[PATCH] D65909: ELF: Move sections referred to by __start_/__stop_ symbols into the main partition.

[Peter Collingbourne via Phabricator via llvm-commits]

pcc updated this revision to Diff 214019.
pcc added a comment.

- Add test


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D65909/new/

https://reviews.llvm.org/D65909

Files:
  lld/ELF/MarkLive.cpp
  lld/test/ELF/partition-move-to-main-startstop.s


Index: lld/test/ELF/partition-move-to-main-startstop.s
===================================================================
--- /dev/null
+++ lld/test/ELF/partition-move-to-main-startstop.s
@@ -0,0 +1,45 @@
+// REQUIRES: x86
+// RUN: llvm-mc %s -o %t.o -filetype=obj --triple=x86_64-unknown-linux
+// RUN: ld.lld %t.o -o %t --export-dynamic --gc-sections
+// RUN: llvm-readelf -S %t | FileCheck %s
+
+// We can't let the has_startstop section be split by partition because it is
+// referenced by __start_ and __stop_ symbols, so the split could result in
+// some sections being moved out of the __start_/__stop_ range. Make sure that
+// that didn't happen by checking that there is only one section.
+//
+// It's fine for us to split no_startstop because of the lack of
+// __start_/__stop_ symbols.
+
+// CHECK: has_startstop
+// CHECK: no_startstop
+
+// CHECK-NOT: has_startstop
+// CHECK: no_startstop
+// CHECK-NOT: has_startstop
+
+.section .llvm_sympart.f1,"", at llvm_sympart
+.asciz "part1"
+.quad f1
+
+.section .text._start,"ax", at progbits
+.globl _start
+_start:
+call __start_has_startstop
+call __stop_has_startstop
+
+.section .text.f1,"ax", at progbits
+.globl f1
+f1:
+
+.section has_startstop,"ao", at progbits,.text._start,unique,1
+.quad 1
+
+.section has_startstop,"ao", at progbits,.text.f1,unique,2
+.quad 2
+
+.section no_startstop,"ao", at progbits,.text._start,unique,1
+.quad 3
+
+.section no_startstop,"ao", at progbits,.text.f1,unique,2
+.quad 4
Index: lld/ELF/MarkLive.cpp
===================================================================
--- lld/ELF/MarkLive.cpp
+++ lld/ELF/MarkLive.cpp
@@ -291,14 +291,31 @@
 // GOT, which means that the ifunc must be available when the main partition is
 // loaded) and TLS symbols (because we only know how to correctly process TLS
 // relocations for the main partition).
+//
+// We also need to move sections whose names are C identifiers that are referred
+// to from __start_/__stop_ symbols because there will only be one set of
+// symbols for the whole program.
 template <class ELFT> void MarkLive<ELFT>::moveToMain() {
-  for (InputFile *file : objectFiles)
-    for (Symbol *s : file->getSymbols())
+  StringSet<> startStopSymbolNames;
+  for (InputFile *file : objectFiles) {
+    for (Symbol *s : file->getSymbols()) {
       if (auto *d = dyn_cast<Defined>(s))
         if ((d->type == STT_GNU_IFUNC || d->type == STT_TLS) && d->section &&
             d->section->isLive())
           markSymbol(s);
 
+      StringRef name = s->getName();
+      if (name.startswith("__start_"))
+        startStopSymbolNames.insert(name.substr(8));
+      else if (name.startswith("__stop_"))
+        startStopSymbolNames.insert(name.substr(7));
+    }
+  }
+
+  for (InputSectionBase *sec : inputSections)
+    if (sec->isLive() && startStopSymbolNames.count(sec->name))
+      enqueue(sec, 0);
+
   mark();
 }
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D65909.214019.patch
Type: text/x-patch
Size: 2868 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190807/f40f13bc/attachment.bin>