mprotector.c
dougm (Doug Moore)
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	dougm
	Jul 26 2019, 4:37 AM

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753 B

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mprotector.c
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	#include <sys/mman.h>
	#include <sys/time.h>
	#include <stdlib.h>
	#include <stdio.h>

	enum {MAX_MAPS = 16384, PAGE_SIZE = 4096 };

	int main(int argc, const char *argv[])
	{
	void *mapping;
	struct timeval beg, end;
	struct timezone tz = {0, 0};
	enum {GIGA = 1<<20, PAGE = 1<<12};

	mapping = mmap(0, GIGA, PROT_WRITE, MAP_ALIGNED(14) \| MAP_ANON, -1, 0);

	int i;
	for (i = 0; i < GIGA; i += 2*PAGE)
	mprotect(mapping+i, PAGE, PROT_NONE);
	gettimeofday(&beg, &tz);
	mprotect(mapping, GIGA, PROT_WRITE);
	gettimeofday(&end, &tz);
	end.tv_sec -= beg.tv_sec;
	end.tv_usec -= beg.tv_usec;
	if (end.tv_usec < 0) {
	end.tv_usec += 1000000;
	end.tv_sec--;
	}
	printf("time %ld.%ld\n",
	(long)end.tv_sec, (long)end.tv_usec);
	return 0;
	}