Re: [PATCH 3/6] x86/cpu: proc - remove "wp" status line in cpuinfo

[Mathias Krause]

On 14 February 2017 at 22:42, Mathias Krause <minipli@xxxxxxxxxxxxxx> wrote:
> On 14 February 2017 at 19:13, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>> On 02/12/17 13:12, Mathias Krause wrote:
>>> As of commit a5c2a893dbd4 ("x86, 386 removal: Remove
>>> CONFIG_X86_WP_WORKS_OK") the kernel won't boot if CR0.WP isn't working
>>> correctly. This makes a process reading this file always see "wp : yes"
>>> here -- otherwise there would be no process to begin with ;)
>>>
>>> As this status line in /proc/cpuinfo serves no purpose for quite some
>>> time now, get rid of it.
>>>
>>> Cc: Borislav Petkov <bp@xxxxxxxxx>
>>> Cc: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
>>> Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
>>> ---
>>>  arch/x86/kernel/cpu/proc.c |    6 ++----
>>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
>>> index 6df621ae62a7..c6c5217a7980 100644
>>> --- a/arch/x86/kernel/cpu/proc.c
>>> +++ b/arch/x86/kernel/cpu/proc.c
>>> @@ -30,8 +30,7 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c)
>>>                  "coma_bug\t: %s\n"
>>>                  "fpu\t\t: %s\n"
>>>                  "fpu_exception\t: %s\n"
>>> -                "cpuid level\t: %d\n"
>>> -                "wp\t\t: yes\n",
>>> +                "cpuid level\t: %d\n",
>>>                  static_cpu_has_bug(X86_BUG_FDIV) ? "yes" : "no",
>>>                  static_cpu_has_bug(X86_BUG_F00F) ? "yes" : "no",
>>>                  static_cpu_has_bug(X86_BUG_COMA) ? "yes" : "no",
>>> @@ -45,8 +44,7 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c)
>>>       seq_printf(m,
>>>                  "fpu\t\t: yes\n"
>>>                  "fpu_exception\t: yes\n"
>>> -                "cpuid level\t: %d\n"
>>> -                "wp\t\t: yes\n",
>>> +                "cpuid level\t: %d\n",
>>>                  c->cpuid_level);
>>>  }
>>>  #endif
>>>
>>
>> Potential userspace breakage, which is why the line was left in the
>> first place despite its value now being hard-coded.  Removing it will
>> save a whopping 9 bytes of kernel rodata; this is a very small price to
>> pay for guaranteeing continued compatibility.
>
> Indeed. That's why I've separated the removal into an extra patch --
> to make it easier not to take it.
>
>>
>> Nacked-by: H. Peter Anvin <hpa@xxxxxxxxx>
>
> Do you want me to send the series again without this patch and patch
> #6 (Geert took it already) or are you okay with sorting them out
> yourself?
>

Ping...
Peter, what's your preference here?

Mathias