEL_* */
> > +#include <linux/cmdline.h>
> >  #include <asm/efi.h>
> >  #include <asm/setup.h>
> >
> > @@ -172,6 +173,40 @@ int efi_printk(const char *fmt, ...)
> >         return printed;
> >  }
> >
> > +/**
> > + * efi_handle_cmdline() - handle adding in building parts of the command line
> > + * @cmdline:   kernel command line
> > + *
> > + * Add in the generic parts of the commandline and start the parsing of the
> > + * command line.
> > + *
> > + * Return:     status code
> > + */
> > +efi_status_t efi_handle_cmdline(char const *cmdline)
> > +{
> > +       efi_status_t status;
> > +
> > +       status = efi_parse_options(CMDLINE_PREPEND);
> > +       if (status != EFI_SUCCESS) {
> > +               efi_err("Failed to parse options\n");
> > +               return status;
> > +       }
> 
> Even though I am not a fan of the 'success handling' pattern,
> duplicating the exact same error handling three times is not great
> either. Could we reuse more of the code here?

How about

efi_status_t status = 0;

status |= efi_parse_options(CMDLINE_PREPEND);

then error checking once ?

> > +
> > +       status = efi_parse_options(IS_ENABLED(CONFIG_CMDLINE_OVERRIDE) ? "" : cmdline);
> 
> What is the point of calling efi_parse_options() with an empty string?
 
I could change it to if ((IS_ENABLED(CONFIG_CMDLINE_OVERRIDE)) ?

> > --- a/drivers/firmware/efi/libstub/efi-stub.c
> > +++ b/drivers/firmware/efi/libstub/efi-stub.c
> > @@ -172,6 +172,12 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
> >                 goto fail;
> >         }
> >
> > +#ifdef CONFIG_GENERIC_CMDLINE
> > +       status = efi_handle_cmdline(cmdline_ptr);
> > +       if (status != EFI_SUCCESS) {
> > +               goto fail_free_cmdline;
> > +       }
> > +#else
> >         if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
> >             IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
> 
> Does this mean CONFIG_GENERIC_CMDLINE does not replace CMDLINE_EXTEND
> / CMDLINE_FORCE etc, but introduces yet another variant on top of
> those?
> 
> That does not seem like an improvement to me. I think it is great that
> you are cleaning this up, but only if it means we can get rid of the
> old implementation.
 
It does replace extend and force. I was under the impression this code was
shared between arm64 and arm32. If that's not the case I can delete the extend
and force section. I haven't submitted a conversion for arm32 yet.

Daniel