Add OUTPUT_FORMAT linker script directive support.

[ruiu]

Summary

This patch adds a support for OUTPUT_FORMAT linker script directive.
Since I'm not 100% confident with BFD names you can use in the directive
for all architectures, I added only a few in this patch. We can add
other names for other archtiectures later.

We still do not support triple-style OUTPUT_FORMAT directive, namely,
OUTPUT_FORMAT(bfdname, big, little). If you pass -EL (little endian)
or -EB (big endian) to the linker, GNU linkers pick up big or little
as a BFD name, correspondingly, so that you can use a single linker
script for bi-endian processor. I'm not sure if we really need to
support that, so I'll leave it alone for now.

Note that -m takes precedence over OUTPUT_FORAMT, but we always parse
a BFD name given to OUTPUT_FORMAT for error checking. You cannot write
an invalid name in the OUTPUT_FORMAT directive.

[grimar]

lld/ELF/ScriptParser.cpp

97

It was confusing naming for me. Was not clear what is "bfd name".
Maybe readBfdArch or readBfdArchName?

394

An observation: bfd code contains both elf64-littleaarch64-cloudabi and elf64-littleaarch64 for example.
Should S == in this function be changed to S.startsWith maybe?

410

So I think this means LLD will error out when seeing the object file with incompatible architecture after parsing the script containing OUTPUT_FORMAT. Behavior is fine, but I think there is no test provided for that case?

lld/test/ELF/linkerscript/output-format.s

5

This tested we are ignoring the big and little parameters. I think the test was useful. Should it be moved to emulation.s?

[ruiu]

lld/ELF/ScriptParser.cpp

97

It seems "BFD name" is an established technical term. You can find "BFD name" in the BFD ld man page.

394

I'd like to address that in another patch, because I don't know what exactly we should do for these BFD names with extensions at the moment.

410

I don't think we need that test case.

lld/test/ELF/linkerscript/output-format.s

5

I don't think so -- I'm not too worried about them.

[grimar]

lld/ELF/ScriptParser.cpp

410

Then you should be able to simplify to

std::tie(Config->EKind, Config->EMachine) = readBfdName();

[ruiu]

lld/ELF/ScriptParser.cpp

410

I'm not too picky about aiming 100% test coverage, and I meant that we don't need a test case for that in that sense. I'll add a test for you but we don't need to test for all possible combinations of conditions.

[ruiu]

• add a test case

[grimar]

LGTM.

lld/ELF/ScriptParser.cpp

410

I meant the following scenario:

If we have file1_386.o (i386), script saying OUTPUT_FORMAT("elf64-x86-64") and file2_x64.o (x64).
And invocation: lld file1_386.o -script script.file file2_x64.o

Then having the if (Config->EKind == ELFNoneKind) line here allows us to the incompatible
architectures error properly. That what I suggested to test initially.

It's also a bit strange that we will accept
lld file1_386.o -script script.file
but will fail on
lld -script script.file file1_386.o

We could have a test explaining the behavior too.

Though I think it is acceptable for now. Let's go as is then.

lld/test/ELF/invalid-linkerscript.test

53

I agree that is not useful. See my comment.

[grimar]

lld/ELF/ScriptParser.cpp

410

allows us to the incompatible -> allows us to report the incompatible

lld/ELF/ScriptParser.cpp

private:
   InputSectionDescription *readInputSectionDescription(StringRef Tok);
   StringMatcher readFilePatterns();
   std::vector<SectionPattern> readInputSectionsList();
   InputSectionDescription *readInputSectionRules(StringRef FilePattern);
   unsigned readPhdrType();
   SortSectionPolicy readSortKind();
   SymbolAssignment *readProvideHidden(bool Provide, bool Hidden);
   SymbolAssignment *readAssignment(StringRef Tok);
+  std::pair<ELFKind, uint16_t> readBfdName();
   void readSort();
   Expr readAssert();
   Expr readConstant();
   Expr getPageSize();
 
   uint64_t readMemoryAssignment(StringRef, StringRef, StringRef);
   std::pair<uint32_t, uint32_t> readMemoryAttributes();
 

 
 void ScriptParser::readOutputArch() {
   // OUTPUT_ARCH is ignored for now.
   expect("(");
   while (!errorCount() && !consume(")"))
     skip();
 }
 
+std::pair<ELFKind, uint16_t> ScriptParser::readBfdName() {
+  StringRef S = next();
+  if (S == "elf32-i386")
+    return {ELF32LEKind, EM_386};
+  if (S == "elf32-iamcu")
+    return {ELF32LEKind, EM_IAMCU};
+  if (S == "elf32-x86-64")
+    return {ELF32LEKind, EM_X86_64};
+  if (S == "elf64-littleaarch64")
+    return {ELF64LEKind, EM_AARCH64};
+  if (S == "elf64-x86-64")
+    return {ELF64LEKind, EM_X86_64};
+
+  setError("unknown output format name: " + S);
+  return {ELFNoneKind, EM_NONE};
+}
+
+// Parse OUTPUT_FORMAT(bfdname) or OUTPUT_FORMAT(bfdname, big, little).
+// Currently we ignore big and little parameters.
 void ScriptParser::readOutputFormat() {
-  // Error checking only for now.
   expect("(");
-  skip();
+
+  std::pair<ELFKind, uint16_t> BfdName = readBfdName();
+  if (Config->EKind == ELFNoneKind)
+    std::tie(Config->EKind, Config->EMachine) = BfdName;
+
   if (consume(")"))
     return;
   expect(",");
   skip();
   expect(",");
   skip();
   expect(")");
 }

lld/test/ELF/emulation.s

 # AMD64-NEXT:   StringTableSectionIndex:
 # AMD64-NEXT: }
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %tx64
 # RUN: ld.lld -m elf_x86_64 %tx64 -o %t2x64
 # RUN: llvm-readobj -file-headers %t2x64 | FileCheck --check-prefix=X86-64 %s
 # RUN: ld.lld %tx64 -o %t3x64
 # RUN: llvm-readobj -file-headers %t3x64 | FileCheck --check-prefix=X86-64 %s
+# RUN: echo 'OUTPUT_FORMAT(elf64-x86-64)' > %t4x64.script
+# RUN: ld.lld %t4x64.script %tx64 -o %t4x64
+# RUN: llvm-readobj -file-headers %t4x64 | FileCheck --check-prefix=X86-64 %s
 # X86-64:      ElfHeader {
 # X86-64-NEXT:   Ident {
 # X86-64-NEXT:     Magic: (7F 45 4C 46)
 # X86-64-NEXT:     Class: 64-bit (0x2)
 # X86-64-NEXT:     DataEncoding: LittleEndian (0x1)
 # X86-64-NEXT:     FileVersion: 1
 # X86-64-NEXT:     OS/ABI: SystemV (0x0)
 # X86-64-NEXT:     ABIVersion: 0

 # X86-64-NEXT:   StringTableSectionIndex:
 # X86-64-NEXT: }
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux-gnux32 %s -o %tx32
 # RUN: ld.lld -m elf32_x86_64 %tx32 -o %t2x32
 # RUN: llvm-readobj -file-headers %t2x32 | FileCheck --check-prefix=X32 %s
 # RUN: ld.lld %tx32 -o %t3x32
 # RUN: llvm-readobj -file-headers %t3x32 | FileCheck --check-prefix=X32 %s
+# RUN: echo 'OUTPUT_FORMAT(elf32-x86-64)' > %t4x32.script
+# RUN: ld.lld %t4x32.script %tx32 -o %t4x32
+# RUN: llvm-readobj -file-headers %t4x32 | FileCheck --check-prefix=X32 %s
 # X32:      ElfHeader {
 # X32-NEXT:   Ident {
 # X32-NEXT:     Magic: (7F 45 4C 46)
 # X32-NEXT:     Class: 32-bit (0x1)
 # X32-NEXT:     DataEncoding: LittleEndian (0x1)
 # X32-NEXT:     FileVersion: 1
 # X32-NEXT:     OS/ABI: SystemV (0x0)
 # X32-NEXT:     ABIVersion: 0

 # X32-NEXT:   StringTableSectionIndex:
 # X32-NEXT: }
 
 # RUN: llvm-mc -filetype=obj -triple=i686-unknown-linux %s -o %tx86
 # RUN: ld.lld -m elf_i386 %tx86 -o %t2x86
 # RUN: llvm-readobj -file-headers %t2x86 | FileCheck --check-prefix=X86 %s
 # RUN: ld.lld %tx86 -o %t3x86
 # RUN: llvm-readobj -file-headers %t3x86 | FileCheck --check-prefix=X86 %s
+# RUN: echo 'OUTPUT_FORMAT(elf32-i386)' > %t4x86.script
+# RUN: ld.lld %t4x86.script %tx86 -o %t4x86
+# RUN: llvm-readobj -file-headers %t4x86 | FileCheck --check-prefix=X86 %s
 # X86:      ElfHeader {
 # X86-NEXT:   Ident {
 # X86-NEXT:     Magic: (7F 45 4C 46)
 # X86-NEXT:     Class: 32-bit (0x1)
 # X86-NEXT:     DataEncoding: LittleEndian (0x1)
 # X86-NEXT:     FileVersion: 1
 # X86-NEXT:     OS/ABI: SystemV (0x0)
 # X86-NEXT:     ABIVersion: 0

 # X86FBSD-NEXT:   StringTableSectionIndex:
 # X86FBSD-NEXT: }
 
 # RUN: llvm-mc -filetype=obj -triple=i586-intel-elfiamcu %s -o %tiamcu
 # RUN: ld.lld -m elf_iamcu %tiamcu -o %t2iamcu
 # RUN: llvm-readobj -file-headers %t2iamcu | FileCheck --check-prefix=IAMCU %s
 # RUN: ld.lld %tiamcu -o %t3iamcu
 # RUN: llvm-readobj -file-headers %t3iamcu | FileCheck --check-prefix=IAMCU %s
+# RUN: echo 'OUTPUT_FORMAT(elf32-iamcu)' > %t4iamcu.script
+# RUN: ld.lld %t4iamcu.script %tiamcu -o %t4iamcu
+# RUN: llvm-readobj -file-headers %t4iamcu | FileCheck --check-prefix=IAMCU %s
 # IAMCU:      ElfHeader {
 # IAMCU-NEXT:   Ident {
 # IAMCU-NEXT:     Magic: (7F 45 4C 46)
 # IAMCU-NEXT:     Class: 32-bit (0x1)
 # IAMCU-NEXT:     DataEncoding: LittleEndian (0x1)
 # IAMCU-NEXT:     FileVersion: 1
 # IAMCU-NEXT:     OS/ABI: SystemV (0x0)
 # IAMCU-NEXT:     ABIVersion: 0

 # RUN: ld.lld -m aarch64linux %taarch64 -o %t2aarch64
 # RUN: llvm-readobj -file-headers %t2aarch64 | FileCheck --check-prefix=AARCH64 %s
 # RUN: ld.lld -m aarch64elf %taarch64 -o %t3aarch64
 # RUN: llvm-readobj -file-headers %t3aarch64 | FileCheck --check-prefix=AARCH64 %s
 # RUN: ld.lld -m aarch64_elf64_le_vec %taarch64 -o %t4aarch64
 # RUN: llvm-readobj -file-headers %t4aarch64 | FileCheck --check-prefix=AARCH64 %s
 # RUN: ld.lld %taarch64 -o %t5aarch64
 # RUN: llvm-readobj -file-headers %t5aarch64 | FileCheck --check-prefix=AARCH64 %s
+# RUN: echo 'OUTPUT_FORMAT(elf64-littleaarch64)' > %t4aarch64.script
+# RUN: ld.lld %t4aarch64.script %taarch64 -o %t4aarch64
+# RUN: llvm-readobj -file-headers %t4aarch64 | FileCheck --check-prefix=AARCH64 %s
 # AARCH64:      ElfHeader {
 # AARCH64-NEXT:   Ident {
 # AARCH64-NEXT:     Magic: (7F 45 4C 46)
 # AARCH64-NEXT:     Class: 64-bit (0x2)
 # AARCH64-NEXT:     DataEncoding: LittleEndian (0x1)
 # AARCH64-NEXT:     FileVersion: 1
 # AARCH64-NEXT:     OS/ABI: SystemV (0x0)
 # AARCH64-NEXT:     ABIVersion: 0

lld/test/ELF/invalid-linkerscript.test

 
 # RUN: echo "INCLUDE /no/such/file" > %t7
 # RUN: not ld.lld %t7 no-such-file 2>&1 | FileCheck -check-prefix=ERR7 %s
 # ERR7: cannot find linker script /no/such/file
 # ERR7: cannot open no-such-file:
 
 # RUN: echo "OUTPUT_FORMAT(x y z)" > %t8
 # RUN: not ld.lld %t8 no-such-file 2>&1 | FileCheck -check-prefix=ERR8 %s
-# ERR8: , expected, but got y
+# RUN: not ld.lld -m elf_amd64 %t8 no-such-file 2>&1 | FileCheck -check-prefix=ERR8 %s
+# ERR8: unknown output format name: x
 # ERR8: cannot open no-such-file:
+
+# RUN: echo "OUTPUT_FORMAT(elf64-x86-64 y z)" > %t9
+# RUN: not ld.lld %t9 no-such-file 2>&1 | FileCheck -check-prefix=ERR9 %s
+# ERR9: , expected, but got y
+# ERR9: cannot open no-such-file:

lld/test/ELF/linkerscript/output-format.s

-# REQUIRES: x86
-# RUN: echo "OUTPUT_FORMAT(x, y, z)" > %t.script
-# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-freebsd %s -o %t1
-# RUN: ld.lld -shared -o %t2 %t1 %t.script
-# RUN: llvm-readobj %t2 > /dev/null
-
-# RUN: echo "OUTPUT_FORMAT(x, y)" > %t.script
-# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-freebsd %s -o %t1
-# RUN: not ld.lld -shared -o %t2 %t1 %t.script