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/*
* libpulp - User-space Livepatching Library
*
* Copyright (C) 2021 SUSE Software Solutions GmbH
*
* This file is part of libpulp.
*
* libpulp is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* libpulp is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with libpulp. If not, see <http://www.gnu.org/licenses/>.
*/
#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <libaddress.h>
/* Do not optimize, otherwise the read/write sequence go away. */
#ifndef __clang__
#pragma GCC push_options
#pragma GCC optimize("O0")
#else
#pragma clang optimize off
#endif
void
disturb_memory(void *addr)
{
int word;
word = *((int *)addr);
*((int *)addr) = word;
}
/* Restore optimization level. */
#ifndef __clang__
#pragma GCC pop_options
#else
#pragma clang optimize on
#endif
int
main(void)
{
char buffer[128];
int retcode;
unsigned long page_size;
uintptr_t page_mask;
void *page_addr;
void *addr;
page_size = getpagesize();
page_mask = ~(page_size - 1);
/* Get an address from the library. */
addr = get_address();
/* Enable writes to the code area. */
page_addr = (void *)((uintptr_t)addr & page_mask);
retcode = mprotect(page_addr, 1, PROT_READ | PROT_WRITE | PROT_EXEC);
if (retcode) {
perror("mprotect");
return 1;
}
/* Loop waiting for any input. */
printf("Waiting for input.\n");
while (1) {
if (fgets(buffer, sizeof(buffer), stdin) == NULL) {
if (errno) {
perror("memory_protection");
return 1;
}
printf("Reached the end of file; quitting.\n");
return 0;
}
/*
* If applying a live patch fails to restore the write permission set
* above, writing to addr (with disturb_memory(addr)) will cause a
* segmentation fault.
*/
disturb_memory(addr);
/* Use the library. */
if (get_address() == NULL)
printf("patched\n");
else
printf("pristine\n");
}
return 1;
}
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