Author: marcel
Date: Sat May 14 14:55:15 2011
New Revision: 221894
URL: http://svn.freebsd.org/changeset/base/221894
Log:
Prefer switching the memory stack from user to kernel *before* switching
the register stack. While the ordering doesn't matter, it creates an
invariant not previously there: the memory stack pointer will always be
larger than the register stack pointer. With this invariant in place,
it's easier to add instrumentation code that detects a stack overflow
because in such a scenario the memory stack pointer and register stack
pointers have crossed each other.
Aside: basic kernel operation needs about half the stack size (~16K)
at most. We have plenty of head room on the kernel stack...
Modified:
head/sys/ia64/ia64/syscall.S
Modified: head/sys/ia64/ia64/syscall.S
==============================================================================
--- head/sys/ia64/ia64/syscall.S Sat May 14 14:47:19 2011
(r221893)
+++ head/sys/ia64/ia64/syscall.S Sat May 14 14:55:15 2011
(r221894)
@@ -239,21 +239,22 @@ ENTRY_NOPROFILE(epc_syscall, 8)
;;
}
{ .mmi
- mov ar.bspstore=r15
+ mov r13=ar.k4
add r30=-SIZEOF_TRAPFRAME,r14
mov r20=sp
;;
}
{ .mii
- mov r13=ar.k4
+ mov r21=ar.unat
dep r30=0,r30,0,10
;;
add sp=-16,r30
;;
}
{ .mmi
+ mov ar.bspstore=r15
+ ;;
mov ar.rnat=r19
- mov r21=ar.unat
add r31=8,r30
;;
}
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