Re: ia32 signed long treated as x64 unsigned int by __ia32_sys*

[Arnd Bergmann]

On Thu, Sep 23, 2021 at 12:01 PM Richard Palethorpe <rpalethorpe@xxxxxxx> wrote:
> Arnd Bergmann <arnd@xxxxxxxx> writes:
> > On Wed, Sep 22, 2021 at 10:46 AM Richard Palethorpe <rpalethorpe@xxxxxxx> wrote:
> >> Richard Palethorpe <rpalethorpe@xxxxxxx> writes:
> >
> > I also noticed that only x86 and s390 even have separate entry
> > points for normal syscalls when called in compat mode, while
> > the others all just zero the upper halves of the registers in the
> > low-level entry code and then call the native entry point.
>
> It looks to me like aarch64 also has something similar? At any rate, I
> can try to fix it for x86 and investigate what else might be effected.

arm64 also has a custom asm/syscall_wrapper.h, but it only does
this for accessing pt_regs (as x86 does), not for doing any
argument conversion. x86 does the 32-to-64 widening in the
wrapper, arm64 relies on the pt_regs already having the upper
halves zeroed.

        Arnd