Here is the patch to provide kernel watch points. This requires
the earlier debug registers patch. The simple interface
provided is:
int register_kwatch(unsigned long addr, u8 length, u8 type,
kwatch_handler_t handler)
return value is the debug register number allocated/used
for setting up this watch point.
and
void unregister_kwatch(int debugreg)
--
Vamsi Krishna S.
Linux Technology Center,
IBM Software Lab, Bangalore.
Ph: +91 80 5044959
Internet: [email protected]
--
diff -urN -X /home/vamsi/.dontdiff 44-pure/arch/i386/config.in 44-kprobes/arch/i386/config.in
--- 44-pure/arch/i386/config.in 2002-10-22 14:08:23.000000000 +0530
+++ 44-kprobes/arch/i386/config.in 2002-10-22 14:09:32.000000000 +0530
@@ -458,6 +458,7 @@
bool 'Kernel debugging' CONFIG_DEBUG_KERNEL
if [ "$CONFIG_DEBUG_KERNEL" != "n" ]; then
bool ' Global Debug Registers' CONFIG_DEBUGREG
+ dep_bool ' Kwatch points' CONFIG_KWATCH $CONFIG_DEBUGREG
bool ' Check for stack overflows' CONFIG_DEBUG_STACKOVERFLOW
bool ' Debug memory allocations' CONFIG_DEBUG_SLAB
bool ' Memory mapped I/O debugging' CONFIG_DEBUG_IOVIRT
diff -urN -X /home/vamsi/.dontdiff 44-pure/arch/i386/kernel/kwatch.c 44-kprobes/arch/i386/kernel/kwatch.c
--- 44-pure/arch/i386/kernel/kwatch.c 1970-01-01 05:30:00.000000000 +0530
+++ 44-kprobes/arch/i386/kernel/kwatch.c 2002-10-22 14:09:11.000000000 +0530
@@ -0,0 +1,135 @@
+/*
+ * Support for kernel watchpoints.
+ * (C) 2002 Vamsi Krishna S <[email protected]>.
+ */
+#include <linux/config.h>
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <asm/kwatch.h>
+#include <asm/debugreg.h>
+#include <asm/bitops.h>
+
+static struct kwatch kwatch_list[DR_MAX];
+static spinlock_t kwatch_lock = SPIN_LOCK_UNLOCKED;
+static unsigned long kwatch_in_progress; /* currently being handled */
+
+struct dr_info {
+ int debugreg;
+ unsigned long addr;
+ int type;
+};
+
+static inline void write_smp_dr(void *info)
+{
+ struct dr_info *dr = (struct dr_info *)info;
+
+ if (cpu_has_de && dr->type == DR_TYPE_IO)
+ set_in_cr4(X86_CR4_DE);
+ write_dr(dr->debugreg, dr->addr);
+}
+
+/* Update the debug register on all CPUs */
+static void sync_dr(int debugreg, unsigned long addr, int type)
+{
+ struct dr_info dr;
+ dr.debugreg = debugreg;
+ dr.addr = addr;
+ dr.type = type;
+ smp_call_function(write_smp_dr, &dr, 0, 0);
+}
+
+/*
+ * Interrupts are disabled on entry as trap1 is an interrupt gate and they
+ * remain disabled thorough out this function.
+ */
+int kwatch_handler(unsigned long condition, struct pt_regs *regs)
+{
+ int debugreg = dr_trap(condition);
+ unsigned long addr = dr_trap_addr(condition);
+ int retval = 0;
+
+ if (!(condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3))) {
+ return 0;
+ }
+
+ /* We're in an interrupt, but this is clear and BUG()-safe. */
+ preempt_disable();
+
+ /* If we are recursing, we already hold the lock. */
+ if (kwatch_in_progress) {
+ goto recursed;
+ }
+ set_bit(debugreg, &kwatch_in_progress);
+
+ spin_lock(&kwatch_lock);
+ if (kwatch_list[debugreg].addr != addr)
+ goto out;
+
+ if (kwatch_list[debugreg].handler) {
+ kwatch_list[debugreg].handler(&kwatch_list[debugreg], regs);
+ }
+
+ if (kwatch_list[debugreg].type == DR_TYPE_EXECUTE)
+ regs->eflags |= RF_MASK;
+out:
+ clear_bit(debugreg, &kwatch_in_progress);
+ spin_unlock(&kwatch_lock);
+ preempt_enable_no_resched();
+ return retval;
+
+recursed:
+ if (kwatch_list[debugreg].type == DR_TYPE_EXECUTE)
+ regs->eflags |= RF_MASK;
+ preempt_enable_no_resched();
+ return 1;
+}
+
+int register_kwatch(unsigned long addr, u8 length, u8 type,
+ kwatch_handler_t handler)
+{
+ int debugreg;
+ unsigned long dr7, flags;
+
+ debugreg = dr_alloc(DR_ANY, DR_ALLOC_GLOBAL);
+ if (debugreg < 0) {
+ return -1;
+ }
+
+ spin_lock_irqsave(&kwatch_lock, flags);
+ kwatch_list[debugreg].addr = addr;
+ kwatch_list[debugreg].length = length;
+ kwatch_list[debugreg].type = type;
+ kwatch_list[debugreg].handler = handler;
+ spin_unlock_irqrestore(&kwatch_lock, flags);
+
+ write_dr(debugreg, (unsigned long)addr);
+ sync_dr(debugreg, (unsigned long)addr, type);
+ if (cpu_has_de && type == DR_TYPE_IO)
+ set_in_cr4(X86_CR4_DE);
+
+ dr7 = read_dr(7);
+ SET_DR7(dr7, debugreg, type, length);
+ write_dr(7, dr7);
+ sync_dr(7, dr7, 0);
+ return debugreg;
+}
+
+void unregister_kwatch(int debugreg)
+{
+ unsigned long flags;
+ unsigned long dr7 = read_dr(7);
+
+ RESET_DR7(dr7, debugreg);
+ write_dr(7, dr7);
+ sync_dr(7, dr7, 0);
+ dr_free(debugreg);
+
+ spin_lock_irqsave(&kwatch_lock, flags);
+ kwatch_list[debugreg].addr = 0;
+ kwatch_list[debugreg].handler = NULL;
+ spin_unlock_irqrestore(&kwatch_lock, flags);
+}
+EXPORT_SYMBOL_GPL(register_kwatch);
+EXPORT_SYMBOL_GPL(unregister_kwatch);
diff -urN -X /home/vamsi/.dontdiff 44-pure/arch/i386/kernel/Makefile 44-kprobes/arch/i386/kernel/Makefile
--- 44-pure/arch/i386/kernel/Makefile 2002-10-22 14:08:23.000000000 +0530
+++ 44-kprobes/arch/i386/kernel/Makefile 2002-10-22 14:09:11.000000000 +0530
@@ -4,7 +4,7 @@
EXTRA_TARGETS := head.o init_task.o
-export-objs := mca.o i386_ksyms.o time.o debugreg.o
+export-objs := mca.o i386_ksyms.o time.o debugreg.o kwatch.o
obj-y := process.o semaphore.o signal.o entry.o traps.o irq.o vm86.o \
ptrace.o i8259.o ioport.o ldt.o setup.o time.o sys_i386.o \
@@ -31,6 +31,7 @@
obj-$(CONFIG_EDD) += edd.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_DEBUGREG) += debugreg.o
+obj-$(CONFIG_KWATCH) += kwatch.o
EXTRA_AFLAGS := -traditional
diff -urN -X /home/vamsi/.dontdiff 44-pure/arch/i386/kernel/traps.c 44-kprobes/arch/i386/kernel/traps.c
--- 44-pure/arch/i386/kernel/traps.c 2002-10-22 14:08:24.000000000 +0530
+++ 44-kprobes/arch/i386/kernel/traps.c 2002-10-22 14:09:11.000000000 +0530
@@ -39,6 +39,7 @@
#include <asm/io.h>
#include <asm/atomic.h>
#include <asm/debugreg.h>
+#include <asm/kwatch.h>
#include <asm/desc.h>
#include <asm/i387.h>
#include <asm/nmi.h>
@@ -591,6 +592,9 @@
if (post_kprobe_handler(regs))
return 1;
+ if (kwatch_handler(condition, regs))
+ return 1;
+
/* Interrupts not disabled for normal trap handling. */
restore_interrupts(regs);
diff -urN -X /home/vamsi/.dontdiff 44-pure/include/asm-i386/kwatch.h 44-kprobes/include/asm-i386/kwatch.h
--- 44-pure/include/asm-i386/kwatch.h 1970-01-01 05:30:00.000000000 +0530
+++ 44-kprobes/include/asm-i386/kwatch.h 2002-10-22 14:09:11.000000000 +0530
@@ -0,0 +1,31 @@
+#ifndef _ASM_KWATCH_H
+#define _ASM_KWATCH_H
+/*
+ * Dynamic Probes (kwatch points) support
+ * Vamsi Krishna S <[email protected]>, Oct, 2002
+ */
+#include <linux/types.h>
+#include <linux/ptrace.h>
+
+struct kwatch;
+typedef void (*kwatch_handler_t)(struct kwatch *, struct pt_regs *);
+
+struct kwatch {
+ unsigned long addr; /* location of watchpoint */
+ u8 length; /* range of address */
+ u8 type; /* type of watchpoint */
+ kwatch_handler_t handler;
+};
+
+#define RF_MASK 0x00010000
+
+#ifdef CONFIG_KWATCH
+extern int register_kwatch(unsigned long addr, u8 length, u8 type, kwatch_handler_t handler);
+extern void unregister_kwatch(int debugreg);
+extern int kwatch_handler(unsigned long condition, struct pt_regs *regs);
+#else
+static inline int register_kwatch(unsigned long addr, u8 length, u8 type, kwatch_handler_t handler) { return -ENOSYS; }
+static inline void unregister_kwatch(int debugreg) { }
+static inline int kwatch_handler(unsigned long condition, struct pt_regs *regs) { return 0; }
+#endif
+#endif /* _ASM_KWATCH_H */