59 lines
1.2 KiB
C
59 lines
1.2 KiB
C
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#include <sys/mman.h>
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#include <signal.h>
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#include <stdio.h>
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#include <unistd.h>
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enum {
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kMmapSize = 0x1000,
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kMagicValue = 47,
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};
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void *address;
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volatile sig_atomic_t signaled = 0;
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void handler(int sig)
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{
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signaled = 1;
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if (munmap(address, kMmapSize) != 0)
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{
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perror("munmap");
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_exit(5);
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}
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void* newaddr = mmap(address, kMmapSize, PROT_READ | PROT_WRITE,
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MAP_ANON | MAP_FIXED | MAP_PRIVATE, -1, 0);
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if (newaddr != address)
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{
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fprintf(stderr, "Newly mmaped address (%p) does not equal old address (%p).\n",
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newaddr, address);
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_exit(6);
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}
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*(int*)newaddr = kMagicValue;
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}
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int main()
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{
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if (signal(SIGSEGV, handler) == SIG_ERR)
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{
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perror("signal");
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return 1;
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}
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address = mmap(NULL, kMmapSize, PROT_NONE, MAP_ANON | MAP_PRIVATE, -1, 0);
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if (address == MAP_FAILED)
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{
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perror("mmap");
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return 2;
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}
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// This should first trigger a segfault. Our handler will make the memory readable and write
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// the magic value into memory.
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if (*(int*)address != kMagicValue)
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return 3;
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if (! signaled)
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return 4;
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return 0;
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}
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