[lld] 162814a - [lld-macho] Include branch extension thunks in linker map (#120496)
via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 7 21:07:55 PST 2025
Author: alx32
Date: 2025-01-07T21:07:51-08:00
New Revision: 162814a7ec00e2c89693f96568b72956d1bf2f0f
URL: https://github.com/llvm/llvm-project/commit/162814a7ec00e2c89693f96568b72956d1bf2f0f
DIFF: https://github.com/llvm/llvm-project/commit/162814a7ec00e2c89693f96568b72956d1bf2f0f.diff
LOG: [lld-macho] Include branch extension thunks in linker map (#120496)
This patch extends the MachO linker's map file generation to include
branch extension thunk symbols. Previously, thunks were omitted from the
map file, making it difficult to understand the final layout of the
binary, especially when debugging issues related to long branch thunks.
This change ensures thunks are included and correctly interleaved with
other symbols based on their address, providing an accurate
representation of the linked output.
Added:
Modified:
lld/MachO/ConcatOutputSection.h
lld/MachO/MapFile.cpp
lld/MachO/OutputSection.h
lld/test/MachO/arm64-thunks.s
Removed:
################################################################################
diff --git a/lld/MachO/ConcatOutputSection.h b/lld/MachO/ConcatOutputSection.h
index 9af661d0ab1e0c..8131c48d31113e 100644
--- a/lld/MachO/ConcatOutputSection.h
+++ b/lld/MachO/ConcatOutputSection.h
@@ -25,8 +25,9 @@ class Defined;
// in the final binary.
class ConcatOutputSection : public OutputSection {
public:
- explicit ConcatOutputSection(StringRef name)
- : OutputSection(ConcatKind, name) {}
+ explicit ConcatOutputSection(StringRef name,
+ OutputSection::Kind kind = ConcatKind)
+ : OutputSection(kind, name) {}
const ConcatInputSection *firstSection() const { return inputs.front(); }
const ConcatInputSection *lastSection() const { return inputs.back(); }
@@ -46,7 +47,7 @@ class ConcatOutputSection : public OutputSection {
void writeTo(uint8_t *buf) const override;
static bool classof(const OutputSection *sec) {
- return sec->kind() == ConcatKind;
+ return sec->kind() == ConcatKind || sec->kind() == TextKind;
}
static ConcatOutputSection *getOrCreateForInput(const InputSection *);
@@ -66,12 +67,18 @@ class ConcatOutputSection : public OutputSection {
// support thunk insertion.
class TextOutputSection : public ConcatOutputSection {
public:
- explicit TextOutputSection(StringRef name) : ConcatOutputSection(name) {}
+ explicit TextOutputSection(StringRef name)
+ : ConcatOutputSection(name, TextKind) {}
void finalizeContents() override {}
void finalize() override;
bool needsThunks() const;
+ ArrayRef<ConcatInputSection *> getThunks() const { return thunks; }
void writeTo(uint8_t *buf) const override;
+ static bool classof(const OutputSection *sec) {
+ return sec->kind() == TextKind;
+ }
+
private:
uint64_t estimateStubsInRangeVA(size_t callIdx) const;
diff --git a/lld/MachO/MapFile.cpp b/lld/MachO/MapFile.cpp
index 9c0621622ae2f0..12417df8cecb8c 100644
--- a/lld/MachO/MapFile.cpp
+++ b/lld/MachO/MapFile.cpp
@@ -161,6 +161,20 @@ static uint64_t getSymSizeForMap(Defined *sym) {
return sym->size;
}
+// Merges two vectors of input sections in order of their outSecOff values.
+// This approach creates a new (temporary) vector which is not ideal but the
+// ideal approach leads to a lot of code duplication.
+static std::vector<ConcatInputSection *>
+mergeOrderedInputs(ArrayRef<ConcatInputSection *> inputs1,
+ ArrayRef<ConcatInputSection *> inputs2) {
+ std::vector<ConcatInputSection *> vec(inputs1.size() + inputs2.size());
+ std::merge(inputs1.begin(), inputs1.end(), inputs2.begin(), inputs2.end(),
+ vec.begin(), [](ConcatInputSection *a, ConcatInputSection *b) {
+ return a->outSecOff < b->outSecOff;
+ });
+ return vec;
+}
+
void macho::writeMapFile() {
if (config->mapFile.empty())
return;
@@ -220,7 +234,11 @@ void macho::writeMapFile() {
os << "# Address\tSize \tFile Name\n";
for (const OutputSegment *seg : outputSegments) {
for (const OutputSection *osec : seg->getSections()) {
- if (auto *concatOsec = dyn_cast<ConcatOutputSection>(osec)) {
+ if (auto *textOsec = dyn_cast<TextOutputSection>(osec)) {
+ auto inputsAndThunks =
+ mergeOrderedInputs(textOsec->inputs, textOsec->getThunks());
+ printIsecArrSyms(inputsAndThunks);
+ } else if (auto *concatOsec = dyn_cast<ConcatOutputSection>(osec)) {
printIsecArrSyms(concatOsec->inputs);
} else if (osec == in.cStringSection || osec == in.objcMethnameSection) {
const auto &liveCStrings = info.liveCStringsForSection.lookup(osec);
diff --git a/lld/MachO/OutputSection.h b/lld/MachO/OutputSection.h
index 5297a03c2cfa7f..9afd3a9eeb1928 100644
--- a/lld/MachO/OutputSection.h
+++ b/lld/MachO/OutputSection.h
@@ -37,6 +37,7 @@ class OutputSection {
enum Kind {
ConcatKind,
SyntheticKind,
+ TextKind,
};
OutputSection(Kind kind, StringRef name) : name(name), sectionKind(kind) {}
diff --git a/lld/test/MachO/arm64-thunks.s b/lld/test/MachO/arm64-thunks.s
index d887359bbc23e1..858a27dfe36af5 100644
--- a/lld/test/MachO/arm64-thunks.s
+++ b/lld/test/MachO/arm64-thunks.s
@@ -8,14 +8,46 @@
## (4) early calls to a dylib stub use a thunk, and later calls the stub
## directly
## (5) Thunks are created for all sections in the text segment with branches.
+## (6) Thunks are in the linker map file.
## Notes:
## 0x4000000 = 64 Mi = half the magnitude of the forward-branch range
# RUN: rm -rf %t; mkdir %t
# RUN: llvm-mc -filetype=obj -triple=arm64-apple-darwin %s -o %t/input.o
-# RUN: %lld -arch arm64 -dead_strip -lSystem -U _extern_sym -o %t/thunk %t/input.o
+# RUN: %lld -arch arm64 -dead_strip -lSystem -U _extern_sym -map %t/thunk.map -o %t/thunk %t/input.o
# RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn %t/thunk | FileCheck %s
+## Check that the thunks appear in the map file and that everything is sorted by address
+# Because of the `.space` instructions, there will end up being a lot of dead symbols in the
+# linker map (linker map will be ~2.7GB). So to avoid the test trying to (slowly) match regex
+# across all the ~2.7GB of the linker map - generate a version of the linker map without dead symbols.
+# RUN: awk '/# Dead Stripped Symbols:/ {exit} {print}' %t/thunk.map > %t/thunk_no_dead_syms.map
+
+# RUN: FileCheck %s --input-file %t/thunk_no_dead_syms.map --check-prefix=MAP
+
+# MAP: 0x{{[[:xdigit:]]+}} {{.*}} _b
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _c
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _d.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _e.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _f.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _g.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _h.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} ___nan.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _d
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _e
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _f
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _g
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _a.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _b.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _h
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _main
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _c.thunk.0
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _d.thunk.1
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _e.thunk.1
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _f.thunk.1
+# MAP-NEXT: 0x{{[[:xdigit:]]+}} {{.*}} _z
+
+
# CHECK: Disassembly of section __TEXT,__text:
# CHECK: [[#%.13x, A_PAGE:]][[#%.3x, A_OFFSET:]] <_a>:
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