diff options
Diffstat (limited to 'src/arch/i386/lib/c_start.S')
| -rw-r--r-- | src/arch/i386/lib/c_start.S | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/src/arch/i386/lib/c_start.S b/src/arch/i386/lib/c_start.S index d2d8b435bc..4ef59799a9 100644 --- a/src/arch/i386/lib/c_start.S +++ b/src/arch/i386/lib/c_start.S @@ -253,7 +253,16 @@ gdtaddr: /* This is the gdt for GCC part of coreboot. * It is different from the gdt in ROMCC/ASM part of coreboot - * which is defined in entry32.inc */ /* BUT WHY?? */ + * which is defined in entry32.inc + * + * When the machine is initially started, we use a very simple + * gdt from rom (that in entry32.inc) which only contains those + * entries we need for protected mode. + * + * When we're executing code from RAM, we want to do more complex + * stuff, like initializing PCI option roms in real mode, or doing + * a resume from a suspend to ram. + */ gdt: /* selgdt 0, unused */ .word 0x0000, 0x0000 /* dummy */ @@ -275,6 +284,8 @@ gdt: .word 0x0000, 0x0000 /* dummy */ .byte 0x00, 0x00, 0x00, 0x00 + /* The next two entries are used for executing VGA option ROMs */ + /* selgdt 0x28 16-bit 64k code at 0x00000000 */ .word 0xffff, 0x0000 .byte 0, 0x9a, 0, 0 @@ -282,6 +293,16 @@ gdt: /* selgdt 0x30 16-bit 64k data at 0x00000000 */ .word 0xffff, 0x0000 .byte 0, 0x92, 0, 0 + + /* The next two entries are used for ACPI S3 RESUME */ + + /* selgdt 0x38, flat data segment 16bit */ + .word 0x0000, 0x0000 /* dummy */ + .byte 0x00, 0x93, 0x8f, 0x00 /* G=1 and 0x0f, So we get 4Gbytes for limit */ + + /* selgdt 0x40, flat code segment 16bit */ + .word 0xffff, 0x0000 + .byte 0x00, 0x9b, 0x8f, 0x00 /* G=1 and 0x0f, So we get 4Gbytes for limit */ gdt_end: idtarg: |