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

[William Kucharski]

I really like that as it’s self-documenting and anyone debugging it can see what is actually being used at a glance.

> On Sep 20, 2020, at 09:15, Matthew Wilcox <willy at infradead.org> 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.