X-Git-Url: https://pd.if.org/git/?p=zos;a=blobdiff_plain;f=bootz.s;fp=bootz.s;h=467a9d176afaa27c639255c5db0726f1272afd4b;hp=0000000000000000000000000000000000000000;hb=dcf9cc4b2cb9bf31f0fd80e4fd2461035c3d3e9c;hpb=bbbb05357f8c1c4e2f4fc039a6b2794e88e63114

diff --git a/bootz.s b/bootz.s
new file mode 100644
index 0000000..467a9d1
--- /dev/null
+++ b/bootz.s
@@ -0,0 +1,144 @@
+USE64
+
+section .text
+
+; TODO if this were aligned to a page, the kernel
+; could reclaim the memory below it from 0x100000 to the start of this section
+
+; import some symbols from boot32.s
+extern GDT64
+extern GDT_load
+extern multiboot_infoptr
+extern multiboot_magic
+
+; export so that boot32.s can find it
+global kernel_bootstrap:function
+
+; export for the kernel
+global _asm_physmap:data
+
+; I think from here the code expects to be using the high memory addresses
+kernel_bootstrap:
+	; zero the other segment registers, we aren't going to use them
+	xor rax, rax
+	mov fs, ax
+	mov gs, ax
+
+	; enable the floating point unit
+	mov rax, cr0
+	and ax, 0xFFFD
+	or ax, 0x10
+	mov cr0, rax
+	fninit
+
+	; Enable Streaming SIMD Extensions
+	mov rax, cr0
+	and ax, 0xFFFB
+	or ax, 0x2
+	mov cr0, rax
+	mov rax, cr4
+	or rax, 0x600
+	mov cr4, rax
+
+	; TODO might as well just enable syscall/sysret here
+
+	jmp beginkernel
+.end:
+size kernel_bootstrap (kernel_bootstrap.end - kernel_bootstrap)
+
+section .text
+
+extern stack
+extern kernel_main
+
+global beginkernel
+type beginkernel function
+beginkernel:
+	; initialize the stack pointer
+	; hard coded kernel stack.  could be freed later with
+	; a dynamic stack, but 64 KB should be enough, and I'd
+	; like to not page fault the kernel, especially for
+	; a stack issue
+	; TODO this stack pretty much leaks once tasking is set
+	; up.  the initial task should probably be freed, and
+	; the 64 KB handed over to the pmm, or used for DMA or
+	; something
+	mov rsp, qword stack
+	add rsp, 65536 ; 64 KB, see kernel.c
+
+	; sets up the 1 GB page maps for the first 512 GB
+	; doing this early makes the pmm's job easier
+	call mapphys
+
+	; reload GDT to high memory
+	mov rax, [ qword _asm_physmap ]
+	add rax, GDT64
+	mov qword [GDT_load + 2], rax
+	lgdt [GDT_load]
+
+	; SysV ABI args for kernel_main, which is written in C
+	mov edi, [multiboot_infoptr]
+	mov esi, [multiboot_magic]
+	call kernel_main
+.end
+size beginkernel beginkernel.end - beginkernel
+
+mapphys:
+	; rdi, rsi, rdx, rcx, r8, r9
+	; scratch rax, rdi, rsi, rdx, rcx, r8, r9, r10, r11
+
+	; now that we're in 64 bit mode, map in the physical memory to
+	; the high addreses
+	; set up 1GB PDPT for physical map at 0xFFFFC00000000000
+	;   1 GB = 0x    4000 0000
+	; 512 GB = 0x 80 0000 0000
+
+	; rax = physical address and bits
+	mov eax, 0x183 ; Global, 1 GB PS, RW, and Present bits
+	; rdi = pdpt slot address, i.e. pdpe address
+	mov rdi, 0x19000
+	; rsi = (1<<30) i.e. 1 GB
+	mov rsi, 0x40000000 ; 1 GB
+	; ecx = GB count
+	xor ecx, ecx
+
+	.nextgb
+	stosq
+	add rax, rsi ; next physical address
+	inc ecx
+	cmp ecx, 512 ; could not use ecx and just cmp rdi to 0x2B000
+	jl .nextgb ; I think I can just do a loop .nextgb and skip the inc and cmp
+
+	; calculate the pml4t offset
+	mov rax, [qword _asm_physmap]
+	mov rdx, rax
+	shr rdx, 39
+	and edx, 0x1ff ; edx is now 384 if the physmap offset is still 0xffffc000000000
+	mov rax, 0x19003 ; physical address of pdpt + ReadWrite and Present
+	mov rdi, cr3
+	; now, set the pml4e
+	mov [rdi + rdx*8], rax
+
+	ret
+
+global allstop:function
+allstop:
+	mov rax, [rsp]
+	mov dr0, rax
+	cli
+	hlt
+	jmp allstop
+.end
+size allstop, allstop.end - allstop
+
+global halt:function
+halt:
+	sti ; ensure that we can receive interrupts
+	hlt
+	ret
+
+section .data
+
+align 8
+_asm_physmap:
+dq 0xFFFFC00000000000