[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>
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index bd21eba..28b3c8e 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -673,7 +673,10 @@
/* error code is on the stack already */
/* handle NMI like exceptions that can happen everywhere */
- .macro paranoidentry sym
+#ifndef DEBUG_IST
+# define DEBUG_IST 0
+#endif
+ .macro paranoidentry sym, ist=0
SAVE_ALL
cld
movl $1,%ebx
@@ -683,10 +686,20 @@
js 1f
swapgs
xorl %ebx,%ebx
-1: movq %rsp,%rdi
+1:
+ .if \ist
+ movq %gs:pda_data_offset, %rbp
+ .endif
+ movq %rsp,%rdi
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)
+ .endif
call \sym
+ .if \ist
+ addq $EXCEPTION_STACK_SIZE, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)
+ .endif
cli
.endm
@@ -904,7 +917,7 @@
INTR_FRAME
pushq $0
CFI_ADJUST_CFA_OFFSET 8
- paranoidentry do_debug
+ paranoidentry do_debug, DEBUG_IST
jmp paranoid_exit
CFI_ENDPROC
.previous .text
@@ -959,7 +972,12 @@
CFI_ENDPROC
KPROBE_ENTRY(int3)
- zeroentry do_int3
+ INTR_FRAME
+ pushq $0
+ CFI_ADJUST_CFA_OFFSET 8
+ paranoidentry do_int3, DEBUG_IST
+ jmp paranoid_exit
+ CFI_ENDPROC
.previous .text
ENTRY(overflow)