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      1 //===-- clear_cache_test.c - Test clear_cache -----------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is dual licensed under the MIT and the University of Illinois Open
      6 // Source Licenses. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 
     11 #include <stdio.h>
     12 #include <string.h>
     13 #include <stdint.h>
     14 #if defined(_WIN32)
     15 #include <windows.h>
     16 void __clear_cache(void* start, void* end)
     17 {
     18     if (!FlushInstructionCache(GetCurrentProcess(), start, end-start))
     19         exit(1);
     20 }
     21 #else
     22 #include <sys/mman.h>
     23 extern void __clear_cache(void* start, void* end);
     24 #endif
     25 
     26 
     27 
     28 
     29 typedef int (*pfunc)(void);
     30 
     31 int func1()
     32 {
     33     return 1;
     34 }
     35 
     36 int func2()
     37 {
     38     return 2;
     39 }
     40 
     41 void *__attribute__((noinline))
     42 memcpy_f(void *dst, const void *src, size_t n) {
     43 // ARM and MIPS nartually align functions, but use the LSB for ISA selection
     44 // (THUMB, MIPS16/uMIPS respectively).  Ensure that the ISA bit is ignored in
     45 // the memcpy
     46 #if defined(__arm__) || defined(__mips__)
     47   return (void *)((uintptr_t)memcpy(dst, (void *)((uintptr_t)src & ~1), n) |
     48                   ((uintptr_t)src & 1));
     49 #else
     50   return memcpy(dst, (void *)((uintptr_t)src), n);
     51 #endif
     52 }
     53 
     54 unsigned char execution_buffer[128];
     55 
     56 int main()
     57 {
     58     // make executable the page containing execution_buffer
     59     char* start = (char*)((uintptr_t)execution_buffer & (-4095));
     60     char* end = (char*)((uintptr_t)(&execution_buffer[128+4096]) & (-4095));
     61 #if defined(_WIN32)
     62     DWORD dummy_oldProt;
     63     MEMORY_BASIC_INFORMATION b;
     64     if (!VirtualQuery(start, &b, sizeof(b)))
     65         return 1;
     66     if (!VirtualProtect(b.BaseAddress, b.RegionSize, PAGE_EXECUTE_READWRITE, &b.Protect))
     67 #else
     68     if (mprotect(start, end-start, PROT_READ|PROT_WRITE|PROT_EXEC) != 0)
     69 #endif
     70         return 1;
     71 
     72     // verify you can copy and execute a function
     73     pfunc f1 = (pfunc)memcpy_f(execution_buffer, func1, 128);
     74     __clear_cache(execution_buffer, &execution_buffer[128]);
     75     if ((*f1)() != 1)
     76         return 1;
     77 
     78     // verify you can overwrite a function with another
     79     pfunc f2 = (pfunc)memcpy_f(execution_buffer, func2, 128);
     80     __clear_cache(execution_buffer, &execution_buffer[128]);
     81     if ((*f2)() != 2)
     82         return 1;
     83 
     84     return 0;
     85 }
     86