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ea99ce5e9b
The --fix-cortex-a8 option implements a linker workaround for the coretex-a8 erratum 657417. A summary of the erratum conditions is: - A 32-bit Thumb-2 branch instruction B.w, Bcc.w, BL, BLX spans two 4KiB regions. - The destination of the branch is to the first 4KiB region. - The instruction before the branch is a 32-bit Thumb-2 non-branch instruction. The linker fix is to redirect the branch to a patch not in the first 4KiB region. The patch forwards the branch on to its target. The cortex-a8, is an old CPU, with the first implementation of this workaround in ld.bfd appearing in 2009. The cortex-a8 has been used in early Android Phones and there are some critical applications that still need to run on a cortex-a8 that have the erratum. The patch is applied roughly 10 times on LLD and 20 on Clang when they are built with --fix-cortex-a8 on an Arm system. The formal erratum description is avaliable in the ARM Core Cortex-A8 (AT400/AT401) Errata Notice document. This is available from Arm on request but it seems to be findable via a web search. Differential Revision: https://reviews.llvm.org/D67284 llvm-svn: 371965
52 lines
1.4 KiB
C++
52 lines
1.4 KiB
C++
//===- ARMErrataFix.h -------------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLD_ELF_ARMA8ERRATAFIX_H
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#define LLD_ELF_ARMA8ERRATAFIX_H
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#include "lld/Common/LLVM.h"
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#include "llvm/ADT/DenseMap.h"
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#include <map>
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#include <vector>
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namespace lld {
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namespace elf {
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class Defined;
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class InputSection;
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struct InputSectionDescription;
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class OutputSection;
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class Patch657417Section;
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class ARMErr657417Patcher {
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public:
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// Return true if Patches have been added to the OutputSections.
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bool createFixes();
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private:
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std::vector<Patch657417Section *>
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patchInputSectionDescription(InputSectionDescription &isd);
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void insertPatches(InputSectionDescription &isd,
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std::vector<Patch657417Section *> &patches);
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void init();
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// A cache of the mapping symbols defined by the InputSection sorted in order
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// of ascending value with redundant symbols removed. These describe
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// the ranges of code and data in an executable InputSection.
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llvm::DenseMap<InputSection *, std::vector<const Defined *>> sectionMap;
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bool initialized = false;
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};
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} // namespace elf
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} // namespace lld
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#endif
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