On 10/10/18, Eugene Syromiatnikov [off-list ref] wrote:

On Tue, Jul 24, 2018 at 08:39:57PM +0300, Yury Norov wrote:

quoted

Hi all,

+ Pavel Machek, Palmer Dabbelt, Wookey.

On Wed, May 16, 2018 at 11:18:45AM +0300, Yury Norov wrote:

quoted

This series enables AARCH64 with ILP32 mode.

As supporting work, it introduces ARCH_32BIT_OFF_T configuration
option that is enabled for existing 32-bit architectures but disabled
for new arches (so 64-bit off_t userspace type is used by new
userspace).
Also it deprecates getrlimit and setrlimit syscalls prior to prlimit64.

Based on kernel v4.16. Tested with LTP, glibc testsuite, trinity,
lmbench,
CPUSpec.

quoted

This is the update of the series based on 4.17 kernel
https://github.com/norov/linux/tree/ilp32-4.17

Hello.

I have some questions regarding AArch64 ILP32 implementation for which I
failed to find an answer myself:
 * How ptrace() tracer is supposed to distinguish between ILP32 and LP64
   tracees? For MIPS N32 and x32 this is possible based on syscall
   number, but for AArch64 ILP32 I do not see such a sign. There's also
   ARM_ip is employed for signalling entering/exiting, I wonder whether
   it's possible to employ it also for signalling tracee's personality.

Don't know.

 * What's the reasoning behind capping syscall arguments to 32 bit? x32
   and MIPS N32 do not have such a restriction (and do not need special
   wrappers for syscalls that pass 64-bit values as a result, except
   when they do,  as it is the case for preadv2 on x32); moreover, that
   would lead to insurmountable difficulties for AArch64 ILP32 tracers
   that try to trace LP64 tracees, as it would be impossible to pass
   64-bit addresses to process_vm_{read,write} or ptrace PEEK/POKE.

The idea is to keep the syscall entry points as similar as possible
between arm (aarch32) emulation and aarch64-ilp32 mode when
you have a kernel that supports both.

      Arnd