[RFC PATCH 2/3] Djprobe improvement patches (Re: Dynamic djprobe)

[Masami Hiramatsu <hiramatu at sdl dot hitachi dot co dot jp>]

Hi,

This patch is for finding the executing address hidden by nested 
interrupts. I introduced an address_stack structure, and 
push/pop_iaddr() macros. push_iaddr() stores interrupted executing 
address into address_stack percpu stacks and increments a counter. 
pop_iaddr() just decrements the counter. We can find hidden addresses 
from address_stack and check it.
But Satoshi pointed out the possibility of performance degradation. So I 
am developing another patch to find hidden address from current thread’s 
stack.

Thanks,

--
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: hiramatu@sdl.hitachi.co.jp


 arch/i386/kernel/apic.c          |    7 +++++++
 arch/i386/kernel/cpu/mcheck/p4.c |    3 +++
 arch/i386/kernel/irq.c           |    3 +++
 arch/i386/kernel/kprobes.c       |    2 +-
 arch/i386/kernel/smp.c           |    3 +++
 arch/i386/kernel/traps.c         |    4 +++-
 include/linux/kprobes.h          |   20 ++++++++++++++++++++
 kernel/kprobes.c                 |   22 ++++++++++++++++++++++
 8 files changed, 62 insertions(+), 2 deletions(-)
diff -Narup linux-2.6.12-djprobe.2/arch/i386/kernel/apic.c linux-2.6.12-djprobe.3/arch/i386/kernel/apic.c
--- linux-2.6.12-djprobe.2/arch/i386/kernel/apic.c	2005-06-18 04:48:29.000000000 +0900
+++ linux-2.6.12-djprobe.3/arch/i386/kernel/apic.c	2005-08-02 20:30:10.000000000 +0900
@@ -26,6 +26,7 @@
 #include <linux/mc146818rtc.h>
 #include <linux/kernel_stat.h>
 #include <linux/sysdev.h>
+#include <linux/kprobes.h>
 
 #include <asm/atomic.h>
 #include <asm/smp.h>
@@ -1178,7 +1179,9 @@ fastcall void smp_apic_timer_interrupt(s
 	 * interrupt lock, which is the WrongThing (tm) to do.
 	 */
 	irq_enter();
+	push_iaddr((void*)regs->eip);
 	smp_local_timer_interrupt(regs);
+	pop_iaddr();
 	irq_exit();
 }
 
@@ -1190,6 +1193,7 @@ fastcall void smp_spurious_interrupt(str
 	unsigned long v;
 
 	irq_enter();
+	push_iaddr((void*)regs->eip);
 	/*
 	 * Check if this really is a spurious interrupt and ACK it
 	 * if it is a vectored one.  Just in case...
@@ -1202,6 +1206,7 @@ fastcall void smp_spurious_interrupt(str
 	/* see sw-dev-man vol 3, chapter 7.4.13.5 */
 	printk(KERN_INFO "spurious APIC interrupt on CPU#%d, should never happen.\n",
 			smp_processor_id());
+	pop_iaddr();
 	irq_exit();
 }
 
@@ -1214,6 +1219,7 @@ fastcall void smp_error_interrupt(struct
 	unsigned long v, v1;
 
 	irq_enter();
+	push_iaddr((void*)regs->eip);
 	/* First tickle the hardware, only then report what went on. -- REW */
 	v = apic_read(APIC_ESR);
 	apic_write(APIC_ESR, 0);
@@ -1233,6 +1239,7 @@ fastcall void smp_error_interrupt(struct
 	*/
 	printk (KERN_DEBUG "APIC error on CPU%d: %02lx(%02lx)\n",
 	        smp_processor_id(), v , v1);
+	pop_iaddr();
 	irq_exit();
 }
 
diff -Narup linux-2.6.12-djprobe.2/arch/i386/kernel/cpu/mcheck/p4.c linux-2.6.12-djprobe.3/arch/i386/kernel/cpu/mcheck/p4.c
--- linux-2.6.12-djprobe.2/arch/i386/kernel/cpu/mcheck/p4.c	2005-06-18 04:48:29.000000000 +0900
+++ linux-2.6.12-djprobe.3/arch/i386/kernel/cpu/mcheck/p4.c	2005-08-02 20:30:10.000000000 +0900
@@ -9,6 +9,7 @@
 #include <linux/irq.h>
 #include <linux/interrupt.h>
 #include <linux/smp.h>
+#include <linux/kprobes.h>
 
 #include <asm/processor.h> 
 #include <asm/system.h>
@@ -73,7 +74,9 @@ static void (*vendor_thermal_interrupt)(
 fastcall void smp_thermal_interrupt(struct pt_regs *regs)
 {
 	irq_enter();
+	push_iaddr((void*)regs->eip);
 	vendor_thermal_interrupt(regs);
+	pop_iaddr();
 	irq_exit();
 }
 
diff -Narup linux-2.6.12-djprobe.2/arch/i386/kernel/irq.c linux-2.6.12-djprobe.3/arch/i386/kernel/irq.c
--- linux-2.6.12-djprobe.2/arch/i386/kernel/irq.c	2005-06-18 04:48:29.000000000 +0900
+++ linux-2.6.12-djprobe.3/arch/i386/kernel/irq.c	2005-08-02 20:30:10.000000000 +0900
@@ -15,6 +15,7 @@
 #include <linux/seq_file.h>
 #include <linux/interrupt.h>
 #include <linux/kernel_stat.h>
+#include <linux/kprobes.h>
 
 DEFINE_PER_CPU(irq_cpustat_t, irq_stat) ____cacheline_maxaligned_in_smp;
 EXPORT_PER_CPU_SYMBOL(irq_stat);
@@ -58,6 +59,7 @@ fastcall unsigned int do_IRQ(struct pt_r
 #endif
 
 	irq_enter();
+	push_iaddr((void*)regs->eip);
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
 	/* Debugging check for stack overflow: is there less than 1KB free? */
 	{
@@ -104,6 +106,7 @@ fastcall unsigned int do_IRQ(struct pt_r
 #endif
 		__do_IRQ(irq, regs);
 
+	pop_iaddr();
 	irq_exit();
 
 	return 1;
diff -Narup linux-2.6.12-djprobe.2/arch/i386/kernel/kprobes.c linux-2.6.12-djprobe.3/arch/i386/kernel/kprobes.c
--- linux-2.6.12-djprobe.2/arch/i386/kernel/kprobes.c	2005-08-01 22:00:17.000000000 +0900
+++ linux-2.6.12-djprobe.3/arch/i386/kernel/kprobes.c	2005-08-02 20:30:10.000000000 +0900
@@ -497,7 +497,7 @@ int djprobe_bypass_handler(struct kprobe
 	kprobe_opcode_t *stub = djpi->stub.insn;
 	int cpu = smp_processor_id();
 
-	if (!DJPI_CHECKED(djpi)) {
+	if (!DJPI_CHECKED(djpi) && check_safety_djprobe_instance(djpi)) {
 		cpu_set(cpu, djpi->checked_cpus); /* check this cpu */
 		
 		if (DJPI_CHECKED(djpi)) { /* all cpus are checked */
diff -Narup linux-2.6.12-djprobe.2/arch/i386/kernel/smp.c linux-2.6.12-djprobe.3/arch/i386/kernel/smp.c
--- linux-2.6.12-djprobe.2/arch/i386/kernel/smp.c	2005-06-18 04:48:29.000000000 +0900
+++ linux-2.6.12-djprobe.3/arch/i386/kernel/smp.c	2005-08-02 20:30:10.000000000 +0900
@@ -19,6 +19,7 @@
 #include <linux/mc146818rtc.h>
 #include <linux/cache.h>
 #include <linux/interrupt.h>
+#include <linux/kprobes.h>
 
 #include <asm/mtrr.h>
 #include <asm/tlbflush.h>
@@ -601,7 +602,9 @@ fastcall void smp_call_function_interrup
 	 * At this point the info structure may be out of scope unless wait==1
 	 */
 	irq_enter();
+	push_iaddr((void*)regs->eip);
 	(*func)(info);
+	pop_iaddr();
 	irq_exit();
 
 	if (wait) {
diff -Narup linux-2.6.12-djprobe.2/arch/i386/kernel/traps.c linux-2.6.12-djprobe.3/arch/i386/kernel/traps.c
--- linux-2.6.12-djprobe.2/arch/i386/kernel/traps.c	2005-06-18 04:48:29.000000000 +0900
+++ linux-2.6.12-djprobe.3/arch/i386/kernel/traps.c	2005-08-02 20:30:10.000000000 +0900
@@ -616,12 +616,13 @@ static int dummy_nmi_callback(struct pt_
 }
  
 static nmi_callback_t nmi_callback = dummy_nmi_callback;
- 
+
 fastcall void do_nmi(struct pt_regs * regs, long error_code)
 {
 	int cpu;
 
 	nmi_enter();
+	push_iaddr((void *)regs->eip);
 
 	cpu = smp_processor_id();
 	++nmi_count(cpu);
@@ -629,6 +630,7 @@ fastcall void do_nmi(struct pt_regs * re
 	if (!nmi_callback(regs, cpu))
 		default_do_nmi(regs);
 
+	pop_iaddr();
 	nmi_exit();
 }
 
diff -Narup linux-2.6.12-djprobe.2/include/linux/kprobes.h linux-2.6.12-djprobe.3/include/linux/kprobes.h
--- linux-2.6.12-djprobe.2/include/linux/kprobes.h	2005-08-02 20:29:44.000000000 +0900
+++ linux-2.6.12-djprobe.3/include/linux/kprobes.h	2005-08-02 20:30:10.000000000 +0900
@@ -33,6 +33,7 @@
 #include <linux/notifier.h>
 #include <linux/smp.h>
 #include <asm/kprobes.h>
+#include <linux/irq.h>
 
 struct kprobe;
 struct pt_regs;
@@ -121,6 +122,24 @@ struct djprobe {
 	struct djprobe_instance * inst;
 };
 
+#ifdef CONFIG_DJPROBE
+# define ADDR_STACK_SIZE  NR_IRQS
+struct address_stack {
+	int sp;
+	void * addrs[ADDR_STACK_SIZE];
+};
+DECLARE_PER_CPU(struct address_stack, iadr_stack);
+/* push/pop interrupted address (should be called from non-preempt area)*/
+# define push_iaddr(addr) { int sp=__get_cpu_var(iadr_stack).sp++; \
+	if (sp < ADDR_STACK_SIZE && sp >= 0) \
+		__get_cpu_var(iadr_stack).addrs[sp]=(addr);}
+# define pop_iaddr() { int sp=__get_cpu_var(iadr_stack).sp--; \
+	if (sp <= 0) __get_cpu_var(iadr_stack).sp=0;}
+#else /*!DJPROBE*/
+# define push_iaddr(addr) do { } while (0)
+# define pop_iaddr()      do { } while (0)
+#endif
+
 #ifdef CONFIG_KPROBES
 /* Locks kprobe: irq must be disabled */
 void lock_kprobes(void);
@@ -155,6 +174,7 @@ extern int arch_prepare_djprobe_instance
 extern int djprobe_bypass_handler(struct kprobe * kp, struct pt_regs * regs);
 extern void arch_uninstall_djprobe_instance(struct djprobe_instance *djpi);
 extern void schdule_release_djprobe_instance(void);
+extern int check_safety_djprobe_instance(struct djprobe_instance *djpi);
 
 int register_djprobe(struct djprobe *p);
 void unregister_djprobe(struct djprobe *p);
diff -Narup linux-2.6.12-djprobe.2/kernel/kprobes.c linux-2.6.12-djprobe.3/kernel/kprobes.c
--- linux-2.6.12-djprobe.2/kernel/kprobes.c	2005-08-01 22:00:17.000000000 +0900
+++ linux-2.6.12-djprobe.3/kernel/kprobes.c	2005-08-02 20:30:10.000000000 +0900
@@ -265,10 +265,32 @@ void unregister_jprobe(struct jprobe *jp
  * This list is operated on registering and unregistering djprobe.
  * Thus, It is not required processing speed. I decided using a 'list'.
  */
+DEFINE_PER_CPU(struct address_stack, iadr_stack);
 static DEFINE_SPINLOCK(djprobe_lock);
 static LIST_HEAD(djprobe_list);
 static int nr_instances = 0;
 
+/* safety check routine */
+int check_safety_djprobe_instance(struct djprobe_instance *djpi)
+{
+	int sp;
+	preempt_disable();
+	sp = __get_cpu_var(iadr_stack).sp;
+	if (sp > ADDR_STACK_SIZE ){
+		return 0;  /*overflowed -- we can't check it*/
+	}
+	
+	for (; sp > 0; sp--) {
+		void * addr = __get_cpu_var(iadr_stack).addrs[sp];
+		if((void*)djpi->kp.addr < addr && 
+		   (void*)djpi->kp.addr + djpi->stub.size > addr)
+			return 0; /*we find insertion address 
+				   in interrupted addresses*/
+	}
+	preempt_enable();
+	return 1;
+}
+
 static void work_free_djprobe_instances(void *data)
 {
 	struct list_head *pos;