[PATCH] x86_64: Move int 3 handler to debug stack and allow to increase it.

This
- switches the INT3 handler to run on an IST stack (to cope with
  breakpoints set by a kernel debugger on places where the kernel's
  %gs base hasn't been set up, yet); the IST stack used is shared with
  the INT1 handler's
[AK: this also allows setting a kprobe on the interrupt/exception entry
points]
- allows nesting of INT1/INT3 handlers so that one can, with a kernel
  debugger, debug (at least) the user-mode portions of the INT1/INT3
  handling; the nesting isn't actively enabled here since a kernel-
  debugger-free kernel doesn't need it

Signed-Off-By: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 19 insertions, 11 deletions

diff --git a/include/asm-x86_64/desc.h b/include/asm-x86_64/desc.h
index 3376486..5ce0e34 100644
--- a/include/asm-x86_64/desc.h
+++ b/include/asm-x86_64/desc.h
@@ -114,6 +114,11 @@ static inline void set_system_gate(int nr, void *func)
 	_set_gate(&idt_table[nr], GATE_INTERRUPT, (unsigned long) func, 3, 0); 
 } 
 
+static inline void set_system_gate_ist(int nr, void *func, unsigned ist)
+{
+	_set_gate(&idt_table[nr], GATE_INTERRUPT, (unsigned long) func, 3, ist);
+}
+
 static inline void set_tssldt_descriptor(void *ptr, unsigned long tss, unsigned type, 
 					 unsigned size) 
 { 
diff --git a/include/asm-x86_64/page.h b/include/asm-x86_64/page.h
index 06e489f..dcbb4fc 100644
--- a/include/asm-x86_64/page.h
+++ b/include/asm-x86_64/page.h
@@ -14,13 +14,18 @@
 #define PHYSICAL_PAGE_MASK	(~(PAGE_SIZE-1) & __PHYSICAL_MASK)
 
 #define THREAD_ORDER 1 
-#ifdef __ASSEMBLY__
-#define THREAD_SIZE  (1 << (PAGE_SHIFT + THREAD_ORDER))
-#else
-#define THREAD_SIZE  (1UL << (PAGE_SHIFT + THREAD_ORDER))
-#endif
+#define THREAD_SIZE  (PAGE_SIZE << THREAD_ORDER)
 #define CURRENT_MASK (~(THREAD_SIZE-1))
 
+#define EXCEPTION_STACK_ORDER 0
+#define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
+
+#define DEBUG_STACK_ORDER EXCEPTION_STACK_ORDER
+#define DEBUG_STKSZ (PAGE_SIZE << DEBUG_STACK_ORDER)
+
+#define IRQSTACK_ORDER 2
+#define IRQSTACKSIZE (PAGE_SIZE << IRQSTACK_ORDER)
+
 #define LARGE_PAGE_MASK (~(LARGE_PAGE_SIZE-1))
 #define LARGE_PAGE_SIZE (1UL << PMD_SHIFT)
 
diff --git a/include/asm-x86_64/pda.h b/include/asm-x86_64/pda.h
index 8733ccf..431a909 100644
--- a/include/asm-x86_64/pda.h
+++ b/include/asm-x86_64/pda.h
@@ -5,6 +5,7 @@
 #include <linux/stddef.h>
 #include <linux/types.h>
 #include <linux/cache.h>
+#include <asm/page.h>
 
 /* Per processor datastructure. %gs points to it while the kernel runs */ 
 struct x8664_pda {
@@ -12,6 +13,9 @@ struct x8664_pda {
 	unsigned long data_offset;	/* Per cpu data offset from linker address */
 	unsigned long kernelstack;  /* top of kernel stack for current */ 
 	unsigned long oldrsp; 	    /* user rsp for system call */
+#if DEBUG_STKSZ > EXCEPTION_STKSZ
+	unsigned long debugstack;   /* #DB/#BP stack. */
+#endif
         int irqcount;		    /* Irq nesting counter. Starts with -1 */  	
 	int cpunumber;		    /* Logical CPU number */
 	char *irqstackptr;	/* top of irqstack */
@@ -23,10 +27,6 @@ struct x8664_pda {
 	unsigned apic_timer_irqs;
 } ____cacheline_aligned_in_smp;
 
-
-#define IRQSTACK_ORDER 2
-#define IRQSTACKSIZE (PAGE_SIZE << IRQSTACK_ORDER) 
-
 extern struct x8664_pda cpu_pda[];
 
 /* 
diff --git a/include/asm-x86_64/processor.h b/include/asm-x86_64/processor.h
index 4861246..5cb1515 100644
--- a/include/asm-x86_64/processor.h
+++ b/include/asm-x86_64/processor.h
@@ -273,8 +273,6 @@ struct thread_struct {
 #define DEBUG_STACK 4 
 #define MCE_STACK 5
 #define N_EXCEPTION_STACKS 5  /* hw limit: 7 */
-#define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
-#define EXCEPTION_STACK_ORDER 0 
 
 #define start_thread(regs,new_rip,new_rsp) do { \
 	asm volatile("movl %0,%%fs; movl %0,%%es; movl %0,%%ds": :"r" (0));	 \