[llvm] [JITLink][AArch32] Multi-stub support for armv7/thumbv7 (PR #78371)
Stefan Gränitz via llvm-commits
llvm-commits at lists.llvm.org
Mon Jan 22 12:26:25 PST 2024
https://github.com/weliveindetail updated https://github.com/llvm/llvm-project/pull/78371
>From 559fe8e78990997821defc9b97190a97bb44c841 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Gr=C3=A4nitz?= <stefan.graenitz at gmail.com>
Date: Sat, 13 Jan 2024 23:58:36 +0100
Subject: [PATCH] [JITLink][AArch32] Multi-stub support for armv7/thumbv7
---
.../llvm/ExecutionEngine/JITLink/aarch32.h | 59 ++-------
llvm/lib/ExecutionEngine/JITLink/aarch32.cpp | 125 ++++++++++++++++--
.../JITLink/AArch32/ELF_stubs_arm.s | 53 ++++++++
.../JITLink/AArch32/ELF_stubs_multi.s | 50 +++++++
llvm/tools/llvm-jitlink/llvm-jitlink.cpp | 46 ++++++-
5 files changed, 274 insertions(+), 59 deletions(-)
create mode 100644 llvm/test/ExecutionEngine/JITLink/AArch32/ELF_stubs_arm.s
create mode 100644 llvm/test/ExecutionEngine/JITLink/AArch32/ELF_stubs_multi.s
diff --git a/llvm/include/llvm/ExecutionEngine/JITLink/aarch32.h b/llvm/include/llvm/ExecutionEngine/JITLink/aarch32.h
index 081f77a85e182a7..ed53fa409ade895 100644
--- a/llvm/include/llvm/ExecutionEngine/JITLink/aarch32.h
+++ b/llvm/include/llvm/ExecutionEngine/JITLink/aarch32.h
@@ -341,64 +341,31 @@ class GOTBuilder : public TableManager<GOTBuilder> {
Section *GOTSection = nullptr;
};
-/// Stubs builder for v7 emits non-position-independent Thumb stubs.
-///
-/// Right now we only have one default stub kind, but we want to extend this
-/// and allow creation of specific kinds in the future (e.g. branch range
-/// extension or interworking).
-///
-/// Let's keep it simple for the moment and not wire this through a GOT.
-///
-class StubsManager_v7 : public TableManager<StubsManager_v7> {
+/// Stubs builder for v7 emits non-position-independent Arm and Thumb stubs.
+class StubsManager_v7 {
public:
StubsManager_v7() = default;
/// Name of the object file section that will contain all our stubs.
static StringRef getSectionName() {
- return "__llvm_jitlink_aarch32_STUBS_Thumbv7";
+ return "__llvm_jitlink_aarch32_STUBS_v7";
}
/// Implements link-graph traversal via visitExistingEdges().
- bool visitEdge(LinkGraph &G, Block *B, Edge &E) {
- if (E.getTarget().isDefined())
- return false;
-
- switch (E.getKind()) {
- case Thumb_Call:
- case Thumb_Jump24: {
- DEBUG_WITH_TYPE("jitlink", {
- dbgs() << " Fixing " << G.getEdgeKindName(E.getKind()) << " edge at "
- << B->getFixupAddress(E) << " (" << B->getAddress() << " + "
- << formatv("{0:x}", E.getOffset()) << ")\n";
- });
- E.setTarget(this->getEntryForTarget(G, E.getTarget()));
- return true;
- }
- }
- return false;
- }
-
- /// Create a branch range extension stub with Thumb encoding for v7 CPUs.
- Symbol &createEntry(LinkGraph &G, Symbol &Target);
+ bool visitEdge(LinkGraph &G, Block *B, Edge &E);
private:
- /// Create a new node in the link-graph for the given stub template.
- template <size_t Size>
- Block &addStub(LinkGraph &G, const uint8_t (&Code)[Size],
- uint64_t Alignment) {
- ArrayRef<char> Template(reinterpret_cast<const char *>(Code), Size);
- return G.createContentBlock(getStubsSection(G), Template,
- orc::ExecutorAddr(), Alignment, 0);
- }
-
- /// Get or create the object file section that will contain all our stubs.
- Section &getStubsSection(LinkGraph &G) {
- if (!StubsSection)
- StubsSection = &G.createSection(getSectionName(),
- orc::MemProt::Read | orc::MemProt::Exec);
- return *StubsSection;
+ // Two slots per external: Arm and Thumb
+ using StubMapEntry = std::tuple<Symbol *, Symbol *>;
+
+ Symbol *&getStubSymbolSlot(StringRef Name, bool Thumb) {
+ StubMapEntry &Stubs = StubMap.try_emplace(Name).first->second;
+ if (Thumb)
+ return std::get<1>(Stubs);
+ return std::get<0>(Stubs);
}
+ DenseMap<StringRef, StubMapEntry> StubMap;
Section *StubsSection = nullptr;
};
diff --git a/llvm/lib/ExecutionEngine/JITLink/aarch32.cpp b/llvm/lib/ExecutionEngine/JITLink/aarch32.cpp
index 1797a0068cd7cdc..9508cde07b42a65 100644
--- a/llvm/lib/ExecutionEngine/JITLink/aarch32.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/aarch32.cpp
@@ -15,6 +15,7 @@
#include "llvm/ADT/StringExtras.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+#include "llvm/ExecutionEngine/Orc/Shared/MemoryFlags.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/ManagedStatic.h"
@@ -724,27 +725,127 @@ bool GOTBuilder::visitEdge(LinkGraph &G, Block *B, Edge &E) {
return true;
}
+const uint8_t Armv7ABS[] = {
+ 0x00, 0xc0, 0x00, 0xe3, // movw r12, #0x0000 ; lower 16-bit
+ 0x00, 0xc0, 0x40, 0xe3, // movt r12, #0x0000 ; upper 16-bit
+ 0x1c, 0xff, 0x2f, 0xe1 // bx r12
+};
+
const uint8_t Thumbv7ABS[] = {
0x40, 0xf2, 0x00, 0x0c, // movw r12, #0x0000 ; lower 16-bit
0xc0, 0xf2, 0x00, 0x0c, // movt r12, #0x0000 ; upper 16-bit
0x60, 0x47 // bx r12
};
-Symbol &StubsManager_v7::createEntry(LinkGraph &G, Symbol &Target) {
+/// Create a new node in the link-graph for the given stub template.
+template <size_t Size>
+static Block &allocStub(LinkGraph &G, Section &S, const uint8_t (&Code)[Size]) {
constexpr uint64_t Alignment = 4;
- Block &B = addStub(G, Thumbv7ABS, Alignment);
- LLVM_DEBUG({
- const char *StubPtr = B.getContent().data();
- HalfWords Reg12 = encodeRegMovtT1MovwT3(12);
- assert(checkRegister<Thumb_MovwAbsNC>(StubPtr, Reg12) &&
- checkRegister<Thumb_MovtAbs>(StubPtr + 4, Reg12) &&
- "Linker generated stubs may only corrupt register r12 (IP)");
- });
+ ArrayRef<char> Template(reinterpret_cast<const char *>(Code), Size);
+ return G.createContentBlock(S, Template, orc::ExecutorAddr(), Alignment, 0);
+}
+
+static Block &createStubThumbv7(LinkGraph &G, Section &S, Symbol &Target) {
+ Block &B = allocStub(G, S, Thumbv7ABS);
B.addEdge(Thumb_MovwAbsNC, 0, Target, 0);
B.addEdge(Thumb_MovtAbs, 4, Target, 0);
- Symbol &Stub = G.addAnonymousSymbol(B, 0, B.getSize(), true, false);
- Stub.setTargetFlags(ThumbSymbol);
- return Stub;
+
+ [[maybe_unused]] const char *StubPtr = B.getContent().data();
+ [[maybe_unused]] HalfWords Reg12 = encodeRegMovtT1MovwT3(12);
+ assert(checkRegister<Thumb_MovwAbsNC>(StubPtr, Reg12) &&
+ checkRegister<Thumb_MovtAbs>(StubPtr + 4, Reg12) &&
+ "Linker generated stubs may only corrupt register r12 (IP)");
+ return B;
+}
+
+static Block &createStubArmv7(LinkGraph &G, Section &S, Symbol &Target) {
+ Block &B = allocStub(G, S, Armv7ABS);
+ B.addEdge(Arm_MovwAbsNC, 0, Target, 0);
+ B.addEdge(Arm_MovtAbs, 4, Target, 0);
+
+ [[maybe_unused]] const char *StubPtr = B.getContent().data();
+ [[maybe_unused]] uint32_t Reg12 = encodeRegMovtA1MovwA2(12);
+ assert(checkRegister<Arm_MovwAbsNC>(StubPtr, Reg12) &&
+ checkRegister<Arm_MovtAbs>(StubPtr + 4, Reg12) &&
+ "Linker generated stubs may only corrupt register r12 (IP)");
+ return B;
+}
+
+static bool needsStub(const Edge &E) {
+ Symbol &Target = E.getTarget();
+
+ // Create stubs for external branch targets.
+ if (!Target.isDefined()) {
+ switch (E.getKind()) {
+ case Arm_Call:
+ case Arm_Jump24:
+ case Thumb_Call:
+ case Thumb_Jump24:
+ return true;
+ default:
+ return false;
+ }
+ }
+
+ // For local targets, create interworking stubs if we switch Arm/Thumb with an
+ // instruction that cannot switch the instruction set state natively.
+ bool TargetIsThumb = Target.getTargetFlags() & ThumbSymbol;
+ switch (E.getKind()) {
+ case Arm_Jump24:
+ return TargetIsThumb; // Branch to Thumb needs interworking stub
+ case Thumb_Jump24:
+ return !TargetIsThumb; // Branch to Arm needs interworking stub
+ default:
+ break;
+ }
+
+ return false;
+}
+
+bool StubsManager_v7::visitEdge(LinkGraph &G, Block *B, Edge &E) {
+ if (!needsStub(E))
+ return false;
+
+ // Stub Arm/Thumb follows instruction set state at relocation site.
+ // TODO: We may reduce them at relaxation time and reuse freed slots.
+ bool MakeThumb = (E.getKind() > LastArmRelocation);
+ LLVM_DEBUG(dbgs() << " Preparing " << (MakeThumb ? "Thumb" : "Arm")
+ << " stub for " << G.getEdgeKindName(E.getKind())
+ << " edge at " << B->getFixupAddress(E) << " ("
+ << B->getAddress() << " + "
+ << formatv("{0:x}", E.getOffset()) << ")\n");
+
+ Symbol &Target = E.getTarget();
+ assert(Target.hasName() && "Edge cannot point to anonymous target");
+ Symbol *&StubSymbol = getStubSymbolSlot(Target.getName(), MakeThumb);
+
+ if (!StubSymbol) {
+ if (!StubsSection)
+ StubsSection = &G.createSection(getSectionName(),
+ orc::MemProt::Read | orc::MemProt::Exec);
+ Block &B = MakeThumb ? createStubThumbv7(G, *StubsSection, Target)
+ : createStubArmv7(G, *StubsSection, Target);
+ StubSymbol = &G.addAnonymousSymbol(B, 0, B.getSize(), true, false);
+ if (MakeThumb)
+ StubSymbol->setTargetFlags(ThumbSymbol);
+
+ LLVM_DEBUG({
+ dbgs() << " Created " << (MakeThumb ? "Thumb" : "Arm") << " entry for "
+ << Target.getName() << " in " << StubsSection->getName() << ": "
+ << *StubSymbol << "\n";
+ });
+ }
+
+ assert(MakeThumb == (StubSymbol->getTargetFlags() & ThumbSymbol) &&
+ "Instruction set states of stub and relocation site should be equal");
+ LLVM_DEBUG({
+ dbgs() << " Using " << (MakeThumb ? "Thumb" : "Arm") << " entry "
+ << *StubSymbol << " in "
+ << StubSymbol->getBlock().getSection().getName() << "\n";
+ });
+
+ E.setTarget(*StubSymbol);
+ return true;
}
const char *getEdgeKindName(Edge::Kind K) {
diff --git a/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_stubs_arm.s b/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_stubs_arm.s
new file mode 100644
index 000000000000000..fb2e0eb2c0bf249
--- /dev/null
+++ b/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_stubs_arm.s
@@ -0,0 +1,53 @@
+# RUN: rm -rf %t && mkdir -p %t
+# RUN: llvm-mc -triple=armv7-linux-gnueabi -arm-add-build-attributes \
+# RUN: -filetype=obj -o %t/out.o %s
+# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 \
+# RUN: -slab-allocate 10Kb -slab-page-size 4096 \
+# RUN: -abs ext=0x76bbe880 \
+# RUN: -check %s %t/out.o
+
+ .text
+ .syntax unified
+
+# Check that calls/jumps to external functions trigger the generation of
+# branch-range extension stubs. These stubs don't follow the default PLT model
+# where the branch-target address is loaded from a GOT entry. Instead, they
+# hard-code it in the immediate field.
+
+# The external function ext will return to the caller directly.
+# jitlink-check: decode_operand(test_arm_jump, 0) = stub_addr(out.o, ext) - (test_arm_jump + 8)
+ .globl test_arm_jump
+ .type test_arm_jump,%function
+ .p2align 2
+test_arm_jump:
+ b ext
+ .size test_arm_jump, .-test_arm_jump
+
+# The branch-with-link sets the LR register so that the external function ext
+# returns to us. We have to save the register (push) and return to main manually
+# (pop). This adds the +4 offset for the bl instruction we decode:
+# jitlink-check: decode_operand(test_arm_call + 4, 0) = stub_addr(out.o, ext) - (test_arm_call + 8) - 4
+ .globl test_arm_call
+ .type test_arm_call,%function
+ .p2align 2
+test_arm_call:
+ push {lr}
+ bl ext
+ pop {pc}
+ .size test_arm_call, .-test_arm_call
+
+# This test is executable with both, Arm and Thumb `ext` functions. It only has
+# to return with `bx lr`. For example:
+# > echo "void ext() {}" | clang -target armv7-linux-gnueabihf -o ext-arm.o -c -xc -
+# > llvm-jitlink ext-arm.o out.o
+#
+ .globl main
+ .type main,%function
+ .p2align 2
+main:
+ push {lr}
+ bl test_arm_call
+ bl test_arm_jump
+ movw r0, #0
+ pop {pc}
+ .size main, .-main
diff --git a/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_stubs_multi.s b/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_stubs_multi.s
new file mode 100644
index 000000000000000..d575f114dcba1e7
--- /dev/null
+++ b/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_stubs_multi.s
@@ -0,0 +1,50 @@
+# RUN: rm -rf %t && mkdir -p %t
+# RUN: llvm-mc -triple=armv7-linux-gnueabi -arm-add-build-attributes \
+# RUN: -filetype=obj -o %t/out.o %s
+# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 \
+# RUN: -slab-allocate=10Kb -slab-page-size=4096 \
+# RUN: -abs ext=0x76bbe880 -check %s %t/out.o
+
+ .text
+ .syntax unified
+
+# Check that a single external symbol can have multiple stubs. We access them
+# with the extra stub-index argument to stub_addr(). Stubs are sorted by
+# ascending size (because the default memory manager lays out blocks by size).
+
+# Thumb relocation site emits thumb stub
+# jitlink-check: decode_operand(test_stub_thumb, 0) = stub_addr(out.o, ext, thumb) - (test_stub_thumb + 4)
+ .globl test_stub_thumb
+ .type test_stub_thumb,%function
+ .p2align 1
+ .code 16
+ .thumb_func
+test_stub_thumb:
+ b ext
+ .size test_stub_thumb, .-test_stub_thumb
+
+# Arm relocation site emits arm stub
+# jitlink-check: decode_operand(test_stub_arm, 0) = stub_addr(out.o, ext, arm) - (test_stub_arm + 8)
+ .globl test_stub_arm
+ .type test_stub_arm,%function
+ .p2align 2
+ .code 32
+test_stub_arm:
+ b ext
+ .size test_stub_arm, .-test_stub_arm
+
+# This test is executable with both, Arm and Thumb `ext` functions. It only has
+# to return (directly to main) with `bx lr`. For example:
+# > echo "void ext() {}" | clang -target armv7-linux-gnueabihf -o ext-arm.o -c -xc -
+# > llvm-jitlink ext-arm.o out.o
+#
+ .globl main
+ .type main,%function
+ .p2align 2
+main:
+ push {lr}
+ bl test_stub_arm
+ bl test_stub_thumb
+ movw r0, #0
+ pop {pc}
+ .size main, .-main
diff --git a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp b/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
index 7e213777a6727e8..b2a133860197dda 100644
--- a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
+++ b/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
@@ -1265,8 +1265,52 @@ Session::findSectionInfo(StringRef FileName, StringRef SectionName) {
return SecInfoItr->second;
}
+class MemoryMatcher {
+public:
+ MemoryMatcher(ArrayRef<char> Content)
+ : Pos(Content.data()), End(Pos + Content.size()) {}
+
+ template <typename MaskType> bool matchMask(MaskType Mask) {
+ if (Mask == (Mask & *reinterpret_cast<const MaskType *>(Pos))) {
+ Pos += sizeof(MaskType);
+ return true;
+ }
+ return false;
+ }
+
+ template <typename ValueType> bool matchEqual(ValueType Value) {
+ if (Value == *reinterpret_cast<const ValueType *>(Pos)) {
+ Pos += sizeof(ValueType);
+ return true;
+ }
+ return false;
+ }
+
+ bool done() const { return Pos == End; }
+
+private:
+ const char *Pos;
+ const char *End;
+};
+
static StringRef detectStubKind(const Session::MemoryRegionInfo &Stub) {
- // Implement acutal stub kind detection
+ constexpr uint32_t Armv7MovWTle = 0xe300c000;
+ constexpr uint32_t Armv7BxR12le = 0xe12fff1c;
+ constexpr uint32_t Thumbv7MovWTle = 0x0c00f240;
+ constexpr uint16_t Thumbv7BxR12le = 0x4760;
+
+ MemoryMatcher M(Stub.getContent());
+ if (M.matchMask(Thumbv7MovWTle)) {
+ if (M.matchMask(Thumbv7MovWTle))
+ if (M.matchEqual(Thumbv7BxR12le))
+ if (M.done())
+ return "thumbv7_abs_le";
+ } else if (M.matchMask(Armv7MovWTle)) {
+ if (M.matchMask(Armv7MovWTle))
+ if (M.matchEqual(Armv7BxR12le))
+ if (M.done())
+ return "armv7_abs_le";
+ }
return "";
}
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