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

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Message-ID: <20201112174954.GA934563@ubuntu-m3-large-x86>
Date:   Thu, 12 Nov 2020 10:49:54 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Matteo Croce <mcroce@...ux.microsoft.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        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>,
        ndesaulniers@...gle.com, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] reboot: Fix variable assignments in type_store

Hi Matteo,

On Thu, Nov 12, 2020 at 12:26:45PM +0100, Matteo Croce wrote:
> On Thu, Nov 12, 2020 at 4:50 AM 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;
> >                             ~ ^~~~~~~~~~~
> > kernel/reboot.c:709:17: warning: implicit conversion from enumeration
> > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > [-Wenum-conversion]
> >                 reboot_mode = BOOT_KBD;
> >                             ~ ^~~~~~~~
> > kernel/reboot.c:711:17: warning: implicit conversion from enumeration
> > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > [-Wenum-conversion]
> >                 reboot_mode = BOOT_BIOS;
> >                             ~ ^~~~~~~~~
> > kernel/reboot.c:713:17: warning: implicit conversion from enumeration
> > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > [-Wenum-conversion]
> >                 reboot_mode = BOOT_ACPI;
> >                             ~ ^~~~~~~~~
> > kernel/reboot.c:715:17: warning: implicit conversion from enumeration
> > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > [-Wenum-conversion]
> >                 reboot_mode = BOOT_EFI;
> >                             ~ ^~~~~~~~
> > kernel/reboot.c:717:17: warning: implicit conversion from enumeration
> > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > [-Wenum-conversion]
> >                 reboot_mode = BOOT_CF9_FORCE;
> >                             ~ ^~~~~~~~~~~~~~
> > kernel/reboot.c:719:17: warning: implicit conversion from enumeration
> > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > [-Wenum-conversion]
> >                 reboot_mode = BOOT_CF9_SAFE;
> >                             ~ ^~~~~~~~~~~~~
> > 7 warnings generated.
> >
> > It seems that these assignment should be to reboot_type, not
> > reboot_mode. Fix it so there are no more warnings and the code works
> > properly.
> >
> > Fixes: eab8da48579d ("reboot: allow to specify reboot mode via sysfs")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1197
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > ---
> >  kernel/reboot.c | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/kernel/reboot.c b/kernel/reboot.c
> > index deba133a071b..8599d0d44aec 100644
> > --- 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;
> >
> >
> > base-commit: 3e14f70c05cda4794901ed8f976de3a88deebcc0
> > --
> > 2.29.2
> >
> 
> Hmm, this was introduced in v3 I think.
> 
> I wonder why my compiler doesn't warn about it, the two variables are
> defined as different enum type.
> I get the same warnings with GCC and -Wenum-conversion.

What version of GCC do you have? -Wenum-conversion is a fairly new
warning in GCC I think. Although if you get it now, maybe it was some
configuration error?

Regardless, thank you for taking a look at the patch!

Cheers,
Nathan