[ELF] Accept first SHT_ARM_ATTRIBUTES section

The eglibc library, as used by Ubuntu 14.04 requires the presence of an
SHT_ARM_ATTRIBUTES section in for the purposes of checking hard/soft float
compatibility when dlopen() is used. Unfortunately when the section is not
present dlopen() fails with a generic could not find file message.
    
This change makes lld keep the first .ARM.attributes section that it
encounters and propagates it to the output. This is not a complete
SHT_ARM_ATTRIBUTES implementation, that would involve reading the contents
of the section and joining each individual attribute. It should suffice
for a homogenous build all libraries and executables on the same system
with a compatible set of command line options.

Differential revision: https://reviews.llvm.org/D27718

llvm-svn: 289642
This commit is contained in:
Peter Smith 2016-12-14 10:36:12 +00:00
parent 3abd1d3e12
commit 532bc984f5
4 changed files with 198 additions and 22 deletions

View File

@ -14,6 +14,7 @@
#include "LinkerScript.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "SyntheticSections.h"
#include "lld/Support/Memory.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Bitcode/BitcodeReader.h"
@ -336,8 +337,14 @@ elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec,
switch (Sec.sh_type) {
case SHT_ARM_ATTRIBUTES:
// FIXME: ARM meta-data section. At present attributes are ignored,
// they can be used to reason about object compatibility.
// FIXME: ARM meta-data section. Retain the first attribute section
// we see. The eglibc ARM dynamic loaders require the presence of an
// attribute section for dlopen to work.
// In a full implementation we would merge all attribute sections.
if (In<ELFT>::ARMAttributes == nullptr) {
In<ELFT>::ARMAttributes = make<InputSection<ELFT>>(this, &Sec, Name);
return In<ELFT>::ARMAttributes;
}
return &InputSection<ELFT>::Discarded;
case SHT_RELA:
case SHT_REL: {

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@ -667,6 +667,7 @@ template <class ELFT> MergeInputSection<ELFT> *createCommentSection();
// Linker generated sections which can be used as inputs.
template <class ELFT> struct In {
static InputSection<ELFT> *ARMAttributes;
static BuildIdSection<ELFT> *BuildId;
static InputSection<ELFT> *Common;
static DynamicSection<ELFT> *Dynamic;
@ -695,6 +696,7 @@ template <class ELFT> struct In {
static VersionNeedSection<ELFT> *VerNeed;
};
template <class ELFT> InputSection<ELFT> *In<ELFT>::ARMAttributes;
template <class ELFT> BuildIdSection<ELFT> *In<ELFT>::BuildId;
template <class ELFT> InputSection<ELFT> *In<ELFT>::Common;
template <class ELFT> DynamicSection<ELFT> *In<ELFT>::Dynamic;

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@ -1,20 +1,4 @@
// RUN: llvm-mc -filetype=obj -triple=armv7a-none-linux-gnueabi %s -o %t.o
// RUN: ld.lld %t.o -o %t
// RUN: llvm-readobj -s %t | FileCheck %s
// RUN: ld.lld %t.o -shared -o %t2
// RUN: llvm-readobj -s %t2 | FileCheck %s
// RUN: ld.lld %t.o -r -o %t3
// RUN: llvm-readobj -s %t3 | FileCheck %s
// The .ARM.attributes section should be removed from executables and
// shared objects.
// At present we remove it from the -r object output as well which isn't ideal.
// Unfortunately combining per-object attributes cannot be safely done by just
// concatentation of input sections.
// CHECK-NOT: Name: .ARM.attributes
// REQUIRES: arm
// Input that generates an object with a populated SHT_ARM_ATTRIBUTES section
.text
.syntax unified
.eabi_attribute 67, "2.09" @ Tag_conformance
@ -38,8 +22,8 @@
.eabi_attribute 26, 2 @ Tag_ABI_enum_size
.eabi_attribute 14, 0 @ Tag_ABI_PCS_R9_use
.eabi_attribute 68, 1 @ Tag_Virtualization_use
.globl _start
.globl func
.p2align 2
.type _start,%function
_start:
.type func,%function
func:
bx lr

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@ -0,0 +1,183 @@
// RUN: llvm-mc -filetype=obj -triple=armv7a-none-linux-gnueabi %S/Inputs/arm-attributes1.s -o %t1.o
// RUN: llvm-mc -filetype=obj -triple=armv7a-none-linux-gnueabi %s -o %t2.o
// RUN: ld.lld %t1.o %t2.o -o %t
// RUN: llvm-readobj -arm-attributes %t | FileCheck %s
// RUN: ld.lld %t1.o %t2.o -shared -o %t2
// RUN: llvm-readobj -arm-attributes %t2 | FileCheck %s
// RUN: ld.lld %t1.o %t2.o -r -o %t3
// RUN: llvm-readobj -arm-attributes %t3 | FileCheck %s
// REQUIRES: arm
// Check that we retain only 1 SHT_ARM_ATTRIBUTES section. At present we do not
// try and merge or use the contents of SHT_ARM_ATTRIBUTES sections. We just
// pass the first one through.
.text
.syntax unified
.eabi_attribute 67, "2.09" @ Tag_conformance
.cpu cortex-a8
.eabi_attribute 6, 10 @ Tag_CPU_arch
.eabi_attribute 7, 65 @ Tag_CPU_arch_profile
.eabi_attribute 8, 1 @ Tag_ARM_ISA_use
.eabi_attribute 9, 2 @ Tag_THUMB_ISA_use
.fpu neon
.eabi_attribute 15, 1 @ Tag_ABI_PCS_RW_data
.eabi_attribute 16, 1 @ Tag_ABI_PCS_RO_data
.eabi_attribute 17, 2 @ Tag_ABI_PCS_GOT_use
.eabi_attribute 20, 1 @ Tag_ABI_FP_denormal
.eabi_attribute 21, 1 @ Tag_ABI_FP_exceptions
.eabi_attribute 23, 3 @ Tag_ABI_FP_number_model
.eabi_attribute 34, 1 @ Tag_CPU_unaligned_access
.eabi_attribute 24, 1 @ Tag_ABI_align_needed
.eabi_attribute 25, 1 @ Tag_ABI_align_preserved
.eabi_attribute 38, 1 @ Tag_ABI_FP_16bit_format
.eabi_attribute 18, 4 @ Tag_ABI_PCS_wchar_t
.eabi_attribute 26, 2 @ Tag_ABI_enum_size
.eabi_attribute 14, 0 @ Tag_ABI_PCS_R9_use
.eabi_attribute 68, 1 @ Tag_Virtualization_use
.globl _start
.p2align 2
.type _start,%function
_start:
.globl func
bl func
bx lr
// CHECK: BuildAttributes {
// CHECK-NEXT: FormatVersion: 0x41
// CHECK-NEXT: Section 1 {
// CHECK-NEXT: SectionLength: 72
// CHECK-NEXT: Vendor: aeabi
// CHECK-NEXT: Tag: Tag_File (0x1)
// CHECK-NEXT: Size: 62
// CHECK-NEXT: FileAttributes {
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 67
// CHECK-NEXT: TagName: conformance
// CHECK-NEXT: Value: 2.09
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 5
// CHECK-NEXT: TagName: CPU_name
// CHECK-NEXT: Value: cortex-a8
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 6
// CHECK-NEXT: Value: 10
// CHECK-NEXT: TagName: CPU_arch
// CHECK-NEXT: Description: ARM v7
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 7
// CHECK-NEXT: Value: 65
// CHECK-NEXT: TagName: CPU_arch_profile
// CHECK-NEXT: Description: Application
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 8
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: ARM_ISA_use
// CHECK-NEXT: Description: Permitted
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 9
// CHECK-NEXT: Value: 2
// CHECK-NEXT: TagName: THUMB_ISA_use
// CHECK-NEXT: Description: Thumb-2
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 10
// CHECK-NEXT: Value: 3
// CHECK-NEXT: TagName: FP_arch
// CHECK-NEXT: Description: VFPv3
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 12
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: Advanced_SIMD_arch
// CHECK-NEXT: Description: NEONv1
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 14
// CHECK-NEXT: Value: 0
// CHECK-NEXT: TagName: ABI_PCS_R9_use
// CHECK-NEXT: Description: v6
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 15
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: ABI_PCS_RW_data
// CHECK-NEXT: Description: PC-relative
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 16
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: ABI_PCS_RO_data
// CHECK-NEXT: Description: PC-relative
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 17
// CHECK-NEXT: Value: 2
// CHECK-NEXT: TagName: ABI_PCS_GOT_use
// CHECK-NEXT: Description: GOT-Indirect
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 18
// CHECK-NEXT: Value: 4
// CHECK-NEXT: TagName: ABI_PCS_wchar_t
// CHECK-NEXT: Description: 4-byte
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 20
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: ABI_FP_denormal
// CHECK-NEXT: Description: IEEE-754
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 21
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: ABI_FP_exceptions
// CHECK-NEXT: Description: IEEE-754
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 23
// CHECK-NEXT: Value: 3
// CHECK-NEXT: TagName: ABI_FP_number_model
// CHECK-NEXT: Description: IEEE-754
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 24
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: ABI_align_needed
// CHECK-NEXT: Description: 8-byte alignment
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 25
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: ABI_align_preserved
// CHECK-NEXT: Description: 8-byte data alignment
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 26
// CHECK-NEXT: Value: 2
// CHECK-NEXT: TagName: ABI_enum_size
// CHECK-NEXT: Description: Int32
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 34
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: CPU_unaligned_access
// CHECK-NEXT: Description: v6-style
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 38
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: ABI_FP_16bit_format
// CHECK-NEXT: Description: IEEE-754
// CHECK-NEXT: }
// CHECK-NEXT: Attribute {
// CHECK-NEXT: Tag: 68
// CHECK-NEXT: Value: 1
// CHECK-NEXT: TagName: Virtualization_use
// CHECK-NEXT: Description: TrustZone
// CHECK-NEXT: }