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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Peter Jones <pjones@redhat.com>
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Date: Mon, 15 Jun 2020 10:58:42 -0400
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Subject: [PATCH] safemath: Add some arithmetic primitives that check for
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overflow
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This adds a new header, include/grub/safemath.h, that includes easy to
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use wrappers for __builtin_{add,sub,mul}_overflow() declared like:
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bool OP(a, b, res)
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where OP is grub_add, grub_sub or grub_mul. OP() returns true in the
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case where the operation would overflow and res is not modified.
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Otherwise, false is returned and the operation is executed.
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These arithmetic primitives require newer compiler versions. So, bump
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these requirements in the INSTALL file too.
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Signed-off-by: Peter Jones <pjones@redhat.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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Upstream-commit-id: de1c315841a
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---
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include/grub/compiler.h | 8 ++++++++
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include/grub/safemath.h | 37 +++++++++++++++++++++++++++++++++++++
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INSTALL | 21 +++------------------
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3 files changed, 48 insertions(+), 18 deletions(-)
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create mode 100644 include/grub/safemath.h
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diff --git a/include/grub/compiler.h b/include/grub/compiler.h
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index a9a684ccba6..60d9c7fae25 100644
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--- a/include/grub/compiler.h
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+++ b/include/grub/compiler.h
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@@ -48,6 +48,14 @@
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# define WARN_UNUSED_RESULT
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#endif
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+#if defined(__clang__) && defined(__clang_major__) && defined(__clang_minor__)
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+# define CLANG_PREREQ(maj,min) \
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+ ((__clang_major__ > (maj)) || \
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+ (__clang_major__ == (maj) && __clang_minor__ >= (min)))
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+#else
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+# define CLANG_PREREQ(maj,min) 0
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+#endif
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+
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#include "types.h"
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union component64
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diff --git a/include/grub/safemath.h b/include/grub/safemath.h
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new file mode 100644
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index 00000000000..c17b89bba17
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--- /dev/null
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+++ b/include/grub/safemath.h
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@@ -0,0 +1,37 @@
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+/*
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+ * GRUB -- GRand Unified Bootloader
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+ * Copyright (C) 2020 Free Software Foundation, Inc.
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+ *
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+ * GRUB is free software: you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation, either version 3 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * GRUB is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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+ *
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+ * Arithmetic operations that protect against overflow.
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+ */
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+
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+#ifndef GRUB_SAFEMATH_H
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+#define GRUB_SAFEMATH_H 1
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+
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+#include <grub/compiler.h>
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+
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+/* These appear in gcc 5.1 and clang 3.8. */
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+#if GNUC_PREREQ(5, 1) || CLANG_PREREQ(3, 8)
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+
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+#define grub_add(a, b, res) __builtin_add_overflow(a, b, res)
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+#define grub_sub(a, b, res) __builtin_sub_overflow(a, b, res)
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+#define grub_mul(a, b, res) __builtin_mul_overflow(a, b, res)
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+
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+#else
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+#error gcc 5.1 or newer or clang 3.8 or newer is required
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+#endif
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+
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+#endif /* GRUB_SAFEMATH_H */
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diff --git a/INSTALL b/INSTALL
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index b67cd7f3476..8f46a3e999c 100644
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--- a/INSTALL
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+++ b/INSTALL
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@@ -11,24 +11,9 @@ GRUB depends on some software packages installed into your system. If
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you don't have any of them, please obtain and install them before
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configuring the GRUB.
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-* GCC 4.1.3 or later
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- Note: older versions may work but support is limited
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- Note: clang 3.2 or later works for i386 and x86_64 targets but results in
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- much bigger binaries.
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- earlier versions not tested
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- Note: clang 3.2 or later works for arm
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- None of tested clang versions generated usable thumb code
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- earlier versions not tested
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- Note: clang 3.3 or later works for arm64
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- earlier versions have no arm64 support
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- Note: clang 3.3 or later works for mips(el)
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- earlier versions fail to generate .reginfo and hence gprel relocations
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- fail.
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- Note: clang 3.2 or later works for powerpc
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- earlier versions not tested
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- Note: clang doesn't support -mno-app-regs and so can't be used for sparc64
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- Note: clang has no support for ia64 and hence you can't compile GRUB
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- for ia64 with clang
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+* GCC 5.1.0 or later
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+ Experimental support for clang 3.8.0 or later (results in much bigger binaries)
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+ for i386, x86_64, arm (including thumb), arm64, mips(el), powerpc, sparc64
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* GNU Make
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* GNU Bison 2.3 or later
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* GNU gettext 0.17 or later
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