Messages in this thread Patch in this message | | | Subject | Re: [patch 5/8] x86/entry/common: Provide trace/kprobe safe exit to user space functions | From | Alexandre Chartre <> | Date | Thu, 27 Feb 2020 16:43:43 +0100 |
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On 2/25/20 11:08 PM, Thomas Gleixner wrote: > Split prepare_enter_to_user_mode() and mark it notrace/noprobe so the irq > flags tracing on return can be put into it.
This splits prepare_exit_to_usermode() not prepare_enter_to_user_mode().
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > arch/x86/entry/common.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > --- a/arch/x86/entry/common.c > +++ b/arch/x86/entry/common.c > @@ -196,7 +196,7 @@ static void exit_to_usermode_loop(struct > } > > /* Called with IRQs disabled. */ > -__visible inline void prepare_exit_to_usermode(struct pt_regs *regs) > +static inline void __prepare_exit_to_usermode(struct pt_regs *regs) > { > struct thread_info *ti = current_thread_info(); > u32 cached_flags; > @@ -241,6 +241,12 @@ static void exit_to_usermode_loop(struct > mds_user_clear_cpu_buffers(); > } > > +__visible inline notrace void prepare_exit_to_usermode(struct pt_regs *regs) > +{ > + __prepare_exit_to_usermode(regs); > +} > +NOKPROBE_SYMBOL(prepare_exit_to_usermode);
Would it be worth grouping local_irq_disable() and prepare_exit_to_usermode() (similarly to what was done entry with syscall_entry_fixups()) and then put trace_hardirqs_on() there too. For example:
static __always_inline void syscall_exit_fixups(struct pt_regs *regs) { local_irq_disable(); prepare_exit_to_usermode(regs); trace_hardirqs_on(); }
Or is this planned once prepare_exit_from_usermode() is not used by idtentry anymore?
Thanks,
alex.
> #define SYSCALL_EXIT_WORK_FLAGS \ > (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ > _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT) > @@ -271,7 +277,7 @@ static void syscall_slow_exit_work(struc > * Called with IRQs on and fully valid regs. Returns with IRQs off in a > * state such that we can immediately switch to user mode. > */ > -__visible inline void syscall_return_slowpath(struct pt_regs *regs) > +__visible inline notrace void syscall_return_slowpath(struct pt_regs *regs) > { > struct thread_info *ti = current_thread_info(); > u32 cached_flags = READ_ONCE(ti->flags); > @@ -292,8 +298,9 @@ static void syscall_slow_exit_work(struc > syscall_slow_exit_work(regs, cached_flags); > > local_irq_disable(); > - prepare_exit_to_usermode(regs); > + __prepare_exit_to_usermode(regs); > } > +NOKPROBE_SYMBOL(syscall_return_slowpath); > > #ifdef CONFIG_X86_64 > static __always_inline > @@ -417,7 +424,7 @@ static __always_inline long do_fast_sysc > /* User code screwed up. */ > local_irq_disable(); > regs->ax = -EFAULT; > - prepare_exit_to_usermode(regs); > + __prepare_exit_to_usermode(regs); > return 0; /* Keep it simple: use IRET. */ > } > >
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