Opened 8 years ago
Closed 8 years ago
#15409 closed defect (worksforme)
MakeAlternativeSource bug
| Reported by: | gim | Owned by: | |
|---|---|---|---|
| Component: | other | Version: | VirtualBox 5.0.20 |
| Keywords: | MakeAlternativeSource, BIOS, | Cc: | |
| Guest type: | Linux | Host type: | all |
Description (last modified by )
Sometime MakeAlternatioveSource generates bad VBoxBiosAlternative.asm dissassebling:
...
lea sp, [bp-002h] ; 8d 66 fe
pop bx ; 5b
pop bp ; 5d
retn ; c3
retf ; cb
xchg di, ax ; 97
xchg di, ax ; 97
cbw ; 98
fst qword [bx-06808h] ; dd 97 f8 97
xchg di, ax ; 97
cbw ; 98
and bx, word [bx+si-06769h] ; 23 98 97 98
sub byte [bx+si-06794h], bl ; 28 98 6c 98
insb ; 6c
cbw ; 98
insb ; 6c
cbw ; 98 <----- !!!
cbw ; 67 98 <----- !!!
insb ; 6c
cbw ; 98
insb ; 6c
cbw ; 98
pushaw ; 60
cbw ; 98
_apm_function: ; 0xf97a8 LB 0xf5
push bp ; 55
mov bp, sp ; 89 e5
push si ; 56
and byte [bp+018h], 0feh ; 80 66 18 fe
mov ax, word [bp+012h] ; 8b 46 12
xor ah, ah ; 30 e4
cmp ax, strict word 0000eh ; 3d 0e 00
jnbe near 0986ch ; 0f 87 b0 00
mov bx, ax ; 89 c3
add bx, ax ; 01 c3
mov dx, word [bp+018h] ; 8b 56 18
...
As you can see here same instructions but different bytes:
cbw ; 98 cbw ; 67 98
Thats because it's not code at all. It's offsets from switch-case table:
BIOS_F:978A CB 97 off_F978A dw offset loc_F97CB ; DATA XREF: BIOS_F:97C6r BIOS_F:978C 97 98 dw offset loc_F9897 BIOS_F:978E DD 97 dw offset loc_F97DD BIOS_F:9790 F8 97 dw offset loc_F97F8 BIOS_F:9792 97 98 dw offset loc_F9897 BIOS_F:9794 23 98 dw offset loc_F9823 BIOS_F:9796 97 98 dw offset loc_F9897 BIOS_F:9798 28 98 dw offset loc_F9828 BIOS_F:979A 6C 98 dw offset loc_F986C BIOS_F:979C 6C 98 dw offset loc_F986C BIOS_F:979E 6C 98 dw offset loc_F986C BIOS_F:97A0 67 98 dw offset loc_F9867 BIOS_F:97A2 6C 98 dw offset loc_F986C BIOS_F:97A4 6C 98 dw offset loc_F986C BIOS_F:97A6 60 98 dw offset loc_F9860 BIOS_F:97A8 ; --------------------------------------------------------------------------- BIOS_F:97A8 55 push bp BIOS_F:97A9 89 E5 mov bp, sp BIOS_F:97AB 56 push si BIOS_F:97AC 80 66 18 FE and byte ptr [bp+18h], 0FEh BIOS_F:97B0 8B 46 12 mov ax, [bp+12h] BIOS_F:97B3 30 E4 xor ah, ah BIOS_F:97B5 3D 0E 00 cmp ax, 0Eh BIOS_F:97B8 0F 87 B0 00 ja loc_F986C BIOS_F:97BC 89 C3 mov bx, ax BIOS_F:97BE 01 C3 add bx, ax BIOS_F:97C0 8B 56 18 mov dx, [bp+18h] BIOS_F:97C3 80 CA 01 or dl, 1 BIOS_F:97C6 2E FF A7 8A 97 jmp cs:off_F978A[bx]
It happens because dissasebler just ignore prefix opcode (0x67) for instruction cbw and not fails.
As a result when we build new BIOS by 'kmk update-pcbios-source' VBoxCmp fail with:
VBoxCmp out/linux.amd64/release/obj/VBoxPcBios/VBoxPcBios.rom out/linux.amd64/release/obj/VBoxPcBios/VBoxBiosAlternative.bin VBoxCmp: 0x0000097a0: 0x67 (103) != 0x98 (152) VBoxCmp: 0x0000097a1: 0x98 (152) != 0x6c (108) VBoxCmp: 0x0000097a2: 0x6c (108) != 0x98 (152) VBoxCmp: 0x0000097a3: 0x98 (152) != 0x6c (108) VBoxCmp: 0x0000097a4: 0x6c (108) != 0x98 (152)
...
Attachments (1)
Change History (6)
comment:1 by , 8 years ago
| Description: | modified (diff) |
|---|
comment:2 by , 8 years ago
Why you generate this disassemble file VBoxBiosAlternative.asm?
Why not just keep binary file VBoxPcBios.rom. And who want to recompile BIOS, must just install OpenWatcom.
comment:3 by , 8 years ago
The alternative asm files are a convenience to some Linux folks, for example Debian, who don't agree that the Watcom tools are free. With the alternative .asm files there is at least a theoretical chance to modify+compile the source code without the Watcom tools (I know, not very convenient).
comment:4 by , 8 years ago
Added more workaround to MakeAlternativeSource
Here results:
apm_out_str_: ; 0xf976f LB 0x39
push bp ; 55
mov bp, sp ; 89 e5
push bx ; 53
mov bx, ax ; 89 c3
cmp byte [bx], 000h ; 80 3f 00
je short 09784h ; 74 0a
mov al, byte [bx] ; 8a 07
out DX, AL ; ee
inc bx ; 43
mov al, byte [bx] ; 8a 07
db 00ah, 0c0h
; or al, al ; 0a c0
jne short 0977ch ; 75 f8
lea sp, [bp-002h] ; 8d 66 fe
pop bx ; 5b
pop bp ; 5d
retn ; c3
retf ; cb
db 097h, 097h, 098h, 0ddh, 097h, 0f8h, 097h, 097h, 098h, 023h, 098h, 097h, 098h, 028h, 098h, 06ch
db 098h, 06ch, 098h, 06ch, 098h, 067h, 098h, 06ch, 098h, 06ch, 098h, 060h, 098h
_apm_function: ; 0xf97a8 LB 0xf5
push bp ; 55
mov bp, sp ; 89 e5
push si ; 56
and byte [bp+018h], 0feh ; 80 66 18 fe
mov ax, word [bp+012h] ; 8b 46 12
xor ah, ah ; 30 e4
cmp ax, strict word 0000eh ; 3d 0e 00
jnbe near 0986ch ; 0f 87 b0 00
mov bx, ax ; 89 c3
add bx, ax ; 01 c3
mov dx, word [bp+018h] ; 8b 56 18
or dl, 001h ; 80 ca 01
jmp word [cs:bx-06876h] ; 2e ff a7 8a 97
Patch added
comment:5 by , 8 years ago
| Resolution: | → worksforme |
|---|---|
| Status: | new → closed |
We will apply such patches if necessary. With the current released versions no patch is required.
Right, but this is nothing which can be easily fixed.