llvm-6502/docs
Peter Collingbourne 7ffec838a2 Protection against stack-based memory corruption errors using SafeStack
This patch adds the safe stack instrumentation pass to LLVM, which separates
the program stack into a safe stack, which stores return addresses, register
spills, and local variables that are statically verified to be accessed
in a safe way, and the unsafe stack, which stores everything else. Such
separation makes it much harder for an attacker to corrupt objects on the
safe stack, including function pointers stored in spilled registers and
return addresses. You can find more information about the safe stack, as
well as other parts of or control-flow hijack protection technique in our
OSDI paper on code-pointer integrity (http://dslab.epfl.ch/pubs/cpi.pdf)
and our project website (http://levee.epfl.ch).

The overhead of our implementation of the safe stack is very close to zero
(0.01% on the Phoronix benchmarks). This is lower than the overhead of
stack cookies, which are supported by LLVM and are commonly used today,
yet the security guarantees of the safe stack are strictly stronger than
stack cookies. In some cases, the safe stack improves performance due to
better cache locality.

Our current implementation of the safe stack is stable and robust, we
used it to recompile multiple projects on Linux including Chromium, and
we also recompiled the entire FreeBSD user-space system and more than 100
packages. We ran unit tests on the FreeBSD system and many of the packages
and observed no errors caused by the safe stack. The safe stack is also fully
binary compatible with non-instrumented code and can be applied to parts of
a program selectively.

This patch is our implementation of the safe stack on top of LLVM. The
patches make the following changes:

- Add the safestack function attribute, similar to the ssp, sspstrong and
  sspreq attributes.

- Add the SafeStack instrumentation pass that applies the safe stack to all
  functions that have the safestack attribute. This pass moves all unsafe local
  variables to the unsafe stack with a separate stack pointer, whereas all
  safe variables remain on the regular stack that is managed by LLVM as usual.

- Invoke the pass as the last stage before code generation (at the same time
  the existing cookie-based stack protector pass is invoked).

- Add unit tests for the safe stack.

Original patch by Volodymyr Kuznetsov and others at the Dependable Systems
Lab at EPFL; updates and upstreaming by myself.

Differential Revision: http://reviews.llvm.org/D6094

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239761 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-15 21:07:11 +00:00
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_static
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_themes/llvm-theme
CommandGuide Update documentation for llvm-profdata. 2015-05-28 21:57:17 +00:00
Frontend [PerformanceTips] Italics are *word*, not _word_ 2015-04-26 22:25:29 +00:00
HistoricalNotes
TableGen [TableGen] Correct the documentation for 'foreach' in the Language Intro. 2015-06-06 00:44:42 +00:00
tutorial IR: Give 'DI' prefix to debug info metadata 2015-04-29 16:38:44 +00:00
AliasAnalysis.rst Update some AliasAnalysis pass docs for getAdjustedAnalysisPointer. 2014-05-22 19:38:25 +00:00
AMDGPUUsage.rst R600 -> AMDGPU rename 2015-06-13 03:28:10 +00:00
ARM-BE-bitcastfail.png [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
ARM-BE-bitcastsuccess.png [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
ARM-BE-ld1.png [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
ARM-BE-ldr.png [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
Atomics.rst [sphinx cleanup] Fix unexpected indentation warning introduced by r218937 2014-10-03 12:28:48 +00:00
BigEndianNEON.rst Fix typos 2014-05-15 01:52:21 +00:00
BitCodeFormat.rst Misc documentation/comment fixes. 2015-02-04 00:42:45 +00:00
BitSets.rst LowerBitSets: Introduce global layout builder. 2015-02-24 23:17:02 +00:00
BlockFrequencyTerminology.rst Fix typos 2014-05-15 01:52:21 +00:00
BranchWeightMetadata.rst Add function entry count metadata. 2015-05-13 15:13:45 +00:00
Bugpoint.rst Correct 'teh' and other typos / repeated words. 2015-04-14 20:52:58 +00:00
BuildingLLVMWithAutotools.rst Clean up docs references to './configure' in preparation for deprecating in-source builds 2015-04-29 20:06:41 +00:00
CMake.rst [ADT][CMake][AutoConf] Fail-fast iterators for DenseMap 2015-03-26 19:25:01 +00:00
CMakeLists.txt [OCaml] Move Llvm.clone_module to its own Llvm_transform_utils module. 2014-12-01 19:50:39 +00:00
CodeGenerator.rst Fix grammar in documentation. 2015-02-19 18:46:25 +00:00
CodingStandards.rst Doxygen: Enable autobrief feature and update coding standards. 2015-05-15 03:34:01 +00:00
CommandLine.rst Update the example of using a command-line option custom parser to 2014-10-13 21:11:22 +00:00
CompilerWriterInfo.rst R600 -> AMDGPU rename 2015-06-13 03:28:10 +00:00
conf.py Trunk is now 3.7.0svn 2015-01-14 17:38:03 +00:00
CoverageMappingFormat.rst Docs: add documentation for the coverage mapping format. 2014-08-19 17:05:58 +00:00
DebuggingJITedCode.rst
DeveloperPolicy.rst docs: Fix up some .rst formatting 2015-05-14 23:56:58 +00:00
doxygen.cfg.in Doxygen: Enable autobrief feature and update coding standards. 2015-05-15 03:34:01 +00:00
doxygen.intro
Dummy.html
ExceptionHandling.rst [WinEH] Sink UnwindHelp completely out of IR 2015-04-03 22:32:26 +00:00
ExtendedIntegerResults.txt
ExtendingLLVM.rst [docs] Update outdated ExtendingLLVM.rst 2015-04-13 16:04:17 +00:00
Extensions.rst Use a comma after the unique keyword. 2015-04-06 16:34:41 +00:00
FAQ.rst Clean up docs references to './configure' in preparation for deprecating in-source builds 2015-04-29 20:06:41 +00:00
FaultMaps.rst Unbreak the build from r239740. 2015-06-15 19:29:44 +00:00
GarbageCollection.rst Document the CoreCLR GC Strategy 2015-05-21 00:50:10 +00:00
gcc-loops.png
GetElementPtr.rst Update LangRef for getelementptr explicit type changes 2015-03-04 22:02:58 +00:00
GettingStarted.rst R600 -> AMDGPU rename 2015-06-13 03:28:10 +00:00
GettingStartedVS.rst Update the docs to require at least MSVC 2013. 2015-02-15 19:34:17 +00:00
GoldPlugin.rst Docs: give binutils/gold instructions for CMake too. 2014-11-04 02:16:03 +00:00
HowToAddABuilder.rst
HowToBuildOnARM.rst Clean up docs references to './configure' in preparation for deprecating in-source builds 2015-04-29 20:06:41 +00:00
HowToCrossCompileLLVM.rst
HowToReleaseLLVM.rst docs: Update relaease documents to include the patch number in the RELEASE tags 2014-07-21 14:28:31 +00:00
HowToSetUpLLVMStyleRTTI.rst [docs][LLVM-style RTTI] Add a mention of multiple inheritance. 2015-02-07 01:16:26 +00:00
HowToSubmitABug.rst Delete -std-compile-opts. 2014-10-16 20:00:02 +00:00
HowToUseAttributes.rst
HowToUseInstrMappings.rst
InAlloca.rst inalloca: *Really* fix the docs 2014-03-27 01:38:48 +00:00
index.rst Unbreak docs build from r239740. 2015-06-15 19:38:15 +00:00
LangRef.rst Protection against stack-based memory corruption errors using SafeStack 2015-06-15 21:07:11 +00:00
Lexicon.rst [docs] Document "LGTM" in the lexicon. 2015-06-04 20:28:09 +00:00
LibFuzzer.rst [lib/Fuzzer] make the fuzzing timeout 1200 seconds by default (was: infinity) 2015-05-26 20:57:47 +00:00
LinkTimeOptimization.rst Fix a typo in the documentation of LTO 2014-12-03 07:32:36 +00:00
linpack-pc.png
LLVMBuild.rst [docs] Fix some links 2014-04-07 22:46:40 +00:00
LLVMBuild.txt
make.bat
Makefile [docs] Update the doxygen configuration file. 2015-03-12 17:26:27 +00:00
Makefile.sphinx Revert "Treat warnings in Sphinx as errors. The reasons for doing this are..." 2014-07-22 18:09:17 +00:00
MakefileGuide.rst Remove projects/sample. 2014-03-12 22:40:22 +00:00
MarkedUpDisassembly.rst undo test commit (whitespace only) 2014-06-30 08:09:35 +00:00
MCJIT-creation.png
MCJIT-dyld-load.png
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MCJITDesignAndImplementation.rst Minor typo. 2014-09-05 04:56:43 +00:00
MergeFunctions.rst Inspired by r231891, use gender neutral pronouns in the places I've 2015-03-11 00:15:44 +00:00
NVPTXUsage.rst [docs] fix the declarations of the llvm.nvvm.ptr.gen.to.* intrinsics 2015-05-29 22:18:03 +00:00
Packaging.rst
Passes.rst Remove the preverify pass from the documentation now that it has been removed 2015-01-30 20:51:09 +00:00
Phabricator.rst Add some more detailed docs about the current state of Phabricator and 2015-05-27 07:20:46 +00:00
ProgrammersManual.rst Fix documentation for Set-Like Containers 2015-05-19 10:21:12 +00:00
Projects.rst Remove projects/sample. 2014-03-12 22:40:22 +00:00
re_format.7
README.txt [docs] Add a note to docs/README.txt 2014-04-22 21:47:53 +00:00
ReleaseNotes.rst Update 3.7 Release Note mentionning the non-optionality of the DataLayout 2015-03-18 22:01:44 +00:00
ReleaseProcess.rst
SegmentedStacks.rst Move the segmented stack switch to a function attribute 2014-04-10 22:58:43 +00:00
SourceLevelDebugging.rst Fixed some typos and broken links in source level debugging docs. 2015-05-14 10:58:59 +00:00
SphinxQuickstartTemplate.rst
StackMaps.rst [PowerPC] Adjust PatchPoints for ppc64le 2015-01-16 04:40:58 +00:00
Statepoints.rst [Statepoints][Docs] Fix a couple of out of date examples. 2015-05-13 20:20:10 +00:00
SystemLibrary.rst
TableGenFundamentals.rst Recover TableGen/LangRef, make it official 2014-04-01 09:51:49 +00:00
TestingGuide.rst Document some of the options in test/lit.cfg 2015-05-04 21:37:00 +00:00
TestSuiteMakefileGuide.rst
Vectorizers.rst Correct 'teh' and other typos / repeated words. 2015-04-14 20:52:58 +00:00
WritingAnLLVMBackend.rst configure.ac lives in autoconf/, not autotools/ 2014-11-10 22:36:04 +00:00
WritingAnLLVMPass.rst [PM] Split the LoopInfo object apart from the legacy pass, creating 2015-01-17 14:16:18 +00:00
yaml2obj.rst Object: rename ARMV7 to ARMNT 2014-03-11 03:08:37 +00:00
YamlIO.rst [YAMLIO] Make line-wrapping configurable and test it. 2015-05-29 17:56:28 +00:00

LLVM Documentation
==================

LLVM's documentation is written in reStructuredText, a lightweight
plaintext markup language (file extension `.rst`). While the
reStructuredText documentation should be quite readable in source form, it
is mostly meant to be processed by the Sphinx documentation generation
system to create HTML pages which are hosted on <http://llvm.org/docs/> and
updated after every commit. Manpage output is also supported, see below.

If you instead would like to generate and view the HTML locally, install
Sphinx <http://sphinx-doc.org/> and then do:

    cd docs/
    make -f Makefile.sphinx
    $BROWSER _build/html/index.html

The mapping between reStructuredText files and generated documentation is
`docs/Foo.rst` <-> `_build/html/Foo.html` <-> `http://llvm.org/docs/Foo.html`.

If you are interested in writing new documentation, you will want to read
`SphinxQuickstartTemplate.rst` which will get you writing documentation
very fast and includes examples of the most important reStructuredText
markup syntax.

Manpage Output
===============

Building the manpages is similar to building the HTML documentation. The
primary difference is to use the `man` makefile target, instead of the
default (which is `html`). Sphinx then produces the man pages in the
directory `_build/man/`.

    cd docs/
    make -f Makefile.sphinx man
    man -l _build/man/FileCheck.1

The correspondence between .rst files and man pages is
`docs/CommandGuide/Foo.rst` <-> `_build/man/Foo.1`.
These .rst files are also included during HTML generation so they are also
viewable online (as noted above) at e.g.
`http://llvm.org/docs/CommandGuide/Foo.html`.

Checking links
==============

The reachibility of external links in the documentation can be checked by
running:

    cd docs/
    make -f Makefile.sphinx linkcheck