From 363cb41c53b4b03af2129fdcaa5f09a8ec37cd17 Mon Sep 17 00:00:00 2001
From: Prakhar Bahuguna <prakhar.bahuguna@arm.com>
Date: Thu, 15 Dec 2016 07:59:24 +0000
Subject: [PATCH] [ARM] Implement execute-only support in CodeGen
Summary:
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.
Reviewers: t.p.northover, rengolin
Subscribers: llvm-commits, aemerson
Differential Revision: https://reviews.llvm.org/D27450
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@289786 91177308-0d34-0410-b5e6-96231b3b80d8
---
include/clang/Basic/DiagnosticCommonKinds.td | 2 +
include/clang/Driver/Options.td | 6 ++
lib/Driver/Tools.cpp | 25 ++++-
test/Driver/arm-execute-only.c | 99 ++++++++++++++++++++
4 files changed, 131 insertions(+), 1 deletion(-)
create mode 100644 test/Driver/arm-execute-only.c
diff --git a/include/clang/Basic/DiagnosticCommonKinds.td b/include/clang/Basic/DiagnosticCommonKinds.td
index adc74d96196..e8180eb1db4 100644
--- a/include/clang/Basic/DiagnosticCommonKinds.td
+++ b/include/clang/Basic/DiagnosticCommonKinds.td
@@ -190,6 +190,8 @@ def err_target_unsupported_fpmath : Error<
"the '%0' unit is not supported with this instruction set">;
def err_target_unsupported_unaligned : Error<
"the %0 sub-architecture does not support unaligned accesses">;
+def err_target_unsupported_execute_only : Error<
+ "execute only is not supported for the %0 sub-architecture">;
def err_opt_not_valid_with_opt : Error<
"option '%0' cannot be specified with '%1'">;
diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index 74f0c2a9dfc..35e15ed8663 100644
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -1455,6 +1455,12 @@ def mlong_calls : Flag<["-"], "mlong-calls">, Group<m_Group>,
HelpText<"Generate branches with extended addressability, usually via indirect jumps.">;
def mno_long_calls : Flag<["-"], "mno-long-calls">, Group<m_Group>,
HelpText<"Restore the default behaviour of not generating long calls">;
+def mexecute_only : Flag<["-"], "mexecute-only">, Group<m_arm_Features_Group>,
+ HelpText<"Disallow generation of data access to code sections (ARM only)">;
+def mno_execute_only : Flag<["-"], "mno-execute-only">, Group<m_arm_Features_Group>,
+ HelpText<"Allow generation of data access to code sections (ARM only)">;
+def mpure_code : Flag<["-"], "mpure-code">, Alias<mexecute_only>; // Alias for GCC compatibility
+def mno_pure_code : Flag<["-"], "mno-pure-code">, Alias<mno_execute_only>;
def mtvos_version_min_EQ : Joined<["-"], "mtvos-version-min=">, Group<m_Group>;
def mappletvos_version_min_EQ : Joined<["-"], "mappletvos-version-min=">, Alias<mtvos_version_min_EQ>;
def mtvos_simulator_version_min_EQ : Joined<["-"], "mtvos-simulator-version-min=">, Alias<mtvos_version_min_EQ>;
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 3b20805c884..8f1f341c7be 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1001,6 +1001,7 @@ arm::FloatABI arm::getARMFloatABI(const ToolChain &TC, const ArgList &Args) {
static void getARMTargetFeatures(const ToolChain &TC,
const llvm::Triple &Triple,
const ArgList &Args,
+ ArgStringList &CmdArgs,
std::vector<StringRef> &Features,
bool ForAS) {
const Driver &D = TC.getDriver();
@@ -1139,6 +1140,28 @@ static void getARMTargetFeatures(const ToolChain &TC,
Features.push_back("+long-calls");
}
+ // Generate execute-only output (no data access to code sections).
+ // Supported only on ARMv6T2 and ARMv7 and above.
+ // Cannot be combined with -mno-movt or -mlong-calls
+ if (Arg *A = Args.getLastArg(options::OPT_mexecute_only, options::OPT_mno_execute_only)) {
+ if (A->getOption().matches(options::OPT_mexecute_only)) {
+ if (getARMSubArchVersionNumber(Triple) < 7 &&
+ llvm::ARM::parseArch(Triple.getArchName()) != llvm::ARM::AK_ARMV6T2)
+ D.Diag(diag::err_target_unsupported_execute_only) << Triple.getArchName();
+ else if (Arg *B = Args.getLastArg(options::OPT_mno_movt))
+ D.Diag(diag::err_opt_not_valid_with_opt) << A->getAsString(Args) << B->getAsString(Args);
+ // Long calls create constant pool entries and have not yet been fixed up
+ // to play nicely with execute-only. Hence, they cannot be used in
+ // execute-only code for now
+ else if (Arg *B = Args.getLastArg(options::OPT_mlong_calls, options::OPT_mno_long_calls)) {
+ if (B->getOption().matches(options::OPT_mlong_calls))
+ D.Diag(diag::err_opt_not_valid_with_opt) << A->getAsString(Args) << B->getAsString(Args);
+ }
+
+ CmdArgs.push_back("-arm-execute-only");
+ }
+ }
+
// Kernel code has more strict alignment requirements.
if (KernelOrKext)
Features.push_back("+strict-align");
@@ -2703,7 +2726,7 @@ static void getTargetFeatures(const ToolChain &TC, const llvm::Triple &Triple,
case llvm::Triple::armeb:
case llvm::Triple::thumb:
case llvm::Triple::thumbeb:
- getARMTargetFeatures(TC, Triple, Args, Features, ForAS);
+ getARMTargetFeatures(TC, Triple, Args, CmdArgs, Features, ForAS);
break;
case llvm::Triple::ppc:
diff --git a/test/Driver/arm-execute-only.c b/test/Driver/arm-execute-only.c
new file mode 100644
index 00000000000..f564594b834
--- /dev/null
+++ b/test/Driver/arm-execute-only.c
@@ -0,0 +1,99 @@
+// RUN: %clang -target armv6t2-eabi -### %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv6t2-eabi -### -mexecute-only %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY
+
+// RUN: %clang -target armv6t2-eabi -### -mexecute-only -mno-execute-only %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv7m-eabi -### %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv7m-eabi -### -mexecute-only %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY
+
+// RUN: %clang -target armv7m-eabi -### -mexecute-only -mno-execute-only %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.base-eabi -### %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.base-eabi -### -mexecute-only %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.base-eabi -### -mexecute-only -mno-execute-only %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.main-eabi -### %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.main-eabi -### -mexecute-only %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.main-eabi -### -mexecute-only -mno-execute-only %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: not %clang -c -target thumbv6m-eabi -mexecute-only %s 2>&1 | \
+// RUN: FileCheck --check-prefix CHECK-EXECUTE-ONLY-NOT-SUPPORTED %s
+
+// RUN: not %clang -target armv8m.main-eabi -mexecute-only -mno-movt %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY-NO-MOVT
+
+// RUN: not %clang -target armv8m.main-eabi -mexecute-only -mlong-calls %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY-LONG-CALLS
+
+
+// -mpure-code flag for GCC compatibility
+// RUN: %clang -target armv6t2-eabi -### %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv6t2-eabi -### -mpure-code %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY
+
+// RUN: %clang -target armv6t2-eabi -### -mpure-code -mno-pure-code %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv7m-eabi -### %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv7m-eabi -### -mpure-code %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY
+
+// RUN: %clang -target armv7m-eabi -### -mpure-code -mno-pure-code %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.base-eabi -### %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.base-eabi -### -mpure-code %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.base-eabi -### -mpure-code -mno-pure-code %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.main-eabi -### %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.main-eabi -### -mpure-code %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY
+
+// RUN: %clang -target armv8m.main-eabi -### -mpure-code -mno-pure-code %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-NO-EXECUTE-ONLY
+
+// RUN: not %clang -c -target thumbv6m-eabi -mpure-code %s 2>&1 | \
+// RUN: FileCheck --check-prefix CHECK-EXECUTE-ONLY-NOT-SUPPORTED %s
+
+// RUN: not %clang -target armv8m.main-eabi -mpure-code -mno-movt %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY-NO-MOVT
+
+// RUN: not %clang -target armv8m.main-eabi -mpure-code -mlong-calls %s 2>&1 \
+// RUN: | FileCheck %s -check-prefix CHECK-EXECUTE-ONLY-LONG-CALLS
+
+//
+// CHECK-NO-EXECUTE-ONLY-NOT: "-arm-execute-only"
+// CHECK-EXECUTE-ONLY: "-arm-execute-only"
+
+// CHECK-EXECUTE-ONLY-NOT-SUPPORTED: error: execute only is not supported for the thumbv6m sub-architecture
+// CHECK-EXECUTE-ONLY-NO-MOVT: error: option '-mexecute-only' cannot be specified with '-mno-movt'
+// CHECK-EXECUTE-ONLY-LONG-CALLS: error: option '-mexecute-only' cannot be specified with '-mlong-calls'
--
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