.section .data caller_return: .long 0 .global wrapper_target wrapper_target: .long null_call #undef __i686 /* gcc define gets in our way */ .section .gnu.linkonce.t.__i686.get_pc_thunk.bx,"ax",@progbits .globl __i686.get_pc_thunk.bx .hidden __i686.get_pc_thunk.bx .type __i686.get_pc_thunk.bx,@function __i686.get_pc_thunk.bx: movl (%esp), %ebx ret .section .text .globl null_call .type null_call, @function .balign 16,0x90 null_call: ret .globl wrapper .type wrapper, @function .balign 16,0x90 wrapper: pushl $0 pusha # store registers (EAX, ECX, EDX, EBX, ESP, EBP, ESI, EDI) pushf # store flags push %ebp # set up a stack frame movl %esp, %ebp call __i686.get_pc_thunk.bx addl $_GLOBAL_OFFSET_TABLE_, %ebx leal 4(%ebp), %eax # push flags addr push %eax leal 8(%ebp), %eax # push registers addr push %eax leal 44(%ebp), %edx movl (%ebp), %eax subl %edx, %eax push %eax push %edx call report_func@PLT # report entry test %eax, %eax jnz .Ldone movl 44(%ebp), %eax # switch return addresses movl %eax, caller_return@GOTOFF(%ebx) leal .Lwrapper_return@GOTOFF(%ebx), %eax movl %eax, 40(%ebp) movl wrapper_target@GOT(%ebx), %eax movl (%eax), %eax mov %eax, 40(%ebp) # wrapper_target should return at .Lwrapper_return leave # restore %esp, %ebp popf # restore flags popa # restore registers ret # fake 'return' to wrapper_target actually .balign 16, 0x90 .Lwrapper_return: pushl $0 pusha # more for reference sake here pushf push %ebp # set up a stack frame movl %esp, %ebp call __i686.get_pc_thunk.bx addl $_GLOBAL_OFFSET_TABLE_, %ebx movl caller_return@GOTOFF(%ebx), %eax movl %eax, 40(%ebp) # restore the original return address leal 4(%ebp), %eax # push flags addr push %eax leal 8(%ebp), %eax # push registers addr push %eax leal 40(%ebp), %edx # push stack top address (relative to our entry) movl (%ebp), %eax subl %edx, %eax # calculate difference between entry and previous frame push %eax push %edx call report_func_ret@PLT# report the return information (same args) .Ldone: leave popf popa ret .section .note.GNU-stack,"",@progbits