[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>

1 files changed, 4 insertions, 4 deletions

diff --git a/include/asm-x86_64/pda.h b/include/asm-x86_64/pda.h
index 8733ccfa442e..431a909fbec9 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[];
 
 /*