diff options
Diffstat (limited to 'src/arch/x86/exit_car.S')
| -rw-r--r-- | src/arch/x86/exit_car.S | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/src/arch/x86/exit_car.S b/src/arch/x86/exit_car.S new file mode 100644 index 0000000000..e04bd04b25 --- /dev/null +++ b/src/arch/x86/exit_car.S @@ -0,0 +1,106 @@ +/* + * This file is part of the coreboot project. + * + * Copyright 2016 Google Inc. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; version 2 of + * the License. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <cpu/x86/mtrr.h> +#include <cpu/x86/cr.h> + +.section ".module_parameters", "aw", @progbits +/* stack_top indicates the stack to pull MTRR information from. */ +stack_top: +.long 0 +.long 0 + +.text +.global _start +_start: + /* chipset_teardown_car() is expected to disable cache-as-ram. */ + call chipset_teardown_car + + /* Enable caching if not already enabled. */ + mov %cr0, %eax + and $(~(CR0_CD | CR0_NW)), %eax + mov %eax, %cr0 + + /* Ensure cache is clean. */ + invd + + /* Set up new stack. */ + mov stack_top, %esp + + /* + * Honor variable MTRR information pushed on the stack with the + * following layout: + * + * Offset: Value + * ... + * 0x14: MTRR mask 0 63:32 + * 0x10: MTRR mask 0 31:0 + * 0x0c: MTRR base 0 63:32 + * 0x08: MTRR base 0 31:0 + * 0x04: Number of variable MTRRs to set + * 0x00: Number of variable MTRRs to clear + */ + + /* Clear variable MTRRs. */ + pop %ebx /* Number to clear */ + test %ebx, %ebx + jz 2f + xor %eax, %eax + xor %edx, %edx + mov $(MTRR_PHYS_BASE(0)), %ecx +1: + wrmsr + inc %ecx + wrmsr + inc %ecx + dec %ebx + jnz 1b +2: + + /* Set Variable MTRRs based on stack contents. */ + pop %ebx /* Number to set. */ + test %ebx, %ebx + jz 2f + mov $(MTRR_PHYS_BASE(0)), %ecx +1: + /* Write MTRR base. */ + pop %eax + pop %edx + wrmsr + inc %ecx + /* Write MTRR mask. */ + pop %eax + pop %edx + wrmsr + inc %ecx + + dec %ebx + jnz 1b +2: + + /* Enable MTRR. */ + mov $(MTRR_DEF_TYPE_MSR), %ecx + rdmsr + /* Make default type uncacheable. */ + and $(~(MTRR_DEF_TYPE_MASK)), %eax + or $(MTRR_DEF_TYPE_EN), %eax + wrmsr + + /* Load and run ramstage. */ + call copy_and_run + /* Should never return. */ +1: + jmp 1b |