test for divide-by-zero, unlike machine insn) from the binutils-2.9.1
sequence to the older binutils-2.8.1 sequence.
gas 2.8.1 emits a div as (in pseudocode)
divu $zer0o, a0, v0; bnez $v0, 1f; nop; break0x7; 1: mflo a0;
gas 2.9.1 emits the shorter sequence
bnez <divisor>, 1f; divu <args>; break0x7; 1:
bnez $v0, 1f; divu $zer0o, a0, v0; /break0x7; 1: mflo a0;
but that on a decstation 5000/150 with a rev 3.0 r4000, for kernel
code, later references to $a0 seem to get a corrupted value. not
reproduced yet on an r4400.
Could be an r4000-specific bug with the interlock on mulhi and mullo?
of the Compaq NetFlex 3/P uses a Thunerlan TNETE100 chip. The PCI variant
use some other PCI chip the ThunderLAN driver can't handle yet.
Also, correct SYNOPSYS.
- there are a couple of registers that are reset after the X server finishes,
which do not have the same values as they do when the machine is powered
on. If the two are mismatched you can't write to the video memory.
- video memory is mapped at offset 4MB to keep the X server happy
- there is now a VGA memory mapping
- DEBUG_ET4000 is now a bit more useful for debugging!
call to __main(), and therefore saves the size of the call and the
size of a stub implementation of __main().
in the primary boot block, don't bother saving/restoring the argument
passed in from the caller. There is no such argument (that we care
about, at least) to the primary. (for secondary, it's the firmware
FD being used.)
Clean up the "Region 1" related definitions, and define load addresses,
max load size, and max total size for as many boot block types as we can.
(types = unified, primary, secondary). We can't always define all
values for all boot blocks, though.
Make CPP flags selection less gross.
Use objcopy rather than headersize (yay, evil gets a stake to the heart!).
Use a little shell script to verify that the sizes of the boot blocks are OK.
Do not compile too much more of libsa than we actually have to.
size to be reduced substantially. (backward compatibility verified
by compiling one of the alpha boot blocks which uses all of the code
before and after, diffing the object files, and manually verifying that
the differences were 'correct'. some differences were "unavoidable,"
it wanting to avoid a double-commit, because e.g. local variables which
were previously used were no longer used.) a README which describes
supported options (or at least the ones mentioned below) is forthcoming.
add support for the preprocessor macro LIBSA_NO_TWIDDLE, which
causes calls to twiddle() to be omitted if it's defined.
add support for the preprocessor macros:
LIBSA_NO_FS_CLOSE
LIBSA_NO_FS_WRITE
LIBSA_NO_FS_SEEK
which, if defined, cause the corresponding file system operations
in the individual file system implementations to be omitted. (note
that all of those macros are not supported by all file systems at
this point. comments were added to individual file system files
to indicate lack of support, and should be cleaned up later. Backward
compatibility options e.g. UFS_NOCLOSE, etc., are supported.)
add support for the preprocessor macro LIBSA_NO_FS_SYMLINK, which
removes support for symbolic links from the file system support
functions. (same notes as for the macros above apply.)
add support for the preprocessor macro LIBSA_FS_SINGLECOMPONENT which
removes all subdirectory and symlink support from the file system
support functions. (same notes as for the macros above apply.)
add support for the preprocessor macro LIBSA_NO_FD_CHECKING, which
causes code relating to libsa file descriptor checks (e.g. range
checking and checking that a file descriptor is valid) to be
omitted if it's defined.
add support for the preprocessor macro LIBSA_NO_RAW_ACCESS, which
causes code relating to raw device access to be omitted if it's
defined.
change some structure copies to use bcopy() instead. that way
use of bcopy vs. memcpy() can easily be selected by
LIBSA_USE_MEMCPY. (without changes like these, you could end up
having both bcopy() and memcpy() included. eventually, all
calls to bcopy should be changed to calls to memcpy() or memmove()
as appropriate -- hopefully never the latter -- with an option to
use bcopy instead.)
add support for the preprocessor macro LIBSA_NO_DISKLABEL_MSGS, which
causes disklabel() to return '1' as msg rather than a string. Can
be used if the boot blocks don't care about the string, and need to
save the space.
add support for the preprocessor macro LIBSA_SINGLE_FILESYSTEM, which
if defined causes all of the file system switch code to be removed.
Its value should be the name of the file system supported by the
boot block, e.g. "ufs" for the FFS file system. calls to the
file system functions open, close, etc., which were previously
done through a function switch are then done via direct invocation
of <fs>_open, <fs>_close, etc. (e.g. ufs_open, ...).
add support for the preprocessor macro LIBSA_SINGLE_DEVICE, which
does the equivalent of LIBSA_SINGLE_FILESYSTEM but for the device
switch table. Device entry pointes are expected to be named
<dev>foo, e.g. the 'strategy' routine used when LIBSA_SINGLE_DEVICE
is set to 'disk' is diskstrategy.
make ufs.c f_nindir array be unsigned ints. the fact that it was signed
caused ufs.c to require signed division routines (which were otherwise
unnecessary for a small boot block).
a small implementation of memcpy(). libsa memcpy() wouldn't
do the right thing if LIBSA_USE_MEMCPY was defined, and the whole
point of that define is to get rid of either bcopy() or memcpy().
(cloned from the bcopy() code.)
scottr