fixed bug in boot2.s: when booting from floppy, the motor would keep

[bootcensus] / src / boot / boot2.s

diff --git a/src/boot/boot2.s b/src/boot/boot2.s
index 572a4f0..5aeebaa 100644 (file)
--- a/src/boot/boot2.s
+++ b/src/boot/boot2.s
@@ -230,7 +230,7 @@ ldloop:
        # just in case we were loaded from floppy, turn all floppy motors off
        mov $0x3f2, %dx
        in %dx, %al
-       and $0xf0, %al
+       and $0xf, %al
        out %al, %dx
 
        mov $10, %ax
@@ -615,16 +615,20 @@ e820_looptop:
        cmp $0x534d4150, %eax
        jnz e820_fail
 
+       # skip areas starting above 4GB as we won't be able to use them
+       cmpl $0, 4(%edi)
+       jnz e820_skip
+
+       # only care for type 1 (usable ram), otherwise ignore
+       cmpl $1, 16(%edi)
+       jnz e820_skip
+
        mov buffer, %eax
        mov $boot_mem_map, %esi
        mov boot_mem_map_size, %ebp
        # again, that's [ebp * 8 + esi]
        mov %eax, (%esi,%ebp,8)
 
-       # only care for type 1 (usable ram), otherwise ignore
-       cmpl $1, 16(%edi)
-       jnz e820_skip
-
        # skip areas with 0 size (also clamp size to 4gb)
        # test high 32bits
        cmpl $0, 12(%edi)
@@ -685,15 +689,21 @@ detect_mem_e801:
        movzx %cx, %eax
        # first size is in KB, convert to bytes
        shl $10, %eax
-       mov %eax, 4(%esi)
-       cmp $0, %dx
+       jnc 0f
+       # overflow means it's >4GB, clamp to 4GB
+       mov $0xffffffff, %eax
+0:     mov %eax, 4(%esi)
        incl boot_mem_map_size
+       cmp $0, %dx
        jz e801_done
        movl $0x1000000, 8(%esi)
        movzx %dx, %eax
        # second size is in 64kb blocks, convert to bytes
        shl $16, %eax
-       mov %eax, 12(%esi)
+       jnc 0f
+       # overflow means it's >4GB, clamp to 4GB
+       mov $0xffffffff, %eax
+0:     mov %eax, 12(%esi)
        incl boot_mem_map_size
 e801_done:
        clc
@@ -753,6 +763,10 @@ rmidt:     .short 0x3ff
 
 saved_esp: .long 0
 saved_ebp: .long 0
+saved_eax: .long 0
+saved_es: .word 0
+saved_ds: .word 0
+saved_flags: .word 0
 
        # drop back to unreal mode to call 16bit interrupt
        .global int86
@@ -765,7 +779,7 @@ int86:
        sidt (saved_idtr)
        lidt (rmidt)
 
-       # modify the int instruction do this here before the
+       # modify the int instruction. do this here before the
        # cs-load jumps, to let them flush the instruction cache
        mov $int_op, %ebx
        movb 8(%ebp), %al
@@ -789,21 +803,34 @@ int86:
        nop
 
        # load registers from the int86regs struct
+       # point esp to the regs struct to load registers with popa/popf
        mov %esp, saved_esp
        mov %ebp, saved_ebp
        mov 12(%ebp), %esp
        popal
+       popfw
+       pop %es
+       pop %ds
+       # ignore fs and gs for now, don't think I'm going to need them
        mov saved_esp, %esp
 
+       # move to the real-mode stack, accessible from ss=0
+       # just in case the BIOS call screws up our unreal mode
+       mov $0x7be0, %esp
+
        # call 16bit interrupt
 int_op:        int $0
+       # BIOS call might have enabled interrupts, cli for good measure
+       cli
 
-       mov saved_ebp, %ebp
-       mov 12(%ebp), %esp
-       add $34, %esp
+       # save all registers that we'll clobber before having the
+       # chance to populate the int86regs structure
+       mov %eax, saved_eax
+       mov %ds, saved_ds
+       mov %es, saved_es
        pushfw
-       pushal
-       mov saved_esp, %esp
+       pop %ax
+       mov %ax, saved_flags
 
        # re-enable protection
        mov %cr0, %eax
@@ -820,6 +847,20 @@ int_op:    int $0
        mov %ax, %ss
        nop
 
+       # point the esp to our regs struct, to fill it with pusha/pushf
+       mov saved_ebp, %ebp
+       mov 12(%ebp), %esp
+       add $38, %esp
+       mov saved_ds, %ax
+       pushw %ax
+       mov saved_es, %ax
+       pushw %ax
+       mov saved_flags, %ax
+       pushw %ax
+       mov saved_eax, %eax
+       pushal
+       mov saved_esp, %esp
+
        # restore 32bit interrupt descriptor table
        lidt (saved_idtr)
        sti
@@ -831,3 +872,5 @@ int_op:     int $0
        # buffer used by the track loader ... to load tracks.
        .align 16
 buffer:
+       .global low_mem_buffer
+low_mem_buffer: