diff options
| author | Prakhar Bahuguna <prakhar.bahuguna@arm.com> | 2016-12-15 07:59:08 +0000 |
|---|---|---|
| committer | Prakhar Bahuguna <prakhar.bahuguna@arm.com> | 2016-12-15 07:59:08 +0000 |
| commit | 52a7dd7d7825b269ae569db0e2bcb193c7698666 (patch) | |
| tree | 7957bd2c8f0c07fbbcfdc331ca848a051dab6613 /llvm/lib/MC | |
| parent | 342beeb91eb03ce92e598d593325c8475673768e (diff) | |
| download | bcm5719-llvm-52a7dd7d7825b269ae569db0e2bcb193c7698666.tar.gz bcm5719-llvm-52a7dd7d7825b269ae569db0e2bcb193c7698666.zip | |
[ARM] Implement execute-only support in CodeGen
This implements execute-only support for ARM code generation, which
prevents the compiler from generating data accesses to code sections.
The following changes are involved:
* Add the CodeGen option "-arm-execute-only" to the ARM code generator.
* Add the clang flag "-mexecute-only" as well as the GCC-compatible
alias "-mpure-code" to enable this option.
* When enabled, literal pools are replaced with MOVW/MOVT instructions,
with VMOV used in addition for floating-point literals. As the MOVT
instruction is required, execute-only support is only available in
Thumb mode for targets supporting ARMv8-M baseline or Thumb2.
* Jump tables are placed in data sections when in execute-only mode.
* The execute-only text section is assigned section ID 0, and is
marked as unreadable with the SHF_ARM_PURECODE flag with symbol 'y'.
This also overrides selection of ELF sections for globals.
llvm-svn: 289784
Diffstat (limited to 'llvm/lib/MC')
| -rw-r--r-- | llvm/lib/MC/MCContext.cpp | 4 | ||||
| -rw-r--r-- | llvm/lib/MC/MCParser/ELFAsmParser.cpp | 3 | ||||
| -rw-r--r-- | llvm/lib/MC/MCSectionELF.cpp | 2 |
3 files changed, 8 insertions, 1 deletions
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp index 8298aff928c..4798991ceed 100644 --- a/llvm/lib/MC/MCContext.cpp +++ b/llvm/lib/MC/MCContext.cpp @@ -368,7 +368,9 @@ MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type, StringRef CachedName = Entry.first.SectionName; SectionKind Kind; - if (Flags & ELF::SHF_EXECINSTR) + if (Flags & ELF::SHF_ARM_PURECODE) + Kind = SectionKind::getExecuteOnly(); + else if (Flags & ELF::SHF_EXECINSTR) Kind = SectionKind::getText(); else Kind = SectionKind::getReadOnly(); diff --git a/llvm/lib/MC/MCParser/ELFAsmParser.cpp b/llvm/lib/MC/MCParser/ELFAsmParser.cpp index 47d19a824d1..8bfb475635c 100644 --- a/llvm/lib/MC/MCParser/ELFAsmParser.cpp +++ b/llvm/lib/MC/MCParser/ELFAsmParser.cpp @@ -293,6 +293,9 @@ static unsigned parseSectionFlags(StringRef flagsStr, bool *UseLastGroup) { case 'd': flags |= ELF::XCORE_SHF_DP_SECTION; break; + case 'y': + flags |= ELF::SHF_ARM_PURECODE; + break; case 'G': flags |= ELF::SHF_GROUP; break; diff --git a/llvm/lib/MC/MCSectionELF.cpp b/llvm/lib/MC/MCSectionELF.cpp index 5a0bb7fe986..587b28f71b7 100644 --- a/llvm/lib/MC/MCSectionELF.cpp +++ b/llvm/lib/MC/MCSectionELF.cpp @@ -110,6 +110,8 @@ void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI, OS << 'c'; if (Flags & ELF::XCORE_SHF_DP_SECTION) OS << 'd'; + if (Flags & ELF::SHF_ARM_PURECODE) + OS << 'y'; OS << '"'; |
