The following commit has been merged into the x86/entry branch of tip:
Commit-ID: 57234891b3287b986e003876f906d95c9871e62e
Gitweb: https://git.kernel.org/tip/57234891b3287b986e003876f906d95c9871e62e
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 29 May 2020 23:27:33 +02:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Sat, 30 May 2020 10:00:07 +02:00
x86/entry: Introduce local_db_{save,restore}()
In order to allow other exceptions than #DB to disable breakpoints,
provide common helpers.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200529213321.012060983@xxxxxxxxxxxxx
---
arch/x86/include/asm/debugreg.h | 30 ++++++++++++++++++++++++++++++
arch/x86/kernel/traps.c | 18 ++----------------
2 files changed, 32 insertions(+), 16 deletions(-)
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 1a8609a..4ef8690 100644
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -113,6 +113,36 @@ static inline void debug_stack_usage_inc(void) { }
static inline void debug_stack_usage_dec(void) { }
#endif /* X86_64 */
+static __always_inline unsigned long local_db_save(void)
+{
+ unsigned long dr7;
+
+ get_debugreg(dr7, 7);
+ dr7 &= ~0x400; /* architecturally set bit */
+ if (dr7)
+ set_debugreg(0, 7);
+ /*
+ * Ensure the compiler doesn't lower the above statements into
+ * the critical section; disabling breakpoints late would not
+ * be good.
+ */
+ barrier();
+
+ return dr7;
+}
+
+static __always_inline void local_db_restore(unsigned long dr7)
+{
+ /*
+ * Ensure the compiler doesn't raise this statement into
+ * the critical section; enabling breakpoints early would
+ * not be good.
+ */
+ barrier();
+ if (dr7)
+ set_debugreg(dr7, 7);
+}
+
#ifdef CONFIG_CPU_SUP_AMD
extern void set_dr_addr_mask(unsigned long mask, int dr);
#else
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 50fb9cd..bcb9dd9 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -727,15 +727,7 @@ static __always_inline void debug_enter(unsigned long *dr6, unsigned long *dr7)
* Entry text is excluded for HW_BP_X and cpu_entry_area, which
* includes the entry stack is excluded for everything.
*/
- get_debugreg(*dr7, 7);
- set_debugreg(0, 7);
-
- /*
- * Ensure the compiler doesn't lower the above statements into
- * the critical section; disabling breakpoints late would not
- * be good.
- */
- barrier();
+ *dr7 = local_db_save();
/*
* The Intel SDM says:
@@ -756,13 +748,7 @@ static __always_inline void debug_enter(unsigned long *dr6, unsigned long *dr7)
static __always_inline void debug_exit(unsigned long dr7)
{
- /*
- * Ensure the compiler doesn't raise this statement into
- * the critical section; enabling breakpoints early would
- * not be good.
- */
- barrier();
- set_debugreg(dr7, 7);
+ local_db_restore(dr7);
}
/*
|