On Fri, Jan 26, 2018 at 10:13 AM, Linus Torvalds
<[email protected]> wrote:
> On Fri, Jan 26, 2018 at 10:07 AM, Al Viro <[email protected]> wrote:
>>
>> Umm... What about other architectures? Or do you want SYSCALL_DEFINE...
>> to be per-arch? I wonder how much would that "go through pt_regs" hurt
>> on something like sparc...
>
> No, but I just talked to Will Deacon about register clearing on entry,
> and so I suspect that arm64 might want something similar too.
>
> So I think some opt-in for letting architectures add their own
> function would be good. Because it wouldn't be all architectures, but
> it probably _would_ be more than just x86.
>
> You need to add architecture-specific "load argX from ptregs" macros anyway.
I mocked that up, and it's straightforward. I ended up with something like:
#define __ARCH_SYSCALL_ARGS(n, ...) (regs->di, ...)
(obviously modified so it actually compiles.)
The issue is that doing it this way gives us, effectively:
long sys_foo(int a, int b)
{
body here;
}
long SyS_foo(const struct pt_regs *regs)
{
return sys_foo(regs->di, regs->si);
}
whereas what we want is *static* long sys_foo(...). So I could split
the macros into:
DEFINE_SYSCALL2(foo, ....)
and
DEFINE_EXTERN_SYSCALL2(foo, ...)
or I could just fix up all the code that expects calling sys_foo()
across files to work.
My mockup patch doesn't actually work because of compat crap, but
that's manageable.
--Andy
