/* uaccess.c: userspace access functions * * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/mm.h> #include <linux/module.h> #include <asm/uaccess.h> /*****************************************************************************/ /* * copy a null terminated string from userspace */ long strncpy_from_user(char *dst, const char __user *src, long count) { unsigned long max; char *p, ch; long err = -EFAULT; if (count < 0) BUG(); p = dst; #ifndef CONFIG_MMU if ((unsigned long) src < memory_start) goto error; #endif if ((unsigned long) src >= get_addr_limit()) goto error; max = get_addr_limit() - (unsigned long) src; if ((unsigned long) count > max) { memset(dst + max, 0, count - max); count = max; } err = 0; for (; count > 0; count--, p++, src++) { __get_user_asm(err, ch, src, "ub", "=r"); if (err < 0) goto error; if (!ch) break; *p = ch; } err = p - dst; /* return length excluding NUL */ error: if (count > 0) memset(p, 0, count); /* clear remainder of buffer [security] */ return err; } /* end strncpy_from_user() */ EXPORT_SYMBOL(strncpy_from_user); /*****************************************************************************/ /* * Return the size of a string (including the ending 0) * * Return 0 on exception, a value greater than N if too long */ long strnlen_user(const char __user *src, long count) { const char __user *p; long err = 0; char ch; if (count < 0) BUG(); #ifndef CONFIG_MMU if ((unsigned long) src < memory_start) return 0; #endif if ((unsigned long) src >= get_addr_limit()) return 0; for (p = src; count > 0; count--, p++) { __get_user_asm(err, ch, p, "ub", "=r"); if (err < 0) return 0; if (!ch) break; } return p - src + 1; /* return length including NUL */ } /* end strnlen_user() */ EXPORT_SYMBOL(strnlen_user);