ref: 44ce0097b612a1fefd754065bdf8d9d2e5ef60c8
dir: /appl/lib/disks.b/
implement Disks;
# adapted from /sys/src/libdisk on Plan 9: subject to Lucent Public License 1.02
include "sys.m";
sys: Sys;
include "bufio.m";
bufio: Bufio;
Iobuf: import bufio;
include "disks.m";
scsiverbose := 0;
Codefile: con "/lib/scsicodes";
Code: adt {
v: int; # (asc<<8) | ascq
s: string;
};
codes: array of Code;
init()
{
sys = load Sys Sys->PATH;
bufio = load Bufio Bufio->PATH;
}
#
# Discover the disk geometry by various sleazeful means.
#
# First, if there is a partition table in sector 0,
# see if all the partitions have the same end head
# and sector; if so, we'll assume that that's the
# right count.
#
# If that fails, we'll try looking at the geometry that the ATA
# driver supplied, if any, and translate that as a
# BIOS might.
#
# If that too fails, which should only happen on a SCSI
# disk with no currently defined partitions, we'll try
# various common (h, s) pairs used by BIOSes when faking
# the geometries.
#
# table entry:
Oactive, # active flag
Ostarth, # starting head
Ostarts, # starting sector
Ostartc, # starting cylinder
Otype, # partition type
Oendh, # ending head
Oends, # ending sector
Oendc: con iota; # ending cylinder
Oxlba: con Oendc+1; # starting LBA from start of disc or partition [4]
Oxsize: con Oxlba+4; # size in sectors[4]
# Table: entry[NTentry][TentrySize] magic[2]
Omagic: con NTentry*TentrySize;
partitiongeometry(d: ref Disk): int
{
buf := array[512] of byte;
t := buf[Toffset:];
#
# look for an MBR first in the /dev/sdXX/data partition, otherwise
# attempt to fall back on the current partition.
#
rawfd := sys->open(d.prefix+"data", Sys->OREAD);
if(rawfd != nil
&& sys->seek(rawfd, big 0, 0) == big 0
&& sys->readn(rawfd, buf, 512) == 512
&& int t[Omagic] == Magic0
&& int t[Omagic+1] == Magic1) {
rawfd = nil;
}else{
rawfd = nil;
if(sys->seek(d.fd, big 0, 0) < big 0
|| sys->readn(d.fd, buf, 512) != 512
|| int t[Omagic] != Magic0
|| int t[Omagic+1] != Magic1)
return -1;
}
h := s := -1;
for(i:=0; i<NTentry*TentrySize; i += TentrySize) {
if(t[i+Otype] == byte 0)
continue;
t[i+Oends] &= byte 63;
if(h == -1) {
h = int t[i+Oendh];
s = int t[i+Oends];
} else {
#
# Only accept the partition info if every
# partition is consistent.
#
if(h != int t[i+Oendh] || s != int t[i+Oends])
return -1;
}
}
if(h == -1)
return -1;
d.h = h+1; # heads count from 0
d.s = s; # sectors count from 1
d.c = int (d.secs / big (d.h*d.s));
d.chssrc = "part";
return 0;
}
#
# If there is ATA geometry, use it, perhaps massaged
#
drivergeometry(d: ref Disk): int
{
if(d.c == 0 || d.h == 0 || d.s == 0)
return -1;
d.chssrc = "disk";
if(d.c < 1024)
return 0;
case d.h {
15 =>
d.h = 255;
d.c /= 17;
* =>
for(m := 2; m*d.h < 256; m *= 2) {
if(d.c/m < 1024) {
d.c /= m;
d.h *= m;
return 0;
}
}
# set to 255, 63 and be done with it
d.h = 255;
d.s = 63;
d.c = int (d.secs / big(d.h * d.s));
}
return 0;
}
#
# There's no ATA geometry and no partitions.
# Our guess is as good as anyone's.
#
Guess: adt {
h: int;
s: int;
};
guess: array of Guess = array[] of {
(64, 32),
(64, 63),
(128, 63),
(255, 63),
};
guessgeometry(d: ref Disk)
{
d.chssrc = "guess";
c := 1024;
for(i:=0; i<len guess; i++)
if(big(c*guess[i].h*guess[i].s) >= d.secs) {
d.h = guess[i].h;
d.s = guess[i].s;
d.c = int(d.secs / big(d.h * d.s));
return;
}
# use maximum values
d.h = 255;
d.s = 63;
d.c = int(d.secs / big(d.h * d.s));
}
findgeometry(disk: ref Disk)
{
disk.h = disk.s = disk.c = 0;
if(partitiongeometry(disk) < 0 &&
drivergeometry(disk) < 0)
guessgeometry(disk);
}
openfile(d: ref Disk): ref Disk
{
(ok, db) := sys->fstat(d.fd);
if(ok < 0)
return nil;
d.secsize = 512;
d.size = db.length;
d.secs = d.size / big d.secsize;
d.offset = big 0;
findgeometry(d);
return mkwidth(d);
}
opensd(d: ref Disk): ref Disk
{
b := bufio->fopen(d.ctlfd, Bufio->OREAD);
while((p := b.gets('\n')) != nil){
p = p[0:len p - 1];
(nf, f) := sys->tokenize(p, " \t"); # might need str->unquote
if(nf >= 3 && hd f == "geometry") {
d.secsize = int hd tl tl f;
if(nf >= 6) {
d.c = int hd tl tl tl f;
d.h = int hd tl tl tl tl f;
d.s = int hd tl tl tl tl tl f;
}
}
if(nf >= 4 && hd f == "part" && hd tl f == d.part) {
d.offset = big hd tl tl f;
d.secs = big hd tl tl tl f - d.offset;
}
}
d.size = d.secs * big d.secsize;
if(d.size <= big 0) {
d.part = "";
d.dtype = "file";
return openfile(d);
}
findgeometry(d);
return mkwidth(d);
}
Disk.open(name: string, mode: int, noctl: int): ref Disk
{
d := ref Disk;
d.rdonly = mode == Sys->OREAD;
d.fd = sys->open(name, Sys->OREAD);
if(d.fd == nil)
return nil;
if(mode != Sys->OREAD){
d.wfd = sys->open(name, Sys->OWRITE);
if(d.wfd == nil)
d.rdonly = 1;
}
if(noctl)
return openfile(d);
# check for floppy(3) disk
if(len name >= 7) {
q := name[len name-7:];
if(q[0] == 'f' && q[1] == 'd' && isdigit(q[2]) && q[3:] == "disk") {
if((d.ctlfd = sys->open(name[0:len name-4]+"ctl", Sys->ORDWR)) != nil) {
d.prefix = name[0:len name-4]; # fdN (unlike Plan 9)
d.dtype = "floppy";
return openfile(d);
}
}
}
# attempt to find sd(3) disk or partition
d.prefix = name;
for(i := len name; --i >= 0;)
if(name[i] == '/'){
d.prefix = name[0:i+1];
break;
}
if((d.ctlfd = sys->open(d.prefix+"ctl", Sys->ORDWR)) != nil) {
d.dtype = "sd";
d.part = name[len d.prefix:];
return opensd(d);
}
# assume we have just a normal file
d.dtype = "file";
return openfile(d);
}
mkwidth(d: ref Disk): ref Disk
{
d.width = len sys->sprint("%bd", d.size);
return d;
}
isdigit(c: int): int
{
return c >= '0' && c <= '9';
}
putchs(d: ref Disk, p: array of byte, lba: big)
{
s := int (lba % big d.s);
h := int (lba / big d.s % big d.h);
c := int (lba / (big d.s * big d.h));
if(c >= 1024) {
c = 1023;
h = d.h - 1;
s = d.s - 1;
}
p[0] = byte h;
p[1] = byte (((s+1) & 16r3F) | ((c>>2) & 16rC0));
p[2] = byte c;
}
PCpart.bytes(p: self PCpart, d: ref Disk): array of byte
{
a := array[TentrySize] of byte;
a[Oactive] = byte p.active;
a[Otype] = byte p.ptype;
putchs(d, a[Ostarth:], p.base+p.offset);
putchs(d, a[Oendh:], p.base+p.offset+p.size-big 1);
putle32(a[Oxlba:], p.offset);
putle32(a[Oxsize:], p.size);
return a;
}
PCpart.extract(a: array of byte, nil: ref Disk): PCpart
{
p: PCpart;
p.active = int a[Oactive];
p.ptype = int a[Otype];
p.base = big 0;
p.offset = getle32(a[Oxlba:]);
p.size = getle32(a[Oxsize:]);
return p;
}
getle32(p: array of byte): big
{
return (big p[3]<<24) | (big p[2]<<16) | (big p[1] << 8) | big p[0];
}
putle32(p: array of byte, i: big)
{
p[0] = byte i;
p[1] = byte (i>>8);
p[2] = byte (i>>16);
p[3] = byte (i>>24);
}
Disk.readn(d: self ref Disk, buf: array of byte, nb: int): int
{
return sys->readn(d.fd, buf, nb);
}
chstext(p: array of byte): string
{
h := int p[0];
c := int p[2];
c |= (int p[1]&16rC0)<<2;
s := (int p[1] & 16r3F);
return sys->sprint("%d/%d/%d", c, h, s);
}