dev: load kernel to 0xc0000000

CMakeLists.txt

@@ -29,7 +29,6 @@ add_subdirectory(gblibc)
 add_subdirectory(user-space-program)
 
 set(BOOTLOADER_SOURCES src/boot.s
-                       src/asm/a20.s
                        src/asm/interrupt.s
                        src/asm/port_io.s
                        src/asm/sys.s

src/asm/a20.s

@@ -1,30 +0,0 @@
-.section .text.kinit
-
-.globl check_a20_on
-.type  check_a20_on @function
-
-check_a20_on:
-    pushal
-    movl $0x112345, %edi
-    movl $0x012345, %esi
-
-    movl (%esi), %eax
-    movl (%edi), %ecx
-
-    movl %esi, (%esi)
-    movl %edi, (%edi)
-    cmpsl
-
-    subl $4, %esi
-    subl $4, %edi
-
-    movl %eax, (%esi)
-    movl %ecx, (%edi)
-
-    popal
-    jne a20_on
-    movl $0, %eax
-    ret
-a20_on:
-    movl $1, %eax
-    ret

src/boot.s

@@ -37,7 +37,7 @@ _get_memory_size_use_ax:
 
 _get_memory_size_error:
     xchgw %bx, %bx
-    jmp loader_halt
+    jmp __stage1_halt
 
 _e820_mem_map_load:
     addl $4, %esp
@@ -96,49 +96,95 @@ _load_gdt:
 .code32
 
 start_32bit:
-    movw $16, %ax
+    movw $0x10, %ax
     movw %ax, %ds
     movw %ax, %es
     movw %ax, %fs
     movw %ax, %gs
     movw %ax, %ss
 
-# set up early stack at 0x001000000
-    movl $0x01000000, %ebp
-    movl $0x01000000, %esp
+# set up temporary stack
+    movl $0x7df0, %esp
+    movl $0x7df0, %ebp
+    movl $0x0, (%esp)
+    movl $0x0, 4(%esp)
 
 setup_early_kernel_page_table:
-# set up early kernel page table
-
-# the early kernel page directory is located at physical
-# address 0x00001000, size 4k, and the empty page is at
-# 0x0000-0x0fff, so we fill the first 6KiB
+# memory map:
+# 0x0000-0x1000: empty page
+# 0x1000-0x2000: early kernel pd
+# 0x2000-0x5000: 3 pts
+# 0x5000-0x7000: early kernel stack
+# so we fill the first 7KiB with zero
     movl $0x00000000, %eax
-    movl $0x6000, %ecx
+    movl $0x7000, %ecx
     call _fill_zero
 
-# map the first 16MiB identically
-# 0x1000-0x1fff: early kernel pd
-# 0x2000-0x5fff: pde 0 - 4
+# pt#0: 0x00000000 to 0x00400000
     movl $0x00001000, %eax
-    movl $0x00002003, %ebx
-_fill_pde_loop:
-    movl %ebx, (%eax)
-    addl $4, %eax
+    movl $0x00002003, (%eax)
+# pt#1: 0xc0000000 to 0xc0400000
+    movl $0x00001c00, %eax
+    movl $0x00003003, (%eax)
+# pt#2: 0xffc00000 to 0xffffffff
+    movl $0x00001ffc, %eax
+    movl $0x00004003, (%eax)
+
+# map early kernel page directory identically
+    movl $0x00002004, %eax
+    movl $0x00001003, (%eax)
+
+# map __stage1_start ---- __kinit_end identically
+    movl $__stage1_start, %ebx
+    shrl $12, %ebx
+    movl %ebx, %edx
+    andl $0x3ff, %edx
+    shll $12, %ebx
+
+    movl $__kinit_end, %ecx
+    addl $0xfff, %ecx
+    shrl $12, %ecx
+    shll $12, %ecx
+
+__map_stage1_kinit:
+    leal 3(%ebx), %eax
+    movl %eax, 0x00002000(, %edx, 4)
     addl $0x1000, %ebx
-    cmpl $0x6003, %ebx
-    jne _fill_pde_loop
-
-# then, create page tables
-    movl $0x00000003, %eax
-    movl $0x00002000, %ecx
-
-_create_page_table_loop1:
-    movl %eax, (%ecx)
-    addl $4, %ecx
-    addl $0x1000, %eax
-    cmpl $0x5ffc, %ecx
-    jle _create_page_table_loop1
+    incl %edx
+    cmpl %ebx, %ecx
+    jne __map_stage1_kinit
+
+# map __text_start ---- __bss_end to 0xc0000000
+    movl %ecx, %ebx
+    movl $__text_start, %edx
+    shrl $12, %edx
+    andl $0x3ff, %edx
+
+    movl $__bss_end, %ecx
+    subl $__text_start, %ecx
+    addl %ebx, %ecx
+
+__map_kernel_space:
+    leal 3(%ebx), %eax
+    movl %eax, 0x00003000(, %edx, 4)
+    addl $0x1000, %ebx
+    incl %edx
+    cmpl %ebx, %ecx
+    jne __map_kernel_space
+
+# map kernel stack 0xffffe000-0xffffffff
+    movl $0x5000, %ebx
+    movl $0x7000, %ecx
+    movl $0x0ffffe, %edx
+    andl $0x3ff, %edx
+
+__map_kernel_stack:
+    leal 3(%ebx), %eax
+    movl %eax, 0x00004000(, %edx, 4)
+    addl $0x1000, %ebx
+    incl %edx
+    cmpl %ebx, %ecx
+    jne __map_kernel_stack
 
 load_early_kernel_page_table:
     movl $0x00001000, %eax
@@ -149,51 +195,34 @@ load_early_kernel_page_table:
     orl $0x80010001, %eax
     movl %eax, %cr0
 
-    jmp start_move_kernel
+# set stack pointer and clear stack bottom
+    movl $0xfffffff0, %esp
+    movl $0xfffffff0, %ebp
+
+    movl $0x00, (%esp)
+    movl $0x00, 4(%esp)
+    movl $0x00, 8(%esp)
+    movl $0x00, 12(%esp)
+
+    call kernel_init
+
+__stage1_halt:
+    hlt
+    jmp __stage1_halt
 
 # quick call
 # %eax: address to fill
 # %ecx: byte count to fill
 _fill_zero:
-    movl %ecx, -4(%esp)
-    movl %eax, -8(%esp)
-
-_fill_zero_loop:
     cmpl $0, %ecx
     jz _fill_zero_end
     subl $4, %ecx
     movl $0, (%eax)
     addl $4, %eax
-    jmp _fill_zero_loop
-
+    jmp _fill_zero
 _fill_zero_end:
-    movl -8(%esp), %eax
-    movl -4(%esp), %ecx
     ret
 
-start_move_kernel:
-# move the kernel to 0x100000
-    movl $__stage1_end, %eax
-    movl $__kinit_start, %ebx
-
-    movl $__data_end, %ecx
-    subl $__kinit_start, %ecx
-
-_move_kernel:
-    movl (%eax), %edx
-    movl %edx, (%ebx)
-    addl $4, %eax
-    addl $4, %ebx
-    subl $4, %ecx
-    cmpl $0, %ecx
-    jge _move_kernel
-
-    call kernel_main
-
-loader_halt:
-    hlt
-    jmp loader_halt
-
 asm_gdt_descriptor:
     .word (5 * 8) - 1 # size
     .long asm_gdt_table  # address

src/kernel.ld

@@ -17,7 +17,7 @@ SECTIONS
         __stage1_end = .;
     } > MEM
 
-    .kinit 0x100000 :
+    .kinit :
         AT(LOADADDR(.stage1) + SIZEOF(.stage1))
     {
         __kinit_start = .;
@@ -58,7 +58,7 @@ SECTIONS
         __kinit_end = .;
     } > MEM
 
-    .text :
+    .text 0xc0000000 :
         AT(LOADADDR(.kinit) + SIZEOF(.kinit))
     {
         __text_start = .;
@@ -102,7 +102,7 @@ SECTIONS
         __data_end = .;
     } > MEM
 
-    .bss ALIGN(0x1000) :
+    .bss :
     {
         __bss_start = .;
         *(.bss)

src/kinit.cpp

@@ -81,14 +81,9 @@ static inline int init_console(const char* name)
 }
 
 extern void init_vfs();
-extern "C" uint32_t check_a20_on(void);
 
-extern "C" SECTION(".text.kinit") void NORETURN kernel_main(void)
+extern "C" SECTION(".text.kinit") void NORETURN kernel_init(void)
 {
-    int ret;
-    ret = check_a20_on();
-    assert(ret == 1);
-
     asm_enable_sse();
 
     init_bss_section();
@@ -105,7 +100,7 @@ extern "C" SECTION(".text.kinit") void NORETURN kernel_main(void)
         (*ctor)();
     }
 
-    ret = init_serial_port(PORT_SERIAL0);
+    int ret = init_serial_port(PORT_SERIAL0);
     assert(ret == GB_OK);
 
     init_idt();