in. Unfortunately, the BPF-only code called a label that wan't also
being #if'ed, and this made the compiler bitch. Now that we compile
with -Werror, this prevented the thing from compiling at all! (sigh)
independent options available during kernel configuration. The man
page is still incomplete, but there is enough in it that it should be
in the repository. Next on the list: port specific versions of this
page.
Many thanks to the cast of thousands who helped contribute text for
this.
- 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.
