[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 214230.
pcc marked 3 inline comments as done.
pcc added a comment.

- Switch to a symbol table lookup
- Use --implicit-check-not


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 +1,43 @@
+// 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 --implicit-check-not=has_startstop %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: no_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
@@ -291,6 +291,10 @@
 // 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())
@@ -299,6 +303,14 @@
             d->section->isLive())
           markSymbol(s);
 
+  for (InputSectionBase *sec : inputSections) {
+    if (!sec->isLive() || !isValidCIdentifier(sec->name))
+      continue;
+    if (symtab->find(("__start_" + sec->name).str()) ||
+        symtab->find(("__stop_" + sec->name).str()))
+      enqueue(sec, 0);
+  }
+
   mark();
 }
 


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