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Diffstat (limited to 'arch/i386/boot/video.h')
| -rw-r--r-- | arch/i386/boot/video.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/i386/boot/video.h b/arch/i386/boot/video.h index 29eca17..b92447d 100644 --- a/arch/i386/boot/video.h +++ b/arch/i386/boot/video.h @@ -117,8 +117,15 @@ extern int graphic_mode; /* Graphics mode with linear frame buffer */ * int $0x10 is notorious for touching registers it shouldn't. * gcc doesn't like %ebp being clobbered, so define it as a push/pop * sequence here. + * + * A number of systems, including the original PC can clobber %bp in + * certain circumstances, like when scrolling. There exists at least + * one Trident video card which could clobber DS under a set of + * circumstances that we are unlikely to encounter (scrolling when + * using an extended graphics mode of more than 800x600 pixels), but + * it's cheap insurance to deal with that here. */ -#define INT10 "pushl %%ebp; int $0x10; popl %%ebp" +#define INT10 "pushl %%ebp; pushw %%ds; int $0x10; popw %%ds; popl %%ebp" /* Accessing VGA indexed registers */ static inline u8 in_idx(u16 port, u8 index) |