[PATCH] x86_64: Allow nesting of int3 by default for kprobes

This unbreaks recursive kprobes which didn't work anymore
due to an earlier patch which converted the debug entry point
to use an IST.

This also allows nesting of the debug entry point too.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/asm-offsets.c

@@ -43,6 +43,7 @@ int main(void)
 	ENTRY(irqcount);
 	ENTRY(cpunumber);
 	ENTRY(irqstackptr);
+	ENTRY(data_offset);
 	BLANK();
 #undef ENTRY
 #ifdef CONFIG_IA32_EMULATION
@@ -66,8 +67,6 @@ int main(void)
 	DEFINE(pbe_orig_address, offsetof(struct pbe, orig_address));
 	DEFINE(pbe_next, offsetof(struct pbe, next));
 	BLANK();
-#if DEBUG_STKSZ > EXCEPTION_STKSZ
-	DEFINE(DEBUG_IST, DEBUG_STACK);
-#endif
+	DEFINE(TSS_ist, offsetof(struct tss_struct, ist));
 	return 0;
 }

arch/x86_64/kernel/entry.S

@@ -41,6 +41,7 @@
 #include <asm/unistd.h>
 #include <asm/thread_info.h>
 #include <asm/hw_irq.h>
+#include <asm/page.h>
 
 	.code64
 
@@ -674,9 +675,6 @@ ENTRY(spurious_interrupt)
 
 	/* error code is on the stack already */
 	/* handle NMI like exceptions that can happen everywhere */
-#ifndef DEBUG_IST
-# define DEBUG_IST 0
-#endif
 	.macro paranoidentry sym, ist=0
 	SAVE_ALL
 	cld
@@ -695,11 +693,11 @@ ENTRY(spurious_interrupt)
 	movq ORIG_RAX(%rsp),%rsi
 	movq $-1,ORIG_RAX(%rsp)
 	.if \ist
-	subq	$EXCEPTION_STACK_SIZE, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)
+	subq	$EXCEPTION_STKSZ, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)
 	.endif
 	call \sym
 	.if \ist
-	addq	$EXCEPTION_STACK_SIZE, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)
+	addq	$EXCEPTION_STKSZ, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)
 	.endif
 	cli
 	.endm
@@ -918,7 +916,7 @@ KPROBE_ENTRY(debug)
  	INTR_FRAME
 	pushq $0
 	CFI_ADJUST_CFA_OFFSET 8		
-	paranoidentry do_debug, DEBUG_IST
+	paranoidentry do_debug, DEBUG_STACK
 	jmp paranoid_exit
 	CFI_ENDPROC
 	.previous .text
@@ -976,7 +974,7 @@ KPROBE_ENTRY(int3)
  	INTR_FRAME
  	pushq $0
  	CFI_ADJUST_CFA_OFFSET 8
- 	paranoidentry do_int3, DEBUG_IST
+ 	paranoidentry do_int3, DEBUG_STACK
  	jmp paranoid_exit
  	CFI_ENDPROC
 	.previous .text

include/asm-x86_64/page.h

@@ -26,6 +26,13 @@
 #define IRQSTACK_ORDER 2
 #define IRQSTACKSIZE (PAGE_SIZE << IRQSTACK_ORDER)
 
+#define STACKFAULT_STACK 1
+#define DOUBLEFAULT_STACK 2
+#define NMI_STACK 3
+#define DEBUG_STACK 4
+#define MCE_STACK 5
+#define N_EXCEPTION_STACKS 5  /* hw limit: 7 */
+
 #define LARGE_PAGE_MASK (~(LARGE_PAGE_SIZE-1))
 #define LARGE_PAGE_SIZE (1UL << PMD_SHIFT)
 

include/asm-x86_64/processor.h

@@ -273,13 +273,6 @@ struct thread_struct {
 #define INIT_MMAP \
 { &init_mm, 0, 0, NULL, PAGE_SHARED, VM_READ | VM_WRITE | VM_EXEC, 1, NULL, NULL }
 
-#define STACKFAULT_STACK 1
-#define DOUBLEFAULT_STACK 2 
-#define NMI_STACK 3 
-#define DEBUG_STACK 4 
-#define MCE_STACK 5
-#define N_EXCEPTION_STACKS 5  /* hw limit: 7 */
-
 #define start_thread(regs,new_rip,new_rsp) do { \
 	asm volatile("movl %0,%%fs; movl %0,%%es; movl %0,%%ds": :"r" (0));	 \
 	load_gs_index(0);							\