[lld] r235498 - [ARM] Replace branches to undefined weak functions with NOP
Leny Kholodov
lkholodov at accesssoftek.com
Wed Apr 22 04:47:54 PDT 2015
Author: lkholodov
Date: Wed Apr 22 06:47:53 2015
New Revision: 235498
URL: http://llvm.org/viewvc/llvm-project?rev=235498&view=rev
Log:
[ARM] Replace branches to undefined weak functions with NOP
According to the code model (ARM, Thumb, Thumb2) this patch updates the b/bl/blx 0 instructions with NOP.
test/elf/ARM/weak-branch.test has been added with tests for all available NOP (A1, T1, T2 encodings).
Differential Revision: http://reviews.llvm.org/D8807
Added:
lld/trunk/test/elf/ARM/weak-branch.test
Modified:
lld/trunk/lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp
Modified: lld/trunk/lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp?rev=235498&r1=235497&r2=235498&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp (original)
+++ lld/trunk/lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp Wed Apr 22 06:47:53 2015
@@ -510,6 +510,32 @@ static void relocR_ARM_LDR_PC_G2(uint8_t
applyArmReloc(location, (uint32_t)result & mask, mask);
}
+/// \brief Fixup unresolved weak reference with NOP instruction
+static bool fixupUnresolvedWeakCall(uint8_t *location,
+ Reference::KindValue kindValue) {
+ //TODO: workaround for archs without NOP instruction
+ switch (kindValue) {
+ case R_ARM_THM_CALL:
+ case R_ARM_THM_JUMP24:
+ // Thumb32 NOP.W
+ write32le(location, 0x8000F3AF);
+ break;
+ case R_ARM_THM_JUMP11:
+ // Thumb16 NOP
+ write16le(location, 0xBF00);
+ break;
+ case R_ARM_CALL:
+ case R_ARM_JUMP24:
+ // A1 NOP<c>, save condition bits
+ applyArmReloc(location, 0x320F000, 0xFFFFFFF);
+ break;
+ default:
+ return false;
+ }
+
+ return true;
+}
+
std::error_code ARMTargetRelocationHandler::applyRelocation(
ELFWriter &writer, llvm::FileOutputBuffer &buf, const AtomLayout &atom,
const Reference &ref) const {
@@ -522,6 +548,19 @@ std::error_code ARMTargetRelocationHandl
return std::error_code();
assert(ref.kindArch() == Reference::KindArch::ARM);
+ // Fixup unresolved weak references
+ if (!target) {
+ bool isCallFixed = fixupUnresolvedWeakCall(loc, ref.kindValue());
+
+ if (isCallFixed) {
+ DEBUG(llvm::dbgs() << "\t\tFixup unresolved weak reference '";
+ llvm::dbgs() << ref.target()->name() << "'";
+ llvm::dbgs() << " at address: 0x" << Twine::utohexstr(reloc);
+ llvm::dbgs() << (isCallFixed ? "\n" : " isn't possible\n"));
+ return std::error_code();
+ }
+ }
+
// Calculate proper initial addend for the relocation
const Reference::Addend addend =
readAddend(loc, ref.kindValue()) + ref.addend();
Added: lld/trunk/test/elf/ARM/weak-branch.test
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf/ARM/weak-branch.test?rev=235498&view=auto
==============================================================================
--- lld/trunk/test/elf/ARM/weak-branch.test (added)
+++ lld/trunk/test/elf/ARM/weak-branch.test Wed Apr 22 06:47:53 2015
@@ -0,0 +1,222 @@
+# Check weak references fixup.
+
+# RUN: yaml2obj -format=elf -docnum 1 %s > %t-jmp11.o
+# RUN: lld -flavor gnu -target arm -m armelf_linux_eabi -Bstatic \
+# RUN: --noinhibit-exec %t-jmp11.o -o %t
+# RUN: llvm-objdump -s -t %t | FileCheck -check-prefix=JMP11-CHECK %s
+
+# JMP11-CHECK: Contents of section .text:
+# JMP11-CHECK: 400194 704700bf 01216be7 012100bf 002167e7
+# ^ NOP (thumb16)
+# 40019c: 2101 movs r1, #1
+# 40019e: bf00 nop
+# JMP11-CHECK: 4001a4 002100bf
+# ^ NOP (thumb16)
+# 4001a4: 2100 movs r1, #0
+# 4001a6: bf00 nop
+# JMP11-CHECK: SYMBOL TABLE:
+# JMP11-CHECK: 00000000 w *UND* 00000000 __gnu_h2f_internal
+
+# RUN: yaml2obj -format=elf -docnum 2 %s > %t-thm-call.o
+# RUN: lld -flavor gnu -target arm -m armelf_linux_eabi -Bstatic \
+# RUN: --noinhibit-exec %t-thm-call.o -o %t
+# RUN: llvm-objdump -s -t %t | FileCheck -check-prefix=THM-CALL-CHECK %s
+
+# THM-CALL-CHECK: Contents of section .text:
+# THM-CALL-CHECK: 400064 80b500af fff7f4ff aff30080 03461846
+# ^ NOP.W
+# 400068: f7ff fff4 bl 400054 <my_fn>
+# 40006c: f3af 8000 nop.w
+# 400070: 4603 mov r3, r0 ; return value has not been changed after weak fn call
+#
+# THM-CALL-CHECK: SYMBOL TABLE:
+# THM-CALL-CHECK: 00000000 w *UND* 00000000 weak_fn
+
+# RUN: yaml2obj -format=elf -docnum 3 %s > %t-arm-call.o
+# RUN: lld -flavor gnu -target arm -m armelf_linux_eabi -Bstatic \
+# RUN: --noinhibit-exec %t-arm-call.o -o %t
+# RUN: llvm-objdump -s -t %t | FileCheck -check-prefix=ARM-CALL-CHECK %s
+
+# ARM-CALL-CHECK: Contents of section .text:
+# ARM-CALL-CHECK: 400074 04b08de2 f5ffffeb 00f020e3 0030a0e1
+# ^ NOP
+# 400078: ebfffff5 bl 400054 <my_fn>
+# 40007c: e320f000 nop {0}
+# 400080: e1a03000 mov r3, r0 ; return value has not been changed after weak fn call
+#
+# ARM-CALL-CHECK: SYMBOL TABLE:
+# ARM-CALL-CHECK: 00000000 w *UND* 00000000 weak_fn
+
+# jump11.o
+---
+FileHeader:
+ Class: ELFCLASS32
+ Data: ELFDATA2LSB
+ Type: ET_REL
+ Machine: EM_ARM
+ Flags: [ EF_ARM_EABI_VER5 ]
+Sections:
+ - Name: .text
+ Type: SHT_PROGBITS
+ Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
+ AddressAlign: 0x0000000000000004
+ Content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
+ - Name: .rel.text
+ Type: SHT_REL
+ Link: .symtab
+ AddressAlign: 0x0000000000000004
+ Info: .text
+ Relocations:
+ - Offset: 0x000000000000012A
+ Symbol: __gnu_h2f_internal
+ Type: R_ARM_THM_JUMP11
+ - Offset: 0x0000000000000132
+ Symbol: __gnu_h2f_internal
+ Type: R_ARM_THM_JUMP11
+ - Name: .data
+ Type: SHT_PROGBITS
+ Flags: [ SHF_WRITE, SHF_ALLOC ]
+ AddressAlign: 0x0000000000000001
+ Content: ''
+ - Name: .bss
+ Type: SHT_NOBITS
+ Flags: [ SHF_WRITE, SHF_ALLOC ]
+ AddressAlign: 0x0000000000000001
+ Content: ''
+Symbols:
+ Local:
+ - Name: .text
+ Type: STT_SECTION
+ Section: .text
+ - Name: .data
+ Type: STT_SECTION
+ Section: .data
+ - Name: .bss
+ Type: STT_SECTION
+ Section: .bss
+ - Name: '$t'
+ Section: .text
+ - Name: __gnu_f2h_internal
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x0000000000000001
+ Size: 0x00000000000000C2
+ Global:
+ - Name: __gnu_f2h_ieee
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x0000000000000125
+ Size: 0x0000000000000004
+ Visibility: STV_HIDDEN
+ - Name: __gnu_h2f_ieee
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x0000000000000129
+ Size: 0x0000000000000004
+ Visibility: STV_HIDDEN
+ - Name: __gnu_f2h_alternative
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x000000000000012D
+ Size: 0x0000000000000004
+ Visibility: STV_HIDDEN
+ - Name: __gnu_h2f_alternative
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x0000000000000131
+ Size: 0x0000000000000004
+ Visibility: STV_HIDDEN
+ Weak:
+ - Name: __gnu_h2f_internal
+# thm-call.o
+---
+FileHeader:
+ Class: ELFCLASS32
+ Data: ELFDATA2LSB
+ Type: ET_REL
+ Machine: EM_ARM
+ Flags: [ EF_ARM_EABI_VER5 ]
+Sections:
+ - Name: .text
+ Type: SHT_PROGBITS
+ Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
+ AddressAlign: 0x0000000000000004
+ Content: 80B400AF01231846BD465DF8047B704780B500AFFFF7FEFFFFF7FEFF0346184680BD00BF
+ - Name: .rel.text
+ Type: SHT_REL
+ Link: .symtab
+ AddressAlign: 0x0000000000000004
+ Info: .text
+ Relocations:
+ - Offset: 0x0000000000000014
+ Symbol: my_fn
+ Type: R_ARM_THM_CALL
+ - Offset: 0x0000000000000018
+ Symbol: weak_fn
+ Type: R_ARM_THM_CALL
+Symbols:
+ Local:
+ - Name: .text
+ Type: STT_SECTION
+ Section: .text
+ - Name: '$t'
+ Section: .text
+ Global:
+ - Name: my_fn
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x0000000000000001
+ Size: 0x0000000000000010
+ - Name: main
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x0000000000000011
+ Size: 0x0000000000000012
+ Weak:
+ - Name: weak_fn
+# arm-call.o
+---
+FileHeader:
+ Class: ELFCLASS32
+ Data: ELFDATA2LSB
+ Type: ET_REL
+ Machine: EM_ARM
+ Flags: [ EF_ARM_EABI_VER5 ]
+Sections:
+ - Name: .text
+ Type: SHT_PROGBITS
+ Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
+ AddressAlign: 0x0000000000000004
+ Content: 04B02DE500B08DE20130A0E30300A0E100D04BE204B09DE41EFF2FE100482DE904B08DE2FEFFFFEBFEFFFFEB0030A0E10300A0E10088BDE8
+ - Name: .rel.text
+ Type: SHT_REL
+ Link: .symtab
+ AddressAlign: 0x0000000000000004
+ Info: .text
+ Relocations:
+ - Offset: 0x0000000000000024
+ Symbol: my_fn
+ Type: R_ARM_CALL
+ - Offset: 0x0000000000000028
+ Symbol: weak_fn
+ Type: R_ARM_CALL
+Symbols:
+ Local:
+ - Name: .text
+ Type: STT_SECTION
+ Section: .text
+ - Name: '$a'
+ Section: .text
+ Global:
+ - Name: my_fn
+ Type: STT_FUNC
+ Section: .text
+ Size: 0x000000000000001C
+ - Name: main
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x000000000000001C
+ Size: 0x000000000000001C
+ Weak:
+ - Name: weak_fn
+...
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