Make tests public. Rewrite most tests. Add tests.

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

diff --git a/src/threads/loader.S b/src/threads/loader.S
index 811d2b60be1f2c89706d51ae4dd6ef48dea99792..796dca8c3dd101b5ef61f2708eeb6f8c9bebf223 100644 (file)
--- a/src/threads/loader.S
+++ b/src/threads/loader.S
@@ -70,12 +70,13 @@ start:
        cli
        cld
 
-# Set up data segments and stack.
+# Set up data segments.
 
        sub ax, ax
        mov es, ax
        mov ds, ax
 
+# Set up stack segment.
 # Stack grows downward starting from us.
 # We don't ever use the stack so this is strictly speaking
 # unnecessary.
@@ -109,7 +110,7 @@ start:
        mov al, 0xdf
        out 0x60, al
 
-#### Get memory size, via interrupt 15h function 88h.  Returns CF
+#### Get memory size, via interrupt 15h function 88h, which returns CF
 #### clear if successful, with AX = (kB of physical memory) - 1024.
 #### This only works for memory sizes <= 65 MB, which should be fine
 #### for our purposes.  We cap memory at 64 MB because that's all we
@@ -118,12 +119,13 @@ start:
        mov ah, 0x88
        int 0x15
        jc panic
+       cli                     # BIOS might have enabled interrupts
        add eax, 1024           # Total kB memory
        cmp eax, 0x10000        # Cap at 64 MB
        jbe 1f
        mov eax, 0x10000
 1:     shr eax, 2              # Total 4 kB pages
-       mov ram_pages, eax 
+       mov ram_pgs, eax 
        
 #### Create temporary page directory and page table and set page
 #### directory base register.
@@ -140,11 +142,17 @@ start:
 # Also add identical PDEs starting at LOADER_PHYS_BASE.
 # See [IA32-v3] section 3.7.6 for a description of the bits in eax.
 
+# A bug in some versions of GAS prevents us from using the straightforward
+#      mov es:[di + LOADER_PHYS_BASE / 1024 / 1024], eax
+# so we calculate the displacement in bx instead.
+
        mov eax, 0x11007
        mov ecx, 0x11
-       sub edi, edi
+       sub di, di
+       mov ebx, LOADER_PHYS_BASE
+       shr ebx, 20
 1:     mov es:[di], eax
-       mov es:LOADER_PHYS_BASE / 1024 / 1024[di], eax 
+       mov es:[bx + di], eax 
        add di, 4
        add eax, 0x1000
        loop 1b
@@ -155,8 +163,8 @@ start:
        mov ax, 0x1100
        mov es, ax
        mov eax, 0x7
-       mov ecx, 0x4000
-       sub edi, edi
+       mov cx, 0x4000
+       sub di, di
 1:     mov es:[di], eax 
        add di, 4 
        add eax, 0x1000
@@ -169,10 +177,6 @@ start:
        
 #### Switch to protected mode.
 
-# First we turn off interrupts because we don't set up an IDT.
-
-       cli
-
 # Then we point the GDTR to our GDT.  Protected mode requires a GDT.
 # We need a data32 prefix to ensure that all 32 bits of the GDT
 # descriptor are loaded (default is to load only 24 bits).
@@ -300,7 +304,7 @@ gdtdesc:
 #### Print panicmsg (with help from the BIOS) and spin.
 
 panic:  .code16                        # We only panic in real mode.
-       mov si, offset panicmsg
+       mov si, offset panic_message
        mov ah, 0xe
        sub bh, bh
 1:     lodsb
@@ -309,22 +313,27 @@ panic:  .code16                   # We only panic in real mode.
        int 0x10
        jmp 1b
 
-panicmsg:
-       .ascii "Loader panic!\r\n"
+panic_message:
+       .ascii "Panic!"
        .byte 0
 
-#### Memory size in 4 kB pages.
-       .org LOADER_RAM_PAGES - LOADER_BASE
-ram_pages:
+#### Physical memory size in 4 kB pages.
+#### This is initialized by the loader and read by the kernel.
+       .org LOADER_RAM_PGS - LOADER_BASE
+ram_pgs:
        .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:
+#### Command-line arguments and their count.
+#### This is written by the `pintos' utility and read by the kernel.
+#### The loader itself does not do anything with the command line.
+       .org LOADER_ARG_CNT - LOADER_BASE
+arg_cnt:       
+       .long 0
+       .org LOADER_ARGS - LOADER_BASE
+args:          
        .fill 0x80, 1, 0
 
-#### Boot-sector signature for BIOS inspection.
-       .org LOADER_BIOS_SIG - LOADER_BASE
+#### Boot-sector signature.
+#### The BIOS checks that this is set properly.
+       .org LOADER_SIG - LOADER_BASE
        .word 0xaa55