linux-kernel - Re: [PATCH] reboot: Fix variable assignments in type

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Message-ID: <CAFnufp1j6ZzxLJA2x28BdxbTtnN_KtnXB49ibPcbze=B2ru3aA@mail.gmail.com>
Date:   Fri, 13 Nov 2020 01:20:29 +0100
From:   Matteo Croce <mcroce@...ux.microsoft.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Petr Mladek <pmladek@...e.com>,
        Mike Rapoport <rppt@...nel.org>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] reboot: Fix variable assignments in type_store

On Fri, Nov 13, 2020 at 12:13 AM Andrew Morton
<akpm@...ux-foundation.org> wrote:
>
> On Wed, 11 Nov 2020 20:50:23 -0700 Nathan Chancellor <natechancellor@...il.com> wrote:
>
> > Clang warns:
> >
> > kernel/reboot.c:707:17: warning: implicit conversion from enumeration
> > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > [-Wenum-conversion]
> >                 reboot_mode = BOOT_TRIPLE;
> >                             ~ ^~~~~~~~~~~
> >
> > ...
> >
> > --- a/kernel/reboot.c
> > +++ b/kernel/reboot.c
> > @@ -704,19 +704,19 @@ static ssize_t type_store(struct kobject *kobj, struct kobj_attribute *attr,
> >               return -EPERM;
> >
> >       if (!strncmp(buf, BOOT_TRIPLE_STR, strlen(BOOT_TRIPLE_STR)))
> > -             reboot_mode = BOOT_TRIPLE;
> > +             reboot_type = BOOT_TRIPLE;
> >       else if (!strncmp(buf, BOOT_KBD_STR, strlen(BOOT_KBD_STR)))
> > -             reboot_mode = BOOT_KBD;
> > +             reboot_type = BOOT_KBD;
> >       else if (!strncmp(buf, BOOT_BIOS_STR, strlen(BOOT_BIOS_STR)))
> > -             reboot_mode = BOOT_BIOS;
> > +             reboot_type = BOOT_BIOS;
> >       else if (!strncmp(buf, BOOT_ACPI_STR, strlen(BOOT_ACPI_STR)))
> > -             reboot_mode = BOOT_ACPI;
> > +             reboot_type = BOOT_ACPI;
> >       else if (!strncmp(buf, BOOT_EFI_STR, strlen(BOOT_EFI_STR)))
> > -             reboot_mode = BOOT_EFI;
> > +             reboot_type = BOOT_EFI;
> >       else if (!strncmp(buf, BOOT_CF9_FORCE_STR, strlen(BOOT_CF9_FORCE_STR)))
> > -             reboot_mode = BOOT_CF9_FORCE;
> > +             reboot_type = BOOT_CF9_FORCE;
> >       else if (!strncmp(buf, BOOT_CF9_SAFE_STR, strlen(BOOT_CF9_SAFE_STR)))
> > -             reboot_mode = BOOT_CF9_SAFE;
> > +             reboot_type = BOOT_CF9_SAFE;
> >       else
> >               return -EINVAL;
>
> This is a fairly dramatic change to the original patch, but it eyeballs
> OK.
>
> Matteo, could you please comment?  And preferably retest?
>

Hi,

I reviewed the patch and it looks good to me.
I tested it with this script which passes now with Nathan's fix:

for i in cold warm hard soft gpio; do
    echo $i > mode
    read j <mode
    [ $i = $j ] || echo "mode $i = $j"
done

for i in bios acpi kbd triple efi cf9_force cf9_safe; do
    echo $i > type
    read j <type
    [ $i = $j ] || echo "type $i = $j"
done

for i in $(seq 0 $(nproc --ignore=1)); do
    echo $i > cpu
    read j <cpu
    [ $i = $j ] || echo "cpu $i = $j"
done

for i in 0 1; do
    echo $i >force
    read j <force
    [ $i = $j ] || echo "force $i = $j"
done

While writing the script I found that in the documentation I left for
'type' the values from
Documentation/admin-guide/kernel-parameters.txt, which is 'pci' for
cf9_force reboot.
While at it, should we update the doc with the values 'cf9_force' and
'cf9_safe', or rename to 'pci' and 'pci_safe' to be coherent with the
kernel cmdline?

In any case, kernel-parameters.txt doesn't mention that reboot=q does
the 'cf9_safe' reboot type, so it must be fixed anyway.

Regards,
-- 
per aspera ad upstream