diff options
| author | H. Peter Anvin <hpa@linux.intel.com> | 2009-04-16 17:19:24 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2009-04-16 17:19:24 -0700 |
| commit | a7dd6590584c7c243bb256989ebd8f230a86b6ab (patch) | |
| tree | 92ecd1b803128cd78f7bc1730064979e5c580abd | |
| parent | 2a37f9de661d6bad79c5cc8fb13dbf63a27cf863 (diff) | |
| download | syslinux-a7dd6590584c7c243bb256989ebd8f230a86b6ab.tar.gz | |
bcopyxx: when going to 16-bit PM, might as well do it right
When entering 16-bit PM after shuffle and boot, we might as well
do so sanely. Specifically, set up the data segments so that they
match the code segment, generating a 16-bit "tiny" model environment.
This makes it a lot saner to bootstrap a proper PM environment from
there if that is what the user intends. For the presumably more
common case of RM entry, it won't do any harm, and it's only a handful
of additional instructions.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
| -rw-r--r-- | core/bcopy32.inc | 6 | ||||
| -rw-r--r-- | core/bcopyxx.inc | 15 | ||||
| -rw-r--r-- | core/com32.inc | 2 | ||||
| -rw-r--r-- | doc/comboot.txt | 5 |
4 files changed, 16 insertions, 12 deletions
diff --git a/core/bcopy32.inc b/core/bcopy32.inc index f058a6f7..c4edc715 100644 --- a/core/bcopy32.inc +++ b/core/bcopy32.inc @@ -127,7 +127,7 @@ simple_pm_call: bits 32 .in_pm: - mov eax,PM_DS32 + mov ax,PM_DS32 mov ss,eax lea esp,[ebp-8*4-2*4] ; Flat mode stack mov es,eax @@ -137,7 +137,7 @@ simple_pm_call: ; machine running on Intel VT hardware -- it can't ; deal with a partial transition, for no good reason. - mov al,PM_DS16_RM ; Real-mode-like segment + mov al,PM_DS16 ; Real-mode-like segment mov fs,eax mov gs,eax mov al,PM_TSS ; Intel VT really doesn't want @@ -151,7 +151,7 @@ simple_pm_call: jmp PM_CS16:.exit bits 16 .exit: - mov eax,PM_DS16_RM ; "Real-mode-like" data segment + mov ax,PM_DS16 ; "Real-mode-like" data segment mov es,eax mov ds,eax mov ss,eax diff --git a/core/bcopyxx.inc b/core/bcopyxx.inc index 60f81723..c42af49e 100644 --- a/core/bcopyxx.inc +++ b/core/bcopyxx.inc @@ -241,12 +241,15 @@ pm_shuffle_real_mode: call .here .here: pop ebx mov eax,edi - add ebx,bcopy_gdt.CS16-.here - mov [ebx+2],ax + add ebx,bcopy_gdt-.here + mov [ebx+PM_CS16+2],ax + mov [ebx+PM_DS16+2],ax shr eax,16 - mov [ebx+4],al - mov [ebx+7],ah - mov eax,PM_DS16_RM + mov [ebx+PM_CS16+4],al + mov [ebx+PM_CS16+7],ah + mov [ebx+PM_DS16+4],al + mov [ebx+PM_DS16+7],ah + mov ax,PM_DS16 mov ds,eax mov es,eax mov fs,eax @@ -278,7 +281,7 @@ bcopy_gdt: desc CS16 dd 0000ffffh ; 10h Code segment, use16, readable, dd 00009b00h ; present, dpl 0, cover 64K - desc DS16_RM + desc DS16 dd 0000ffffh ; 18h Data segment, use16, read/write, dd 00009300h ; present, dpl 0, cover 64K desc CS32 diff --git a/core/com32.inc b/core/com32.inc index 3a762a6b..72327929 100644 --- a/core/com32.inc +++ b/core/com32.inc @@ -196,7 +196,7 @@ com32_enter_rm: bits 16 .in_pm16: - mov ax,PM_DS16_RM ; Real-mode-like segment + mov ax,PM_DS16 ; Real-mode-like segment mov es,ax mov ds,ax mov ss,ax diff --git a/doc/comboot.txt b/doc/comboot.txt index cf18b2b6..f5fefdaf 100644 --- a/doc/comboot.txt +++ b/doc/comboot.txt @@ -952,5 +952,6 @@ AX=0024h [3.80] Cleanup, shuffle and boot, raw version and possibly other virtualization solutions. In both mode 0 and mode 1, the data segments will be loaded - with base-zero read/write segments. For mode 0, B=0 and the - limits will be 64K, for mode 1, B=1 and the limits will be 4 GB. + with read/write data segments, matching the respective code + segment. For mode 0, B=0 and the limits will be 64K, for mode + 1, B=1 and the limits will be 4 GB. |