fresh install in a dual boot scenario to fail. This is because fstab will be
referencing wd(4) and the kernel expecting dk(4).
Closes PR port-macppc/51160
it's not a 16750 either. Like the 16750 it has the IIR_BUSY interrupt,
which is triggered when writing to LCR while the chip
can't accept it. But unlike the 16750, it has a specific register,
HALT, to allow writing to the LCR and divisor registers, and then
commit the changes.
Tested on an A20 SoC, changing the baud rate while keeping the
tty device open and incoming data.
amd64 and i386.
The fillkpt loop is equivalent to the following:
do {
/* fill in the slot */
/* increment %ebx to the next slot */
/* increment %eax to the next pa */
} while (%ecx > 0)
The issue here is that if %ecx = 0 (i.e., the chunk we are trying to
map is zero-sized), there is still one entry created in the page table.
The kernel expects the va<->pa translation to be linear in low memory.
If there is a zero-sized chunk, the dead entry creates a +4096 offset in
the virtual space, with two consecutive entries that point to the same
physical address. In other words, the mappings are not linear anymore,
which causes the kernel to die.
Before my recent changes, there were only two big chunks that were
mapped, and neither of these could be zero-sized. Now, with multiple,
fine-grained chunks, it is possible that the [SYMS]+[PRELOADED_MODULES]
chunk could be zero-sized.
[PRELOADED_MODULES] is almost never here, and [SYMS] is always here on
default kernels. Except for floppies, where the bootloader does not load
[SYMS].
Should fix PR 51148.
When allocating memory, the kernel allocates physical pages and virtual
addresses for these pages. In order to optimize allocations smaller
than PAGE_SIZE, uvm_km_kmem_alloc can allocate a single physical page
and take its virtual address in the direct map in high virtual memory.
This direct map is set up at boot time, its PTEs do not change, and
therefore they don't need to be kentered. These high virtual PTEs being
constant, the permissions of the areas they point to are fixed at boot
time and cannot change.
The problem is that at boot time, they are created with RWX permissions.
Therefore, allocations smaller than PAGE_SIZE in the kernel heap are all
executable: mbufs, pnbufs, small kmem allocations, etc.
Fix this by setting the NOX bit in the direct map pages at boot time. We
also set the NOX bit in the temporary tmpva, since it does not need to
be executable either.
This also makes the U-area non executable on amd64.
But there is a difference in the way it is done here. If PAE is not enabled,
PDE_SIZE = 4, so there is no NOX bit set. If PAE is enabled, PDE_SIZE = 8,
so the NOX bit is set.
This works exactly as intended, since NOX does not exist in the non-PAE
case.
