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Make stack change safer

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Setting the stack to zero is hosing the image somehow in 86box.
This change appears to fix it. Would be nice to learn more.
This commit is contained in:
Justine Tunney 2021-11-27 20:58:26 -08:00
parent 920babb3e7
commit d5afd05ef8
1 changed files with 4 additions and 4 deletions
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8
sectorlisp.S
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@ -36,13 +36,13 @@ kCdr: .asciz "CDR" # ordering matters
kCons: .asciz "CONS" # ordering matters kCons: .asciz "CONS" # ordering matters
kEq: .asciz "EQ" # needs to be last kEq: .asciz "EQ" # needs to be last
begin: xor %sp,%sp # use highest address as stack begin: mov $0x8000,%sp # uses higher address as stack
# set independently of SS! # and set independently of SS!
# 8088 doesn't stop interrupts # 8088 doesn't stop interrupts
# after SS is set, and PC BIOS # after SS is set, and PC BIOS
# sets SP to a value that will # sets SP to a value that will
# damage our code if int fires # damage our code if int fires
# between setting SS and SP # between it setting SS and SP
push %cs # that means ss = ds = es = cs push %cs # that means ss = ds = es = cs
pop %ds # noting ljmp set cs to 0x7c00 pop %ds # noting ljmp set cs to 0x7c00
push %cs # that's the bios load address push %cs # that's the bios load address
@ -50,7 +50,7 @@ begin: xor %sp,%sp # use highest address as stack
push %cs # terminated NIL string above! push %cs # terminated NIL string above!
pop %ss # errata exists but don't care pop %ss # errata exists but don't care
mov $2,%bx mov $2,%bx
main: mov $0x8000,%cx # dl (g_look) is zero or cr main: mov %sp,%cx
call GetToken call GetToken
call GetObject call GetObject
call Eval call Eval