[Patch 2/2] HW-BKPT: Allow kernel breakpoints to be modified through a new API

K.Prasad
2009-08-25T20:22:09Z

[-- Attachment #1: modify_kernel_hbp_02 --]
[-- Type: text/plain, Size: 3125 bytes --]

Introduce modify_kernel_hw_breakpoint() API that can quickly change the
characteristics (such as address, length, type but not cpumask) of a
kernel-space breakpoint without having to unregister first and then
re-register it.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
---
include/asm-generic/hw_breakpoint.h | 2 +
kernel/hw_breakpoint.c | 49 ++++++++++++++++++++++++++++++++++++
2 files changed, 51 insertions(+)

Index: linux-2.6-tip.hbkpt/include/asm-generic/hw_breakpoint.h
===================================================================
--- linux-2.6-tip.hbkpt.orig/include/asm-generic/hw_breakpoint.h
+++ 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;
Index: linux-2.6-tip.hbkpt/kernel/hw_breakpoint.c
===================================================================
--- linux-2.6-tip.hbkpt.orig/kernel/hw_breakpoint.c
+++ linux-2.6-tip.hbkpt/kernel/hw_breakpoint.c
@@ -362,6 +362,55 @@ err_ret:
}
EXPORT_SYMBOL_GPL(register_kernel_hw_breakpoint);

+/**
+ * modify_kernel_hw_breakpoint - modify characteristics of a previously registered breakpoint request
+ * @old_bp: pointer to the registered breakpoint structure
+ * @new_bp: pointer to the breakpoint structure that replaces @old_bp
+ *
+ */
+int modify_kernel_hw_breakpoint(struct hw_breakpoint *old_bp,
+ struct hw_breakpoint *new_bp)
+{
+ int i, rc;
+ unsigned int cpu;
+ const cpumask_t *new_cpumask = new_bp->cpumask;
+
+ /* Default to ALL CPUs if cpumask is not specified */
+ if (!new_cpumask)
+ new_cpumask = new_bp->cpumask = cpu_possible_mask;
+ /*
+ * The user cannot modify the cpumask of the registered breakpoint
+ * It requires non-trivial amount of code and new data-structures to
+ * allow a change in cpumask value. The user must instead 'unregister'
+ * and re-register a new breakpoint if 'cpumask' should be changed
+ */
+ if (!cpumask_equal(old_bp->cpumask, new_cpumask))
+ return -EINVAL;
+
+ rc = arch_validate_hwbkpt_settings(new_bp, NULL);
+ if (rc)
+ return rc;
+
+ spin_lock_bh(&hw_breakpoint_lock);
+ for_each_cpu(cpu, new_cpumask) {
+ for (i = HBP_NUM-1; i >= hbp_kernel_pos; i--) {
+ if (per_cpu(this_hbp_kernel[i], cpu) == old_bp) {
+ per_cpu(this_hbp_kernel[i], cpu) = new_bp;
+ break;
+ }
+ }
+ }
+
+ if (cpumask_test_cpu(smp_processor_id(), new_cpumask))
+ arch_update_kernel_hw_breakpoint(NULL);
+ smp_call_function_many(new_cpumask,
+ arch_update_kernel_hw_breakpoint, NULL, 1);
+
+ spin_unlock_bh(&hw_breakpoint_lock);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(modify_kernel_hw_breakpoint);
+
/* Removes breakpoint structure from the per-cpu breakpoint data-structure */
static void remove_each_cpu_kernel_hbp(void *bp_param)
{