From 10faa81e102e2b7695f386812055cd2ef9e44b4c Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Wed, 30 Jan 2008 13:30:54 +0100 Subject: x86: debugctlmsr arch_has_block_step This implements user-mode step-until-branch on x86 using the BTF bit in MSR_IA32_DEBUGCTLMSR. It's just like single-step, only less so. Signed-off-by: Roland McGrath Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- arch/x86/kernel/step.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 61 insertions(+), 3 deletions(-) (limited to 'arch/x86/kernel/step.c') diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c index 243bff650ca..cf4b9dac4a0 100644 --- a/arch/x86/kernel/step.c +++ b/arch/x86/kernel/step.c @@ -107,7 +107,10 @@ static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs) return 0; } -void user_enable_single_step(struct task_struct *child) +/* + * Enable single-stepping. Return nonzero if user mode is not using TF itself. + */ +static int enable_single_step(struct task_struct *child) { struct pt_regs *regs = task_pt_regs(child); @@ -122,7 +125,7 @@ void user_enable_single_step(struct task_struct *child) * If TF was already set, don't do anything else */ if (regs->eflags & X86_EFLAGS_TF) - return; + return 0; /* Set TF on the kernel stack.. */ regs->eflags |= X86_EFLAGS_TF; @@ -133,13 +136,68 @@ void user_enable_single_step(struct task_struct *child) * won't clear it by hand later. */ if (is_setting_trap_flag(child, regs)) - return; + return 0; set_tsk_thread_flag(child, TIF_FORCED_TF); + + return 1; +} + +/* + * Install this value in MSR_IA32_DEBUGCTLMSR whenever child is running. + */ +static void write_debugctlmsr(struct task_struct *child, unsigned long val) +{ + child->thread.debugctlmsr = val; + + if (child != current) + return; + +#ifdef CONFIG_X86_64 + wrmsrl(MSR_IA32_DEBUGCTLMSR, val); +#else + wrmsr(MSR_IA32_DEBUGCTLMSR, val, 0); +#endif +} + +/* + * Enable single or block step. + */ +static void enable_step(struct task_struct *child, bool block) +{ + /* + * Make sure block stepping (BTF) is not enabled unless it should be. + * Note that we don't try to worry about any is_setting_trap_flag() + * instructions after the first when using block stepping. + * So noone should try to use debugger block stepping in a program + * that uses user-mode single stepping itself. + */ + if (enable_single_step(child) && block) { + set_tsk_thread_flag(child, TIF_DEBUGCTLMSR); + write_debugctlmsr(child, DEBUGCTLMSR_BTF); + } else if (test_and_clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR)) { + write_debugctlmsr(child, 0); + } +} + +void user_enable_single_step(struct task_struct *child) +{ + enable_step(child, 0); +} + +void user_enable_block_step(struct task_struct *child) +{ + enable_step(child, 1); } void user_disable_single_step(struct task_struct *child) { + /* + * Make sure block stepping (BTF) is disabled. + */ + if (test_and_clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR)) + write_debugctlmsr(child, 0); + /* Always clear TIF_SINGLESTEP... */ clear_tsk_thread_flag(child, TIF_SINGLESTEP); -- cgit v1.2.3