[lld] ldd: add support for NOCROSSREFS(_TO) (PR #95714)
Pavel Skripkin via llvm-commits
llvm-commits at lists.llvm.org
Sun Jun 16 10:53:52 PDT 2024
https://github.com/pskrgag created https://github.com/llvm/llvm-project/pull/95714
Patch introduces supprot for NOCROSSREFS_(TO) linker script commands. These commands specify which cross-section references should be threated as errors. See more in ld documenmtation [0]
Implementation is straightforward -- traverse all relocations in all object files and report an error if there is prohibited one.
[0] https://sourceware.org/binutils/docs/ld/Miscellaneous-Commands.html
Closes: #41825
>From d7baadb71a0590e1950cd4eb744103ece8690eb3 Mon Sep 17 00:00:00 2001
From: Pavel Skripkin <paskripkin at gmail.com>
Date: Sun, 16 Jun 2024 20:02:23 +0300
Subject: [PATCH] ldd: add support for NOCROSSREFS(_TO)
Patch introduces supprot for NOCROSSREFS_(TO) linker script commands.
These commands specify which cross-section references should be threated
as errors. See more in ld documenmtation [0]
Implementation is straightforward -- traverse all relocations in all
object files and report an error if there is prohibited one.
[0] https://sourceware.org/binutils/docs/ld/Miscellaneous-Commands.html
Closes: #41825
Signed-off-by: Pavel Skripkin <paskripkin at gmail.com>
---
lld/ELF/LinkerScript.h | 8 +++
lld/ELF/Relocations.cpp | 59 ++++++++++++++++++
lld/ELF/Relocations.h | 1 +
lld/ELF/ScriptParser.cpp | 20 ++++++
lld/ELF/Writer.cpp | 3 +
lld/test/ELF/gnu-nocrossrefs.s | 110 +++++++++++++++++++++++++++++++++
6 files changed, 201 insertions(+)
create mode 100644 lld/test/ELF/gnu-nocrossrefs.s
diff --git a/lld/ELF/LinkerScript.h b/lld/ELF/LinkerScript.h
index 734d4e7498aa2..5821b0fc587aa 100644
--- a/lld/ELF/LinkerScript.h
+++ b/lld/ELF/LinkerScript.h
@@ -256,6 +256,11 @@ struct InsertCommand {
StringRef where;
};
+struct CrossRefList {
+ SmallVector<StringRef, 2> refs;
+ bool firstOnly;
+};
+
struct PhdrsCommand {
StringRef name;
unsigned type = llvm::ELF::PT_NULL;
@@ -394,6 +399,9 @@ class LinkerScript final {
// OutputSections specified by OVERWRITE_SECTIONS.
SmallVector<OutputDesc *, 0> overwriteSections;
+ // Nocrossrefs sections.
+ SmallVector<CrossRefList, 0> nocrossrefs;
+
// Sections that will be warned/errored by --orphan-handling.
SmallVector<const InputSectionBase *, 0> orphanSections;
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 2c02c2e572bfd..400013adf53dd 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -2358,3 +2358,62 @@ template void elf::scanRelocations<ELF32LE>();
template void elf::scanRelocations<ELF32BE>();
template void elf::scanRelocations<ELF64LE>();
template void elf::scanRelocations<ELF64BE>();
+
+static bool isNoCrefFromSection(const CrossRefList &list,
+ const OutputSection *section) {
+ const auto *begin =
+ list.firstOnly ? list.refs.begin() + 1 : list.refs.begin();
+
+ return std::find(begin, list.refs.end(), section->name) != list.refs.end();
+}
+
+static bool isNoCrefToSection(const CrossRefList &list,
+ const OutputSection *section) {
+ if (list.firstOnly)
+ return list.refs[0] == section->name;
+
+ return std::find(list.refs.begin(), list.refs.end(), section->name) !=
+ list.refs.end();
+}
+
+void elf::checkNoCrossRefs() {
+ // Basic brute-force algorithm, since in reality NOCROSSRES lists are quite
+ // small.
+ //
+ // Idea is to traverse all relocations in all sections and report if
+ // prohibited reference was found. Note that NOCROSSREFS works with output section
+ // names.
+ for (ELFFileBase *file : ctx.objectFiles) {
+ auto sections = file->getSections();
+ std::string message = "";
+
+ for (size_t i = 0; i < sections.size(); ++i) {
+ if (sections[i]) {
+ StringRef sectionName = sections[i]->name;
+
+ if (const auto *outSec = dyn_cast_or_null<OutputSection>(sections[i]->parent)) {
+ for (const auto &refs : script->nocrossrefs) {
+ if (isNoCrefFromSection(refs, outSec)) {
+
+ for (const auto &j : sections[i]->relocations) {
+ if (auto *def = dyn_cast<Defined>(j.sym)) {
+ const auto *outSecSym =
+ cast<InputSection>(def->section)->getParent();
+
+ if (isNoCrefToSection(refs, outSecSym)) {
+ message +=
+ (sections[i]->getLocation(j.offset) +
+ ": prohibited cross reference from " +
+ sectionName.str() + " to " + def->getName().str() +
+ " in " + outSecSym->name.str());
+ error(message);
+ }
+ }
+ }
+ }
+ }
+ }
+ }
+ }
+ }
+}
diff --git a/lld/ELF/Relocations.h b/lld/ELF/Relocations.h
index b7b9c09e1b892..eabae26283c24 100644
--- a/lld/ELF/Relocations.h
+++ b/lld/ELF/Relocations.h
@@ -141,6 +141,7 @@ struct JumpInstrMod {
// the diagnostics.
template <class ELFT> void scanRelocations();
void reportUndefinedSymbols();
+void checkNoCrossRefs();
void postScanRelocations();
void addGotEntry(Symbol &sym);
diff --git a/lld/ELF/ScriptParser.cpp b/lld/ELF/ScriptParser.cpp
index f90ce6fa74075..0c14f43fc5f05 100644
--- a/lld/ELF/ScriptParser.cpp
+++ b/lld/ELF/ScriptParser.cpp
@@ -87,6 +87,7 @@ class ScriptParser final : ScriptLexer {
void readTarget();
void readVersion();
void readVersionScriptCommand();
+ void readNoCrossRefs(bool to = false);
SymbolAssignment *readSymbolAssignment(StringRef name);
ByteCommand *readByteCommand(StringRef tok);
@@ -235,6 +236,21 @@ void ScriptParser::readVersionScriptCommand() {
}
}
+void ScriptParser::readNoCrossRefs(bool to) {
+ expect("(");
+
+ script->nocrossrefs.push_back({});
+
+ script->nocrossrefs.back().firstOnly = to;
+
+ while (!atEOF() && !errorCount() && peek() != ")") {
+ StringRef section = next();
+ script->nocrossrefs.back().refs.push_back(section);
+ }
+
+ expect(")");
+}
+
void ScriptParser::readVersion() {
expect("{");
readVersionScriptCommand();
@@ -279,6 +295,10 @@ void ScriptParser::readLinkerScript() {
readTarget();
} else if (tok == "VERSION") {
readVersion();
+ } else if (tok == "NOCROSSREFS") {
+ readNoCrossRefs();
+ } else if (tok == "NOCROSSREFS_TO") {
+ readNoCrossRefs(true);
} else if (SymbolAssignment *cmd = readAssignment(tok)) {
script->sectionCommands.push_back(cmd);
} else {
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index fe2e1900520a4..9466d383607c4 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -309,6 +309,9 @@ template <class ELFT> void Writer<ELFT>::run() {
finalizeSections();
checkExecuteOnly();
+ if (script->nocrossrefs.size())
+ checkNoCrossRefs();
+
// If --compressed-debug-sections is specified, compress .debug_* sections.
// Do it right now because it changes the size of output sections.
for (OutputSection *sec : outputSections)
diff --git a/lld/test/ELF/gnu-nocrossrefs.s b/lld/test/ELF/gnu-nocrossrefs.s
new file mode 100644
index 0000000000000..67d98482cad78
--- /dev/null
+++ b/lld/test/ELF/gnu-nocrossrefs.s
@@ -0,0 +1,110 @@
+// REQUIRES: x86
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS(.text .text1); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: not ld.lld %t.o -o %t --script %t.script 2>&1 | FileCheck -check-prefix=ERR %s
+// ERR: ld.lld: error: {{.*}}.o:(.text+{{.*}}): prohibited cross reference from .text to in .text1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS_TO(.text1 .text); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: not ld.lld %t.o -o %t --script %t.script 2>&1 | FileCheck -check-prefix=ERR1 %s
+// ERR1: ld.lld: error: {{.*}}.o:(.text+{{.*}}): prohibited cross reference from .text to in .text1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS(.text1 .text .text2); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: not ld.lld %t.o -o %t --script %t.script 2>&1 | FileCheck -check-prefix=ERR2 %s
+// ERR2: ld.lld: error: {{.*}}.o:(.text+{{.*}}): prohibited cross reference from .text to in .text1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS_TO(.text .text1); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: ld.lld %t.o -o %t --script %t.script 2>&1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS_TO(); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: ld.lld %t.o -o %t --script %t.script 2>&1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS(); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: ld.lld %t.o -o %t --script %t.script 2>&1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS(.text); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: ld.lld %t.o -o %t --script %t.script 2>&1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS_TO(.text); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: ld.lld %t.o -o %t --script %t.script 2>&1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS_TO(.text2 .text); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: ld.lld %t.o -o %t --script %t.script 2>&1
+
+// RUN: llvm-mc -filetype=obj -o %t.o %s
+// RUN: echo "NOCROSSREFS(.text .text2); \
+// RUN: SECTIONS { \
+// RUN: .text : { *(.text) } \
+// RUN: .text1 : { *(.text1) } \
+// RUN: .text2 : { *(.text2) } \
+// RUN: } " > %t.script
+// RUN: ld.lld %t.o -o %t --script %t.script 2>&1
+
+.global _start
+_start:
+ nop
+
+.section .text
+test:
+ call test1
+
+.section .text2
+test2:
+ nop
+
+.section .text1
+test1:
+ nop
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