Saved a few bytes by copying `dosdev' and/or `name' to local variables.
This optimization (for dosdev) was done in one place before but this
was lost in the devread() cleanup. This optimization (for dosdev)
can almost be done by bogusly declaring dosdev as const, but gcc still
often space-pessimizes code like the following:
extern const int dosdev; ... foo(dosdev); bar(dosdev);
gcc often doesn't bother to copy dosdev to a temporary local because
the local would have to be preserved in memory across the call to
foo(). OTOH, for
extern int dosdev; ... auto int dosdev_copy = dosdev; ...
foo(dosdev_copy); bar(dosdev_copy);
the copy must be made because foo() might alter dosdev.
the pointer to the string "/kernel". This pointer was once only
statically to once save space, but it has had to be dynamically
initialized for some time, so the static initialization just wastes
space. The string gets moved to the text section, so the actual
savings may be negative due to padding.
- avoiding strcmp("?" saved 12 bytes. gcc inlined the strcmp()
but this takes as much or more code as a function call. The
inlining was bogus because the strcmp() in the bootstrap isn't
standard.
- using a char instead of an int for the boolean `last_only' saved 8
bytes. Booleans should usually be represented as chars on the i386.
- simplifying the return tests saved 9 bytes.
- using putc instead of printf to print a newline saved 3 bytes of code
and 2 bytes of const data.
- avoiding `else's by always doing the else clause and fixing it up
saved 4+8 bytes.
gcc always generates large code for accesses to globals. For locals
it only generates large code if there are more than 128 bytes of
locals. It sorts scalar locals after array locals to pessimize for
space in the usual case when there are more (static) references to
scalars than to arrays.
Saved another 16 bytes (13 before padding) by adding a `continue'.
Fall-through tests normally save space, but here one of them made
gcc do space-unoptimal register allocation (it allocates ch in %bl
because preserving this register across function calls is "free",
but comparisions with %bl take one byte fewer than comparsions with
%bl).
I just couldn't get the code to be as small as it should have gotten..
atill a LITTLE bigger than before as I need to allow the
default string to have options as well
1/ Makefile: the maximum size for boot2 is 7.5K not 7K,
so don't complain until it reaches THAT size..
newfs leaves 8K and boot 1 is 512k. leaving 7.5K becasue the disklabel
is considered to part of the boot2 file.
[512 boot1][512 disklabel][ 7K boot2 code ]
[boot1 file][ boot2 file ]
2/ Boot2.S: move the soring of the default name read from block 2 to AFTER
clearing the BSS.
3/ boot.c:
Move the parsing of the command line into the
place it's called for clarity.. alsoi comment it a bit and clean it
up a bit.. for some reason this seems ot have made it a little
larger, but I can't work out why.. maybe bruce might have ideas?
compensated for by shrinkage elsewhere..
the practical result of this is htat the default string can now contain args
e.g. if you change the default string to have -gd
then the machine will boot to the dgb debugger stub by default..
this is mostly useful with the nextboot utility..
as it now allows you to remotely force a machine to reboot into
the debugger.
is only appropriate to use in the special environment of start.S (real
mode plus some conventions about not saving registers), and asm.h is
supposed to be for generic macros.
Removed some unnecessary parentheses.
Add code to the boot blocks to allow the user to place default boot strings
on block 1 of the disk (2nd block), should the correct magic numbers be present.
If the correct options are used it will 'delete' the name used from block1,
thereby assuring that if the boot fails it won't be stuck in an infinite loop.
the boot strings are set by the utility "nextboot"
(not yet checked in, but being tested.)
By default these changes should have no effect on existing installations
and if compiled without the NAMEBLOCK option should be essentially identical
to the old ones.
hd essentially wired the FreeBSD drive number to 0 without changing
the BIOS drive number. Now the numbers can be specified independently.
Replaced the BOOT_HD compile time flag with with BOOT_HD_BIAS. Defining
the new flag as 1 should give the same behaviour as defining the old
flag as anything. I haven't tested defining these flags.
is defined and FORCE_COMCONSOLE isn't defined.
Don't compile any keyboard probing code if PROBE_KEYBOARD isn't defined.
Makefile:
Removed -I paths. They weren't used, and the one to /sys hasn't worked
since the source directory was moved down one level.
counter instead of the BIOS time call to save space.
Reworked the anti-noise timeout to avoid duplicating code. The timeout
in the outer loop is now restarted after every noise timeout, so it is
now possible for the total timeout to be infinite; previously, the maximum
total timeout was 150000 seconds.
must have limit 0xffff and attribute G = 0 (byte granularity) as well
as other properties that they already had (see e.g., the Intel i486
manual section 22.5). Not restoring them broke Ctrl-Alt-Del in the
bootstrap for my ASUS P55TP4XE system, probably because the Award BIOS
does anti-tracing stuff involving inaccessible %esp's.
asm.S:
Don't use lret in prot_to_real(). This reduces the risk of using an
incompletely intialized stack segment and saves space.
Submitted by: "K.Higashino" <a00303@cc.hc.keio.ac.jp> (on 13 Jan 1995!)
reworked by me
