diff options
| author | cinap_lenrek <cinap_lenrek@centraldogma> | 2011-06-13 05:34:19 +0000 |
|---|---|---|
| committer | cinap_lenrek <cinap_lenrek@centraldogma> | 2011-06-13 05:34:19 +0000 |
| commit | cd5cef000fc6decd40fc25d8a1760cf58884547c (patch) | |
| tree | 89d4eca6b61847c8c8068fe5e63fb78328dee666 /sys/src | |
| parent | e3e57027803f617d43d0a2ca74279c58b402bf87 (diff) | |
pbs: dont rely on chainloader to hand us a partition table and properly get the partition offset from nhidden in the fat header, add compare after mul because MUL doesnt set ZF but makes it undefined!
Diffstat (limited to 'sys/src')
| -rw-r--r-- | sys/src/boot/pc/pbs.s | 52 |
1 files changed, 27 insertions, 25 deletions
diff --git a/sys/src/boot/pc/pbs.s b/sys/src/boot/pc/pbs.s index 07c189e1c..8a11b8279 100644 --- a/sys/src/boot/pc/pbs.s +++ b/sys/src/boot/pc/pbs.s @@ -36,8 +36,10 @@ TEXT _nhiddenhi(SB), $0 TEXT _bigvolsize(SB), $0 BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00; /* FAT32 structure, starting @0x24 */ -TEXT _fatsz32(SB), $0 - BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00 +TEXT _fatsz32lo(SB), $0 + BYTE $0x00; BYTE $0x00 +TEXT _fatsz32hi(SB), $0 + BYTE $0x00; BYTE $0x00 TEXT _extflags(SB), $0 BYTE $0x00; BYTE $0x00 TEXT _fsver(SB), $0 @@ -76,14 +78,12 @@ _start0x5A: MTSR(rAX, rES) LWI(0x100, rCX) - MW(rSI,rBX) /* address of partition record -> rBX */ LWI(RELOC, rSI) MW(rSI, rSP) LWI(_magic(SB), rDI) CLD REP; MOVSL /* MOV DS:[(E)SI] -> ES:[(E)DI] */ - PUSHA MW(rSP, rBP) PUSHR(rCX) @@ -96,39 +96,41 @@ _halt: TEXT start16(SB), $0 STI + LWI(hello(SB), rSI) CALL16(print16(SB)) - PUSHR(rDX) - PUSHR(rBX) + PUSHR(rDX) /* drive */ - LB(_nfats(SB), rCL) /* # of fats */ - LW(_fatsize(SB), rAX) /* fat size */ - MUL(rCX) /* DX:AX = #sectors */ - JNE _fatszok /* zero? it's FAT32 */ + CLR(rDX) + LW(_fatsize(SB), rAX) + CLR(rCX) + LB(_nfats(SB), rCL) + MUL(rCX) + OR(rCX, rCX) + JNE _fatszok /* zero? it's FAT32 */ - LW(_fatsz32+2(SB), rBX) /* hi word */ - IMUL(rCX, rBX) /* ... in sectors */ - LW(_fatsz32(SB), rAX) /* lo word */ - MUL(rCX) /* ... in sectors */ - ADD(rBX, rDX) /* DX:AX = #sectors */ + LW(_fatsz32hi(SB), rBX) + IMUL(rCX, rBX) + LW(_fatsz32lo(SB), rAX) + MUL(rCX) + ADD(rBX, rDX) _fatszok: - POPR(rBX) /* address of partition record */ - - LXW(8, xBX, rCX) /* lo partition LBA */ + LW(_nhiddenlo(SB), rCX) ADD(rCX, rAX) - LXW(10, xBX, rCX) /* hi partition LBA */ + LW(_nhiddenhi(SB), rCX) ADC(rCX, rDX) CLR(rBX) - LW(_nresrv(SB), rCX) /* # of reserved */ + LW(_nresrv(SB), rCX) ADD(rCX, rAX) ADC(rDX, rBX) - SW(rAX, _volid(SB)) /* save for later use */ - SW(rDX, _volid+2(SB)) - POPR(rDX) + SW(rAX, _volid(SB)) /* save for later use */ + SW(rBX, _volid+2(SB)) + + POPR(rDX) /* drive */ PUSHR(rBP) LW(_sectsize(SB), rCX) @@ -164,7 +166,7 @@ _nextdir: JMP _nextsect _found: - PUSHR(rDX) + PUSHR(rDX) /* drive */ CLR(rBX) @@ -208,7 +210,7 @@ _found: MW(rAX, rCX) POPR(rBX) POPR(rAX) - POPR(rDX) + POPR(rDX) /* drive */ LWI(RELOC, rSI) PUSHR(rSI) |