diff options
| author | Glauber Costa <glommer@redhat.com> | 2008-12-01 15:01:32 -0500 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2008-12-02 14:13:15 +0200 |
| commit | 7e8f23c5916af00d05e4b4343e8587459d359d99 (patch) | |
| tree | f79f55f29045b1a802521ecd201e79e43b554520 /extboot | |
| parent | 945ea856a1db71cedaa091dbdeb40929920d1962 (diff) | |
kvm: extboot: properly set int 0x13 return value
Callers of int 0x13 usually rely on the carry flag being
clear/set to indicate the status of the interrupt execution.
However, our current code clear or set the flags register,
which is totally useless. Whichever value it has, will
be overwritten by the flags value _before_ the interrupt, due to
the iret instruction.
This fixes a bug that prevents slackware (and possibly win2k, untested)
to boot.
Signed-off-by: Glauber Costa <glommer@redhat.com>
Acked-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'extboot')
| -rw-r--r-- | extboot/extboot.S | 52 |
1 files changed, 26 insertions, 26 deletions
diff --git a/extboot/extboot.S b/extboot/extboot.S index 2630abb4..e3d1adf8 100644 --- a/extboot/extboot.S +++ b/extboot/extboot.S @@ -99,24 +99,24 @@ int19_handler: #define FLAGS_CF 0x01 -.macro clc - push %ax - pushf - pop %ax - and $(~FLAGS_CF), %ax - push %ax - popf - pop %ax +/* The two macro below clear/set the carry flag to indicate the status + * of the interrupt execution. It is not enough to issue a clc/stc instruction, + * since the value of the flags register will be overwritten by whatever is + * in the stack frame + */ +.macro clc_stack + push %bp + mov %sp, %bp + /* 8 = 2 (bp, just pushed) + 2 (ip) + 3 (real mode interrupt frame) */ + and $(~FLAGS_CF), 8(%bp) + pop %bp .endm -.macro stc - push %ax - pushf - pop %ax - or $(FLAGS_CF), %ax - push %ax - popf - pop %ax +.macro stc_stack + push %bp + /* 8 = 2 (bp, just pushed) + 2 (ip) + 3 (real mode interrupt frame) */ + or $(FLAGS_CF), 8(%bp) + pop %bp .endm /* we clobber %bx */ @@ -292,7 +292,7 @@ mul32: /* lo, hi, lo, hi */ disk_reset: movb $0, %ah - clc + clc_stack ret /* this really should be a function, not a macro but i'm lazy */ @@ -395,7 +395,7 @@ disk_reset: pop %ax mov $0, %ah - clc + clc_stack ret .endm @@ -454,12 +454,12 @@ read_disk_drive_parameters: pop %bx /* do this last since it's the most sensitive */ - clc + clc_stack ret alternate_disk_reset: movb $0, %ah - clc + clc_stack ret read_disk_drive_size: @@ -498,21 +498,21 @@ read_disk_drive_size: freea pop %bx - clc + clc_stack ret check_if_extensions_present: mov $0x30, %ah mov $0xAA55, %bx mov $0x07, %cx - clc + clc_stack ret .macro extended_read_write_sectors cmd cmpb $10, 0(%si) jg 1f mov $1, %ah - stc + stc_stack ret 1: push %ax @@ -544,7 +544,7 @@ check_if_extensions_present: pop %ax mov $0, %ah - clc + clc_stack ret .endm @@ -612,12 +612,12 @@ get_extended_drive_parameters: pop %ax mov $0, %ah - clc + clc_stack ret terminate_disk_emulation: mov $1, %ah - stc + stc_stack ret int13_handler: |