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SubjectRe: [patch V4 part 4 07/24] x86/traps: Split int3 handler up
On Wed, May 13, 2020 at 10:03:13PM -0700, Andy Lutomirski wrote:
> On Tue, May 5, 2020 at 7:16 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > For code simplicity split up the int3 handler into a kernel and user part
> > which makes the code flow simpler to understand.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > ---
> > arch/x86/kernel/traps.c | 67 +++++++++++++++++++++++++++---------------------
> > 1 file changed, 39 insertions(+), 28 deletions(-)
> >
> > --- a/arch/x86/kernel/traps.c
> > +++ b/arch/x86/kernel/traps.c
> > @@ -564,6 +564,35 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_pr
> > cond_local_irq_disable(regs);
> > }
> >
> > +static bool do_int3(struct pt_regs *regs)
> > +{
> > + int res;
> > +
> > +#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
> > + if (kgdb_ll_trap(DIE_INT3, "int3", regs, 0, X86_TRAP_BP,
> > + SIGTRAP) == NOTIFY_STOP)
> > + return true;
> > +#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
> > +
> > +#ifdef CONFIG_KPROBES
> > + if (kprobe_int3_handler(regs))
> > + return true;
> > +#endif
> > + res = notify_die(DIE_INT3, "int3", regs, 0, X86_TRAP_BP, SIGTRAP);
> > +
> > + return res == NOTIFY_STOP;
> > +}
> > +
> > +static void do_int3_user(struct pt_regs *regs)
> > +{
> > + if (do_int3(regs))
> > + return;
> > +
> > + cond_local_irq_enable(regs);
> > + do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, 0, 0, NULL);
> > + cond_local_irq_disable(regs);
> > +}
> > +
> > DEFINE_IDTENTRY_RAW(exc_int3)
> > {
> > /*
> > @@ -581,37 +610,19 @@ DEFINE_IDTENTRY_RAW(exc_int3)
> > * because the INT3 could have been hit in any context including
> > * NMI.
> > */
> > + if (user_mode(regs)) {
> > idtentry_enter(regs);
> > + instr_begin();
> > + do_int3_user(regs);
> > + instr_end();
> > idtentry_exit(regs);
> > + } else {
> > + nmi_enter();
> > + instr_begin();
> > + do_int3(regs);
>
> I think you should be checking the return value here. Presumably this
> should die() if it's not handled, since otherwise it will just
> infinite loop.

Indeed. Thanks!

> > + instr_end();
> > nmi_exit();
> > + }
> > }
> >
> > #ifdef CONFIG_X86_64
> >

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