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Prefer switching the memory stack from user to kernel *before* switching

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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...
This commit is contained in:
Marcel Moolenaar 2011-05-14 14:55:15 +00:00
parent 65385d6d79
commit 767ca6ed1a
1 changed files with 4 additions and 3 deletions
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7
sys/ia64/ia64/syscall.S
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@ -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
;;
}