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/* -*- linux-c -*-
* Copy from user space functions
* Copyright (C) 2012 Red Hat Inc.
*
* This file is part of systemtap, and is free software. You can
* redistribute it and/or modify it under the terms of the GNU General
* Public License (GPL); either version 2, or (at your option) any
* later version.
*/
#ifndef _STAPDYN_COPY_C_
#define _STAPDYN_COPY_C_
#include "stp_string.c"
static int _stp_mem_fd = -1;
static inline __must_check long __copy_from_user(void *to,
const void __user * from, unsigned long n)
{
int rc = 0;
/*
* The pread syscall is faster than lseek()/read() (since it
* is only one syscall). Also, if we used lseek()/read() we
* couldn't use a cached fd - since 2 threads might hit this
* code at the same time and the 2nd lseek() might finish
* before the 1st read()...
*/
if (pread(_stp_mem_fd, to, n, (off_t)(uintptr_t)from) != n)
rc = -EFAULT;
return rc;
}
static inline __must_check long __copy_to_user(void *to, const void *from,
unsigned long n)
{
int rc = 0;
/*
* The pwrite syscall is faster than lseek()/write() (since it
* is only one syscall).
*/
if (pwrite(_stp_mem_fd, from, n, (off_t)(uintptr_t)to) != n)
rc = -EFAULT;
return rc;
}
static long
_stp_strncpy_from_user(char *dst, const char *src, long count)
{
if (count <= 0)
return -EINVAL;
/* Reads are batched on aligned 4k boundaries, approximately
* page size, to reduce the number of pread syscalls. It will
* likely read past the terminating '\0', but shouldn't fault.
* NB: We shouldn't try to read the entire 'count' at once, in
* case some small string is already near the end of its page.
*/
long i = 0;
while (i < count) {
long n = 0x1000 - ((long)(src + i) & 0xFFF);
n = min(n, count - i);
if (__copy_from_user(dst + i, src + i, n))
return -EFAULT;
char *dst0 = memchr(dst + i, 0, n);
if (dst0 != NULL)
return (dst0 - dst);
i += n;
}
dst[i - 1] = 0;
return i - 1;
}
static unsigned long _stp_copy_from_user(char *dst, const char *src, unsigned long count)
{
if (count && __copy_from_user(dst, src, count) == 0)
return 0;
return count;
}
#endif /* _STAPDYN_COPY_C_ */
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