X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Fboot%2Fboot2.s;h=5aeebaa66a0e54dd2c043bbec8620a808d5c8c32;hp=15b1cb1bd6e64e55fb78c71c3400cdc48066f739;hb=6ddbba6fc0185f6aaf64c661c303549eb088010f;hpb=79be435fcf61613617025a2c4ef5fddf00a09178

diff --git a/src/boot/boot2.s b/src/boot/boot2.s
index 15b1cb1..5aeebaa 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"
 
@@ -228,7 +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
@@ -557,19 +559,69 @@ kbc_wait_write:
 numbuf: .space 16
 
 
-	# sets the carry flag on failure
 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
 
-memdet_looptop:
+e820_looptop:
 	mov $0xe820, %eax
 	mov $24, %ecx
 	int $0x15
-	jc memdet_fail
+	jc e820_fail
 	cmp $0x534d4150, %eax
-	jnz memdet_fail
+	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
@@ -577,49 +629,115 @@ memdet_looptop:
 	# 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 memdet_skip
-
 	# skip areas with 0 size (also clamp size to 4gb)
 	# test high 32bits
 	cmpl $0, 12(%edi)
-	jz memdet_highzero
+	jz e820_highzero
 	# high part is non-zero, make low part ffffffff
 	xor %eax, %eax
 	not %eax
 	jmp 0f
 
-memdet_highzero:
+e820_highzero:
 	# if both high and low parts are zero, ignore
 	mov 8(%edi), %eax
 	cmpl $0, %eax
-	jz memdet_skip
+	jz e820_skip
 
 0:	mov %eax, 4(%esi,%ebp,8)
 	incl boot_mem_map_size
 
-memdet_skip:
+e820_skip:
 	# terminate the loop if ebx was reset to 0
 	cmp $0, %ebx
-	jz memdet_done
-	jmp memdet_looptop
+	jz e820_done
+	jmp e820_looptop
 
-memdet_done:
+e820_done:
+	clc
 	ret
 
-memdet_fail:
+e820_fail:
 	# if size > 0, then it's not a failure, just the end
 	cmpl $0, boot_mem_map_size
-	jnz memdet_done
+	jnz e820_done
 
-	# just panic...
-	mov $memdet_fail_msg, %esi
-	call putstr
-0:	hlt
-	jmp 0b
+	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
 
-memdet_fail_msg: .asciz "Failed to detect available memory!\n"
 
 	.global boot_mem_map_size
 boot_mem_map_size: .long 0
@@ -645,6 +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
@@ -657,7 +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
@@ -681,21 +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
@@ -712,6 +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
@@ -723,3 +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: