GCC forwards the -N flag directly to ld. This flag is not documented and
not supported by (for example) Clang. Just use -Wl,-N.
Submitted by: Pawel Worach
The old BTX passed the general purpose registers from the 32-bit client to
the routines called via virtual 86 mode. The new BTX did the same thing.
However, it turns out that some instructions behave differently in virtual 86
mode and real mode (even though this is under-documented). For example, the
LEAVE instruction will cause an exception in real mode if any of the upper
16-bits of %ebp are non-zero after it executes. In virtual 8086 mode the
upper 16-bits are simply ignored. This could cause faults in hardware
interrupt handlers that inherited an %ebp larger than 0xffff from the 32-bit
client (loader, boot2, etc.) while running in real mode.
To fix, when executing hardware interrupt handlers provide an explicit clean
state where all the general purpose and segment registers are zero upon
entry to the interrupt handler. While here, I attempted to simplify the
control flow in the 'intusr' code that sets up the various stack frames
and exits protected mode to invoke the requested routine via real mode.
A huge thanks to Tor Egge (tegge@) for debugging this issue.
Submitted by: tegge
Reviewed by: tegge
Tested by: bz
MFC after: 1 week
- I had errantly assumed that all user requests should run with interrupts
enabled. User requests for software interrupts, however, need to disable
interrupts (and tracing) just like hardware interrupts.
- Disable alignment checking when emulating a hardware interrupt as well
(based on the description of the real mode operation of the 'INT'
instruction in the IA-32 manuals).
- Use constants for fields in %eflags.
Tested by: bz
MFC after: 3 days
routines (V86 requests from the client and hardware interrupt handlers):
- Install trampoline real mode interrupt handlers at IDT vectors 0x20-0x2f
to handle hardware interrupts by invoking the appropriate vector (0x8-0xf
or 0x70-0x78). This allows the 8259As to use vectors 0x20-0x2f in real
mode as well as protected mode will ensuring that the master 8259A
doesn't share IDT space with CPU exceptions in protected mode.
- Since we don't need to reserve space for page tables and a page directory
anymore since dropping paging support, move the TSS and protected mode
IDT up by 16k. Grow the ring 1 link stack by 16k as a result.
- Repurpose the ring 1 link stack to be used as a real mode stack when
invoking real mode routines either via a V86 request or a hardware
interrupts. This simplifies a few things as we avoid disturbing the
original user stack.
- Add some more block comments to explain how the code interacts with the
V86 structure as this wasn't immediately obvious from the prior comments
(e.g. that we explicitly copy the seg regs for real mode out of the V86
struct onto the stack to be popped off when going into real mode, etc.).
Also, document some of the stack frames we create going to real mode and
back.
- Remove all of the virtual 86 related code including having to simulate
various instructions and BIOS calls on a trap from virtual 86 mode.
- Explicitly panic if a user client attempts to perform a V86 CALL
request that isn't a far call.
- Bump version to 1.2.
Assuming this works ok this should fix some of the long standing issues
with USB booting as well as etherboot.
MFC after: 2 weeks
Submitted by: kib (some parts from his original real mode patch)
rather than treating them as a fatal exception and halting. At least one
storage BIOS (some newer mpt(4) parts) have a breakpoint instruction in
their disk read routine.
MFC after: 3 days
commits. For some reason I thought the scale factor was a shift count
rather than the multiplicand (that is, I thought leal (%eax,%edx,4) was
going to generate %eax + %edx << 4 rather than %eax + %edx * 4). What
I need is to multiply by 16 to convert a real-mode (seg, offset) tuple
into a flat address. However, the max multiplicand for scaled/index
addressing on i386 is 8, so go back to using a shl and an add.
- Convert two more inter-register mov instructions where we don't need to
preserve the source register to xchg instructions to keep our space
savings.
Tested by: Ian FREISLICH if at hetzner.co.za
MFC after: 1 week
another 16 bytes off of BTX (and thus boot2):
- Compare against the value of %eax that is saved on the stack instead of
loading it into %eax (which requires saving the current %eax on the
stack).
- Use %ch to examine the keyboard flag state in the BIOS to see if
Ctrl-Alt-Del is pressed instead of %al so we don't have to save %eax on
the stack anymore.
MFC after: 1 week
BTX (and thus boot2):
- Don't bother saving %eax, %ebx, or %ecx as it is not necessary.
- Use a more compact sequence to load the base value out of a GDT entry
by loading the contiguous low 24 bits into the upper 24 bits of %eax,
loading the high 8 bits into %al, and using a ror to rotate the bits
(2 mov's and a ror) rather than loading the pieces in smaller chunks
(3 mov's and a shl).
- Use movzwl + leal instead of movl + movw + shll + addl.
- Use 'xchgl %eax,%foo' rather than 'movl %eax,%foo' for cases where
it's ok to trash %eax. xchgl %eax, foo is a 1-byte opcode whereas the
mov is a 2-byte opcode.
- Use movzwl rather than xorl + movw.
MFC after: 1 week
rather than just emulating mov cr0, eax. This fixes some Compaq/HP BIOS
with DMA (as the BIOS tried to read cr3 so it could translate addresses
if paging was enabled).
MFC after: 1 week
assembler to cpp(1) comment conversions. This allows btx to compile again
when BTX_SERIAL is defined.
Reported by: Danny Braniss danny at cs dot huji dot ac dot il
MFC after: 1 month
have clear idea on boot2 BSS size and leaves portion of it not zeroed out.
btxcsu.s is in much better position for this job.
Obtained from: DragonflyBSD (with minor adjustments)
switch to using C99-style comments everywhere in preprocessed
assembler. The reason is that lines starting with the regexp
'^[[:space:]]#' are treated as preprocessing directives, and
while it seems to work now with GCC, it's not necessarily has
to work. Use C99 comments `//' for the trailing comments to
save whitespace.
- Now that bsd.prog.mk deals with programs linked with -nostdlib
better, and has a notion of an "internal" program, use PROG
where possible. This has a good impact on the contents of
.depend files and causes programs to be linked with cc(1).
XXX: boot2 couldn't be converted as it's actually two programs.
Tested on: i386, amd64
- do not use PROG for what's not a real C program,
- use sys.mk transformation rules where possible,
- only create the "machine" symlink on AMD64,
- removed MAINTAINER lines in individual makefiles,
- added the LIBSTAND defitinion to <bsd.libnames.mk>,
- somewhat better contents in .depend files.
Tested on: i386, amd64
Prodded by: bde
While we end up the same place, we end up with two different CS register
values after the jump and 0xf000 is compatible with the hardware reset
value.
This makes a difference if the BIOS does a near jump before a far jump.
Detective work and patch by: Adrian Steinmann <ast@marabu.ch>
It seems that the existence of a "depend" target in src/sys/boot is not
to be taken as an indication that it actually does what one would expect,
at least it clearly threw my testing off.
Apologies to: jhb
Load 4 sectors more than we used to. This is harmless overhead for
the UFS1_ONLY case, but sufficient for boot2(UFS1+2).
Sponsored by: DARPA & NAI Labs
under way to move the remnants of the a.out toolchain to ports. As the
comment in src/Makefile said, this stuff is deprecated and one should not
expect this to remain beyond 4.0-REL. It has already lasted WAY beyond
that.
Notable exceptions:
gcc - I have not touched the a.out generation stuff there.
ldd/ldconfig - still have some code to interface with a.out rtld.
old as/ld/etc - I have not removed these yet, pending their move to ports.
some includes - necessary for ldd/ldconfig for now.
Tested on: i386 (extensively), alpha
Get rid of the INTERNALSTATICLIB knob and just use plain INTERNALLIB.
INTERNALLIB now means to build static library only and don't install
anything. Added a NOINSTALLLIB knob for libpam/modules. To not
build any library at all, just do not set LIB.
when debugging boot problems. It is not on by default but is enabled via
the BTX_SERIAL variable. The port and speed can be set via the same
variables used by boot2 and the loader.
fatal trap. Also, reload the GDT register to point to BTX's GDT before
playing around with the segment registers to return to real mode. This is
helpful if the kernel causes a fatal exception before it has setup its own
IDT and fault handlers. For example, if one happens to break mtx_init().
Without these changes BTX would recursively page fault (if paging was not
disabled) or triple fault and reset the CPU (without the GDT reload)
instead of providing a potentially useful register dump.
Reviewed by: rnordier
BOOT_BTX_NOHANG, then BTX will be compiled with the appropriate flags so
that it reboots after a fault instead of hanging forever.
Requested by: ps
Approved by: rnordier
