[PATCH] x86/64: Add CONFIG_DEVMEM=y for targets/x86/64

[Bjørn Mork]

Alberto Bursi <bobafetthotmail at gmail.com> writes:

> On 09/02/21 17:46, Supriya Mane wrote:
>> Setting 'CONFIG_DEVMEM=y' provides access to /dev/mem.
>> Fixes "cannot access '/dev/mem' : No such file or directory"
>> Signed-off-by: Supriya Mane <sm.supriya at globaledgesoft.com>
>> ---
>>   target/linux/x86/64/config-5.4 | 1 +
>>   1 file changed, 1 insertion(+)
>> diff --git a/target/linux/x86/64/config-5.4
>> b/target/linux/x86/64/config-5.4
>> index f09deca5b0..a483d6ea2a 100644
>> --- a/target/linux/x86/64/config-5.4
>> +++ b/target/linux/x86/64/config-5.4
>> @@ -115,6 +115,7 @@ CONFIG_CRYPTO_SIMD=y
>>   # CONFIG_CRYPTO_TWOFISH_X86_64_3WAY is not set
>>   CONFIG_CRYPTO_XTS=y
>>   # CONFIG_DEBUG_HOTPLUG_CPU0 is not set
>> +CONFIG_DEVMEM=y
>>   CONFIG_DMA_ACPI=y
>>   CONFIG_DMA_SHARED_BUFFER=y
>>   # CONFIG_DPTF_POWER is not set
>> 
>
> It's disabled by default because it is a debugging feature that is not
> terribly secure (lets anyone see the RAM contents, to an extent).
>
> I'm not sure this should be enabled for all x86_64 target like that.

Sure you aren't thinking about DEVKMEM now?

DEVMEM is a standard feature, defaulting to Y in the kernel config:

config DEVMEM
        bool "/dev/mem virtual device support"
        default y
        help
          Say Y here if you want to support the /dev/mem device.
          The /dev/mem device is used to access areas of physical
          memory.
          When in doubt, say "Y".



and it's enabled in other distro kernels, like Debian (stable and
unstable) and RHEL (7 and 8).



Bjørn