[llvm-objcopy] Add support for large indexes

Because of -ffunction-sections (and maybe other use cases I'm not aware of?) it
can occur that we need more than 0xfeff sections but ELF dosn't support that
many sections. To solve this problem SHN_XINDEX exists and with it come a whole
host of changes for section indexes everywhere. This change adds support for
those cases which should allow llvm-objcopy to copy binaries that have an
arbitrary number of sections.

Differential Revision: https://reviews.llvm.org/D42516

llvm-svn: 326940

llvm/test/tools/llvm-objcopy/auto-remove-shndx.test

@@ -0,0 +1,5 @@
+RUN: unzip -p %p/Inputs/many-sections.o.zip > %t
+RUN: llvm-objcopy -R=.text -R=s0 -R=s1 -R=s2 -R=s3 -R=s4 -R=s5 -R=s6 %t %t2
+RUN: llvm-readobj -sections %t2 | FileCheck --check-prefix=SECS %s
+
+SECS-NOT: Name: .symtab_shndx

llvm/test/tools/llvm-objcopy/many-sections.test

@@ -0,0 +1,53 @@
+RUN: unzip -p %p/Inputs/many-sections.o.zip > %t
+RUN: llvm-objcopy %t %t2
+RUN: llvm-readobj -file-headers %t2 | FileCheck --check-prefix=EHDR %s
+RUN: llvm-readobj -sections %t2 | FileCheck --check-prefix=SECS %s
+RUN: llvm-readobj -symbols %t2 | grep "Symbol {" | wc -l | FileCheck --check-prefix=SYMS %s
+
+EHDR:      Format: ELF64-x86-64
+EHDR-NEXT: Arch: x86_64
+EHDR-NEXT: AddressSize: 64bit
+EHDR-NEXT: LoadName:
+EHDR-NEXT: ElfHeader {
+EHDR-NEXT:   Ident {
+EHDR-NEXT:     Magic: (7F 45 4C 46)
+EHDR-NEXT:     Class: 64-bit (0x2)
+EHDR-NEXT:     DataEncoding: LittleEndian (0x1)
+EHDR-NEXT:     FileVersion: 1
+EHDR-NEXT:     OS/ABI: SystemV (0x0)
+EHDR-NEXT:     ABIVersion: 0
+EHDR-NEXT:     Unused: (00 00 00 00 00 00 00)
+EHDR-NEXT:   }
+EHDR-NEXT:   Type: Relocatable (0x1)
+EHDR-NEXT:   Machine: EM_X86_64 (0x3E)
+EHDR-NEXT:   Version: 1
+EHDR-NEXT:   Entry: 0x0
+EHDR-NEXT:   ProgramHeaderOffset: 0x40
+EHDR-NEXT:   SectionHeaderOffset:
+EHDR-NEXT:   Flags [ (0x0)
+EHDR-NEXT:   ]
+EHDR-NEXT:   HeaderSize: 64
+EHDR-NEXT:   ProgramHeaderEntrySize: 56
+EHDR-NEXT:   ProgramHeaderCount: 0
+EHDR-NEXT:   SectionHeaderEntrySize: 64
+EHDR-NEXT:   SectionHeaderCount: 0
+EHDR-NEXT:   StringTableSectionIndex: 65535
+EHDR-NEXT: }
+
+SECS: Index: 65285
+SECS-NEXT: Name: .symtab
+SECS-NEXT: Type: SHT_SYMTAB
+SECS: Name: .symtab_shndx
+SECS-NEXT: Type: SHT_SYMTAB_SHNDX
+SECS-NEXT: Flags [ (0x0)
+SECS-NEXT: ]
+SECS-NEXT: Address: 0x0
+SECS-NEXT: Offset:
+# There should be #syms * EntrySize bytes.
+SECS-NEXT: Size: 261136
+SECS-NEXT: Link: 65285
+SECS-NEXT: Info:
+SECS-NEXT: AddressAlignment: 4
+SECS-NEXT: EntrySize: 4
+SECS: Index: 65287
+SYMS: 65284

llvm/test/tools/llvm-objcopy/remove-shndx.test

@@ -0,0 +1,6 @@
+RUN: unzip -p %p/Inputs/many-sections.o.zip > %t
+RUN: llvm-objcopy -R=.symtab_shndxr %t %t2
+RUN: llvm-readobj -sections %t2 | FileCheck %s
+
+CHECK: Name: .symtab_shndx (
+

llvm/test/tools/llvm-objcopy/strict-no-add.test

@@ -0,0 +1,10 @@
+# This test makes sure that sections added at the end that don't have symbols
+# defined in them don't trigger the creation of a large index table.
+
+RUN: unzip -p %p/Inputs/many-sections.o.zip > %t.0
+RUN: cat %p/Inputs/alloc-symtab.o > %t
+RUN: llvm-objcopy -R=.text -R=s0 -R=s1 -R=s2 -R=s3 -R=s4 -R=s5 -R=s6 %t.0 %t2
+RUN: llvm-objcopy -add-section=.s0=%t -add-section=.s1=%t -add-section=.s2=%t %t2 %t2
+RUN: llvm-readobj -sections %t2 | FileCheck --check-prefix=SECS %s
+
+SECS-NOT: Name: .symtab_shndx