[PATCH v4 1/7] um: allow the use of glibc functions instead of builtins

[Johannes Berg]

On Fri, 2020-12-11 at 17:45 +0000, anton.ivanov at cambridgegreys.com
wrote:
> From: Anton Ivanov <anton.ivanov at cambridgegreys.com>
> 
> The UML kernel runs as a normal userspace process and can use most
> of glibc string.h functionality instead of built-ins. At present,
> when using built-ins, it is also limited to their unoptimized
> versions, because it does not have the runtime code patching present
> on x86 via apply_alternatives()
> 
> Allowing the use of glibc for memcpy, memmove, etc provides 1-5%
> boost on common file io as measured by cat and dd. The size of
> the linux executable is also reduced by ~10KBytes.
> 
> It is possible to turn this on/off via the kernel configuration.
> 
> Signed-off-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>

Reviewed-by: Johannes Berg <johannes at sipsolutions.net>

johannes