Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag

From: Pavel Begunkov
Date: Mon Sep 21 2020 - 12:23:21 EST

On 20/09/2020 18:55, William Kucharski wrote:
> I really like that as it’s self-documenting and anyone debugging it can see what is actually being used at a glance.

Also creates special cases for things that few people care about,
and makes it a pain for cross-platform (cross-bitness) development.

>> On Sep 20, 2020, at 09:15, Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>> On Fri, Sep 18, 2020 at 02:45:25PM +0200, Christoph Hellwig wrote:
>>> Add a flag to force processing a syscall as a compat syscall. This is
>>> required so that in_compat_syscall() works for I/O submitted by io_uring
>>> helper threads on behalf of compat syscalls.
>> Al doesn't like this much, but my suggestion is to introduce two new
>> opcodes -- IORING_OP_READV32 and IORING_OP_WRITEV32. The compat code
>> can translate IORING_OP_READV to IORING_OP_READV32 and then the core
>> code can know what that user pointer is pointing to.

Pavel Begunkov