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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/user.h>
#include <unistd.h>
int fib(int n)
{
int first = 0, second = 1, next = 0, i = 0;
while(i <= n)
{
if(i < 2)
{
next = i;
}
else
{
next = first + second;
first = second;
second = next;
}
i++;
}
return next;
}
int pass_test()
{
return 0x42;
}
void fatal(char *msg)
{
fprintf(stderr, "*** FATAL ERROR: %s\n", (msg ? msg : "no message"));
fflush(stderr);
abort();
}
void test_shared()
{
static char filename[] = "/tmp/DoubleMapXXXXXX";
int fd = mkstemp(filename);
if(fd == -1)
{
fatal("mkstemp");
}
if(ftruncate(fd, PAGE_SIZE) == -1)
{
fatal("ftruncate");
}
uint8_t *const write_addr = mmap(0, 2 * PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
uint8_t *const exec_addr = mmap(write_addr+PAGE_SIZE, PAGE_SIZE,
PROT_READ | PROT_WRITE | PROT_EXEC, MAP_SHARED | MAP_FIXED, fd, 0);
if(write_addr == MAP_FAILED || exec_addr == MAP_FAILED)
{
fatal("mmap");
}
size_t size = PAGE_SIZE;
memcpy(write_addr, fib, size);
int (*fun_pointer)() = (void*)exec_addr;
// Give the JIT something to potentially cache
for(int i = 0; i < 15000; i++)
{
if(fun_pointer(20) != 6765)
{
fatal("fibonacci");
}
}
memcpy(write_addr, pass_test, size);
if(fun_pointer() == 0x42)
{
printf("test_shared passed\n");
}
munmap(write_addr, 2 * size);
munmap(exec_addr, size);
}
void test_consecutive()
{
uint8_t *const page0 = mmap(NULL,
2 * PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
// throwaway mmap to reduce likelhood of page0 and page1 mapping to consecutive physical frames
uint8_t *const throwaway = mmap(NULL,
PAGE_SIZE, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
uint8_t *const page1 = mmap(page0 + PAGE_SIZE, PAGE_SIZE,
PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
if(page0 == MAP_FAILED || throwaway == MAP_FAILED || page1 == MAP_FAILED)
{
fatal("mmap");
}
// Attempt to influence virtual to physical mapping - we want page0->page1 to not be contiguous
// physically
page0[0] = 0;
throwaway[0] = 0;
page1[0] = 0;
for(int32_t i = 0; i < 100; i++)
{
uint8_t* start = (uint8_t*)(page1 - i - 1);
memcpy(start, fib, PAGE_SIZE);
int (*fun_pointer)() = (void*)start;
for(int j = 0; j < 15000; j++)
{
if(fun_pointer(20) != 6765)
{
fatal("fibonacci");
}
}
}
printf("test_consecutive passed\n");
}
void test_consecutive_written()
{
uint8_t *const page0 = mmap(NULL,
2 * PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
// throwaway mmap to reduce likelhood of page0 and page1 mapping to consecutive physical frames
uint8_t *const throwaway = mmap(NULL,
PAGE_SIZE, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
uint8_t *const page1 = mmap(page0 + PAGE_SIZE, PAGE_SIZE,
PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
if(page0 == MAP_FAILED || throwaway == MAP_FAILED || page1 == MAP_FAILED)
{
fatal("mmap");
}
// Attempt to influence virtual to physical mapping - we want page0->page1 to not be contiguous
// physically
page0[0] = 0;
throwaway[0] = 0;
page1[0] = 0;
uint8_t* start = page1 - 8;
uint8_t* ptr = start;
const int32_t INC_COUNT = 16;
// xor eax, eax
*ptr++ = 0x31;
*ptr++ = 0xc0;
for(int i = 0; i < INC_COUNT; i++)
{
// inc eax
*ptr++ = 0x40;
}
// ret
*ptr++ = 0xC3;
int (*fun_pointer)() = (void*)start;
for(int i = 0; i < 15000; i++)
{
int32_t result = fun_pointer();
if(result != INC_COUNT)
{
fatal("test_consecutive_written");
}
}
// overwrite one INC at the start of the second page with a NOP
*page1 = 0x90;
int32_t result = fun_pointer();
if(result != INC_COUNT - 1)
{
fatal("test_consecutive_written after overwrite");
}
printf("test_consecutive_written passed\n");
}
int main()
{
test_shared();
// disabled for now, takes long and not sure if it actually catches bugs
//test_consecutive();
test_consecutive_written();
return 0;
}
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