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glibc/libio/bits/stdio2.h
Siddhesh Poyarekar a643f60c53 Make sure that the fortified function conditionals are constant 
In _FORTIFY_SOURCE=3, the size expression may be non-constant,
resulting in branches in the inline functions remaining intact and
causing a tiny overhead.  Clang (and in future, gcc) make sure that
the -1 case is always safe, i.e. any comparison of the generated
expression with (size_t)-1 is always false so that bit is taken care
of.  The rest is avoidable since we want the _chk variant whenever we
have a size expression and it's not -1.

Rework the conditionals in a uniform way to clearly indicate two
conditions at compile time:

- Either the size is unknown (-1) or we know at compile time that the
  operation length is less than the object size.  We can call the
  original function in this case.  It could be that either the length,
  object size or both are non-constant, but the compiler, through
  range analysis, is able to fold the *comparison* to a constant.

- The size and length are known and the compiler can see at compile
  time that operation length > object size.  This is valid grounds for
  a warning at compile time, followed by emitting the _chk variant.

For everything else, emit the _chk variant.

This simplifies most of the fortified function implementations and at
the same time, ensures that only one call from _chk or the regular
function is emitted.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-10-20 18:12:41 +05:30

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/* Checking macros for stdio functions.
Copyright (C) 2004-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library 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.
The GNU C Library 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 Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef _BITS_STDIO2_H
#define _BITS_STDIO2_H 1
#ifndef _STDIO_H
# error "Never include <bits/stdio2.h> directly; use <stdio.h> instead."
#endif
extern int __sprintf_chk (char *__restrict __s, int __flag, size_t __slen,
const char *__restrict __format, ...) __THROW
__attr_access ((__write_only__, 1, 3));
extern int __vsprintf_chk (char *__restrict __s, int __flag, size_t __slen,
const char *__restrict __format,
__gnuc_va_list __ap) __THROW
__attr_access ((__write_only__, 1, 3));
#ifdef __va_arg_pack
__fortify_function int
__NTH (sprintf (char *__restrict __s, const char *__restrict __fmt, ...))
{
return __builtin___sprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
__glibc_objsize (__s), __fmt,
__va_arg_pack ());
}
#elif !defined __cplusplus
# define sprintf(str, ...) \
__builtin___sprintf_chk (str, __USE_FORTIFY_LEVEL - 1, \
__glibc_objsize (str), __VA_ARGS__)
#endif
__fortify_function int
__NTH (vsprintf (char *__restrict __s, const char *__restrict __fmt,
__gnuc_va_list __ap))
{
return __builtin___vsprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
__glibc_objsize (__s), __fmt, __ap);
}
#if defined __USE_ISOC99 || defined __USE_UNIX98
extern int __snprintf_chk (char *__restrict __s, size_t __n, int __flag,
size_t __slen, const char *__restrict __format,
...) __THROW
__attr_access ((__write_only__, 1, 2));
extern int __vsnprintf_chk (char *__restrict __s, size_t __n, int __flag,
size_t __slen, const char *__restrict __format,
__gnuc_va_list __ap) __THROW;
# ifdef __va_arg_pack
__fortify_function int
__NTH (snprintf (char *__restrict __s, size_t __n,
const char *__restrict __fmt, ...))
{
return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
__glibc_objsize (__s), __fmt,
__va_arg_pack ());
}
# elif !defined __cplusplus
# define snprintf(str, len, ...) \
__builtin___snprintf_chk (str, len, __USE_FORTIFY_LEVEL - 1, \
__glibc_objsize (str), __VA_ARGS__)
# endif
__fortify_function int
__NTH (vsnprintf (char *__restrict __s, size_t __n,
const char *__restrict __fmt, __gnuc_va_list __ap))
{
return __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
__glibc_objsize (__s), __fmt, __ap);
}
#endif
#if __USE_FORTIFY_LEVEL > 1
extern int __fprintf_chk (FILE *__restrict __stream, int __flag,
const char *__restrict __format, ...);
extern int __printf_chk (int __flag, const char *__restrict __format, ...);
extern int __vfprintf_chk (FILE *__restrict __stream, int __flag,
const char *__restrict __format, __gnuc_va_list __ap);
extern int __vprintf_chk (int __flag, const char *__restrict __format,
__gnuc_va_list __ap);
# ifdef __va_arg_pack
__fortify_function int
fprintf (FILE *__restrict __stream, const char *__restrict __fmt, ...)
{
return __fprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
__fortify_function int
printf (const char *__restrict __fmt, ...)
{
return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __va_arg_pack ());
}
# elif !defined __cplusplus
# define printf(...) \
__printf_chk (__USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# define fprintf(stream, ...) \
__fprintf_chk (stream, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# endif
__fortify_function int
vprintf (const char *__restrict __fmt, __gnuc_va_list __ap)
{
#ifdef __USE_EXTERN_INLINES
return __vfprintf_chk (stdout, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
#else
return __vprintf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __ap);
#endif
}
__fortify_function int
vfprintf (FILE *__restrict __stream,
const char *__restrict __fmt, __gnuc_va_list __ap)
{
return __vfprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
}
# ifdef __USE_XOPEN2K8
extern int __dprintf_chk (int __fd, int __flag, const char *__restrict __fmt,
...) __attribute__ ((__format__ (__printf__, 3, 4)));
extern int __vdprintf_chk (int __fd, int __flag,
const char *__restrict __fmt, __gnuc_va_list __arg)
__attribute__ ((__format__ (__printf__, 3, 0)));
# ifdef __va_arg_pack
__fortify_function int
dprintf (int __fd, const char *__restrict __fmt, ...)
{
return __dprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
# elif !defined __cplusplus
# define dprintf(fd, ...) \
__dprintf_chk (fd, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# endif
__fortify_function int
vdprintf (int __fd, const char *__restrict __fmt, __gnuc_va_list __ap)
{
return __vdprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
}
# endif
# ifdef __USE_GNU
extern int __asprintf_chk (char **__restrict __ptr, int __flag,
const char *__restrict __fmt, ...)
__THROW __attribute__ ((__format__ (__printf__, 3, 4))) __wur;
extern int __vasprintf_chk (char **__restrict __ptr, int __flag,
const char *__restrict __fmt, __gnuc_va_list __arg)
__THROW __attribute__ ((__format__ (__printf__, 3, 0))) __wur;
extern int __obstack_printf_chk (struct obstack *__restrict __obstack,
int __flag, const char *__restrict __format,
...)
__THROW __attribute__ ((__format__ (__printf__, 3, 4)));
extern int __obstack_vprintf_chk (struct obstack *__restrict __obstack,
int __flag,
const char *__restrict __format,
__gnuc_va_list __args)
__THROW __attribute__ ((__format__ (__printf__, 3, 0)));
# ifdef __va_arg_pack
__fortify_function int
__NTH (asprintf (char **__restrict __ptr, const char *__restrict __fmt, ...))
{
return __asprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
__fortify_function int
__NTH (__asprintf (char **__restrict __ptr, const char *__restrict __fmt,
...))
{
return __asprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
__fortify_function int
__NTH (obstack_printf (struct obstack *__restrict __obstack,
const char *__restrict __fmt, ...))
{
return __obstack_printf_chk (__obstack, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
# elif !defined __cplusplus
# define asprintf(ptr, ...) \
__asprintf_chk (ptr, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# define __asprintf(ptr, ...) \
__asprintf_chk (ptr, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# define obstack_printf(obstack, ...) \
__obstack_printf_chk (obstack, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# endif
__fortify_function int
__NTH (vasprintf (char **__restrict __ptr, const char *__restrict __fmt,
__gnuc_va_list __ap))
{
return __vasprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
}
__fortify_function int
__NTH (obstack_vprintf (struct obstack *__restrict __obstack,
const char *__restrict __fmt, __gnuc_va_list __ap))
{
return __obstack_vprintf_chk (__obstack, __USE_FORTIFY_LEVEL - 1, __fmt,
__ap);
}
# endif
#endif
#if __GLIBC_USE (DEPRECATED_GETS)
extern char *__gets_chk (char *__str, size_t) __wur;
extern char *__REDIRECT (__gets_warn, (char *__str), gets)
__wur __warnattr ("please use fgets or getline instead, gets can't "
"specify buffer size");
__fortify_function __wur char *
gets (char *__str)
{
if (__glibc_objsize (__str) != (size_t) -1)
return __gets_chk (__str, __glibc_objsize (__str));
return __gets_warn (__str);
}
#endif
extern char *__fgets_chk (char *__restrict __s, size_t __size, int __n,
FILE *__restrict __stream)
__wur __attr_access ((__write_only__, 1, 3));
extern char *__REDIRECT (__fgets_alias,
(char *__restrict __s, int __n,
FILE *__restrict __stream), fgets)
__wur __attr_access ((__write_only__, 1, 2));
extern char *__REDIRECT (__fgets_chk_warn,
(char *__restrict __s, size_t __size, int __n,
FILE *__restrict __stream), __fgets_chk)
__wur __warnattr ("fgets called with bigger size than length "
"of destination buffer");
__fortify_function __wur __fortified_attr_access (__write_only__, 1, 2) char *
fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
{
size_t sz = __glibc_objsize (__s);
if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
return __fgets_alias (__s, __n, __stream);
if (__glibc_unsafe_len (__n, sizeof (char), sz))
return __fgets_chk_warn (__s, sz, __n, __stream);
return __fgets_chk (__s, sz, __n, __stream);
}
extern size_t __fread_chk (void *__restrict __ptr, size_t __ptrlen,
size_t __size, size_t __n,
FILE *__restrict __stream) __wur;
extern size_t __REDIRECT (__fread_alias,
(void *__restrict __ptr, size_t __size,
size_t __n, FILE *__restrict __stream),
fread) __wur;
extern size_t __REDIRECT (__fread_chk_warn,
(void *__restrict __ptr, size_t __ptrlen,
size_t __size, size_t __n,
FILE *__restrict __stream),
__fread_chk)
__wur __warnattr ("fread called with bigger size * nmemb than length "
"of destination buffer");
__fortify_function __wur size_t
fread (void *__restrict __ptr, size_t __size, size_t __n,
FILE *__restrict __stream)
{
size_t sz = __glibc_objsize0 (__ptr);
if (__glibc_safe_or_unknown_len (__n, __size, sz))
return __fread_alias (__ptr, __size, __n, __stream);
if (__glibc_unsafe_len (__n, __size, sz))
return __fread_chk_warn (__ptr, sz, __size, __n, __stream);
return __fread_chk (__ptr, sz, __size, __n, __stream);
}
#ifdef __USE_GNU
extern char *__fgets_unlocked_chk (char *__restrict __s, size_t __size,
int __n, FILE *__restrict __stream)
__wur __attr_access ((__write_only__, 1, 3));
extern char *__REDIRECT (__fgets_unlocked_alias,
(char *__restrict __s, int __n,
FILE *__restrict __stream), fgets_unlocked)
__wur __attr_access ((__write_only__, 1, 2));
extern char *__REDIRECT (__fgets_unlocked_chk_warn,
(char *__restrict __s, size_t __size, int __n,
FILE *__restrict __stream), __fgets_unlocked_chk)
__wur __warnattr ("fgets_unlocked called with bigger size than length "
"of destination buffer");
__fortify_function __wur __fortified_attr_access (__write_only__, 1, 2) char *
fgets_unlocked (char *__restrict __s, int __n, FILE *__restrict __stream)
{
size_t sz = __glibc_objsize (__s);
if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
return __fgets_unlocked_alias (__s, __n, __stream);
if (__glibc_unsafe_len (__n, sizeof (char), sz))
return __fgets_unlocked_chk_warn (__s, sz, __n, __stream);
return __fgets_unlocked_chk (__s, sz, __n, __stream);
}
#endif
#ifdef __USE_MISC
# undef fread_unlocked
extern size_t __fread_unlocked_chk (void *__restrict __ptr, size_t __ptrlen,
size_t __size, size_t __n,
FILE *__restrict __stream) __wur;
extern size_t __REDIRECT (__fread_unlocked_alias,
(void *__restrict __ptr, size_t __size,
size_t __n, FILE *__restrict __stream),
fread_unlocked) __wur;
extern size_t __REDIRECT (__fread_unlocked_chk_warn,
(void *__restrict __ptr, size_t __ptrlen,
size_t __size, size_t __n,
FILE *__restrict __stream),
__fread_unlocked_chk)
__wur __warnattr ("fread_unlocked called with bigger size * nmemb than "
"length of destination buffer");
__fortify_function __wur size_t
fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
FILE *__restrict __stream)
{
size_t sz = __glibc_objsize0 (__ptr);
if (__glibc_safe_or_unknown_len (__n, __size, sz))
{
# ifdef __USE_EXTERN_INLINES
if (__builtin_constant_p (__size)
&& __builtin_constant_p (__n)
&& (__size | __n) < (((size_t) 1) << (8 * sizeof (size_t) / 2))
&& __size * __n <= 8)
{
size_t __cnt = __size * __n;
char *__cptr = (char *) __ptr;
if (__cnt == 0)
return 0;
for (; __cnt > 0; --__cnt)
{
int __c = getc_unlocked (__stream);
if (__c == EOF)
break;
*__cptr++ = __c;
}
return (__cptr - (char *) __ptr) / __size;
}
# endif
return __fread_unlocked_alias (__ptr, __size, __n, __stream);
}
if (__glibc_unsafe_len (__n, __size, sz))
return __fread_unlocked_chk_warn (__ptr, sz, __size, __n, __stream);
return __fread_unlocked_chk (__ptr, sz, __size, __n, __stream);
}
#endif
#endif /* bits/stdio2.h. */
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