1 // REQUIRES: native-run 2 // RUN: %clang_builtins %s %librt -o %t && %run_nomprotect %t 3 // REQUIRES: librt_has_enable_execute_stack 4 5 #include <stdio.h> 6 #include <string.h> 7 #include <stdint.h> 8 extern void __clear_cache(void* start, void* end); 9 extern void __enable_execute_stack(void* addr); 10 11 typedef int (*pfunc)(void); 12 13 // Make these static to avoid ILT jumps for incremental linking on Windows. 14 static int func1() { return 1; } 15 static int func2() { return 2; } 16 17 void *__attribute__((noinline)) 18 memcpy_f(void *dst, const void *src, size_t n) { 19 // ARM and MIPS naturally align functions, but use the LSB for ISA selection 20 // (THUMB, MIPS16/uMIPS respectively). Ensure that the ISA bit is ignored in 21 // the memcpy 22 #if defined(__arm__) || defined(__mips__) 23 return (void *)((uintptr_t)memcpy(dst, (void *)((uintptr_t)src & ~1), n) | 24 ((uintptr_t)src & 1)); 25 #else 26 return memcpy(dst, (void *)((uintptr_t)src), n); 27 #endif 28 } 29 30 int main() 31 { 32 unsigned char execution_buffer[128]; 33 // mark stack page containing execution_buffer to be executable 34 __enable_execute_stack(execution_buffer); 35 36 // verify you can copy and execute a function 37 pfunc f1 = (pfunc)memcpy_f(execution_buffer, func1, 128); 38 __clear_cache(execution_buffer, &execution_buffer[128]); 39 printf("f1: %p\n", f1); 40 if ((*f1)() != 1) 41 return 1; 42 43 // verify you can overwrite a function with another 44 pfunc f2 = (pfunc)memcpy_f(execution_buffer, func2, 128); 45 __clear_cache(execution_buffer, &execution_buffer[128]); 46 if ((*f2)() != 2) 47 return 1; 48 49 return 0; 50 } 51