On Wed, Mar 17 2021 at 11:12, Andy Lutomirski wrote:
> The new common syscall API had a large and confusing API surface. Simplify
> it. Now there is exactly one way to use it. It's a bit more verbose than
> the old way for the simple x86_64 native case, but it's much easier to use
> right,
and therefore much easier to get wrong...
> __visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs)
> {
> - nr = syscall_enter_from_user_mode(regs, nr);
> -
> + kentry_enter_from_user_mode(regs);
> + local_irq_enable();
... That needs to be _after_ instrumentation_begin(). If you fiddle
with this then please make sure that objtool validates noinstr...
> + kentry_enter_from_user_mode(regs);
> + local_irq_enable();
Ditto
> + instrumentation_begin();
> static noinstr bool __do_fast_syscall_32(struct pt_regs *regs)
> {
> unsigned int nr = syscall_32_enter(regs);
> + bool ret;
> int res;
>
> - /*
> - * This cannot use syscall_enter_from_user_mode() as it has to
> - * fetch EBP before invoking any of the syscall entry work
> - * functions.
> - */
> - syscall_enter_from_user_mode_prepare(regs);
> -
> + kentry_enter_from_user_mode(regs);
> + local_irq_enable();
...
> instrumentation_begin();
Thanks,
tglx
