[ELF] nmagic or omagic: don't allocate PT_PHDR or PF_R PT_LOAD for the !hasPhdrsCommands case

[MaskRay]

Summary

part.phdrs = script->hasPhdrsCommands() ? script->createPhdrs() : createPhdrs(part);

createPhdrs() allocates a PT_PHDR and a PF_R PT_LOAD, which will be
deleted later in LinkerScript::allocateHeaders, but leave a gap between
the program headers and the first section. Don't allocate them to avoid
the gap. PT_INTERP is likely not needed as well.

[MaskRay]

Delete variable paged

[ruiu]

LGTM

lld/trunk/ELF/Writer.cpp

std::vector<PhdrEntry *> Writer<ELFT>::createPhdrs(Partition &part) {
   auto addHdr = [&](unsigned type, unsigned flags) -> PhdrEntry * {
     ret.push_back(make<PhdrEntry>(type, flags));
     return ret.back();
   };
 
   unsigned partNo = part.getNumber();
   bool isMain = partNo == 1;
 
-  // The first phdr entry is PT_PHDR which describes the program header itself.
+  // Add the first PT_LOAD segment for regular output sections.
+  uint64_t flags = computeFlags(PF_R);
+  PhdrEntry *load = nullptr;
+
+  // nmagic or omagic output does not have PT_PHDR, PT_INTERP, or the readonly
+  // PT_LOAD.
+  if (!config->nmagic && !config->omagic) {
+    // The first phdr entry is PT_PHDR which describes the program header
+    // itself.
     if (isMain)
       addHdr(PT_PHDR, PF_R)->add(Out::programHeaders);
     else
       addHdr(PT_PHDR, PF_R)->add(part.programHeaders->getParent());
 
     // PT_INTERP must be the second entry if exists.
     if (OutputSection *cmd = findSection(".interp", partNo))
       addHdr(PT_INTERP, cmd->getPhdrFlags())->add(cmd);
 
-  // Add the first PT_LOAD segment for regular output sections.
-  uint64_t flags = computeFlags(PF_R);
-  PhdrEntry *load = nullptr;
-
     // Add the headers. We will remove them if they don't fit.
     // In the other partitions the headers are ordinary sections, so they don't
     // need to be added here.
     if (isMain) {
       load = addHdr(PT_LOAD, flags);
       load->add(Out::elfHeader);
       load->add(Out::programHeaders);
     }
+  }
 
   // PT_GNU_RELRO includes all sections that should be marked as
   // read-only by dynamic linker after proccessing relocations.
   // Current dynamic loaders only support one PT_GNU_RELRO PHDR, give
   // an error message if more than one PT_GNU_RELRO PHDR is required.
   PhdrEntry *relRo = make<PhdrEntry>(PT_GNU_RELRO, PF_R);
   bool inRelroPhdr = false;
   OutputSection *relroEnd = nullptr;

lld/trunk/test/ELF/magic-page-combo-warn.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 
 # Test that we warn when a page size is set and paging is disabled by -n or -N.
 
 # RUN: ld.lld -z max-page-size=0x10 -z common-page-size=0x10 -N %t -o %t2 2>&1 | FileCheck --check-prefix=WARN %s
 # RUN: llvm-readobj --program-headers %t2 | FileCheck --check-prefix=OMAGIC %s
 # RUN: ld.lld -z max-page-size=0x10 -z common-page-size=0x10 --omagic %t -o %t2  2>&1 | FileCheck --check-prefix=WARN %s
 # RUN: llvm-readobj --program-headers %t2 | FileCheck --check-prefix=OMAGIC %s
 
 # WARN: ld.lld: warning: -z max-page-size set, but paging disabled by omagic or nmagic
 # WARN-NEXT: ld.lld: warning: -z common-page-size set, but paging disabled by omagic or nmagic
 
 # OMAGIC:     ProgramHeader {
 # OMAGIC:      Type: PT_LOAD
-# OMAGIC-NEXT:   Offset: 0xE8
+# OMAGIC-NEXT:   Offset: 0xB0
 # OMAGIC-NEXT:   VirtualAddress:
 # OMAGIC-NEXT:   PhysicalAddress:
 # OMAGIC-NEXT:   FileSize:
 # OMAGIC-NEXT:   MemSize:
 # OMAGIC-NEXT:   Flags [
 # OMAGIC-NEXT:     PF_R
 # OMAGIC-NEXT:     PF_W
 # OMAGIC-NEXT:     PF_X
 # OMAGIC-NEXT:   ]
-# OMAGIC-NEXT:   Alignment: 8
+# OMAGIC-NEXT:   Alignment: 4
 # OMAGIC-NEXT: }
 # OMAGIC-NEXT: ProgramHeader {
 # OMAGIC-NEXT:   Type: PT_GNU_STACK
 
 # RUN: ld.lld -z max-page-size=0x10 -z common-page-size=0x10 -n %t -o %t3  2>&1 | FileCheck --check-prefix=WARN %s
 # RUN: llvm-readobj --program-headers %t3 | FileCheck --check-prefix=NMAGIC %s
 # RUN: ld.lld -z max-page-size=0x10 -z common-page-size=0x10 --nmagic %t -o %t3  2>&1 | FileCheck --check-prefix=WARN %s
 # RUN: llvm-readobj --program-headers %t3 | FileCheck --check-prefix=NMAGIC %s
 
 # NMAGIC:   ProgramHeader {
 # NMAGIC-NEXT:     Type: PT_LOAD
-# NMAGIC-NEXT:     Offset: 0x158
+# NMAGIC-NEXT:     Offset: 0x120
 # NMAGIC-NEXT:     VirtualAddress:
 # NMAGIC-NEXT:     PhysicalAddress:
 # NMAGIC-NEXT:     FileSize: 1
 # NMAGIC-NEXT:     MemSize: 1
 # NMAGIC-NEXT:     Flags [
 # NMAGIC-NEXT:       PF_R
 # NMAGIC-NEXT:     ]
-# NMAGIC-NEXT:     Alignment: 8
+# NMAGIC-NEXT:     Alignment: 1
 # NMAGIC-NEXT:   }
 # NMAGIC-NEXT:   ProgramHeader {
 # NMAGIC-NEXT:     Type: PT_LOAD
-# NMAGIC-NEXT:     Offset: 0x15C
+# NMAGIC-NEXT:     Offset: 0x124
 # NMAGIC-NEXT:     VirtualAddress:
 # NMAGIC-NEXT:     PhysicalAddress:
 # NMAGIC-NEXT:     FileSize: 2
 # NMAGIC-NEXT:     MemSize: 2
 # NMAGIC-NEXT:     Flags [
 # NMAGIC-NEXT:       PF_R
 # NMAGIC-NEXT:       PF_X
 # NMAGIC-NEXT:     ]
 # NMAGIC-NEXT:     Alignment: 4
 # NMAGIC-NEXT:   }
 # NMAGIC-NEXT:   ProgramHeader {
 # NMAGIC-NEXT:     Type: PT_LOAD (0x1)
-# NMAGIC-NEXT:     Offset: 0x15E
+# NMAGIC-NEXT:     Offset: 0x126
 # NMAGIC-NEXT:     VirtualAddress:
 # NMAGIC-NEXT:     PhysicalAddress:
 # NMAGIC-NEXT:     FileSize: 1
 # NMAGIC-NEXT:     MemSize: 1
 # NMAGIC-NEXT:     Flags [
 # NMAGIC-NEXT:       PF_R
 # NMAGIC-NEXT:       PF_W
 # NMAGIC-NEXT:     ]

lld/trunk/test/ELF/nmagic.s

 # REQUIRES: x86
 # Verify that .rodata is aligned to a 8 byte boundary.
 
 # RUN: llvm-mc -filetype=obj -triple=i386 %s -o %t.o
 # RUN: ld.lld %t.o -o %t.exe -n -Ttext 0
 # RUN: llvm-readelf --section-headers %t.exe | FileCheck %s
 
 # CHECK: [ 0]           NULL     00000000 000000 000000 00      0   0  0
-# CHECK: [ 1] .text     PROGBITS 00000000 0000d4 000001 00  AX  0   0  4
-# CHECK: [ 2] .rodata   PROGBITS 00000008 0000d8 000008 00   A  0   0  8
-# CHECK: [ 3] .comment  PROGBITS 00000000 0000e0 000008 01  MS  0   0  1
-# CHECK: [ 4] .symtab   SYMTAB   00000000 0000e8 000020 10      6   1  4
-# CHECK: [ 5] .shstrtab STRTAB   00000000 000108 000032 00      0   0  1
-# CHECK: [ 6] .strtab   STRTAB   00000000 00013a 000008 00      0   0  1
+# CHECK: [ 1] .text     PROGBITS 00000000 000094 000001 00  AX  0   0  4
+# CHECK: [ 2] .rodata   PROGBITS 00000008 000098 000008 00   A  0   0  8
+# CHECK: [ 3] .comment  PROGBITS 00000000 0000a0 000008 01  MS  0   0  1
+# CHECK: [ 4] .symtab   SYMTAB   00000000 0000a8 000020 10      6   1  4
+# CHECK: [ 5] .shstrtab STRTAB   00000000 0000c8 000032 00      0   0  1
+# CHECK: [ 6] .strtab   STRTAB   00000000 0000fa 000008 00      0   0  1
 
 .globl _start
 .text
 _start:
   ret
 
 .rodata
 .align 8
 .quad 42

lld/trunk/test/ELF/relro-omagic.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/shared.s -o %t2.o
 # RUN: ld.lld -shared %t2.o -o %t2.so -soname relro-omagic.s.tmp2.so
 # RUN: ld.lld --hash-style=sysv -N %t.o -Bdynamic %t2.so -o %t
 # RUN: llvm-objdump -section-headers %t | FileCheck --check-prefix=NORELRO %s
 # RUN: llvm-readobj --program-headers %t | FileCheck --check-prefix=NOPHDRS %s
 
 # NORELRO:      Sections:
 # NORELRO-NEXT: Idx Name          Size     VMA              Type
 # NORELRO-NEXT:   0               00000000 0000000000000000
-# NORELRO-NEXT:   1 .dynsym       00000048 0000000000200120
-# NORELRO-NEXT:   2 .hash         00000020 0000000000200168
-# NORELRO-NEXT:   3 .dynstr       00000021 0000000000200188
-# NORELRO-NEXT:   4 .rela.dyn     00000018 00000000002001b0
-# NORELRO-NEXT:   5 .rela.plt     00000018 00000000002001c8
-# NORELRO-NEXT:   6 .text         0000000a 00000000002001e0 TEXT
-# NORELRO-NEXT:   7 .plt          00000020 00000000002001f0 TEXT
-# NORELRO-NEXT:   8 .data         00000008 0000000000200210 DATA
-# NORELRO-NEXT:   9 .foo          00000004 0000000000200218 DATA
-# NORELRO-NEXT:  10 .dynamic      000000f0 0000000000200220
-# NORELRO-NEXT:  11 .got          00000008 0000000000200310 DATA
-# NORELRO-NEXT:  12 .got.plt      00000020 0000000000200318 DATA
+# NORELRO-NEXT:   1 .dynsym       00000048 00000000002000e8
+# NORELRO-NEXT:   2 .hash         00000020 0000000000200130
+# NORELRO-NEXT:   3 .dynstr       00000021 0000000000200150
+# NORELRO-NEXT:   4 .rela.dyn     00000018 0000000000200178
+# NORELRO-NEXT:   5 .rela.plt     00000018 0000000000200190
+# NORELRO-NEXT:   6 .text         0000000a 00000000002001a8 TEXT
+# NORELRO-NEXT:   7 .plt          00000020 00000000002001c0 TEXT
+# NORELRO-NEXT:   8 .data         00000008 00000000002001e0 DATA
+# NORELRO-NEXT:   9 .foo          00000004 00000000002001e8 DATA
+# NORELRO-NEXT:  10 .dynamic      000000f0 00000000002001f0
+# NORELRO-NEXT:  11 .got          00000008 00000000002002e0 DATA
+# NORELRO-NEXT:  12 .got.plt      00000020 00000000002002e8 DATA
 
 # NOPHDRS:     ProgramHeaders [
 # NOPHDRS-NOT: PT_GNU_RELRO
 
 .long bar
 jmp *bar2@GOTPCREL(%rip)
 
 .section .data,"aw"
 .quad 0
 
 .section .foo,"aw"
 .zero 4

lld/trunk/test/ELF/segments.s

 
 # RUN: ld.lld -N %t -o %t3
 # RUN: llvm-readobj --program-headers %t3 | FileCheck --check-prefix=OMAGIC %s
 # RUN: ld.lld --omagic %t -o %t3
 # RUN: llvm-readobj --program-headers %t3 | FileCheck --check-prefix=OMAGIC %s
 
 # OMAGIC:     ProgramHeader {
 # OMAGIC:      Type: PT_LOAD
-# OMAGIC-NEXT:   Offset: 0xE8
+# OMAGIC-NEXT:   Offset: 0xB0
 # OMAGIC-NEXT:   VirtualAddress:
 # OMAGIC-NEXT:   PhysicalAddress:
 # OMAGIC-NEXT:   FileSize:
 # OMAGIC-NEXT:   MemSize:
 # OMAGIC-NEXT:   Flags [
 # OMAGIC-NEXT:     PF_R
 # OMAGIC-NEXT:     PF_W
 # OMAGIC-NEXT:     PF_X
 # OMAGIC-NEXT:   ]
-# OMAGIC-NEXT:   Alignment: 8
+# OMAGIC-NEXT:   Alignment: 4
 # OMAGIC-NEXT: }
 # OMAGIC-NEXT: ProgramHeader {
 # OMAGIC-NEXT:   Type: PT_GNU_STACK
 
 # RUN: ld.lld -n %t -o %t4
 # RUN: llvm-readobj --program-headers %t4 | FileCheck --check-prefix=NMAGIC %s
 # RUN: ld.lld --nmagic %t -o %t4
 # RUN: llvm-readobj --program-headers %t4 | FileCheck --check-prefix=NMAGIC %s
 
 # NMAGIC:   ProgramHeader {
 # NMAGIC-NEXT:     Type: PT_LOAD
-# NMAGIC-NEXT:     Offset: 0x158
+# NMAGIC-NEXT:     Offset: 0x120
 # NMAGIC-NEXT:     VirtualAddress:
 # NMAGIC-NEXT:     PhysicalAddress:
 # NMAGIC-NEXT:     FileSize: 1
 # NMAGIC-NEXT:     MemSize: 1
 # NMAGIC-NEXT:     Flags [
 # NMAGIC-NEXT:       PF_R
 # NMAGIC-NEXT:     ]
-# NMAGIC-NEXT:     Alignment: 8
+# NMAGIC-NEXT:     Alignment: 1
 # NMAGIC-NEXT:   }
 # NMAGIC-NEXT:   ProgramHeader {
 # NMAGIC-NEXT:     Type: PT_LOAD
-# NMAGIC-NEXT:     Offset: 0x15C
+# NMAGIC-NEXT:     Offset: 0x124
 # NMAGIC-NEXT:     VirtualAddress:
 # NMAGIC-NEXT:     PhysicalAddress:
 # NMAGIC-NEXT:     FileSize: 2
 # NMAGIC-NEXT:     MemSize: 2
 # NMAGIC-NEXT:     Flags [
 # NMAGIC-NEXT:       PF_R
 # NMAGIC-NEXT:       PF_X
 # NMAGIC-NEXT:     ]
 # NMAGIC-NEXT:     Alignment: 4
 # NMAGIC-NEXT:   }
 # NMAGIC-NEXT:   ProgramHeader {
 # NMAGIC-NEXT:     Type: PT_LOAD (0x1)
-# NMAGIC-NEXT:     Offset: 0x15E
+# NMAGIC-NEXT:     Offset: 0x126
 # NMAGIC-NEXT:     VirtualAddress:
 # NMAGIC-NEXT:     PhysicalAddress:
 # NMAGIC-NEXT:     FileSize: 1
 # NMAGIC-NEXT:     MemSize: 1
 # NMAGIC-NEXT:     Flags [
 # NMAGIC-NEXT:       PF_R
 # NMAGIC-NEXT:       PF_W
 # NMAGIC-NEXT:     ]