[ELF] Fix ARM TLS global dynamic TlsOffsetRel for non-preemtible symbols

smithp35 · smithp35 · commit 99a992343c73 · 2017-04-07T09:37:30.000Z
When the target of the TlsOffsetRel is non-preemptible we can write the offset directly into the GOT without needing a dynamic relocation. This is optional for dynamically linked executables but is required for static linking. This change adds the relocation to the GOT entry and a test case for non-0 offsets so that if we miss out the offset the test won't spuriously pass by virtue of the default value being 0. Differential Revision: https://reviews.llvm.org/D31749 llvm-svn: 299751
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
@@ -181,6 +181,9 @@ static unsigned handleARMTlsRelocation(GotSection<ELFT> *Got, uint32_t Type,
       if (Body.isPreemptible())
         In<ELFT>::RelaDyn->addReloc({Target->TlsOffsetRel, Got,
                                      Off + Config->Wordsize, false, &Body, 0});
+      else
+        Got->Relocations.push_back(
+            {R_ABS, R_ARM_ABS32, Off + Config->Wordsize, 0, &Body});
     }
     C.Relocations.push_back({Expr, Type, Offset, Addend, &Body});
     return 1;
diff --git a/lld/test/ELF/arm-tls-gd-nonpreemptible.s b/lld/test/ELF/arm-tls-gd-nonpreemptible.s
@@ -0,0 +1,72 @@
+// RUN: llvm-mc -filetype=obj -triple=armv7a-none-linux-gnueabi %s -o %t
+// RUN: ld.lld %t -o %t2
+// RUN: llvm-mc %s -o %t.o -filetype=obj -triple=armv7a-linux-gnueabi
+// RUN: llvm-objdump -s %t2 | FileCheck %s
+// RUN: ld.lld %t --shared -o %t3.so
+// RUN: llvm-objdump -s %t3.so | FileCheck -check-prefix=CHECK-SHARED %s
+// REQUIRES: arm
+
+// For an executable, we write the module index 1 and the offset into the TLS
+// directly into the GOT. For a shared library we can only write the offset
+// into the TLS directly if the symbol is non-preemptible
+
+ .text
+ .syntax unified
+ .globl __tls_get_addr
+ .type __tls_get_addr,%function
+__tls_get_addr:
+ bx lr
+
+ .globl  _start
+ .p2align        2
+ .type   _start,%function
+func:
+.L0:
+ nop
+.L1:
+ nop
+.L2:
+ nop
+.L3:
+ nop
+ .p2align        2
+// Generate R_ARM_TLS_GD32 relocations
+// These can be resolved at static link time for executables as 1 is always the
+// module index and the offset into tls is known at static link time
+.Lt0: .word   x1(TLSGD) + (. - .L0 - 8)
+.Lt1: .word   x2(TLSGD) + (. - .L1 - 8)
+.Lt2: .word   x3(TLSGD) + (. - .L2 - 8)
+.Lt3: .word   x4(TLSGD) + (. - .L3 - 8)
+ .hidden x1
+ .globl  x1
+ .hidden x2
+ .globl  x2
+ .globl  x3
+ .globl  x4
+
+ .section       .tdata,"awT",%progbits
+ .p2align  2
+.TLSSTART:
+ .type  x1, %object
+x1:
+ .word 10
+ .type  x2, %object
+x2:
+ .word 20
+
+ .section       .tbss,"awT",%nobits
+ .p2align 2
+ .type  x3, %object
+x3:
+ .space 4
+ .type  x4, %object
+x4:
+ .space 4
+
+// CHECK: Contents of section .got:
+// CHECK-NEXT:  12008 01000000 00000000 01000000 04000000
+// CHECK-NEXT:  12018 01000000 08000000 01000000 0c000000
+
+// CHECK-SHARED: Contents of section .got:
+// CHECK-SHARED-NEXT:  2050 00000000 00000000 00000000 04000000
+// CHECK-SHARED-NEXT:  2060 00000000 00000000 00000000 00000000
