http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51500
--- Comment #16 from Uros Bizjak <ubizjak at gmail dot com> 2012-01-30 23:04:54
UTC ---
(In reply to comment #15)
> #define FFI_INIT_TRAMPOLINE_THISCALL(TRAMP,FUN,CTX,SIZE) \
> { unsigned char *__tramp = (unsigned char*)(TRAMP); \
> unsigned int __fun = (unsigned int)(FUN); \
> unsigned int __ctx = (unsigned int)(CTX); \
> unsigned int __dis = __fun - (__ctx + 22); \
> *(unsigned int *) &__tramp[0] = 0x8924048b; /* mov (%esp), %eax */ \
> *(unsigned int *) &__tramp[4] = 0xec83240c; /* mov %ecx, (%esp) */ \
> *(unsigned int *) &__tramp[8] = 0x24048904; /* sub $4,(%esp) */ \
> /* mov %eax, (%esp) */ \
> *(unsigned char*) &__tramp[12] = 0xb8; \
> *(unsigned int*) &__tramp[13] = __ctx; /* movl __ctx, %eax */ \
> *(unsigned char *) &__tramp[17] = 0xe8; \
> *(unsigned int*) &__tramp[18] = __dis; /* call __fun */ \
> *(unsigned int*) &__tramp[22] = 0x83240c8b; /* mov (%esp), %ecx */ \
> *(unsigned int*) &__tramp[26] = 0x0c8904c4; /* add $4, %esp */ \
> *(unsigned char*) &__tramp[30] = 0x24; /* mov %ecx, (%esp) */ \
> *(unsigned short*) &__tramp[31] = 0xc3; /* ret */ \
> }
IMO, you will need to keep 16byte stack alignment at function call, so:
movl (%esp), %eax
movl %ecx, (%esp)
subl $12, %esp
movl %eax, (%esp)
movl __ctx, %eax
call fun
mov (%esp), %ecx
addl $16, %esp
jmp *%ecx
