vbatts/grub
1
0
Fork 0
Code Issues Pull requests Releases Wiki Activity

safemath: Add some arithmetic primitives that check for overflow

Browse source 
This adds a new header, include/grub/safemath.h, that includes easy to
use wrappers for __builtin_{add,sub,mul}_overflow() declared like:

  bool OP(a, b, res)

where OP is grub_add, grub_sub or grub_mul. OP() returns true in the
case where the operation would overflow and res is not modified.
Otherwise, false is returned and the operation is executed.

These arithmetic primitives require newer compiler versions. So, bump
these requirements in the INSTALL file too.

Signed-off-by: Peter Jones <pjones@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Peter Jones 2020-06-15 10:58:42 -04:00 • committed by Daniel Kiper
parent a4d3fbdff1
commit 68708c4503
3 changed files with 47 additions and 20 deletions
Download patch file Download diff file Expand all files Collapse all files

8
include/grub/compiler.h
View file

@ -48,4 +48,12 @@
# define WARN_UNUSED_RESULT
#endif
#if defined(__clang__) && defined(__clang_major__) && defined(__clang_minor__)
# define CLANG_PREREQ(maj,min) \
((__clang_major__ > (maj)) || \
(__clang_major__ == (maj) && __clang_minor__ >= (min)))
#else
# define CLANG_PREREQ(maj,min) 0
#endif
#endif /* ! GRUB_COMPILER_HEADER */

37
include/grub/safemath.h Normal file
View file

@ -0,0 +1,37 @@
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2020 Free Software Foundation, Inc.
*
* GRUB 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 3 of the License, or
* (at your option) any later version.
*
* GRUB 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*
* Arithmetic operations that protect against overflow.
*/
#ifndef GRUB_SAFEMATH_H
#define GRUB_SAFEMATH_H 1
#include <grub/compiler.h>
/* These appear in gcc 5.1 and clang 3.8. */
#if GNUC_PREREQ(5, 1) || CLANG_PREREQ(3, 8)
#define grub_add(a, b, res) __builtin_add_overflow(a, b, res)
#define grub_sub(a, b, res) __builtin_sub_overflow(a, b, res)
#define grub_mul(a, b, res) __builtin_mul_overflow(a, b, res)
#else
#error gcc 5.1 or newer or clang 3.8 or newer is required
#endif
#endif /* GRUB_SAFEMATH_H */