1 2; Copyright Oliver Kowalke 2009. 3; Distributed under the Boost Software License, Version 1.0. 4; (See accompanying file LICENSE_1_0.txt or copy at 5; http://www.boost.org/LICENSE_1_0.txt) 6 7; --------------------------------------------------------------------------------- 8; | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 9; --------------------------------------------------------------------------------- 10; | 0h | 04h | 08h | 0ch | 010h | 014h | 018h | 01ch | 11; --------------------------------------------------------------------------------- 12; | fc_mxcsr|fc_x87_cw| fc_strg |fc_deallo| limit | base | fc_seh | EDI | 13; --------------------------------------------------------------------------------- 14; --------------------------------------------------------------------------------- 15; | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16; --------------------------------------------------------------------------------- 17; | 020h | 024h | 028h | 02ch | 030h | 034h | 038h | 03ch | 18; --------------------------------------------------------------------------------- 19; | ESI | EBX | EBP | EIP | to | data | EH NXT |SEH HNDLR| 20; --------------------------------------------------------------------------------- 21 22.386 23.XMM 24.model flat, c 25; standard C library function 26_exit PROTO, value:SDWORD 27.code 28 29make_fcontext PROC BOOST_CONTEXT_EXPORT 30 ; first arg of make_fcontext() == top of context-stack 31 mov eax, [esp+04h] 32 33 ; reserve space for first argument of context-function 34 ; EAX might already point to a 16byte border 35 lea eax, [eax-08h] 36 37 ; shift address in EAX to lower 16 byte boundary 38 and eax, -16 39 40 ; reserve space for context-data on context-stack 41 ; on context-function entry: (ESP -0x4) % 8 == 0 42 ; additional space is required for SEH 43 lea eax, [eax-040h] 44 45 ; save MMX control- and status-word 46 stmxcsr [eax] 47 ; save x87 control-word 48 fnstcw [eax+04h] 49 50 ; first arg of make_fcontext() == top of context-stack 51 mov ecx, [esp+04h] 52 ; save top address of context stack as 'base' 53 mov [eax+014h], ecx 54 ; second arg of make_fcontext() == size of context-stack 55 mov edx, [esp+08h] 56 ; negate stack size for LEA instruction (== substraction) 57 neg edx 58 ; compute bottom address of context stack (limit) 59 lea ecx, [ecx+edx] 60 ; save bottom address of context-stack as 'limit' 61 mov [eax+010h], ecx 62 ; save bottom address of context-stack as 'dealloction stack' 63 mov [eax+0ch], ecx 64 ; set fiber-storage to zero 65 xor ecx, ecx 66 mov [eax+08h], ecx 67 68 ; third arg of make_fcontext() == address of context-function 69 ; stored in EBX 70 mov ecx, [esp+0ch] 71 mov [eax+024h], ecx 72 73 ; compute abs address of label trampoline 74 mov ecx, trampoline 75 ; save address of trampoline as return-address for context-function 76 ; will be entered after calling jump_fcontext() first time 77 mov [eax+02ch], ecx 78 79 ; compute abs address of label finish 80 mov ecx, finish 81 ; save address of finish as return-address for context-function in EBP 82 ; will be entered after context-function returns 83 mov [eax+028h], ecx 84 85 ; traverse current seh chain to get the last exception handler installed by Windows 86 ; note that on Windows Server 2008 and 2008 R2, SEHOP is activated by default 87 ; the exception handler chain is tested for the presence of ntdll.dll!FinalExceptionHandler 88 ; at its end by RaiseException all seh-handlers are disregarded if not present and the 89 ; program is aborted 90 assume fs:nothing 91 ; load NT_TIB into ECX 92 mov ecx, fs:[0h] 93 assume fs:error 94 95walk: 96 ; load 'next' member of current SEH into EDX 97 mov edx, [ecx] 98 ; test if 'next' of current SEH is last (== 0xffffffff) 99 inc edx 100 jz found 101 dec edx 102 ; exchange content; ECX contains address of next SEH 103 xchg edx, ecx 104 ; inspect next SEH 105 jmp walk 106 107found: 108 ; load 'handler' member of SEH == address of last SEH handler installed by Windows 109 mov ecx, [ecx+04h] 110 ; save address in ECX as SEH handler for context 111 mov [eax+03ch], ecx 112 ; set ECX to -1 113 mov ecx, 0ffffffffh 114 ; save ECX as next SEH item 115 mov [eax+038h], ecx 116 ; load address of next SEH item 117 lea ecx, [eax+038h] 118 ; save next SEH 119 mov [eax+018h], ecx 120 121 ret ; return pointer to context-data 122 123trampoline: 124 ; move transport_t for entering context-function 125 ; FCTX == EAX, DATA == EDX 126 mov [esp], eax 127 mov [esp+04h], edx 128 push ebp 129 ; jump to context-function 130 jmp ebx 131 132finish: 133 ; exit code is zero 134 xor eax, eax 135 mov [esp], eax 136 ; exit application 137 call _exit 138 hlt 139make_fcontext ENDP 140END 141
