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-rw-r--r--arch/x86/kernel/step.c46
1 files changed, 17 insertions, 29 deletions
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index 3149032ff107..58de45ee08b6 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -158,22 +158,6 @@ static int enable_single_step(struct task_struct *child)
}
/*
- * Install this value in MSR_IA32_DEBUGCTLMSR whenever child is running.
- */
-static void write_debugctlmsr(struct task_struct *child, unsigned long val)
-{
- if (child->thread.debugctlmsr == val)
- return;
-
- child->thread.debugctlmsr = val;
-
- if (child != current)
- return;
-
- update_debugctlmsr(val);
-}
-
-/*
* Enable single or block step.
*/
static void enable_step(struct task_struct *child, bool block)
@@ -186,15 +170,17 @@ static void enable_step(struct task_struct *child, bool block)
* that uses user-mode single stepping itself.
*/
if (enable_single_step(child) && block) {
- set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
- write_debugctlmsr(child,
- child->thread.debugctlmsr | DEBUGCTLMSR_BTF);
- } else {
- write_debugctlmsr(child,
- child->thread.debugctlmsr & ~DEBUGCTLMSR_BTF);
-
- if (!child->thread.debugctlmsr)
- clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
+ 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);
}
}
@@ -213,11 +199,13 @@ void user_disable_single_step(struct task_struct *child)
/*
* Make sure block stepping (BTF) is disabled.
*/
- write_debugctlmsr(child,
- child->thread.debugctlmsr & ~DEBUGCTLMSR_BTF);
+ if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {
+ unsigned long debugctl = get_debugctlmsr();
- if (!child->thread.debugctlmsr)
- clear_tsk_thread_flag(child, TIF_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);