diff options
| -rw-r--r-- | arch/x86/kernel/step.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c index 7a514986ca09..f89cdc6ccd5b 100644 --- a/arch/x86/kernel/step.c +++ b/arch/x86/kernel/step.c @@ -161,6 +161,16 @@ static void set_task_blockstep(struct task_struct *task, bool on) { unsigned long debugctl; + /* + * Ensure irq/preemption can't change debugctl in between. + * Note also that both TIF_BLOCKSTEP and debugctl should + * be changed atomically wrt preemption. + * FIXME: this means that set/clear TIF_BLOCKSTEP is simply + * wrong if task != current, SIGKILL can wakeup the stopped + * tracee and set/clear can play with the running task, this + * can confuse the next __switch_to_xtra(). + */ + local_irq_disable(); debugctl = get_debugctlmsr(); if (on) { debugctl |= DEBUGCTLMSR_BTF; @@ -169,7 +179,9 @@ static void set_task_blockstep(struct task_struct *task, bool on) debugctl &= ~DEBUGCTLMSR_BTF; clear_tsk_thread_flag(task, TIF_BLOCKSTEP); } - update_debugctlmsr(debugctl); + if (task == current) + update_debugctlmsr(debugctl); + local_irq_enable(); } /* |