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| author | Kevin O'Connor <kevin@koconnor.net> | 2015-03-17 11:37:25 -0400 |
|---|---|---|
| committer | Kevin O'Connor <kevin@koconnor.net> | 2015-03-18 01:46:56 -0400 |
| commit | 251e26388b83f4bfd8a5ae28263db295e5b683b5 (patch) | |
| tree | 0d4c0430771f91336580d1ed83510a8524d65597 /vgasrc | |
| parent | 184496863a40ac1eff5612ba0da11399535bfa40 (diff) | |
| download | qemu-seabios-251e26388b83f4bfd8a5ae28263db295e5b683b5.tar.gz | |
vgabios: Don't use extra stack if it appears a modern OS is in use
If the last mode set (while not in vm86 mode) was done from a VBE mode
set call then disable the extra stack. This works under the premise
that only a modern OS would invoke the VBE mode changing facilities
and a modern OS would always call the vgabios with sufficient stack
space.
This is an ugly hack to work around a problem Windows Vista (and
possibly later Windows releases) has with the VGA BIOS using a stack
in the e-segment.
Reported-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Diffstat (limited to 'vgasrc')
| -rw-r--r-- | vgasrc/vgabios.c | 6 | ||||
| -rw-r--r-- | vgasrc/vgabios.h | 4 | ||||
| -rw-r--r-- | vgasrc/vgaentry.S | 18 |
3 files changed, 25 insertions, 3 deletions
diff --git a/vgasrc/vgabios.c b/vgasrc/vgabios.c index 4aa50e1..7c1f0b8 100644 --- a/vgasrc/vgabios.c +++ b/vgasrc/vgabios.c @@ -304,6 +304,12 @@ vga_set_mode(int mode, int flags) SET_BDA(video_mode, 0xff); SET_BDA_EXT(vbe_mode, mode | (flags & MF_VBEFLAGS)); SET_BDA_EXT(vgamode_offset, (u32)vmode_g); + if (CONFIG_VGA_ALLOCATE_EXTRA_STACK && !(getcr0_vm86() & CR0_PE)) + // Disable extra stack if it appears a modern OS is in use. + // This works around bugs in some versions of Windows (Vista + // and possibly later) when the stack is in the e-segment. + MASK_BDA_EXT(flags, BF_EXTRA_STACK + , (flags & MF_LEGACY) ? BF_EXTRA_STACK : 0); if (memmodel == MM_TEXT) { SET_BDA(video_cols, width); SET_BDA(video_rows, height-1); diff --git a/vgasrc/vgabios.h b/vgasrc/vgabios.h index fd796f2..831f694 100644 --- a/vgasrc/vgabios.h +++ b/vgasrc/vgabios.h @@ -62,7 +62,8 @@ struct gfx_op { #define GO_MEMSET 3 #define GO_MEMMOVE 4 -// Custom internal storage in BDA +// Custom internal storage in BDA (don't change here without also +// updating vgaentry.S) #define VGA_CUSTOM_BDA 0xb9 struct vga_bda_s { @@ -74,6 +75,7 @@ struct vga_bda_s { #define BF_PM_MASK 0x0f #define BF_EMULATE_TEXT 0x10 #define BF_SWCURSOR 0x20 +#define BF_EXTRA_STACK 0x40 #define GET_BDA_EXT(var) \ GET_FARVAR(SEG_BDA, ((struct vga_bda_s *)VGA_CUSTOM_BDA)->var) diff --git a/vgasrc/vgaentry.S b/vgasrc/vgaentry.S index f9cf656..e0ab954 100644 --- a/vgasrc/vgaentry.S +++ b/vgasrc/vgaentry.S @@ -104,14 +104,23 @@ entry_10: ENTRY_ARG_VGA handle_10 iretw +#define VGA_CUSTOM_BDA_FLAGS 0xb9 +#define BF_EXTRA_STACK 0x40 + // Entry point using extra stack DECLFUNC entry_10_extrastack entry_10_extrastack: cli cld - pushw %ds // Set %ds:%eax to space on ExtraStack + pushw %ds pushl %eax - movw %cs:ExtraStackSeg, %ds + + movw $SEG_BDA, %ax // Check if extra stack is enabled + movw %ax, %ds + testb $BF_EXTRA_STACK, VGA_CUSTOM_BDA_FLAGS + jz 1f + + movw %cs:ExtraStackSeg, %ds // Set %ds:%eax to space on ExtraStack movl $(CONFIG_VGA_EXTRA_STACK_SIZE-PUSHBREGS_size-16), %eax SAVEBREGS_POP_DSEAX // Save registers on extra stack movl %esp, PUSHBREGS_size+8(%eax) @@ -134,6 +143,11 @@ entry_10_extrastack: RESTOREBREGS_DSEAX iretw +1: // Use regular entry point if the extra stack is disabled + popl %eax + popw %ds + jmp entry_10 + // Timer irq handling DECLFUNC entry_timer_hook entry_timer_hook: |