[PATCH] D33700: Define __executable_start

[Rafael Ávila de Espíndola via Phabricator via llvm-commits]

rafael created this revision.
Herald added subscribers: emaste, srhines.

It is a bit odd to define two symbols pointing to the same location, but it is a trivial change, so it is probably ok.

This is defined by both gold and bfd.


https://reviews.llvm.org/D33700

Files:
  ELF/Writer.cpp
  test/ELF/ehdr_start.s


Index: test/ELF/ehdr_start.s
===================================================================
--- test/ELF/ehdr_start.s
+++ test/ELF/ehdr_start.s
@@ -13,10 +13,21 @@
 # CHECK-NEXT:    ]
 # CHECK-NEXT:    Section: .text (0x1)
 
+# CHECK:    Name: __executable_start
+# CHECK-NEXT:    Value: 0x200000
+# CHECK-NEXT:    Size: 0
+# CHECK-NEXT:    Binding: Local
+# CHECK-NEXT:    Type: None
+# CHECK-NEXT:    Other [
+# CHECK-NEXT:      STV_HIDDEN
+# CHECK-NEXT:    ]
+# CHECK-NEXT:    Section: .text
+
 .text
 .global _start, __ehdr_start
 _start:
   .quad __ehdr_start
+  .quad __executable_start
 
 # RUN: ld.lld -r %t.o -o %t.r
 # RUN: llvm-readobj -symbols %t.r | FileCheck %s --check-prefix=RELOCATABLE
Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -911,7 +911,10 @@
   // this symbol unconditionally even when using a linker script, which
   // differs from the behavior implemented by GNU linker which only define
   // this symbol if ELF headers are in the memory mapped segment.
-  addOptionalRegular<ELFT>("__ehdr_start", Out::ElfHeader, 0, STV_HIDDEN);
+  // __executable_start is not documented, but the expectation of at
+  // least the android libc is that it points to the elf header too.
+  for (const char *Name : {"__ehdr_start", "__executable_start"})
+    addOptionalRegular<ELFT>(Name, Out::ElfHeader, 0, STV_HIDDEN);
 
   // If linker script do layout we do not need to create any standart symbols.
   if (Script->Opt.HasSections)


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