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From: Jens Kallup <jkallup@web.de>
Newsgroups: comp.compilers
Subject: Re: Executing from dynamically allocated memory
Date: Sun, 13 Oct 2013 10:44:09 +0200
Organization: 1&1 Internet AG
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Xref: csiph.com comp.compilers:993

Hello,

this should be work:


#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>

extern int errno;
static volatile sig_atomic_t sflag;
static sigset_t signal_neu, signal_alt, signal_leer;
void sigfunc1(int);
void sigfunc2(int);

void signale_mmap(void)
{
   if(signal(SIGSEGV, sigfunc1) == SIG_ERR)
    {
      fprintf(stderr, "Konnte signalhandler fC<r SIGSEGV nicht
einrichten\n");
      exit(0);
     }
   if(signal(SIGBUS, sigfunc2) == SIG_ERR)
     {
       fprintf(stderr, "Konnte signalhandler fC<r SIGBUS nicht
einrichten\n");
       exit(0);
     }

   sigemptyset(&signal_leer);
   sigemptyset(&signal_neu);

   sigaddset(&signal_neu, SIGSEGV);
   sigaddset(&signal_neu, SIGBUS);

   if(sigprocmask(SIG_BLOCK, &signal_neu, &signal_alt) < 0)
      exit(0);
}

void sigfunc1(int sig)
{
   printf("SIGSEGV: Versuch auf einen unerlaubten Speicherbereich zu
schreiben\n");
   exit(0);
}

void sigfunc2(int sig)
{
   printf("SIGBUS: Der Speicherbereich ist nicht mehr gC<ltig\n");
   exit(0);
}

void fun1(int v)
{
   printf("value --> 0x%x\n",v);
}

int main(int argc, char **argv)
{
   int fd,fd1;

   void (*callback1)(int);

   printf("exit-> 0x%x\n",exit);
   printf("puts-> 0x%x\n",puts);
   printf("fun1-> 0x%x\n",fun1);


   struct stat attr;

   signale_mmap();

   if((fd1=open(argv[1],O_RDONLY)) < 0)
   {
       fprintf(stderr,"%s : Konnte %s nicht
C6ffnen\n",strerror(errno),argv[2]);
       exit(0);
   }

   if(fstat(fd1, &attr) == -1)
   {
       fprintf(stderr,"Fehler bei fstat.......\n");
       exit(0);
   }

   callback1 = mmap(0, attr.st_size, PROT_READ | PROT_EXEC, MAP_SHARED,
fd1, 0);
   printf("val: 0x%x\n",callback1);

   if((callback1 == ((caddr_t) -1)) )
     {
       fprintf(stderr, "%s: Fehler bei mmap ...........\n",strerror(errno));
       exit(0);
     }
   close(fd1);

   printf("start...\n");
   callback1((int)callback1);
   printf("ende...\n");

   exit(0);
}

// the following code is compiled with nasm 32 bit

bits 32
org 0x0

;-----------------------------------
; Version 1.0
;-----------------------------------
%define FuncPuts	1
%define FuncFun1	2

segment .text
start:
	push	ebp
	mov	ebp, esp

	mov	eax, [ebp + 8]
	add	eax, LC1
	push	eax

	mov	eax,  [ebp + 8]
	call	dword [eax + func_entry + (FuncPuts * 4)]

	pop	eax

	leave
	ret

segment .data
LC1:	db "Hello You!", 10, 0


func_entry:
	dd 31102011	; version
	dd 0x4015d0	; puts

; cheers and good luck
; Jens