[PATCH] x86_64: Clean up double fault handling

Since a double fault always implies that kernel data structures are
corrupt, this fault should neither be handed to user mode handling,
nor should the handler allow resuming the faulting code stream (since
architecturally this isn't a fault, but an abort).

Note that this slightly depends on the previously submitted patch
adjusting the prototype of notify_die() (a compiler warning will result
without that other patch).

AK: Removed obsolete CONFIG_CHECKING code, added comments

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

diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 0266b523e8d0b37d2a0daf10b1145093ad996b1a..bd71ddac0dc5d0fb06ebbc4b6d10d9399e406d21 100644 (file)
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -489,7 +489,23 @@ DO_ERROR(11, SIGBUS,  "segment not present", segment_not_present)
 DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0)
 DO_ERROR(18, SIGSEGV, "reserved", reserved)
 DO_ERROR(12, SIGBUS,  "stack segment", stack_segment)
-DO_ERROR( 8, SIGSEGV, "double fault", double_fault)
+
+asmlinkage void do_double_fault(struct pt_regs * regs, long error_code)
+{
+       static const char str[] = "double fault";
+       struct task_struct *tsk = current;
+
+       /* Return not checked because double check cannot be ignored */
+       notify_die(DIE_TRAP, str, regs, error_code, 8, SIGSEGV);
+
+       tsk->thread.error_code = error_code;
+       tsk->thread.trap_no = 8;
+
+       /* This is always a kernel trap and never fixable (and thus must
+          never return). */
+       for (;;)
+               die(str, regs, error_code);
+}
 
 asmlinkage void __kprobes do_general_protection(struct pt_regs * regs,
                                                long error_code)