Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v4 4/9] kentry: Simplify the common syscall API | Date | Fri, 19 Mar 2021 17:09:53 +0100 |
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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
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