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Revert r329960 "Do not keep shared symbols created from garbage-collected eliminated DSOs." 

This is causing large numbers of Chromium test executables to crash on
shutdown. The relevant symbol seems to be __cxa_finalize, which gets
removed from the dynamic symbol table for some of the support libraries.

llvm-svn: 330164
This commit is contained in:
Reid Kleckner 2018-04-16 22:45:23 +00:00
parent 9b294d1e90
commit 9c86a31307
3 changed files with 23 additions and 35 deletions
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13
lld/ELF/Driver.cpp
View File

@ -1059,18 +1059,6 @@ template <class ELFT> static void handleUndefined(StringRef Name) {
Symtab->fetchLazy<ELFT>(Sym);
}
// If all references to a DSO happen to be weak, the DSO is not added
// to DT_NEEDED. If that happens, we need to eliminate shared symbols
// created from the DSO. Otherwise, they become dangling references
// that point to a non-existent DSO.
template <class ELFT> static void demoteSharedSymbols() {
for (Symbol *Sym : Symtab->getSymbols())
if (auto *S = dyn_cast<SharedSymbol>(Sym))
if (!S->getFile<ELFT>().IsNeeded)
replaceSymbol<Undefined>(S, nullptr, S->getName(), STB_WEAK, S->StOther,
S->Type);
}
// Do actual linking. Note that when this function is called,
// all linker scripts have already been parsed.
template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
@ -1231,7 +1219,6 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
// Do size optimizations: garbage collection, merging of SHF_MERGE sections
// and identical code folding.
markLive<ELFT>();
demoteSharedSymbols<ELFT>();
decompressSections();
mergeSections();
if (Config->ICF)

22
lld/test/ELF/as-needed-weak.s
View File

@ -1,22 +0,0 @@
# REQUIRES: x86
# RUN: echo '.globl foo; .type foo, @function; foo:' | \
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux - -o %t1.o
# RUN: ld.lld -shared -o %t1.so -soname libfoo %t1.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t2.o
# RUN: ld.lld -o %t.exe %t2.o --as-needed %t1.so
# RUN: llvm-readelf -dynamic-table -dyn-symbols %t.exe | FileCheck %s
# CHECK-NOT: libfoo
# CHECK: Symbol table of .hash for image:
# CHECK-NEXT: Num Buc: Value Size Type Bind Vis Ndx Name
# CHECK-NEXT: 1 1: 0000000000000000 0 FUNC WEAK DEFAULT UND foo@
.globl _start
.weak foo
_start:
mov $foo, %eax
callq foo

23
lld/test/ELF/gc-sections-shared.s
View File

@ -9,6 +9,11 @@
# RUN: ld.lld --gc-sections --export-dynamic-symbol foo -o %t %t.o --as-needed %t2.so %t3.so %t4.so
# RUN: llvm-readobj --dynamic-table --dyn-symbols %t | FileCheck %s
# This test the property that we have a needed line for every undefined.
# It would also be OK to keep bar2 and the need for %t2.so
# At the same time, weak symbols should not cause adding DT_NEEDED;
# this case is checked with symbol qux and %t4.so.
# CHECK: DynamicSymbols [
# CHECK-NEXT: Symbol {
# CHECK-NEXT: Name:
@ -46,6 +51,15 @@
# CHECK-NEXT: Other:
# CHECK-NEXT: Section: .text
# CHECK-NEXT: }
# CHECK-NEXT: Symbol {
# CHECK-NEXT: Name: qux
# CHECK-NEXT: Value:
# CHECK-NEXT: Size:
# CHECK-NEXT: Binding: Weak
# CHECK-NEXT: Type:
# CHECK-NEXT: Other:
# CHECK-NEXT: Section: Undefined
# CHECK-NEXT: }
# CHECK-NEXT: ]
# CHECK-NOT: NEEDED
@ -85,6 +99,15 @@
# CHECK2-NEXT: Section: Undefined
# CHECK2-NEXT: }
# CHECK2-NEXT: Symbol {
# CHECK2-NEXT: Name: qux
# CHECK2-NEXT: Value:
# CHECK2-NEXT: Size:
# CHECK2-NEXT: Binding: Weak
# CHECK2-NEXT: Type:
# CHECK2-NEXT: Other:
# CHECK2-NEXT: Section: Undefined
# CHECK2-NEXT: }
# CHECK2-NEXT: Symbol {
# CHECK2-NEXT: Name: foo
# CHECK2-NEXT: Value:
# CHECK2-NEXT: Size: