Skip to contentSkip to conversation

HW-BKPT: Allow per-cpu kernel-space Hardware Breakpoint requests

PATCH New K.Prasad 1 participant 3 messages Aug 28, 2009 1 message not in the archive

Subsystems (2)
x86 Generic include/asm header files
lore
Share & tools
lore

K.Prasad

author
#1 lore raw

PATCH 1/3 HW-BKPT: Allow per-cpu kernel-space Hardware Breakpoint requests

In reply to a message not in the archive

Allow kernel-space hw-breakpoints to be restricted only for a subset of CPUs using a cpumask field in 'struct hw_breakpoint'.

Signed-off-by K.Prasad <[email protected]>
---
 arch/x86/include/asm/hw_breakpoint.h |    1 
 arch/x86/kernel/hw_breakpoint.c      |   12 +++
 include/asm-generic/hw_breakpoint.h  |    2 
 kernel/hw_breakpoint.c               |  124 +++++++++++++++++++++++++----------
 4 files changed, 104 insertions(+), 35 deletions(-)
arch/x86/kernel/hw_breakpoint.c +11 -1
Index: linux-2.6-tip.hbkpt/arch/x86/kernel/hw_breakpoint.c
===================================================================
@@ -68,6 +68,12 @@ static unsigned long encode_dr7(int drnu
 	return bp_info;
 }
 
+/* Disable breakpoints on the physical debug registers */
+void arch_disable_hw_breakpoint(void)
+{
+	set_debugreg(0UL, 7);
+}
+
 void arch_update_kernel_hw_breakpoint(void *unused)
 {
 	struct hw_breakpoint *bp;

@@ -78,7 +84,7 @@ void arch_update_kernel_hw_breakpoint(vo
 	set_debugreg(0UL, 7);
 
 	for (i = hbp_kernel_pos; i < HBP_NUM; i++) {
-		per_cpu(this_hbp_kernel[i], cpu) = bp = hbp_kernel[i];
+		bp = per_cpu(this_hbp_kernel[i], cpu);
 		if (bp) {
 			temp_kdr7 |= encode_dr7(i, bp->info.len, bp->info.type);
 			set_debugreg(bp->info.address, i);

@@ -207,6 +213,10 @@ int arch_validate_hwbkpt_settings(struct
 	unsigned int align;
 	int ret = -EINVAL;
 
+	/* User-space breakpoints cannot be restricted to a subset of CPUs */
+	if (tsk && bp->cpumask)
+		return ret;
+
 	switch (bp->info.type) {
 	/*
 	 * Ptrace-refactoring code
include/asm-generic/hw_breakpoint.h +2 -0
Index: linux-2.6-tip.hbkpt/include/asm-generic/hw_breakpoint.h
===================================================================
@@ -8,6 +8,7 @@
 #ifdef	__KERNEL__
 #include <linux/list.h>
 #include <linux/types.h>
+#include <linux/cpumask.h>
 #include <linux/kallsyms.h>
 
 /**

@@ -102,6 +103,7 @@
  */
 struct hw_breakpoint {
 	void (*triggered)(struct hw_breakpoint *, struct pt_regs *);
+	const cpumask_t *cpumask;
 	struct arch_hw_breakpoint info;
 };
kernel/hw_breakpoint.c +90 -34

175 lines not on this page · raw message

arch/x86/include/asm/hw_breakpoint.h +1 -0
Index: linux-2.6-tip.hbkpt/arch/x86/include/asm/hw_breakpoint.h
===================================================================
@@ -48,6 +48,7 @@ extern int arch_validate_hwbkpt_settings
 extern void arch_update_user_hw_breakpoint(int pos, struct task_struct *tsk);
 extern void arch_flush_thread_hw_breakpoint(struct task_struct *tsk);
 extern void arch_update_kernel_hw_breakpoint(void *);
+extern void arch_disable_hw_breakpoint(void);
 extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
 				     unsigned long val, void *data);
 #endif	/* __KERNEL__ */
author
#2 lore raw

PATCH 2/3 HW-BKPT: Allow kernel breakpoints to be modified through a new API

In reply to a message not in the archive

Introduce modify_kernel_hw_breakpoint() API that can quickly change the characteristics (such as address, length, type) of a kernel-space breakpoint without having to unregister first and then re-register it.

Signed-off-by K.Prasad <[email protected]>
---
 include/asm-generic/hw_breakpoint.h |    2 +
 kernel/hw_breakpoint.c              |   49 ++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)
include/asm-generic/hw_breakpoint.h +2 -0
Index: linux-2.6-tip.hbkpt/include/asm-generic/hw_breakpoint.h
===================================================================
@@ -133,6 +133,8 @@ extern void unregister_user_hw_breakpoin
  * Kernel breakpoints are not associated with any particular thread.
  */
 extern int register_kernel_hw_breakpoint(struct hw_breakpoint *bp);
+extern int modify_kernel_hw_breakpoint(struct hw_breakpoint *old_bp,
+					struct hw_breakpoint *new_bp);
 extern void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp);
 
 extern unsigned int hbp_kernel_pos;
kernel/hw_breakpoint.c +49 -0

55 lines not on this page · raw message

author
#3 lore raw

PATCH 3/3 HW-BKPT: Enable/disable the breakpoints when still registered

In reply to a message not in the archive

Allow breakpoints to be enabled/disabled without yielding the breakpoint request through new APIs - <enable><disable>_hw_breakpoint()

Signed-off-by K.Prasad <[email protected]>
---
 arch/x86/kernel/hw_breakpoint.c     |   12 +++---
 include/asm-generic/hw_breakpoint.h |   10 +++++
 kernel/hw_breakpoint.c              |   66 ++++++++++++++++++++++++++++++++++++
 3 files changed, 83 insertions(+), 5 deletions(-)
arch/x86/kernel/hw_breakpoint.c +7 -5
Index: linux-2.6-tip.hbkpt/arch/x86/kernel/hw_breakpoint.c
===================================================================
@@ -85,10 +85,11 @@ void arch_update_kernel_hw_breakpoint(vo
 
 	for (i = hbp_kernel_pos; i < HBP_NUM; i++) {
 		bp = per_cpu(this_hbp_kernel[i], cpu);
-		if (bp) {
+		if (!bp)
+			continue;
+		set_debugreg(bp->info.address, i);
+		if (bp->enabled)
 			temp_kdr7 |= encode_dr7(i, bp->info.len, bp->info.type);
-			set_debugreg(bp->info.address, i);
-		}
 	}
 
 	/* No need to set DR6. Update the debug registers with kernel-space

@@ -288,8 +289,9 @@ void arch_update_user_hw_breakpoint(int 
 	thread->debugreg7 &= ~dr7_masks[pos];
 	if (bp) {
 		thread->debugreg[pos] = bp->info.address;
-		thread->debugreg7 |= encode_dr7(pos, bp->info.len,
-							bp->info.type);
+		if (bp->enabled)
+			thread->debugreg7 |= encode_dr7(pos, bp->info.len,
+								bp->info.type);
 	} else
 		thread->debugreg[pos] = 0;
 }
include/asm-generic/hw_breakpoint.h +10 -0
Index: linux-2.6-tip.hbkpt/include/asm-generic/hw_breakpoint.h
===================================================================
@@ -102,6 +102,12 @@
  * ----------------------------------------------------------------------
  */
 struct hw_breakpoint {
+	/*
+	 * Denotes if a breakpoint is currently enabled in physical debug
+	 * registers. Not to be set directly by the end-user. Must be
+	 * operated through <enable><disable>_hw_breakpoint() APIs only.
+	 */
+	bool enabled;
 	void (*triggered)(struct hw_breakpoint *, struct pt_regs *);
 	const cpumask_t *cpumask;
 	struct arch_hw_breakpoint info;

@@ -137,6 +143,10 @@ extern int modify_kernel_hw_breakpoint(s
 					struct hw_breakpoint *new_bp);
 extern void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp);
 
+extern void enable_hw_breakpoint(struct hw_breakpoint *bp,
+				 struct task_struct *tsk);
+extern void disable_hw_breakpoint(struct hw_breakpoint *bp,
+				  struct task_struct *tsk);
 extern unsigned int hbp_kernel_pos;
 
 #endif	/* __KERNEL__ */
kernel/hw_breakpoint.c +66 -0

78 lines not on this page · raw message