- Try V3 first for diskless booting. Fall back to V2 if V3 fails.
- optionally (option NFS_BOOT_TCP) try a TCP mount first
for diskless booting. Fall back to UDP if it fails.
- Enable switching between UDP and TCP for remounts.
VM_PROT_READ|VM_PROT_EXECUTE. The previous default (VM_PROT_ALL)
would cause the following scenario:
- someone attempts to write kernel text (my test was writing
to an offset of /dev/kmem which was known to be in the text
segment, while in single-user mode).
- enter trap() with MMU fault (because of RO pte).
- trap() calls vm_fault(), which looks up vm_map_entry for
fauling address.
- vm_fault interprets write fault and VM_PROT_WRITE (in VM_PROT_ALL)
as COW; new page allocated, data copied to new page, new page
mapped in at trunc_page(<faulting va>).
- wow, look at the fireworks!
Fixes two potential symptoms:
- kernacc() returns TRUE when checking for permission to write
an offset in kernel text, which is bogus, since the text has
been mapped RO by pmap_bootstrap().
- Handling of a stray pointer that attempted to scribble into
kernel text would not be executed properly.
SYSCALL_NOERROR(x): Like SYSCALL except that "x" is a syscall
that can never fail.
RSYSCALL_NOERROR(x): Like RSYSCALL except that "x" is a syscall
that can never fail.
These macros simply call SYSCALL / RSYSCALL, and serve as placeholders
until an optimized implementation is done.
Changed all instances of ENTRY() to match the new calling convention
(it takes a second argument ).
Added new macros:
SYSTRAP(x): Expands to the code used to call syscall x.
This is used to simplify other macros.
SYSCALL_NOERROR(x): Like SYSCALL except that "x" is a syscall
that can never fail.
RSYSCALL_NOERROR(x): Like RSYSCALL except that "x" is a syscall
that can never fail.
don't do this, kernacc() will bogusly return TRUE for page 0, causing a
NULL pointer dereference in uiomove() when reading /dev/kmem.
Thanks to Scott Reynolds for noticing the problem.
pk