[PATCH] D76915: [LLD][ELF] Allow empty (.init|.preinit|.fini)_array to be RELRO

[Peter Smith via Phabricator via llvm-commits]

psmith updated this revision to Diff 253627.
psmith added a comment.

Thanks for the comments, I've added some tests to check that the _array sections are zero size, also to show the extent of the RELRO includes the section before and after.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76915/new/

https://reviews.llvm.org/D76915

Files:
  lld/ELF/Writer.cpp
  lld/test/ELF/relro-init-fini-script.s


Index: lld/test/ELF/relro-init-fini-script.s
===================================================================
--- /dev/null
+++ lld/test/ELF/relro-init-fini-script.s
@@ -0,0 +1,39 @@
+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-none-elf %s -o %t.o
+// RUN: echo "SECTIONS { \
+// RUN:  .dynamic 0x10000 : { *(.dynamic) } \
+// RUN:  .preinit_array : { PROVIDE_HIDDEN (__preinit_array_start = .); \
+// RUN:                  KEEP (*(.preinit_array)) } \
+// RUN:  .init_array : { PROVIDE_HIDDEN (__init_array_start = .); \
+// RUN:                  KEEP (*(.init_array)) } \
+// RUN:  .fini_array : { PROVIDE_HIDDEN (__fini_array_start = .); \
+// RUN:                  KEEP (*(.fini_array)) } \
+// RUN:  .data.rel.ro : { *(.data.rel.ro) } \
+// RUN:  .data : { *(.data) } } " > %t.script
+// RUN: ld.lld %t.o -o %t.so --shared --script=%t.script
+// RUN: llvm-readelf -S %t.so | FileCheck %s
+// RUN: llvm-readobj --segments %t.so | FileCheck %s --check-prefix=PHDR
+
+/// Check that an empty .init_array, .fini_array or .preinit_array that is
+/// kept due to symbol references, is still counted as RELRO. The _array
+/// sections are zero size. The RELRO extent is [.dynamic, .data.rel.ro)
+
+// CHECK:      .dynamic       DYNAMIC         0000000000010000 002000 000110
+// CHECK-NEXT: .preinit_array PROGBITS        {{0+}}[[# %x,ADDR:]]
+// CHECK-NEXT: .init_array    PROGBITS        {{0+}}[[# ADDR]]
+// CHECK-NEXT: .fini_array    PROGBITS        {{0+}}[[# ADDR]]
+// CHECK-NEXT: .data.rel.ro   PROGBITS        0000000000010110 002110 000008
+
+// PHDR:      Type: PT_GNU_RELRO
+// PHDR-NEXT: Offset: 0x2000
+// PHDR-NEXT: VirtualAddress: 0x10000
+// PHDR-NEXT: PhysicalAddress: 0x10000
+// PHDR-NEXT: FileSize: 280
+ .section .data.rel.ro, "aw", %progbits
+ .global foo
+ .quad foo
+
+ .data
+ .quad __init_array_start
+ .quad __fini_array_start
+ .quad __preinit_array_start
Index: lld/ELF/Writer.cpp
===================================================================
--- lld/ELF/Writer.cpp
+++ lld/ELF/Writer.cpp
@@ -819,7 +819,8 @@
   StringRef s = sec->name;
   return s == ".data.rel.ro" || s == ".bss.rel.ro" || s == ".ctors" ||
          s == ".dtors" || s == ".jcr" || s == ".eh_frame" ||
-         s == ".openbsd.randomdata";
+         s == ".fini_array" || s == ".init_array" ||
+         s == ".openbsd.randomdata" || s == ".preinit_array";
 }
 
 // We compute a rank for each section. The rank indicates where the


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