166 lines
4.6 KiB
C
166 lines
4.6 KiB
C
/*
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* linux_trampoline
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*
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* Copyright (C) 2013 Patrick Georgi <patrick@georgi-clan.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#if 0
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/* NOTE: THIS CODE MUST REMAIN POSITION INDEPENDENT
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* IT SHOULDN'T USE THE STACK
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* AND IN GENERAL EXPECT NOTHING BUT RAM TO WORK
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*/
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.code32
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.data
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#include "linux_trampoline.h"
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#define HEADER_SIG 0x4f49424c // LBIO little endian
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#define CB_TAG_FORWARD 0x11
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#define CB_TAG_MEMORY 0x1
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#define CB_TAG_FRAMEBUFFER 0x12
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#define E820_NR_OFFSET 0x1e8
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#define LINUX_ENTRY_OFFSET 0x214
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#define E820_OFFSET 0x2d0
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.trampoline_start:
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cld
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xor %edx, %edx
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mov $0, %ecx
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.headerSearch:
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mov $0x10000, %ebx
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add %ecx, %ebx
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mov (%ecx), %eax
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cmp $HEADER_SIG, %eax
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je .headerSearchDone // found the header
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add $16, %ecx
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cmp %ecx, %ebx
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jne .headerSearch
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.headerSearchDone:
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cmp %ecx, %ebx // reached the end == not found anything?
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je 2f // give up
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// we assume the checksum is okay, no test
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mov 4(%ecx), %ebx
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add %ecx, %ebx // ebx = cb_header + header_bytes
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mov 20(%ecx), %ecx // ecx = table_entries
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.tableScan:
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cmp $CB_TAG_FORWARD, (%ebx)
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jne .testMemory
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/* forward tag: assume 32bit pointer */
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mov 8(%ebx), %ecx
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jmp .headerSearch
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.testMemory:
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cmp $CB_TAG_MEMORY, (%ebx)
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jne .testFramebuffer
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/* memory tag: copy e820 map and entry count. also determine alt_mem_k */
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mov 4(%ebx), %eax
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sub $8, %eax
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shr $2, %eax /* eax = number of dwords of e820 data */
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cmp $(32 * 5), %eax /* linux wants at most 32 entries of 5 dwords */
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jng 1f
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mov $(32 * 5), %eax /* only copy 32 entries */
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1:
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mov %eax, %esi
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mov $5, %edi
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div %edi
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mov %eax, (LINUX_PARAM_LOC + E820_NR_OFFSET)
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mov %esi, %eax
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xchg %eax, %ecx
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lea 8(%ebx), %esi /* e820 data source */
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mov $(LINUX_PARAM_LOC + E820_OFFSET), %edi
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rep movsl
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xchg %eax, %ecx
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jmp .endScan
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.testFramebuffer:
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cmp $CB_TAG_FRAMEBUFFER, (%ebx)
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jne .endScan
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/* TODO: handle framebuffer tag */
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.endScan:
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add 4(%ebx), %ebx
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dec %ecx
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jnz .tableScan
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/* Setup basic code and data segment selectors for Linux
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**
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** Flat code segment descriptor:
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** selector: 0x10
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** base : 0x00000000
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** limit : 0xFFFFFFFF
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** type : code, execute, read
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**
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** Flat data segment descriptor:
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** selector: 0x18
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** base : 0x00000000
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** limit : 0xFFFFFFFF
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** type : data, read/write
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**
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** Use TRAMPOLINE_ENTRY_LOC as a scratchpad.
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*/
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mov $TRAMPOLINE_ENTRY_LOC, %eax
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sgdt (%eax)
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mov 2(%eax), %ebx
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movl $0x0000ffff, 16(%ebx)
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movl $0x00cf9b00, 20(%ebx)
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movl $0x0000ffff, 24(%ebx)
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movl $0x00cf9300, 28(%ebx)
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/* finally: jump to kernel */
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mov $LINUX_PARAM_LOC, %esi
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jmp *(LINUX_PARAM_LOC + LINUX_ENTRY_OFFSET)
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2:
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hlt
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jmp 2b
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.trampoline_end:
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.global trampoline_start, trampoline_size
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trampoline_start:
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.long .trampoline_start
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trampoline_size:
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.long .trampoline_end - .trampoline_start
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#endif
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/* The code above is hand-crafted to fit various contraints.
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* To simplify porting, the below matches the above.
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* When changing any code in here, compile the above as a .S
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* file, objcopy it to binary and paste the result below (minus
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* the last 8 bytes which are trampoline_start and trampoline_size).
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*/
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const unsigned char trampoline[] = {
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0xfc, 0x31, 0xd2, 0xb9, 0x00, 0x00, 0x00, 0x00, 0xbb, 0x00, 0x00, 0x01, 0x00, 0x01, 0xcb, 0x8b,
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0x01, 0x3d, 0x4c, 0x42, 0x49, 0x4f, 0x74, 0x07, 0x83, 0xc1, 0x10, 0x39, 0xcb, 0x75, 0xe9, 0x39,
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0xcb, 0x0f, 0x84, 0x85, 0x00, 0x00, 0x00, 0x8b, 0x59, 0x04, 0x01, 0xcb, 0x8b, 0x49, 0x14, 0x83,
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0x3b, 0x11, 0x75, 0x05, 0x8b, 0x4b, 0x08, 0xeb, 0xcf, 0x83, 0x3b, 0x01, 0x75, 0x33, 0x8b, 0x43,
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0x04, 0x83, 0xe8, 0x08, 0xc1, 0xe8, 0x02, 0x3d, 0xa0, 0x00, 0x00, 0x00, 0x7e, 0x05, 0xb8, 0xa0,
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0x00, 0x00, 0x00, 0x89, 0xc6, 0xbf, 0x05, 0x00, 0x00, 0x00, 0xf7, 0xf7, 0xa3, 0xe8, 0x01, 0x09,
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0x00, 0x89, 0xf0, 0x91, 0x8d, 0x73, 0x08, 0xbf, 0xd0, 0x02, 0x09, 0x00, 0xf3, 0xa5, 0x91, 0xeb,
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0x05, 0x83, 0x3b, 0x12, 0x75, 0x00, 0x03, 0x5b, 0x04, 0x49, 0x75, 0xb3, 0xb8, 0x00, 0x00, 0x04,
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0x00, 0x0f, 0x01, 0x00, 0x8b, 0x58, 0x02, 0xc7, 0x43, 0x10, 0xff, 0xff, 0x00, 0x00, 0xc7, 0x43,
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0x14, 0x00, 0x9b, 0xcf, 0x00, 0xc7, 0x43, 0x18, 0xff, 0xff, 0x00, 0x00, 0xc7, 0x43, 0x1c, 0x00,
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0x93, 0xcf, 0x00, 0xbe, 0x00, 0x00, 0x09, 0x00, 0xff, 0x25, 0x14, 0x02, 0x09, 0x00, 0xf4, 0xeb,
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0xfd
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};
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const void * const trampoline_start = &trampoline;
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const unsigned long trampoline_size = sizeof trampoline;
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