[lld] abd70fb - [lld-macho] Export trie addresses should be relative to the image base
Jez Ng via llvm-commits
llvm-commits at lists.llvm.org
Sun Sep 20 20:43:52 PDT 2020
Author: Jez Ng
Date: 2020-09-20T20:43:15-07:00
New Revision: abd70fb3983f342bc1c90f9c70a7b59790ad5206
URL: https://github.com/llvm/llvm-project/commit/abd70fb3983f342bc1c90f9c70a7b59790ad5206
DIFF: https://github.com/llvm/llvm-project/commit/abd70fb3983f342bc1c90f9c70a7b59790ad5206.diff
LOG: [lld-macho] Export trie addresses should be relative to the image base
We didn't notice this earlier this we were only testing the export trie
encoded in a dylib, whose image base starts at zero. But a regular
executable contains `__PAGEZERO`, which means it has a non-zero image
base. This bug was discovered after attempting to run some programs that
performed `dlopen` on an executable.
Reviewed By: #lld-macho, smeenai
Differential Revision: https://reviews.llvm.org/D87780
Added:
Modified:
lld/MachO/ExportTrie.cpp
lld/MachO/ExportTrie.h
lld/MachO/SyntheticSections.cpp
lld/test/MachO/export-trie.s
Removed:
################################################################################
diff --git a/lld/MachO/ExportTrie.cpp b/lld/MachO/ExportTrie.cpp
index f1c58d6e146b..0093907ea959 100644
--- a/lld/MachO/ExportTrie.cpp
+++ b/lld/MachO/ExportTrie.cpp
@@ -60,7 +60,8 @@ struct Edge {
struct ExportInfo {
uint64_t address;
uint8_t flags = 0;
- explicit ExportInfo(const Symbol &sym) : address(sym.getVA()) {
+ ExportInfo(const Symbol &sym, uint64_t imageBase)
+ : address(sym.getVA() - imageBase) {
if (sym.isWeakDef())
flags |= EXPORT_SYMBOL_FLAGS_WEAK_DEFINITION;
if (sym.isTlv())
@@ -199,7 +200,7 @@ void TrieBuilder::sortAndBuild(MutableArrayRef<const Symbol *> vec,
if (isTerminal) {
assert(j - i == 1); // no duplicate symbols
- node->info = ExportInfo(*pivotSymbol);
+ node->info = ExportInfo(*pivotSymbol, imageBase);
} else {
// This is the tail-call-optimized version of the following:
// sortAndBuild(vec.slice(i, j - i), node, lastPos, pos + 1);
diff --git a/lld/MachO/ExportTrie.h b/lld/MachO/ExportTrie.h
index 2bd8c33db9a0..a43f4f2cce98 100644
--- a/lld/MachO/ExportTrie.h
+++ b/lld/MachO/ExportTrie.h
@@ -22,6 +22,7 @@ class Symbol;
class TrieBuilder {
public:
+ void setImageBase(uint64_t addr) { imageBase = addr; }
void addSymbol(const Symbol &sym) { exported.push_back(&sym); }
// Returns the size in bytes of the serialized trie.
size_t build();
@@ -32,6 +33,7 @@ class TrieBuilder {
void sortAndBuild(llvm::MutableArrayRef<const Symbol *> vec, TrieNode *node,
size_t lastPos, size_t pos);
+ uint64_t imageBase = 0;
std::vector<const Symbol *> exported;
std::vector<TrieNode *> nodes;
};
diff --git a/lld/MachO/SyntheticSections.cpp b/lld/MachO/SyntheticSections.cpp
index 0106426f5ddc..2c8065cabee0 100644
--- a/lld/MachO/SyntheticSections.cpp
+++ b/lld/MachO/SyntheticSections.cpp
@@ -441,6 +441,7 @@ ExportSection::ExportSection()
: LinkEditSection(segment_names::linkEdit, section_names::export_) {}
void ExportSection::finalizeContents() {
+ trieBuilder.setImageBase(in.header->addr);
// TODO: We should check symbol visibility.
for (const Symbol *sym : symtab->getSymbols()) {
if (const auto *defined = dyn_cast<Defined>(sym)) {
diff --git a/lld/test/MachO/export-trie.s b/lld/test/MachO/export-trie.s
index fc1f6d110dba..7f628c543b5c 100644
--- a/lld/test/MachO/export-trie.s
+++ b/lld/test/MachO/export-trie.s
@@ -1,33 +1,42 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
-# RUN: lld -flavor darwinnew -dylib %t.o -o %t.dylib
-# RUN: llvm-objdump --syms --exports-trie %t.dylib | \
-# RUN: FileCheck %s --check-prefix=EXPORTS
+## We are intentionally building an executable here instead of a dylib / bundle
+## in order that the `__PAGEZERO` segment is present, which in turn means that
+## the image base starts at a non-zero address. This allows us to verify that
+## addresses in the export trie are correctly encoded as relative to the image
+## base.
+# RUN: lld -flavor darwinnew %t.o -o %t
+
+# RUN: llvm-objdump --syms --exports-trie %t | FileCheck %s --check-prefix=EXPORTS
# EXPORTS-LABEL: SYMBOL TABLE:
+# EXPORTS-DAG: [[#%x, MAIN_ADDR:]] {{.*}} _main
# EXPORTS-DAG: [[#%x, HELLO_ADDR:]] {{.*}} _hello
# EXPORTS-DAG: [[#%x, HELLO_WORLD_ADDR:]] {{.*}} _hello_world
# EXPORTS-DAG: [[#%x, HELLO_ITS_ME_ADDR:]] {{.*}} _hello_its_me
# EXPORTS-DAG: [[#%x, HELLO_ITS_YOU_ADDR:]] {{.*}} _hello_its_you
# EXPORTS-LABEL: Exports trie:
+# EXPORTS-DAG: 0x{{0*}}[[#%X, MAIN_ADDR]] _main
# EXPORTS-DAG: 0x{{0*}}[[#%X, HELLO_ADDR]] _hello
# EXPORTS-DAG: 0x{{0*}}[[#%X, HELLO_WORLD_ADDR]] _hello_world
# EXPORTS-DAG: 0x{{0*}}[[#%x, HELLO_ITS_ME_ADDR:]] _hello_its_me
# EXPORTS-DAG: 0x{{0*}}[[#%x, HELLO_ITS_YOU_ADDR:]] _hello_its_you
## Check that we are sharing prefixes in the trie.
-# RUN: obj2yaml %t.dylib | FileCheck %s
+# RUN: obj2yaml %t | FileCheck %s
# CHECK-LABEL: ExportTrie:
# CHECK: Name: ''
-# CHECK: Name: _hello
+# CHECK: Name: _
+# CHECK: Name: main
+# CHECK: Name: hello
# CHECK: Name: _
# CHECK: Name: world
# CHECK: Name: its_
-# CHECK: Name: me
# CHECK: Name: you
+# CHECK: Name: me
.section __TEXT,__cstring
-.globl _hello, _hello_world, _hello_its_me, _hello_its_you
+.globl _hello, _hello_world, _hello_its_me, _hello_its_you, _main
## Test for when an entire symbol name is a prefix of another.
_hello:
@@ -42,3 +51,6 @@ _hello_its_me:
_hello_its_you:
.asciz "Hello, it's you\n"
+
+_main:
+ ret
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