90 lines
2.9 KiB
Diff
90 lines
2.9 KiB
Diff
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From 68708c4503018d61dbcce7ac11cbb511d6425f4d 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 02/27] 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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---
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include/grub/compiler.h | 8 ++++++++
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include/grub/safemath.h | 37 +++++++++++++++++++++++++++++++++++++
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2 files changed, 45 insertions(+)
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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 9859ff4..61c0cb3 100644
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--- a/include/grub/compiler.h
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+++ b/include/grub/compiler.h
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@@ -50,4 +50,12 @@
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#define UNUSED __attribute__((__unused__))
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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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#endif /* ! GRUB_COMPILER_HEADER */
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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 0000000..c17b89b
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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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--
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2.23.0
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