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

Arnd Bergmann
2020-09-20T16:00:30Z

On Sun, Sep 20, 2020 at 5:15 PM Matthew Wilcox <willy@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.

How is that different from the current approach of storing the ABI as
a flag in ctx->compat?

Arnd