Re: [patch V4 12/36] entry: Inline irqentry_enter/exit_from/to_user_mode()

[Mathieu Desnoyers]

On 2025-09-09 10:10, Thomas Gleixner wrote:
> On Tue, Sep 09 2025 at 09:38, Mathieu Desnoyers wrote:
>
> > On 2025-09-08 17:31, Thomas Gleixner wrote:
> > > There is no point to have this as a function which just inlines
> > > enter_from_user_mode(). The function call overhead is larger than the
> > > function itself.
> >
> > I'm wondering if there is a reason for making those actual functions and
> > not inlines.
> >
> > The functions sit in kernel/entry/common.c, which are built with
> > specific compiler flags in kernel/entry/Makefile:
> >
> > # Prevent the noinstr section from being pestered by sanitizer and other
> > goodies
> > # as long as these things cannot be disabled per function.
> > KASAN_SANITIZE := n
> > UBSAN_SANITIZE := n
> > KCOV_INSTRUMENT := n
> >
> > # Branch profiling isn't noinstr-safe
> > ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
> >
> > CFLAGS_REMOVE_common.o   = -fstack-protector -fstack-protector-strong
> > CFLAGS_common.o         += -fno-stack-protector
> >
> > So I wonder if we're not breaking something in the area of "noinstr"
> > tagging by inlining those into their caller ?
>
> No, because the call sites have to be non-instrumented as well.

OK.

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>



--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com