x86: debugctlmsr kprobes
This adjusts the x86 kprobes implementation to cope with per-thread
MSR_IA32_DEBUGCTLMSR being set for user mode. I haven't delved deep
enough into the kprobes code to be really sure this covers all the
cases where the user-mode BTF setting needs to be cleared or restored.
It looks about right to me.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c
index 5df19a9..10d66e3 100644
--- a/arch/x86/kernel/kprobes_64.c
+++ b/arch/x86/kernel/kprobes_64.c
@@ -256,8 +256,21 @@
kcb->kprobe_saved_rflags &= ~IF_MASK;
}
+static __always_inline void clear_btf(void)
+{
+ if (test_thread_flag(TIF_DEBUGCTLMSR))
+ wrmsrl(MSR_IA32_DEBUGCTLMSR, 0);
+}
+
+static __always_inline void restore_btf(void)
+{
+ if (test_thread_flag(TIF_DEBUGCTLMSR))
+ wrmsrl(MSR_IA32_DEBUGCTLMSR, current->thread.debugctlmsr);
+}
+
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
+ clear_btf();
regs->eflags |= TF_MASK;
regs->eflags &= ~IF_MASK;
/*single step inline if the instruction is an int3*/
@@ -527,6 +540,7 @@
regs->rip = orig_rip + (regs->rip - copy_rip);
no_change:
+ restore_btf();
return;
}
