X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Fboot%2Fboot2.s;h=f782d7ef50aca782b0cb16a80bb692e89d3b02dd;hp=6372557ee2e3be08783404529b2713fbcfc354d5;hb=6e5ec45bc9c248586ec797646158b4caa3aa9d68;hpb=559dd7c3c836a69eac46bd12c7ef61bb5de8882c

diff --git a/src/boot/boot2.s b/src/boot/boot2.s
index 6372557..f782d7e 100644
--- a/src/boot/boot2.s
+++ b/src/boot/boot2.s
@@ -15,6 +15,8 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 # this is the second-stage boot loader
+# plus some other code that needs to run below 1mb (int86 implementation).
+
 	.code16
 	.section .boot2,"ax"
 
@@ -34,11 +36,14 @@
 	# enable A20 address line
 	call enable_a20
 
+	# detect available memory
+	call detect_memory
+
 	# load the whole program into memory starting at 1MB
 	call load_main
 
-	mov $0x13, %ax
-	int $0x10
+	#mov $0x13, %ax
+	#int $0x10
 
 	# load initial GDT
 	lgdt (gdt_lim)
@@ -196,10 +201,11 @@ ldloop:
 	push %ecx
 	call read_track
 
-	mov buffer, %eax
-	call print_num
-	mov $10, %al
-	call putchar
+	# debug: print the first 32bits of the track
+	#mov buffer, %eax
+	#call print_num
+	#mov $10, %al
+	#call putchar
 
 	# copy to high memory
 	mov $buffer, %esi
@@ -348,14 +354,15 @@ abort_read:
 	jmp 0b
 
 
-
 	# better print routines, since we're not constrainted by the 512b of
 	# the boot sector.
+	.global cursor_x
+	.global cursor_y
 cursor_x: .long 0
 cursor_y: .long 0
 
 putchar:
-	pusha
+	pushal
 	call ser_putchar
 
 	cmp $10, %al
@@ -381,7 +388,7 @@ putchar:
 	jnz 1f
 	call video_newline
 
-1:	popa
+1:	popal
 	ret
 	
 	# expects string pointer in esi
@@ -397,7 +404,7 @@ putstr:
 	# expects number in eax
 print_num:
 	# save registers
-	pusha
+	pushal
 
 	mov $numbuf + 16, %esi
 	movb $0, (%esi)
@@ -414,7 +421,7 @@ convloop:
 	call putstr
 
 	# restore regs
-	popa
+	popal
 	ret
 
 
@@ -428,7 +435,7 @@ video_newline:
 0:	ret
 
 scrollup:
-	pusha
+	pushal
 	# move 80 * 24 lines from b80a0 -> b8000
 	mov $0xb8000, %edi
 	mov $0xb80a0, %esi
@@ -439,7 +446,7 @@ scrollup:
 	xor %eax, %eax
 	mov $40, %ecx
 	addr32 rep stosl
-	popa
+	popal
 	ret
 
 clearscr:
@@ -551,5 +558,319 @@ kbc_wait_write:
 
 numbuf: .space 16
 
+
+detect_memory:
+	mov $memdet_e820_msg, %esi
+	call putstr
+	call detect_mem_e820
+	jnc memdet_done
+	mov $rdfail_msg, %esi
+	call putstr
+
+	mov $memdet_e801_msg, %esi
+	call putstr
+	call detect_mem_e801
+	jnc memdet_done
+	mov $rdfail_msg, %esi
+	call putstr
+
+	mov $memdet_88_msg, %esi
+	call putstr
+	call detect_mem_88
+	jnc memdet_done
+	mov $rdfail_msg, %esi
+	call putstr
+
+	# just panic...
+	mov $memdet_fail_msg, %esi
+	call putstr
+0:	hlt
+	jmp 0b
+
+memdet_done:
+	mov $rdok_msg, %esi
+	call putstr
+	ret
+
+memdet_fail_msg: .ascii "Failed to detect available memory!\n"
+		 .ascii "Please file a bug report: https://github.com/jtsiomb/pcboot/issues\n"
+		 .asciz " or contact me through email: nuclear@member.fsf.org\n"
+memdet_e820_msg: .asciz "Detecting RAM (BIOS 15h/0xe820)... "
+memdet_e801_msg: .asciz "Detecting RAM (BIOS 15h/0xe801)... " 
+memdet_88_msg:	 .asciz "Detecting RAM (BIOS 15h/0x88, max 64mb)... "
+
+	# detect extended memory using BIOS call 15h/e820
+detect_mem_e820:
+	movl $0, boot_mem_map_size
+
+	mov $buffer, %edi
+	xor %ebx, %ebx
+	mov $0x534d4150, %edx
+
+e820_looptop:
+	mov $0xe820, %eax
+	mov $24, %ecx
+	int $0x15
+	jc e820_fail
+	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)
+
+	# skip areas with 0 size (also clamp size to 4gb)
+	# test high 32bits
+	cmpl $0, 12(%edi)
+	jz e820_highzero
+	# high part is non-zero, make low part ffffffff
+	xor %eax, %eax
+	not %eax
+	jmp 0f
+
+e820_highzero:
+	# if both high and low parts are zero, ignore
+	mov 8(%edi), %eax
+	cmpl $0, %eax
+	jz e820_skip
+
+0:	mov %eax, 4(%esi,%ebp,8)
+	incl boot_mem_map_size
+
+e820_skip:
+	# terminate the loop if ebx was reset to 0
+	cmp $0, %ebx
+	jz e820_done
+	jmp e820_looptop
+
+e820_done:
+	clc
+	ret
+
+e820_fail:
+	# if size > 0, then it's not a failure, just the end
+	cmpl $0, boot_mem_map_size
+	jnz e820_done
+
+	stc
+	ret
+
+
+	# detect extended memory using BIOS call 15h/e801
+detect_mem_e801:
+	mov $boot_mem_map, %esi
+	mov boot_mem_map_size, %ebp
+	movl $0, (%ebp)
+
+	xor %cx, %cx
+	xor %dx, %dx
+	mov $0xe801, %ax
+	int $0x15
+	jc e801_fail
+
+	cmp $0, %cx
+	jnz 0f
+	cmp $0, %ax
+	jz e801_fail
+	mov %ax, %cx
+	mov %bx, %dx
+
+0:	movl $0x100000, (%esi)
+	movzx %cx, %eax
+	# first size is in KB, convert to bytes
+	shl $10, %eax
+	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
+	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
+	ret
+e801_fail:
+	stc
+	ret
+
+detect_mem_88:
+	# reportedly some BIOS implementations fail to clear CF on success
+	clc
+	mov $0x88, %ah
+	int $0x15
+	jc x88_fail
+
+	cmp $0, %ax
+	jz x88_fail
+
+	# ax has size in KB, convert to bytes in eax
+	and $0xffff, %eax
+	shl $10, %eax
+
+	mov $boot_mem_map, %esi
+	movl $0x100000, (%esi)
+	mov %eax, 4(%esi)
+
+	movl $1, boot_mem_map_size
+	clc
+	ret
+
+x88_fail:
+	stc
+	ret
+
+
+	.global boot_mem_map_size
+boot_mem_map_size: .long 0
+	.global boot_mem_map
+boot_mem_map: .space 128
+
+
+# this is not boot loader code. It's called later on by the main kernel
+# code in 32bit protected mode. It's placed here because it needs to be
+# located in base memory as it returns and runs in real mode.
+	.code32
+	.align 4
+	# place to save the protected mode IDTR pseudo-descriptor
+	# with sidt, so that it can be restored before returning
+	.short 0
+saved_idtr:
+idtlim:	.short 0
+idtaddr:.long 0
+	# real mode IDTR pseudo-descriptor pointing to the IVT at addr 0
+	.short 0
+rmidt:	.short 0x3ff
+	.long 0
+
+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
+int86:
+	push %ebp
+	mov %esp, %ebp
+	pushal
+	cli
+	# save protected mode IDTR and replace it with the real mode vectors
+	sidt (saved_idtr)
+	lidt (rmidt)
+
+	# 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
+	movb %al, 1(%ebx)
+
+	# long jump to load code selector for 16bit code (6)
+	ljmp $0x30,$0f
+0:
+	.code16
+	# disable protection
+	mov %cr0, %eax
+	and $0xfffe, %ax
+	mov %eax, %cr0
+	# load cs <- 0
+	ljmp $0,$0f
+0:	# zero data segments
+	xor %ax, %ax
+	mov %ax, %ds
+	mov %ax, %es
+	mov %ax, %ss
+	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
+
+	# 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
+	pop %ax
+	mov %ax, saved_flags
+
+	# re-enable protection
+	mov %cr0, %eax
+	or $1, %ax
+	mov %eax, %cr0
+	# long jump to load code selector for 32bit code (1)
+	ljmp $0x8,$0f
+0:
+	.code32
+	# set data selector (2) to all segment regs
+	mov $0x10, %ax
+	mov %ax, %ds
+	mov %ax, %es
+	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
+	popal
+	pop %ebp
+	ret
+
+
+	# buffer used by the track loader ... to load tracks.
 	.align 16
 buffer:
+	.global low_mem_buffer
+low_mem_buffer: