diff options
| -rw-r--r-- | arch/x86/kernel/step.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c index 92c20fee678..0d2cb363ea7 100644 --- a/arch/x86/kernel/step.c +++ b/arch/x86/kernel/step.c @@ -105,6 +105,7 @@ static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs) static int enable_single_step(struct task_struct *child) { struct pt_regs *regs = task_pt_regs(child); + unsigned long oflags; /* * Always set TIF_SINGLESTEP - this guarantees that @@ -113,11 +114,7 @@ static int enable_single_step(struct task_struct *child) */ set_tsk_thread_flag(child, TIF_SINGLESTEP); - /* - * If TF was already set, don't do anything else - */ - if (regs->flags & X86_EFLAGS_TF) - return 0; + oflags = regs->flags; /* Set TF on the kernel stack.. */ regs->flags |= X86_EFLAGS_TF; @@ -126,9 +123,22 @@ static int enable_single_step(struct task_struct *child) * ..but if TF is changed by the instruction we will trace, * don't mark it as being "us" that set it, so that we * won't clear it by hand later. + * + * Note that if we don't actually execute the popf because + * of a signal arriving right now or suchlike, we will lose + * track of the fact that it really was "us" that set it. */ - if (is_setting_trap_flag(child, regs)) + if (is_setting_trap_flag(child, regs)) { + clear_tsk_thread_flag(child, TIF_FORCED_TF); return 0; + } + + /* + * If TF was already set, check whether it was us who set it. + * If not, we should never attempt a block step. + */ + if (oflags & X86_EFLAGS_TF) + return test_tsk_thread_flag(child, TIF_FORCED_TF); set_tsk_thread_flag(child, TIF_FORCED_TF); |