| Simon Glass | 6f92ed8 | 2015-08-04 12:33:55 -0600 | [diff] [blame] | 1 | /* |
| 2 | * (C) Copyright 2015 Google, Inc |
| 3 | * Written by Simon Glass <sjg@chromium.org> |
| 4 | * |
| 5 | * SPDX-License-Identifier: GPL-2.0+ |
| 6 | */ |
| 7 | |
| 8 | #include <asm/global_data.h> |
| 9 | #include <asm/msr-index.h> |
| 10 | #include <asm/processor-flags.h> |
| 11 | |
| 12 | /* |
| 13 | * rdi - 32-bit code segment selector |
| 14 | * rsi - target address |
| 15 | * rdx - table address (0 if none) |
| 16 | */ |
| 17 | .code64 |
| 18 | .globl cpu_call32 |
| 19 | cpu_call32: |
| 20 | cli |
| 21 | |
| 22 | /* Save table pointer */ |
| 23 | mov %edx, %ebx |
| 24 | |
| 25 | /* |
| 26 | * Debugging option, this outputs characters to the console UART |
| 27 | * mov $0x3f8,%edx |
| 28 | * mov $'a',%al |
| 29 | * out %al,(%dx) |
| 30 | */ |
| 31 | |
| 32 | pushf |
| 33 | push %rdi /* 32-bit code segment */ |
| 34 | lea compat(%rip), %rax |
| 35 | push %rax |
| 36 | .byte 0x48 /* REX prefix to force 64-bit far return */ |
| 37 | retf |
| 38 | .code32 |
| 39 | compat: |
| 40 | /* |
| 41 | * We are now in compatibility mode with a default operand size of |
| 42 | * 32 bits. First disable paging. |
| 43 | */ |
| 44 | movl %cr0, %eax |
| 45 | andl $~X86_CR0_PG, %eax |
| 46 | movl %eax, %cr0 |
| 47 | |
| 48 | /* Invalidate TLB */ |
| 49 | xorl %eax, %eax |
| 50 | movl %eax, %cr3 |
| 51 | |
| 52 | /* Disable Long mode in EFER (Extended Feature Enable Register) */ |
| 53 | movl $MSR_EFER, %ecx |
| 54 | rdmsr |
| 55 | btr $_EFER_LME, %eax |
| 56 | wrmsr |
| 57 | |
| 58 | /* Set up table pointer for _x86boot_start */ |
| 59 | mov %ebx, %ecx |
| 60 | |
| 61 | /* Jump to the required target */ |
| 62 | pushl %edi /* 32-bit code segment */ |
| 63 | pushl %esi /* 32-bit target address */ |
| 64 | retf |