| /* |
| * |
| * Copyright 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. |
| */ |
| |
| /* |
| * For reference see "AMD64 Architecture Programmer's Manual Volume 2", |
| * Document 24593-Rev. 3.31-July 2019 Chapter 5.3.4 |
| * |
| * Page table attributes: WB, User+Supervisor, Present, Writeable, Accessed, Dirty |
| */ |
| |
| .section .bss |
| #define _PRES (1ULL << 0) |
| #define _RW (1ULL << 1) |
| #define _US (1ULL << 2) |
| #define _A (1ULL << 5) |
| #define _D (1ULL << 6) |
| #define _PS (1ULL << 7) |
| |
| .section .bss.pm4le |
| .global pm4le |
| .align 4096 |
| pm4le: |
| .skip 8 |
| |
| .section .bss.main_page_table |
| .global main_page_table |
| .align 4096 |
| main_page_table: |
| .skip 8192 |
| |
| .section .bss.extra_page_table |
| .global extra_page_table |
| .align 4096 |
| extra_page_table: |
| .skip 32 |
| |
| /* |
| * WARNING: 32-bit/64-bit Mode Compatibility for Page Table Initialization |
| * This `init_page_table` function is designed to work in both 32-bit protected |
| * mode AND 64-bit long mode. |
| * |
| * Key Considerations: |
| * - Assembly Instructions: Use ONLY instructions that have the SAME binary representation |
| * in both 32-bit and 64-bit modes. |
| * - `.code64` Directive: We're compiling with `.code64` to ensure the assembler uses |
| * the correct 64-bit version of instructions (e.g., `inc`). |
| * - Register Notation: |
| * - Use 64-bit register names (like `%rsi`) for register-indirect addressing to avoid |
| * incorrect address size prefixes. |
| * - It's safe to use `%esi` with `mov` instructions, as the high 32 bits are zeroed |
| * in 64-bit mode. |
| * |
| * IMPORTANT: |
| * Thoroughly test ANY changes to this function in BOTH 32-bit and 64-bit boot environments. |
| */ |
| |
| .code64 |
| .section .text.init_page_table |
| .globl init_page_table |
| .type init_page_table, @function |
| |
| init_page_table: |
| mov $0x80000001, %eax |
| cpuid |
| test $(1 << 26), %edx |
| jnz setup_1gb |
| |
| setup_2mb: |
| mov $2048, %edi |
| mov $(_PRES + _RW + _US + _PS + _A + _D), %eax |
| mov $0, %ecx |
| mov $main_page_table, %esi |
| |
| loop_2mb: |
| mov %eax, (%rsi, %rcx, 8) |
| mov $0, 4(%rsi, %rcx, 8) |
| add $0x200000, %eax |
| inc %ecx |
| cmp %edi, %ecx |
| jb loop_2mb |
| |
| mov $4, %edi |
| mov $main_page_table, %eax |
| add $(_PRES + _RW + _US + _A), %eax |
| mov $0, %ecx |
| mov $extra_page_table, %esi |
| |
| fill_extra_page_table: |
| mov %eax, (%rsi, %rcx, 8) |
| mov $0, 4(%rsi, %rcx, 8) |
| add $4096, %eax |
| inc %ecx |
| cmp %edi, %ecx |
| jb fill_extra_page_table |
| |
| mov $extra_page_table, %eax |
| jmp leave |
| |
| setup_1gb: |
| mov $512, %edi |
| mov $(_PRES + _RW + _US + _PS + _A + _D), %eax |
| mov $0, %ebx |
| mov $0, %ecx |
| mov $main_page_table, %esi |
| |
| loop_1gb: |
| mov %eax, (%rsi, %rcx, 8) |
| mov %ebx, 4(%rsi, %rcx, 8) |
| add $0x40000000, %eax |
| cmp $0x40000000, %eax |
| ja no_overflow_1gb |
| inc %ebx |
| no_overflow_1gb: |
| inc %ecx |
| cmp %edi, %ecx |
| jb loop_1gb |
| |
| mov $main_page_table, %eax |
| |
| leave: |
| or $(_PRES + _RW + _US + _A), %eax |
| mov %eax, pm4le |
| |
| ret |