#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <errno.h>
#include <limits.h>
#include <sys/mman.h>
#include "stub.h"
static long pagesize = -1;
static inline void *pageof(const void* p)
{
return (void *)((unsigned long)p & ~(pagesize - 1));
}
void stub_set(struct func_stub *pstub, void *fn, void *fn_stub)
{
pstub->fn = fn;
memcpy(pstub->code_buf, fn, CODESIZE);
if (-1 == mprotect(pageof(fn), pagesize * 2, PROT_READ | PROT_WRITE | PROT_EXEC))
{
perror("mprotect to w+r+x faild");
exit(errno);
}
*(unsigned char *)fn = (unsigned char)0xE9;
*(unsigned int *)((unsigned char *)fn + 1) = (unsigned char *)fn_stub - (unsigned char *)fn - CODESIZE;
if (-1 == mprotect(pageof(fn), pagesize * 2, PROT_READ | PROT_EXEC))
{
perror("mprotect to r+x failed");
exit(errno);
}
return;
}
void stub_reset(struct func_stub *pstub)
{
if (NULL == pstub->fn)
{
return;
}
if (-1 == mprotect(pageof(pstub->fn), pagesize * 2, PROT_READ | PROT_WRITE | PROT_EXEC))
{
perror("mprotect to w+r+x faild");
exit(errno);
}
memcpy(pstub->fn, pstub->code_buf, CODESIZE);
if (-1 == mprotect(pageof(pstub->fn), pagesize * 2, PROT_READ | PROT_EXEC))
{
perror("mprotect to r+x failed");
exit(errno);
}
memset(pstub, 0, sizeof(struct func_stub));
return;
}
int stub_init(void)
{
int ret;
pagesize = sysconf(_SC_PAGE_SIZE);
ret = 0;
if (pagesize < 0)
{
perror("get system _SC_PAGE_SIZE configure failed");
ret = -1;
}
return ret;
}
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