| /* |
| * |
| * Copyright (C) 2024 Google Inc. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #define IA32_EFER 0xC0000080 |
| #define EFER_LME (1 << 8) |
| |
| .code32 |
| .global _entry |
| .section .text._entry |
| .align 4 |
| |
| /* |
| * WARNING: Critical Code Section - 32/64-bit Compatibility |
| * This code between `_entry` and `jnz _init64` is executed during system initialization. |
| * It MUST function correctly regardless of whether the system is booting in: |
| * - 32-bit protected mode |
| * - 64-bit long mode |
| * To achieve this, ONLY use instructions that produce identical binary output in both modes. |
| * Thoroughly test ALL modifications to this section in BOTH 32-bit and 64-bit boot |
| * environments. |
| */ |
| |
| _entry: |
| |
| /* Add multiboot header and jump around it when building with multiboot support. */ |
| #if CONFIG(LP_MULTIBOOT) |
| #include "multiboot_header.inc" |
| #endif |
| /* No interrupts, please. */ |
| cli |
| |
| movl $IA32_EFER, %ecx |
| rdmsr |
| testl $EFER_LME, %eax |
| jnz _init64 |
| |
| lgdt %cs:gdt_ptr |
| |
| /* save pointer to coreboot tables */ |
| movl 4(%esp), %eax |
| /* |
| * NOTE: coreboot tables has passed over the top of the stack |
| * while calling in protected mode. |
| */ |
| movl %eax, cb_header_ptr |
| |
| call init_page_table |
| movl $pm4le, %eax |
| |
| /* load identity mapped page tables */ |
| movl %eax, %cr3 |
| |
| /* enable PAE */ |
| movl %cr4, %eax |
| btsl $5, %eax |
| movl %eax, %cr4 |
| |
| /* enable long mode */ |
| movl $(IA32_EFER), %ecx |
| rdmsr |
| btsl $8, %eax |
| wrmsr |
| |
| /* enable paging */ |
| movl %cr0, %eax |
| btsl $31, %eax |
| movl %eax, %cr0 |
| |
| /* Jump to selgdt 0x20, flat x64 code segment */ |
| ljmp $0x20, $_entry64 |
| |
| .code64 |
| .align 16 |
| _init64: |
| movabs $gdt_ptr, %rax |
| lgdt (%rax) |
| |
| /* |
| * Note: The `cb_header_ptr` has passed as the first argument |
| * to the x86-64 calling convention. |
| */ |
| movq %rdi, cb_header_ptr |
| |
| call init_page_table |
| movq $pm4le, %rax |
| |
| /* load identity mapped page tables */ |
| movq %rax, %cr3 |
| |
| _entry64: |
| /* Store current stack pointer and set up new stack. */ |
| movq %rsp, %rax |
| movabs $_estack, %rsp |
| |
| push %rax |
| |
| fninit |
| movq %cr0, %rax |
| andq $0xFFFFFFFFFFFFFFFB, %rax /* clear EM */ |
| orq $0x00000022, %rax /* set MP, NE */ |
| movq %rax, %cr0 |
| |
| movq %cr4, %rax |
| orq $0x00000600, %rax /* set OSFXSR, OSXMMEXCPT */ |
| movq %rax, %cr4 |
| |
| /* Let's rock. */ |
| call start_main |
| |
| /* %rax has the return value - pass it on unmolested */ |
| _leave: |
| /* Restore old stack. */ |
| pop %rsp |
| |
| /* Return to the original context. */ |
| ret |