Redo and improve thread scheduling startup.

[pintos-anon] / src / threads / loader.S

diff --git a/src/threads/loader.S b/src/threads/loader.S
index fd8285a16a6589300d40d179dc91f2d650522488..d67af3858f2cbefd592742c1dbab02827f4e00f2 100644 (file)
--- a/src/threads/loader.S
+++ b/src/threads/loader.S
@@ -1,3 +1,4 @@
+#include "loader.h"
 #include "mmu.h"
        
 ##############################################################################
@@ -11,6 +12,12 @@
 # first byte of the kernel, where start.S is linked.
 ##############################################################################
        
+/* Flags in control register 0 */
+#define CR0_PE 0x00000001      /* Protection Enable. */
+#define CR0_EM 0x00000004      /* (Floating-point) Emulation. */
+#define CR0_PG 0x80000000      /* Paging. */
+#define CR0_WP 0x00010000      /* Write-Protect enable in kernel mode. */
+
 .globl start                           # Entry point   
 start: .code16                         # This runs in real mode
        cli                             # Disable interrupts
@@ -60,9 +67,10 @@ start:       .code16                         # This runs in real mode
        movl %cr0, %eax         # turn on protected mode
        orl $CR0_PE, %eax       # 
        movl %eax, %cr0         # 
-       ### CPU magic: jump to relocation, flush prefetch queue, and reload %cs
-       ### Has the effect of just jmp to the next instruction, but simultaneous
-       ### loads CS with $PROT_MODE_CSEG.
+       ### CPU magic: jump to relocation, flush prefetch queue, and
+       ### reload %cs Has the effect of just jmp to the next
+       ### instruction, but simultaneous loads CS with
+       ### $PROT_MODE_CSEG.
        ljmp $SEL_KCSEG, $protcseg
        
 #### We are in protected mode in a 32-bit segment (hence the .code32)
@@ -75,10 +83,11 @@ protcseg:
        movw %ax, %gs           
        movw %ax, %ss
 
-#### Load kernel at 1 MB by frobbing the IDE controller directly.
+#### Load kernel starting at physical address LOADER_KERN_BASE by
+#### frobbing the IDE controller directly.
 
        movl $1, %ebx
-       movl $0x100000, %edi
+       movl $LOADER_KERN_BASE, %edi
 read_sector:
 
        ### Poll status register while controller busy.
@@ -130,27 +139,35 @@ read_sector:
        cmpl $KERNEL_LOAD_PAGES*8 + 1, %ebx
        jnz read_sector
 
-##### Create temporary PDE and PTE and set page directory pointer
+##### Create temporary page directory and page table, set page
+##### directory pointer, and turn on paging.
 ##### FIXME? We could use a single 4 MB page instead of 1024 4 kB pages.
 
-       movl $0x10000, %edi
+       # Create page directory at 64 kB.
+       movl $0x10000, %edi             
        movl %edi, %cr3
+
+       # Fill page directory with zeroes.
        subl %eax, %eax
        movl $0x400, %ecx
        rep stosl
+
+       # Set PDEs for 0 and LOADER_PHYS_BASE to point to the
+       # page table.
        movl $0x11000 | PG_U | PG_W | PG_P, %eax
        movl %eax, 0x10000
-       movl %eax, 0x10c00
+       movl %eax, 0x10000 | (LOADER_PHYS_BASE >> 20)
+
+       # Initialize page table.
        movl $PG_U | PG_W | PG_P, %eax
        movl $0x400, %ecx
 1:     stosl
        addl $0x1000, %eax
        loop 1b
 
-##### Enable paging.
-
+       # Turn on paging and kernel write-protect.
        movl %cr0, %eax
-       orl $CR0_PG, %eax
+       orl $CR0_PG | CR0_WP, %eax
        movl %eax, %cr0
        jmp 1f
 1:
@@ -164,9 +181,10 @@ read_sector:
        
 ##### Jump to kernel entry point.
 
-       movl $0xc0007c00, %esp
-       movl $0xc0100000, %eax
-       jmp *%eax
+       movl $LOADER_PHYS_BASE + 0x20000, %esp
+       movl $LOADER_PHYS_BASE + LOADER_KERN_BASE, %eax
+       call *%eax
+       jmp panic
 
 ##### GDT
 
@@ -194,17 +212,18 @@ panicmsg:
        .ascii "Loader panic!\r\n"
        .byte 0
 
-##### Command-line arguments inserted by another utility.
-##### The loader doesn't use these, but we note their
-##### location here for easy reference.
-       .org 0x200 - 0x80
-cmd_line:      
-
 ##### Memory size in 4 kB pages.
-       .org 0x200 - 6
+       .org LOADER_RAM_PAGES - LOADER_BASE
 ram_pages:
        .long 0
 
+##### Command-line arguments inserted by another utility.
+##### The loader doesn't use these, but we note their
+##### location here for easy reference.
+       .org LOADER_CMD_LINE - LOADER_BASE
+cmd_line:
+       .fill 0x80, 1, 0
+
 ##### Boot-sector signature for BIOS inspection.
-       .org 0x200 - 2
+       .org LOADER_BIOS_SIG - LOADER_BASE
        .word 0xaa55