diff options
| -rw-r--r-- | arch/x86/cpu/Makefile | 2 | ||||
| -rw-r--r-- | arch/x86/cpu/call64.S | 93 | ||||
| -rw-r--r-- | arch/x86/cpu/cpu.c | 45 | ||||
| -rw-r--r-- | arch/x86/include/asm/cpu.h | 26 |
4 files changed, 165 insertions, 1 deletions
diff --git a/arch/x86/cpu/Makefile b/arch/x86/cpu/Makefile index e7bb3e3..9d38ef7 100644 --- a/arch/x86/cpu/Makefile +++ b/arch/x86/cpu/Makefile @@ -10,4 +10,4 @@ extra-y = start.o obj-$(CONFIG_X86_RESET_VECTOR) += resetvec.o start16.o -obj-y += interrupts.o cpu.o +obj-y += interrupts.o cpu.o call64.o diff --git a/arch/x86/cpu/call64.S b/arch/x86/cpu/call64.S new file mode 100644 index 0000000..74dd5a8 --- /dev/null +++ b/arch/x86/cpu/call64.S @@ -0,0 +1,93 @@ +/* + * (C) Copyright 2014 Google, Inc + * Copyright (C) 1991, 1992, 1993 Linus Torvalds + * + * Parts of this copied from Linux arch/x86/boot/compressed/head_64.S + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <asm/global_data.h> +#include <asm/msr-index.h> +#include <asm/processor-flags.h> + +.code32 +.globl cpu_call64 +cpu_call64: + /* + * cpu_call64(ulong pgtable, ulong setup_base, ulong target) + * + * eax - pgtable + * edx - setup_base + * ecx - target + */ + cli + push %ecx /* arg2 = target */ + push %edx /* arg1 = setup_base */ + mov %eax, %ebx + + /* Load new GDT with the 64bit segments using 32bit descriptor */ + leal gdt, %eax + movl %eax, gdt+2 + lgdt gdt + + /* Enable PAE mode */ + movl $(X86_CR4_PAE), %eax + movl %eax, %cr4 + + /* Enable the boot page tables */ + leal (%ebx), %eax + movl %eax, %cr3 + + /* Enable Long mode in EFER (Extended Feature Enable Register) */ + movl $MSR_EFER, %ecx + rdmsr + btsl $_EFER_LME, %eax + wrmsr + + /* After gdt is loaded */ + xorl %eax, %eax + lldt %ax + movl $0x20, %eax + ltr %ax + + /* + * Setup for the jump to 64bit mode + * + * When the jump is performed we will be in long mode but + * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1 + * (and in turn EFER.LMA = 1). To jump into 64bit mode we use + * the new gdt/idt that has __KERNEL_CS with CS.L = 1. + * We place all of the values on our mini stack so lret can + * used to perform that far jump. See the gdt below. + */ + pop %esi /* setup_base */ + + pushl $0x10 + leal lret_target, %eax + pushl %eax + + /* Enter paged protected Mode, activating Long Mode */ + movl $(X86_CR0_PG | X86_CR0_PE), %eax + movl %eax, %cr0 + + /* Jump from 32bit compatibility mode into 64bit mode. */ + lret + +code64: +lret_target: + pop %eax /* target */ + mov %eax, %eax /* Clear bits 63:32 */ + jmp *%eax /* Jump to the 64-bit target */ + + .data +gdt: + .word gdt_end - gdt + .long gdt + .word 0 + .quad 0x0000000000000000 /* NULL descriptor */ + .quad 0x00af9a000000ffff /* __KERNEL_CS */ + .quad 0x00cf92000000ffff /* __KERNEL_DS */ + .quad 0x0080890000000000 /* TS descriptor */ + .quad 0x0000000000000000 /* TS continued */ +gdt_end: diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c index 8c1eacc..2e25253 100644 --- a/arch/x86/cpu/cpu.c +++ b/arch/x86/cpu/cpu.c @@ -18,7 +18,10 @@ #include <common.h> #include <command.h> +#include <errno.h> +#include <malloc.h> #include <asm/control_regs.h> +#include <asm/cpu.h> #include <asm/processor.h> #include <asm/processor-flags.h> #include <asm/interrupt.h> @@ -339,3 +342,45 @@ int print_cpuinfo(void) return 0; } + +#define PAGETABLE_SIZE (6 * 4096) + +/** + * build_pagetable() - build a flat 4GiB page table structure for 64-bti mode + * + * @pgtable: Pointer to a 24iKB block of memory + */ +static void build_pagetable(uint32_t *pgtable) +{ + uint i; + + memset(pgtable, '\0', PAGETABLE_SIZE); + + /* Level 4 needs a single entry */ + pgtable[0] = (uint32_t)&pgtable[1024] + 7; + + /* Level 3 has one 64-bit entry for each GiB of memory */ + for (i = 0; i < 4; i++) { + pgtable[1024 + i * 2] = (uint32_t)&pgtable[2048] + + 0x1000 * i + 7; + } + + /* Level 2 has 2048 64-bit entries, each repesenting 2MiB */ + for (i = 0; i < 2048; i++) + pgtable[2048 + i * 2] = 0x183 + (i << 21UL); +} + +int cpu_jump_to_64bit(ulong setup_base, ulong target) +{ + uint32_t *pgtable; + + pgtable = memalign(4096, PAGETABLE_SIZE); + if (!pgtable) + return -ENOMEM; + + build_pagetable(pgtable); + cpu_call64((ulong)pgtable, setup_base, target); + free(pgtable); + + return -EFAULT; +} diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index 32930bd..6c6774a 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -26,4 +26,30 @@ void cpu_disable_paging_pae(void); */ int cpu_has_64bit(void); +/** + * cpu_call64() - Jump to a 64-bit Linux kernel (internal function) + * + * The kernel is uncompressed and the 64-bit entry point is expected to be + * at @target. + * + * This function is used internally - see cpu_jump_to_64bit() for a more + * useful function. + * + * @pgtable: Address of 24KB area containing the page table + * @setup_base: Pointer to the setup.bin information for the kernel + * @target: Pointer to the start of the kernel image + */ +void cpu_call64(ulong pgtable, ulong setup_base, ulong target); + +/** + * cpu_jump_to_64bit() - Jump to a 64-bit Linux kernel + * + * The kernel is uncompressed and the 64-bit entry point is expected to be + * at @target. + * + * @setup_base: Pointer to the setup.bin information for the kernel + * @target: Pointer to the start of the kernel image + */ +int cpu_jump_to_64bit(ulong setup_base, ulong target); + #endif |