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

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Date:   Thu, 12 Nov 2020 12:26:45 +0100
From:   Matteo Croce <mcroce@...ux.microsoft.com>
To:     Nathan Chancellor <natechancellor@...il.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

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.

Thanks,
--
per aspera ad upstream