73 lines
1.5 KiB
C
73 lines
1.5 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <signal.h>
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#include <setjmp.h>
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// Global flag and jump buffer for recovery
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static jmp_buf env_buffer;
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static volatile int enable_handler = 0;
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void segfault_handler(int signal_num) {
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if (enable_handler == 1) {
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longjmp(env_buffer, 1);
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} else {
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printf("Segmentation Fault :(");
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exit(signal_num);
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}
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}
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int tryDereference(uintptr_t* pointer, uintptr_t* output) {
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uintptr_t val;
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if (setjmp(env_buffer) == 0) {
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enable_handler = 1;
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*output = *pointer;
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enable_handler = 0;
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return 1;
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}
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else {
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enable_handler = 0;
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return 0;
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}
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}
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void printMem(uint8_t* location) {
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if (setjmp(env_buffer) == 0) {
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enable_handler = 1;
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printf("%p: 0x%02x\n", location, *location);
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enable_handler = 0;
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}
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else {
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enable_handler = 0;
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printf("%p: SEGFAULT\n", location);
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}
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}
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uint8_t* flipBit(uint8_t* data, int bit) {
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return (uint8_t*)((1<<bit) ^ (uintptr_t)data);
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}
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uint32_t nBits() {
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//NOTE: Just use UINTPTR_MAX
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uint32_t n = 0;
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for(uintptr_t p = 1;p > 0; p<<=1) ++n;
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return n;
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}
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int main(int argc, char *argv[])
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{
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signal(SIGSEGV, segfault_handler);
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uint32_t nbits = nBits();
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printf("Using %u bit addresses\n", nbits);
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uint8_t a = 0x55;
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uint8_t* var = &a;
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printMem(var-1);
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printMem(var);
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printMem(var+1);
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for (uint32_t i = 0; i < nbits; ++i) {
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//printf("flipping bit %u\n", i);
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printMem(flipBit(var, i));
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}
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return EXIT_SUCCESS;
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}
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