| H. Peter Anvin | 7a734e7 | 2009-04-01 18:08:28 -0700 | [diff] [blame] | 1 | /* ----------------------------------------------------------------------- |
| 2 | * |
| 3 | * Copyright 2009 Intel Corporation; author H. Peter Anvin |
| 4 | * |
| 5 | * This file is part of the Linux kernel, and is made available under |
| 6 | * the terms of the GNU General Public License version 2 or (at your |
| 7 | * option) any later version; incorporated herein by reference. |
| 8 | * |
| 9 | * ----------------------------------------------------------------------- */ |
| 10 | |
| 11 | /* |
| 12 | * "Glove box" for BIOS calls. Avoids the constant problems with BIOSes |
| H. Peter Anvin | cf9972a | 2009-04-11 22:24:05 -0700 | [diff] [blame] | 13 | * touching registers they shouldn't be. |
| H. Peter Anvin | 7a734e7 | 2009-04-01 18:08:28 -0700 | [diff] [blame] | 14 | */ |
| 15 | |
| H. Peter Anvin | 28b4868 | 2009-06-16 17:39:04 -0700 | [diff] [blame] | 16 | .code16gcc |
| H. Peter Anvin | 7a734e7 | 2009-04-01 18:08:28 -0700 | [diff] [blame] | 17 | .text |
| 18 | .globl intcall |
| 19 | .type intcall, @function |
| 20 | intcall: |
| 21 | /* Self-modify the INT instruction. Ugly, but works. */ |
| 22 | cmpb %al, 3f |
| 23 | je 1f |
| 24 | movb %al, 3f |
| 25 | jmp 1f /* Synchronize pipeline */ |
| 26 | 1: |
| 27 | /* Save state */ |
| 28 | pushfl |
| 29 | pushw %fs |
| 30 | pushw %gs |
| 31 | pushal |
| 32 | |
| 33 | /* Copy input state to stack frame */ |
| 34 | subw $44, %sp |
| 35 | movw %dx, %si |
| 36 | movw %sp, %di |
| 37 | movw $11, %cx |
| 38 | rep; movsd |
| 39 | |
| 40 | /* Pop full state from the stack */ |
| 41 | popal |
| 42 | popw %gs |
| 43 | popw %fs |
| 44 | popw %es |
| 45 | popw %ds |
| 46 | popfl |
| 47 | |
| 48 | /* Actual INT */ |
| 49 | .byte 0xcd /* INT opcode */ |
| 50 | 3: .byte 0 |
| 51 | |
| 52 | /* Push full state to the stack */ |
| 53 | pushfl |
| 54 | pushw %ds |
| 55 | pushw %es |
| 56 | pushw %fs |
| 57 | pushw %gs |
| 58 | pushal |
| 59 | |
| 60 | /* Re-establish C environment invariants */ |
| 61 | cld |
| 62 | movzwl %sp, %esp |
| 63 | movw %cs, %ax |
| 64 | movw %ax, %ds |
| 65 | movw %ax, %es |
| 66 | |
| 67 | /* Copy output state from stack frame */ |
| 68 | movw 68(%esp), %di /* Original %cx == 3rd argument */ |
| 69 | andw %di, %di |
| 70 | jz 4f |
| 71 | movw %sp, %si |
| 72 | movw $11, %cx |
| 73 | rep; movsd |
| 74 | 4: addw $44, %sp |
| 75 | |
| 76 | /* Restore state and return */ |
| 77 | popal |
| 78 | popw %gs |
| 79 | popw %fs |
| 80 | popfl |
| 81 | retl |
| 82 | .size intcall, .-intcall |