x86, ptrace: Fix block-step
Implement ptrace-block-step using TIF_BLOCKSTEP which will set
DEBUGCTLMSR_BTF when set for a task while preserving any other
DEBUGCTLMSR bits.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100325135414.017536066@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 5bec21a..32428b4 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -799,7 +799,7 @@
static inline unsigned long get_debugctlmsr(void)
{
- unsigned long debugctlmsr = 0;
+ unsigned long debugctlmsr = 0;
#ifndef CONFIG_X86_DEBUGCTLMSR
if (boot_cpu_data.x86 < 6)
@@ -807,7 +807,7 @@
#endif
rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctlmsr);
- return debugctlmsr;
+ return debugctlmsr;
}
static inline void update_debugctlmsr(unsigned long debugctlmsr)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index dc85e12..d017ed55 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -92,6 +92,7 @@
#define TIF_IO_BITMAP 22 /* uses I/O bitmap */
#define TIF_FREEZE 23 /* is freezing for suspend */
#define TIF_FORCED_TF 24 /* true if TF in eflags artificially */
+#define TIF_BLOCKSTEP 25 /* set when we want DEBUGCTLMSR_BTF */
#define TIF_LAZY_MMU_UPDATES 27 /* task is updating the mmu lazily */
#define TIF_SYSCALL_TRACEPOINT 28 /* syscall tracepoint instrumentation */
@@ -113,6 +114,7 @@
#define _TIF_IO_BITMAP (1 << TIF_IO_BITMAP)
#define _TIF_FREEZE (1 << TIF_FREEZE)
#define _TIF_FORCED_TF (1 << TIF_FORCED_TF)
+#define _TIF_BLOCKSTEP (1 << TIF_BLOCKSTEP)
#define _TIF_LAZY_MMU_UPDATES (1 << TIF_LAZY_MMU_UPDATES)
#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
@@ -143,7 +145,7 @@
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW \
- (_TIF_IO_BITMAP|_TIF_NOTSC)
+ (_TIF_IO_BITMAP|_TIF_NOTSC|_TIF_BLOCKSTEP)
#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW|_TIF_DEBUG)
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 7a880ad..f2f56c0 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -422,12 +422,22 @@
static void __kprobes clear_btf(void)
{
- /* XXX */
+ if (test_thread_flag(TIF_BLOCKSTEP)) {
+ unsigned long debugctl = get_debugctlmsr();
+
+ debugctl &= ~DEBUGCTLMSR_BTF;
+ update_debugctlmsr(debugctl);
+ }
}
static void __kprobes restore_btf(void)
{
- /* XXX */
+ if (test_thread_flag(TIF_BLOCKSTEP)) {
+ unsigned long debugctl = get_debugctlmsr();
+
+ debugctl |= DEBUGCTLMSR_BTF;
+ update_debugctlmsr(debugctl);
+ }
}
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 1a60beb..8328009 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -195,6 +195,17 @@
prev = &prev_p->thread;
next = &next_p->thread;
+ if (test_tsk_thread_flag(prev_p, TIF_BLOCKSTEP) ^
+ test_tsk_thread_flag(next_p, TIF_BLOCKSTEP)) {
+ unsigned long debugctl = get_debugctlmsr();
+
+ debugctl &= ~DEBUGCTLMSR_BTF;
+ if (test_tsk_thread_flag(next_p, TIF_BLOCKSTEP))
+ debugctl |= DEBUGCTLMSR_BTF;
+
+ update_debugctlmsr(debugctl);
+ }
+
if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
test_tsk_thread_flag(next_p, TIF_NOTSC)) {
/* prev and next are different */
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index 7beba07..58de45e 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -169,9 +169,19 @@
* So noone should try to use debugger block stepping in a program
* that uses user-mode single stepping itself.
*/
- if (!enable_single_step(child))
- return;
- /* XXX */
+ if (enable_single_step(child) && block) {
+ unsigned long debugctl = get_debugctlmsr();
+
+ debugctl |= DEBUGCTLMSR_BTF;
+ update_debugctlmsr(debugctl);
+ set_tsk_thread_flag(child, TIF_BLOCKSTEP);
+ } else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {
+ unsigned long debugctl = get_debugctlmsr();
+
+ debugctl &= ~DEBUGCTLMSR_BTF;
+ update_debugctlmsr(debugctl);
+ clear_tsk_thread_flag(child, TIF_BLOCKSTEP);
+ }
}
void user_enable_single_step(struct task_struct *child)
@@ -189,7 +199,13 @@
/*
* Make sure block stepping (BTF) is disabled.
*/
- /* XXX */
+ if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {
+ unsigned long debugctl = get_debugctlmsr();
+
+ debugctl &= ~DEBUGCTLMSR_BTF;
+ update_debugctlmsr(debugctl);
+ clear_tsk_thread_flag(child, TIF_BLOCKSTEP);
+ }
/* Always clear TIF_SINGLESTEP... */
clear_tsk_thread_flag(child, TIF_SINGLESTEP);
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index e3da5d7..36f1bd9 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -544,6 +544,11 @@
/* DR6 may or may not be cleared by the CPU */
set_debugreg(0, 6);
+ /*
+ * The processor cleared BTF, so don't mark that we need it set.
+ */
+ clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP);
+
/* Store the virtualized DR6 value */
tsk->thread.debugreg6 = dr6;
