[lld] r286353 - [ELF] ARM and AArch64 undefined weak reference values
Peter Smith via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 9 02:22:30 PST 2016
Author: psmith
Date: Wed Nov 9 04:22:29 2016
New Revision: 286353
URL: http://llvm.org/viewvc/llvm-project?rev=286353&view=rev
Log:
[ELF] ARM and AArch64 undefined weak reference values
The ARM 32 and 64-bit ABI does not use 0 for undefined weak references
that are used in PC relative relocations. In particular:
- A branch relocation to an undefined weak resolves to the next
instruction. Effectively making the branch a no-op
- In all other cases the symbol resolves to the place so that S + A - P
resolves to A.
Differential Revision: https://reviews.llvm.org/D26240
Added:
lld/trunk/test/ELF/aarch64-undefined-weak.s (with props)
lld/trunk/test/ELF/arm-thumb-undefined-weak.s (with props)
lld/trunk/test/ELF/arm-undefined-weak.s (with props)
Modified:
lld/trunk/ELF/InputSection.cpp
lld/trunk/test/ELF/arm-thumb-no-undefined-thunk.s
Modified: lld/trunk/ELF/InputSection.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=286353&r1=286352&r2=286353&view=diff
==============================================================================
--- lld/trunk/ELF/InputSection.cpp (original)
+++ lld/trunk/ELF/InputSection.cpp Wed Nov 9 04:22:29 2016
@@ -258,6 +258,42 @@ static uint64_t getAArch64Page(uint64_t
return Expr & (~static_cast<uint64_t>(0xFFF));
}
+static uint32_t getARMUndefinedRelativeWeakVA(uint32_t Type,
+ uint32_t A,
+ uint32_t P) {
+ switch (Type) {
+ case R_ARM_THM_JUMP11:
+ return P + 2;
+ case R_ARM_CALL:
+ case R_ARM_JUMP24:
+ case R_ARM_PC24:
+ case R_ARM_PLT32:
+ case R_ARM_PREL31:
+ case R_ARM_THM_JUMP19:
+ case R_ARM_THM_JUMP24:
+ return P + 4;
+ case R_ARM_THM_CALL:
+ // We don't want an interworking BLX to ARM
+ return P + 5;
+ default:
+ return A;
+ }
+}
+
+static uint64_t getAArch64UndefinedRelativeWeakVA(uint64_t Type,
+ uint64_t A,
+ uint64_t P) {
+ switch (Type) {
+ case R_AARCH64_CALL26:
+ case R_AARCH64_CONDBR19:
+ case R_AARCH64_JUMP26:
+ case R_AARCH64_TSTBR14:
+ return P + 4;
+ default:
+ return A;
+ }
+}
+
template <class ELFT>
static typename ELFT::uint getSymVA(uint32_t Type, typename ELFT::uint A,
typename ELFT::uint P,
@@ -373,10 +409,20 @@ static typename ELFT::uint getSymVA(uint
return SymVA - P;
}
case R_PC:
+ if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak()) {
+ // On ARM and AArch64 a branch to an undefined weak resolves to the
+ // next instruction, otherwise the place.
+ if (Config->EMachine == EM_ARM)
+ return getARMUndefinedRelativeWeakVA(Type, A, P);
+ if (Config->EMachine == EM_AARCH64)
+ return getAArch64UndefinedRelativeWeakVA(Type, A, P);
+ }
case R_RELAX_GOT_PC:
return Body.getVA<ELFT>(A) - P;
case R_PLT_PAGE_PC:
case R_PAGE_PC:
+ if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak())
+ return getAArch64Page(A);
return getAArch64Page(Body.getVA<ELFT>(A)) - getAArch64Page(P);
}
llvm_unreachable("Invalid expression");
Added: lld/trunk/test/ELF/aarch64-undefined-weak.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/aarch64-undefined-weak.s?rev=286353&view=auto
==============================================================================
--- lld/trunk/test/ELF/aarch64-undefined-weak.s (added)
+++ lld/trunk/test/ELF/aarch64-undefined-weak.s Wed Nov 9 04:22:29 2016
@@ -0,0 +1,45 @@
+// RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux %s -o %t
+// RUN: ld.lld %t -o %t2 2>&1
+// RUN: llvm-objdump -triple=aarch64-none-linux -d %t2 | FileCheck %s
+// REQUIRES: aarch64
+
+// Check that the ARM 64-bit ABI rules for undefined weak symbols are applied.
+// Branch instructions are resolved to the next instruction. Undefined
+// Symbols in relative are resolved to the place so S - P + A = A.
+
+ .weak target
+
+ .text
+ .global _start
+_start:
+// R_AARCH64_JUMP26
+ b target
+// R_AARCH64_CALL26
+ bl target
+// R_AARCH64_CONDBR19
+ b.eq target
+// R_AARCH64_TSTBR14
+ cbz x1, target
+// R_AARCH64_ADR_PREL_LO21
+ adr x0, target
+// R_AARCH64_ADR_PREL_PG_HI21
+ adrp x0, target
+// R_AARCH64_PREL32
+ .word target - .
+// R_AARCH64_PREL64
+ .xword target - .
+// R_AARCH64_PREL16
+ .hword target - .
+
+// CHECK: Disassembly of section .text:
+// 131076 = 0x20004
+// CHECK: 20000: 01 80 00 14 b #131076
+// CHECK-NEXT: 20004: 02 80 00 94 bl #131080
+// CHECK-NEXT: 20008: 60 00 10 54 b.eq #131084
+// CHECK-NEXT: 2000c: 81 00 10 b4 cbz x1, #131088
+// CHECK-NEXT: 20010: 00 00 00 10 adr x0, #0
+// CHECK-NEXT: 20014: 00 00 00 90 adrp x0, #0
+// CHECK: 20018: 00 00 00 00 .word 0x00000000
+// CHECK-NEXT: 2001c: 00 00 00 00 .word 0x00000000
+// CHECK-NEXT: 20020: 00 00 00 00 .word 0x00000000
+// CHECK-NEXT: 20024: 00 00 .short 0x0000
Propchange: lld/trunk/test/ELF/aarch64-undefined-weak.s
------------------------------------------------------------------------------
svn:eol-style = native
Propchange: lld/trunk/test/ELF/aarch64-undefined-weak.s
------------------------------------------------------------------------------
svn:keywords = Rev Date Author URL Id
Modified: lld/trunk/test/ELF/arm-thumb-no-undefined-thunk.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/arm-thumb-no-undefined-thunk.s?rev=286353&r1=286352&r2=286353&view=diff
==============================================================================
--- lld/trunk/test/ELF/arm-thumb-no-undefined-thunk.s (original)
+++ lld/trunk/test/ELF/arm-thumb-no-undefined-thunk.s Wed Nov 9 04:22:29 2016
@@ -18,6 +18,7 @@ _start:
// CHECK: Disassembly of section .text:
// CHECK-NEXT: _start:
-// CHECK-NEXT: 11000: ee f7 fe ef blx #-69636
-// CHECK-NEXT: 11004: ee f7 fc bf b.w #-69640
-// CHECK-NEXT: 11008: ee f7 fa bf b.w #-69644
+// 69636 = 0x11004 = next instruction
+// CHECK: 11000: 11 f0 02 f8 bl #69636
+// CHECK-NEXT: 11004: 11 f0 04 b8 b.w #69640
+// CHECK-NEXT: 11008: 11 f0 06 b8 b.w #69644
Added: lld/trunk/test/ELF/arm-thumb-undefined-weak.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/arm-thumb-undefined-weak.s?rev=286353&view=auto
==============================================================================
--- lld/trunk/test/ELF/arm-thumb-undefined-weak.s (added)
+++ lld/trunk/test/ELF/arm-thumb-undefined-weak.s Wed Nov 9 04:22:29 2016
@@ -0,0 +1,38 @@
+// RUN: llvm-mc -filetype=obj -triple=thumbv7a-none-linux-gnueabi %s -o %t
+// RUN: ld.lld %t -o %t2 2>&1
+// RUN: llvm-objdump -triple=thumbv7a-none-linux-gnueabi -d %t2 | FileCheck %s
+// REQUIRES: arm
+
+// Check that the ARM ABI rules for undefined weak symbols are applied.
+// Branch instructions are resolved to the next instruction. Relative
+// relocations are resolved to the place.
+
+ .syntax unified
+
+ .weak target
+
+ .text
+ .global _start
+_start:
+// R_ARM_THM_JUMP19
+ beq.w target
+// R_ARM_THM_JUMP24
+ b.w target
+// R_ARM_THM_CALL
+ bl target
+// R_ARM_THM_CALL with exchange
+ blx target
+// R_ARM_THM_MOVT_PREL
+ movt r0, :upper16:target - .
+// R_ARM_THM_MOVW_PREL_NC
+ movw r0, :lower16:target - .
+
+// CHECK: Disassembly of section .text:
+// 69636 = 0x11004
+// CHECK: 11000: 11 f0 02 80 beq.w #69636
+// CHECK-NEXT: 11004: 11 f0 04 b8 b.w #69640
+// CHECK-NEXT: 11008: 11 f0 06 f8 bl #69644
+// blx is transformed into bl so we don't change state
+// CHECK-NEXT: 1100c: 11 f0 08 f8 bl #69648
+// CHECK-NEXT: 11010: c0 f2 00 00 movt r0, #0
+// CHECK-NEXT: 11014: 40 f2 00 00 movw r0, #0
Propchange: lld/trunk/test/ELF/arm-thumb-undefined-weak.s
------------------------------------------------------------------------------
svn:eol-style = native
Propchange: lld/trunk/test/ELF/arm-thumb-undefined-weak.s
------------------------------------------------------------------------------
svn:keywords = Rev Date Author URL Id
Added: lld/trunk/test/ELF/arm-undefined-weak.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/arm-undefined-weak.s?rev=286353&view=auto
==============================================================================
--- lld/trunk/test/ELF/arm-undefined-weak.s (added)
+++ lld/trunk/test/ELF/arm-undefined-weak.s Wed Nov 9 04:22:29 2016
@@ -0,0 +1,39 @@
+// RUN: llvm-mc -filetype=obj -triple=armv7a-none-linux-gnueabi %s -o %t
+// RUN: ld.lld %t -o %t2 2>&1
+// RUN: llvm-objdump -triple=armv7a-none-linux-gnueabi -d %t2 | FileCheck %s
+// REQUIRES: arm
+
+// Check that the ARM ABI rules for undefined weak symbols are applied.
+// Branch instructions are resolved to the next instruction. Undefined
+// Symbols in relative are resolved to the place so S - P + A = A.
+
+ .syntax unified
+
+ .weak target
+
+ .text
+ .global _start
+_start:
+// R_ARM_JUMP24
+ b target
+// R_ARM_CALL
+ bl target
+// R_ARM_CALL with exchange
+ blx target
+// R_ARM_MOVT_PREL
+ movt r0, :upper16:target - .
+// R_ARM_MOVW_PREL_NC
+ movw r0, :lower16:target - .
+// R_ARM_REL32
+ .word target - .
+
+// CHECK: Disassembly of section .text:
+// 69636 = 0x11004
+// CHECK: 11000: 01 44 00 ea b #69636
+// CHECK-NEXT: 11004: 02 44 00 eb bl #69640
+// blx is transformed into bl so we don't change state
+// CHECK-NEXT: 11008: 03 44 00 eb bl #69644
+// CHECK-NEXT: 1100c: 00 00 40 e3 movt r0, #0
+// CHECK-NEXT: 11010: 00 00 00 e3 movw r0, #0
+// CHECK: 11014: 00 00 00 00 .word 0x00000000
+
Propchange: lld/trunk/test/ELF/arm-undefined-weak.s
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svn:eol-style = native
Propchange: lld/trunk/test/ELF/arm-undefined-weak.s
------------------------------------------------------------------------------
svn:keywords = Rev Date Author URL Id
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