diff options
Diffstat (limited to 'util/cbfstool/linux_trampoline.c')
-rw-r--r-- | util/cbfstool/linux_trampoline.c | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/util/cbfstool/linux_trampoline.c b/util/cbfstool/linux_trampoline.c new file mode 100644 index 0000000000..79d15769a2 --- /dev/null +++ b/util/cbfstool/linux_trampoline.c @@ -0,0 +1,141 @@ +/* + * linux_trampoline + * + * Copyright (C) 2013 Patrick Georgi <patrick@georgi-clan.de> + * + * 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; version 2 of the License. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA, 02110-1301 USA + */ + +#if 0 +/* NOTE: THIS CODE MUST REMAIN POSITION INDEPENDENT + * IT SHOULDN'T USE THE STACK + * AND IN GENERAL EXPECT NOTHING BUT RAM TO WORK + */ +.code32 +.data +#define HEADER_SIG 0x4f49424c // LBIO little endian +#define CB_TAG_FORWARD 0x11 +#define CB_TAG_MEMORY 0x1 +#define CB_TAG_FRAMEBUFFER 0x12 + +#define LINUX_PARAM_LOC 0x90000 +#define E820_NR_OFFSET 0x1e8 +#define LINUX_ENTRY_OFFSET 0x214 +#define E820_OFFSET 0x2d0 + +.trampoline_start: + +cld +xor %edx, %edx +mov $0, %ecx + +.headerSearch: +mov $0x10000, %ebx +add %ecx, %ebx +mov (%ecx), %eax +cmp $HEADER_SIG, %eax +je .headerSearchDone // found the header +add $16, %ecx +cmp %ecx, %ebx +jne .headerSearch + +.headerSearchDone: +cmp %ecx, %ebx // reached the end == not found anything? +je 2f // give up + +// we assume the checksum is okay, no test +mov 4(%ecx), %ebx +add %ecx, %ebx // ebx = cb_header + header_bytes +mov 20(%ecx), %ecx // ecx = table_entries + +.tableScan: +cmp $CB_TAG_FORWARD, (%ebx) +jne .testMemory + +/* forward tag: assume 32bit pointer */ +mov 8(%ebx), %ecx +jmp .headerSearch + +.testMemory: +cmp $CB_TAG_MEMORY, (%ebx) +jne .testFramebuffer + +/* memory tag: copy e820 map and entry count. also determine alt_mem_k */ +mov 4(%ebx), %eax +sub $8, %eax +shr $2, %eax /* eax = number of dwords of e820 data */ +cmp $(32 * 5), %eax /* linux wants at most 32 entries of 5 dwords */ +jng 1f +mov $(32 * 5), %eax /* only copy 32 entries */ +1: +mov %eax, %esi +mov $5, %edi +div %edi +mov %eax, (LINUX_PARAM_LOC + E820_NR_OFFSET) +mov %esi, %eax +xchg %eax, %ecx +lea 8(%ebx), %esi /* e820 data source */ +mov $(LINUX_PARAM_LOC + E820_OFFSET), %edi +rep movsl +xchg %eax, %ecx +jmp .endScan + +.testFramebuffer: +cmp $CB_TAG_FRAMEBUFFER, (%ebx) +jne .endScan +/* TODO: handle framebuffer tag */ + +.endScan: +add 4(%ebx), %ebx +dec %ecx +jnz .tableScan + +/* finally: jump to kernel */ +mov $LINUX_PARAM_LOC, %esi +jmp *(LINUX_PARAM_LOC + LINUX_ENTRY_OFFSET) + + +2: +hlt +jmp 2b + +.trampoline_end: + +.global trampoline_start, trampoline_size +trampoline_start: +.long .trampoline_start +trampoline_size: +.long .trampoline_end - .trampoline_start +#endif + +/* The code above is hand-crafted to fit various contraints. + * To simplify porting, the below matches the above. + * When changing any code in here, compile the above as a .S + * file, objcopy it to binary and paste the result below (minus + * the last 8 bytes which are trampoline_start and trampoline_size). + */ +const unsigned char trampoline[] = { +0xfc, 0x31, 0xd2, 0xb9, 0x00, 0x00, 0x00, 0x00, 0xbb, 0x00, 0x00, 0x01, 0x00, 0x01, 0xcb, 0x8b, +0x01, 0x3d, 0x4c, 0x42, 0x49, 0x4f, 0x74, 0x07, 0x83, 0xc1, 0x10, 0x39, 0xcb, 0x75, 0xe9, 0x39, +0xcb, 0x74, 0x60, 0x8b, 0x59, 0x04, 0x01, 0xcb, 0x8b, 0x49, 0x14, 0x83, 0x3b, 0x11, 0x75, 0x05, +0x8b, 0x4b, 0x08, 0xeb, 0xd3, 0x83, 0x3b, 0x01, 0x75, 0x33, 0x8b, 0x43, 0x04, 0x83, 0xe8, 0x08, +0xc1, 0xe8, 0x02, 0x3d, 0xa0, 0x00, 0x00, 0x00, 0x7e, 0x05, 0xb8, 0xa0, 0x00, 0x00, 0x00, 0x89, +0xc6, 0xbf, 0x05, 0x00, 0x00, 0x00, 0xf7, 0xf7, 0xa3, 0xe8, 0x01, 0x09, 0x00, 0x89, 0xf0, 0x91, +0x8d, 0x73, 0x08, 0xbf, 0xd0, 0x02, 0x09, 0x00, 0xf3, 0xa5, 0x91, 0xeb, 0x05, 0x83, 0x3b, 0x12, +0x75, 0x00, 0x03, 0x5b, 0x04, 0x49, 0x75, 0xb3, 0xbe, 0x00, 0x00, 0x09, 0x00, 0xff, 0x25, 0x14, +0x02, 0x09, 0x00, 0xf4, 0xeb, 0xfd +}; + +void * const trampoline_start = &trampoline; +const unsigned long trampoline_size = sizeof trampoline; |