[ELF][MIPS] Allow .MIPS.abiflags larger than one Elf_Mips_ABIFlags struct

Older versions of BFD generate libraries with .MIPS.abiflags that only
concatenate the individual .MIPS.abiflags sections instead of merging.

Patch by Alexander Richardson.

Differential revision: https://reviews.llvm.org/D27770

llvm-svn: 290237

3 files changed, 70 insertions, 2 deletions

diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index ea5e924e493..2dbe749029c 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -134,8 +134,13 @@ MipsAbiFlagsSection<ELFT> *MipsAbiFlagsSection<ELFT>::create() {
     Create = true;
 
     std::string Filename = toString(Sec->getFile());
-    if (Sec->Data.size() != sizeof(Elf_Mips_ABIFlags)) {
-      error(Filename + ": invalid size of .MIPS.abiflags section");
+    const size_t Size = Sec->Data.size();
+    // Older version of BFD (such as the default FreeBSD linker) concatenate
+    // .MIPS.abiflags instead of merging. To allow for this case (or potential
+    // zero padding) we ignore everything after the first Elf_Mips_ABIFlags
+    if (Size < sizeof(Elf_Mips_ABIFlags)) {
+      error(Filename + ": invalid size of .MIPS.abiflags section: got " +
+            Twine(Size) + " instead of " + Twine(sizeof(Elf_Mips_ABIFlags)));
       return nullptr;
     }
     auto *S = reinterpret_cast<const Elf_Mips_ABIFlags *>(Sec->Data.data());
diff --git a/lld/test/ELF/Inputs/mips-concatenated-abiflags.o b/lld/test/ELF/Inputs/mips-concatenated-abiflags.o
new file mode 100644
index 00000000000..404530919fc
--- /dev/null
+++ b/lld/test/ELF/Inputs/mips-concatenated-abiflags.o
diff --git a/lld/test/ELF/mips-merge-abiflags.s b/lld/test/ELF/mips-merge-abiflags.s
new file mode 100644
index 00000000000..2e8b43bcc3b
--- /dev/null
+++ b/lld/test/ELF/mips-merge-abiflags.s
@@ -0,0 +1,63 @@
+# Test that lld handles input files with concatenated .MIPS.abiflags sections
+# This happens e.g. with the FreeBSD BFD (BFD 2.17.50 [FreeBSD] 2007-07-03)
+
+# RUN: llvm-mc -filetype=obj -triple=mips64-unknown-freebsd %s -o %t.o
+# RUN: ld.lld %t.o %p/Inputs/mips-concatenated-abiflags.o -o %t.exe
+# RUN: llvm-readobj -sections -mips-abi-flags %t.exe | FileCheck %s
+# RUN: llvm-readobj -sections -mips-abi-flags \
+# RUN:     %p/Inputs/mips-concatenated-abiflags.o | \
+# RUN:   FileCheck --check-prefix=INPUT-OBJECT %s
+
+# REQUIRES: mips
+        .globl  __start
+__start:
+        nop
+
+# CHECK:      Section {
+# CHECK:        Index: 1
+# CHECK-NEXT:   Name: .MIPS.abiflags
+# CHECK-NEXT:   Type: SHT_MIPS_ABIFLAGS
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_ALLOC
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address:
+# CHECK-NEXT:   Offset:
+# CHECK-NEXT:   Size: 24
+# CHECK-NEXT:   Link: 0
+# CHECK-NEXT:   Info: 0
+# CHECK-NEXT:   AddressAlignment: 8
+# CHECK-NEXT:   EntrySize: 24
+# CHECK-NEXT: }
+
+# CHECK:      MIPS ABI Flags {
+# CHECK-NEXT:   Version: 0
+# CHECK-NEXT:   ISA: MIPS64
+# CHECK-NEXT:   ISA Extension: None
+# CHECK-NEXT:   ASEs [
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   FP ABI: Hard float (double precision)
+# CHECK-NEXT:   GPR size: 64
+# CHECK-NEXT:   CPR1 size: 64
+# CHECK-NEXT:   CPR2 size: 0
+# CHECK-NEXT:   Flags 1 [
+# CHECK-NEXT:     ODDSPREG
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Flags 2: 0x0
+# CHECK-NEXT: }
+
+# INPUT-OBJECT:       Section {
+# INPUT-OBJECT:         Index: 3
+# INPUT-OBJECT-NEXT:    Name: .MIPS.abiflags
+# INPUT-OBJECT-NEXT:    Type: SHT_MIPS_ABIFLAGS
+# INPUT-OBJECT-NEXT:    Flags [
+# INPUT-OBJECT-NEXT:      SHF_ALLOC
+# INPUT-OBJECT-NEXT:    ]
+# INPUT-OBJECT-NEXT:    Address:
+# INPUT-OBJECT-NEXT:    Offset:
+# INPUT-OBJECT-NEXT:    Size: 48
+# INPUT-OBJECT-NEXT:    Link: 0
+# INPUT-OBJECT-NEXT:    Info: 0
+# INPUT-OBJECT-NEXT:    AddressAlignment: 8
+# INPUT-OBJECT-NEXT:    EntrySize: 0
+# INPUT-OBJECT-NEXT:  }
+# INPUT-OBJECT:       The .MIPS.abiflags section has a wrong size.