[PATCH] D80872: [ELF] Set DF_1_PIE for -pie

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: grimar, jhenderson, psmith, ruiu.
Herald added subscribers: llvm-commits, fedor.sergeev, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.

DF_1_PIE originated from Solaris.
GNU ld since
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=5fe2850dd96483f176858fd75c098313d5b20bc2
sets the flag on non-Solaris platforms.

It can help distinguish PIE from ET_DYN.
eu-classify from elfutils uses this to recognize PIE (https://sourceware.org/git/?p=elfutils.git;a=commit;h=3f489b5c7c78df6d52f8982f79c36e9a220e8951)

glibc uses this flag to reject dlopen'ing a PIE (https://sourceware.org/bugzilla/show_bug.cgi?id=24323)

If this looks good, I'll fix then 10+ tests.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D80872

Files:
  lld/ELF/SyntheticSections.cpp
  lld/test/ELF/pie.s


Index: lld/test/ELF/pie.s
===================================================================
--- lld/test/ELF/pie.s
+++ lld/test/ELF/pie.s
@@ -8,11 +8,11 @@
 
 ## Check -pie.
 # RUN: ld.lld -pie %t1.o -o %t
-# RUN: llvm-readobj --file-headers --sections -l --symbols -r %t | FileCheck %s
+# RUN: llvm-readobj --file-headers --sections -l -d --symbols -r %t | FileCheck %s
 
 ## Test --pic-executable alias
 # RUN: ld.lld --pic-executable %t1.o -o %t
-# RUN: llvm-readobj --file-headers --sections -l --symbols -r %t | FileCheck %s
+# RUN: llvm-readobj --file-headers --sections -l -d --symbols -r %t | FileCheck %s
 
 # CHECK:      ElfHeader {
 # CHECK-NEXT:  Ident {
@@ -47,6 +47,9 @@
 
 # CHECK:         Type: PT_DYNAMIC
 
+# CHECK:      DynamicSection [
+# CHECK:        0x000000006FFFFFFB FLAGS_1 PIE
+
 ## Check -nopie
 # RUN: ld.lld -no-pie %t1.o -o %t2
 # RUN: llvm-readobj --file-headers -r %t2 | FileCheck %s --check-prefix=NOPIE
Index: lld/ELF/SyntheticSections.cpp
===================================================================
--- lld/ELF/SyntheticSections.cpp
+++ lld/ELF/SyntheticSections.cpp
@@ -1317,6 +1317,8 @@
     dtFlags1 |= DF_1_NODELETE;
   if (config->zNodlopen)
     dtFlags1 |= DF_1_NOOPEN;
+  if (config->pie)
+    dtFlags1 |= DF_1_PIE;
   if (config->zNow) {
     dtFlags |= DF_BIND_NOW;
     dtFlags1 |= DF_1_NOW;


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