On Fri, Jun 12, 2020 at 07:50:08PM -0000, tip-bot2 for Andy Lutomirski wrote:
> +DEFINE_IDTENTRY_RAW(exc_invalid_op)
> {
> + bool rcu_exit;
> +
> + /*
> + * Handle BUG/WARN like NMIs instead of like normal idtentries:
> + * if we bugged/warned in a bad RCU context, for example, the last
> + * thing we want is to BUG/WARN again in the idtentry code, ad
> + * infinitum.
> + */
> + if (!user_mode(regs) && is_valid_bugaddr(regs->ip)) {
vmlinux.o: warning: objtool: exc_invalid_op()+0x47: call to probe_kernel_read()
leaves .noinstr.text section
> + enum bug_trap_type type;
> +
> + nmi_enter();
> + instrumentation_begin();
> + trace_hardirqs_off_finish();
> + type = report_bug(regs->ip, regs);
> + if (regs->flags & X86_EFLAGS_IF)
> + trace_hardirqs_on_prepare();
> + instrumentation_end();
> + nmi_exit();
> +
> + if (type == BUG_TRAP_TYPE_WARN) {
> + /* Skip the ud2. */
> + regs->ip += LEN_UD2;
> + return;
> + }
> +
> + /*
> + * Else, if this was a BUG and report_bug returns or if this
> + * was just a normal #UD, we want to continue onward and
> + * crash.
> + */
> + }
> +
> + rcu_exit = idtentry_enter_cond_rcu(regs);
> + instrumentation_begin();
> handle_invalid_op(regs);
> + instrumentation_end();
> + idtentry_exit_cond_rcu(regs, rcu_exit);
> }
For now something like so will do, but we need a DEFINE_IDTENTRY_foo()
for the whole:
if (user_mode()) {
rcu = idtentry_enter_cond_rcu()
foo_user()
idtentry_exit_cond_rcu(rcu);
} else {
nmi_enter();
foo_kernel()
nmi_exit()
}
thing, we're repeating that far too often.
---
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index af75109485c26..a47e74923c4c8 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -218,21 +218,22 @@ static inline void handle_invalid_op(struct pt_regs *regs)
DEFINE_IDTENTRY_RAW(exc_invalid_op)
{
- bool rcu_exit;
-
/*
* Handle BUG/WARN like NMIs instead of like normal idtentries:
* if we bugged/warned in a bad RCU context, for example, the last
* thing we want is to BUG/WARN again in the idtentry code, ad
* infinitum.
*/
- if (!user_mode(regs) && is_valid_bugaddr(regs->ip)) {
- enum bug_trap_type type;
+ if (!user_mode(regs)) {
+ enum bug_trap_type type = BUG_TRAP_TYPE_NONE;
nmi_enter();
instrumentation_begin();
trace_hardirqs_off_finish();
- type = report_bug(regs->ip, regs);
+
+ if (is_valid_bugaddr(regs->ip))
+ type = report_bug(regs->ip, regs);
+
if (regs->flags & X86_EFLAGS_IF)
trace_hardirqs_on_prepare();
instrumentation_end();
@@ -249,13 +250,16 @@ DEFINE_IDTENTRY_RAW(exc_invalid_op)
* was just a normal #UD, we want to continue onward and
* crash.
*/
- }
+ handle_invalid_op(regs);
+ } else {
+ bool rcu_exit;
- rcu_exit = idtentry_enter_cond_rcu(regs);
- instrumentation_begin();
- handle_invalid_op(regs);
- instrumentation_end();
- idtentry_exit_cond_rcu(regs, rcu_exit);
+ rcu_exit = idtentry_enter_cond_rcu(regs);
+ instrumentation_begin();
+ handle_invalid_op(regs);
+ instrumentation_end();
+ idtentry_exit_cond_rcu(regs, rcu_exit);
+ }
}
DEFINE_IDTENTRY(exc_coproc_segment_overrun)
