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Diffstat (limited to 'contrib/syslinux-4.02/core/highmem.inc')
| -rw-r--r-- | contrib/syslinux-4.02/core/highmem.inc | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/core/highmem.inc b/contrib/syslinux-4.02/core/highmem.inc new file mode 100644 index 0000000..ea386ff --- /dev/null +++ b/contrib/syslinux-4.02/core/highmem.inc @@ -0,0 +1,158 @@ +;; ----------------------------------------------------------------------- +;; +;; Copyright 1994-2008 H. Peter Anvin - All Rights Reserved +;; +;; This program is free software; you can redistribute it and/or modify +;; it under the terms of the GNU General Public License as published by +;; the Free Software Foundation, Inc., 53 Temple Place Ste 330, +;; Boston MA 02111-1307, USA; either version 2 of the License, or +;; (at your option) any later version; incorporated herein by reference. +;; +;; ----------------------------------------------------------------------- + +;; +;; highmem.inc +;; +;; Probe for the size of high memory. This can be overridden by a +;; mem= command on the command line while booting a new kernel. +;; + + section .text16 + +; +; This is set up as a subroutine; it will set up the global variable +; HighMemSize. All registers are preserved. +; +highmemsize: + push es + pushfd + pushad + + push cs + pop es + +; +; First, try INT 15:E820 (get BIOS memory map) +; +; Note: we may have to scan this multiple times, because some (daft) BIOSes +; report main memory as multiple contiguous ranges... +; +get_e820: + mov dword [E820Max],-(1 << 20) ; Max amount of high memory + mov dword [E820Mem],(1 << 20) ; End of detected high memory +.start_over: + mov di,E820Buf + xor ax,ax + mov cx,10 + rep stosw ; Clear buffer + xor ebx,ebx ; Start with first record + jmp short .do_e820 ; Skip "at end" check first time! +.int_loop: and ebx,ebx ; If we're back at beginning... + jz .e820_done ; ... we're done +.do_e820: mov eax,0000E820h + mov edx,534D4150h ; "SMAP" backwards + xor ecx,ecx + mov cl,20 ; ECX <- 20 (size of buffer) + mov di,E820Buf + int 15h + jnc .no_carry + ; If carry, ebx == 0 means error, ebx != 0 means we're done + and ebx,ebx + jnz .e820_done + jmp no_e820 +.no_carry: + cmp eax,534D4150h + jne no_e820 + cmp cx,20 + jb no_e820 + +; +; Look for a memory block starting at <= 1 MB and continuing upward +; + cmp dword [E820Buf+4], byte 0 + ja .int_loop ; Start >= 4 GB? + mov eax, [E820Buf] + cmp dword [E820Buf+16],1 + je .is_ram ; Is it memory? + ; + ; Non-memory range. Remember this as a limit; some BIOSes get the length + ; of primary RAM incorrect! + ; +.not_ram: + cmp eax, (1 << 20) + jb .int_loop ; Starts in lowmem region + cmp eax,[E820Max] + jae .int_loop ; Already above limit + mov [E820Max],eax ; Set limit + jmp .int_loop + +.is_ram: + cmp eax,[E820Mem] + ja .int_loop ; Not contiguous with our starting point + add eax,[E820Buf+8] + jc .overflow + cmp dword [E820Buf+12],0 + je .nooverflow +.overflow: + or eax,-1 +.nooverflow: + cmp eax,[E820Mem] + jbe .int_loop ; All is below our baseline + mov [E820Mem],eax + jmp .start_over ; Start over in case we find an adjacent range + +.e820_done: + mov eax,[E820Mem] + cmp eax,[E820Max] + jna .not_limited + mov eax,[E820Max] +.not_limited: + cmp eax,(1 << 20) + ja got_highmem ; Did we actually find memory? + ; otherwise fall through + +; +; INT 15:E820 failed. Try INT 15:E801. +; +no_e820: + mov ax,0e801h ; Query high memory (semi-recent) + int 15h + jc no_e801 + cmp ax,3c00h + ja no_e801 ; > 3C00h something's wrong with this call + jb e801_hole ; If memory hole we can only use low part + + mov ax,bx + shl eax,16 ; 64K chunks + add eax,(16 << 20) ; Add first 16M + jmp short got_highmem + +; +; INT 15:E801 failed. Try INT 15:88. +; +no_e801: + mov ah,88h ; Query high memory (oldest) + int 15h + cmp ax,14*1024 ; Don't trust memory >15M + jna e801_hole + mov ax,14*1024 +e801_hole: + and eax,0ffffh + shl eax,10 ; Convert from kilobytes + add eax,(1 << 20) ; First megabyte +got_highmem: +%if HIGHMEM_SLOP != 0 + sub eax,HIGHMEM_SLOP +%endif + mov [HighMemSize],eax + popad + popfd + pop es + ret ; Done! + + section .bss16 + alignb 4 +E820Buf resd 5 ; INT 15:E820 data buffer +E820Mem resd 1 ; Memory detected by E820 +E820Max resd 1 ; Is E820 memory capped? +; HighMemSize is defined in com32.inc |