why mprotect next page memory in function unprotect_address？

[yeyuzhen]

#include <stdio.h>
#include "ExtremeCMock.h"

static int test() {
	int i = 10;
	return i;
}

int test_mock() {
	return (100);
}

int main(void) {
	MOCK_FUNC(test, test_mock);
	printf("test result is %d\n", test());
	unmock_all();
	printf("test result is %d\n", test());
	return 0;
}

I use ExtremeCMock to mock self static function，console show "could not set protection on next page: Cannot allocate memory".I found the reason is function unprotect_address try to mprotect next page memory of real function. What is the purpose to mprotect next page memory?

static void unprotect_address(mocked_function_t * functionp) {
	char *p;
	long psize = sysconf(_SC_PAGESIZE);
	for (p = (char *)functionp->addr; (unsigned long)p % psize; --p)
		;
	if (-1 == mprotect(p,128, PROT_WRITE|PROT_READ|PROT_EXEC)){ 
		perror("could not set protection");
		exit(-1);
	}
	if (-1 == mprotect(p+psize,128, PROT_WRITE|PROT_READ|PROT_EXEC)){  // why unprotect next page ?
		perror("could not set protection on next page");
		exit(-1);
	}
	my_memcpy(functionp->backup_function_data,functionp->addr,STUB_SIZE);
}

[acgreek]

Sorry, it's been a while since I looked at this and didn't realize I had an issue filed. In hi_jack_function, we overwrite the machine code at my_memcpy(functionp->addr, hijack_stub, sizeof(hijack_stub));. I unprotecting the next page just in case that over-write crosses into the next page.