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[ELF] Keep non-alloc orphan sections at the end
https://reviews.llvm.org/D85867 changed the way we assign file offsets (alloc sections first, then non-alloc sections). It also removed a non-alloc special case from `findOrphanPos`. Looking at the memory-nonalloc-no-warn.test change, which would be needed by #93761, it makes sense to restore the previous behavior: when placing non-alloc orphan sections, keep these sections at the end so that the section index order matches the file offset order. This change is cosmetic. In sections-nonalloc.s, GNU ld places the orphan `other3` in the middle and the orphan .symtab/.shstrtab/.strtab at the end. Pull Request: #94519
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4 files changed

+31
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‎lld/ELF/Writer.cpp

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -921,7 +921,11 @@ static bool shouldSkip(SectionCommand *cmd) {
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static SmallVectorImpl<SectionCommand *>::iterator
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findOrphanPos(SmallVectorImpl<SectionCommand *>::iterator b,
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SmallVectorImpl<SectionCommand *>::iterator e) {
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// Place non-alloc orphan sections at the end. This matches how we assign file
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// offsets to non-alloc sections.
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OutputSection *sec = &cast<OutputDesc>(*e)->osec;
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if (!(sec->flags & SHF_ALLOC))
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return e;
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// As a special case, place .relro_padding before the SymbolAssignment using
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// DATA_SEGMENT_RELRO_END, if present.

‎lld/test/ELF/linkerscript/memory-nonalloc-no-warn.test

Lines changed: 11 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -16,20 +16,20 @@
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## The output file must include all sections.
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# RUN: llvm-readelf -S %t/a.elf | FileCheck %s
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19-
# CHECK: There are 12 section headers, starting at offset 0x2140:
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# CHECK: There are 12 section headers, starting at offset 0x2138:
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# CHECK: [Nr] Name Type Address Off Size ES Flg Lk Inf Al
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# CHECK-NEXT: [ 0] NULL 0000000000000000 000000 000000 00 0 0 0
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# CHECK-NEXT: [ 1] .nonalloc PROGBITS 0000000000000000 001064 001000 00 W 0 0 1
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# CHECK-NEXT: [ 2] .comment PROGBITS 0000000000000000 {{.*}} {{.*}} 01 MS 0 0 1
24-
# CHECK-NEXT: [ 3] .symtab SYMTAB 0000000000000000 {{.*}} {{.*}} 18 5 1 8
25-
# CHECK-NEXT: [ 4] .shstrtab STRTAB 0000000000000000 {{.*}} {{.*}} 00 0 0 1
26-
# CHECK-NEXT: [ 5] .strtab STRTAB 0000000000000000 {{.*}} {{.*}} 00 0 0 1
27-
# CHECK-NEXT: [ 6] .dat PROGBITS 0000000000000000 002137 000004 00 W 0 0 1
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# CHECK-NEXT: [ 7] .intvec0_out PROGBITS 0000000000000000 00213b 000000 00 W 0 0 1
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# CHECK-NEXT: [ 8] .intvec1_out PROGBITS 0000000000000000 00213b 000000 00 W 0 0 1
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# CHECK-NEXT: [ 9] .intvec2_out PROGBITS 0000000000000000 00213b 000000 00 W 0 0 1
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# CHECK-NEXT: [10] .intvec3_out PROGBITS 00000000803fe060 001060 000004 00 AX 0 0 1
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# CHECK-NEXT: [11] .text PROGBITS 00000000803fe064 001064 000000 00 AX 0 0 4
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# CHECK-NEXT: [ 2] .dat PROGBITS 0000000000000000 002064 000004 00 W 0 0 1
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# CHECK-NEXT: [ 3] .intvec0_out PROGBITS 0000000000000000 002068 000000 00 W 0 0 1
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# CHECK-NEXT: [ 4] .intvec1_out PROGBITS 0000000000000000 002068 000000 00 W 0 0 1
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# CHECK-NEXT: [ 5] .intvec2_out PROGBITS 0000000000000000 002068 000000 00 W 0 0 1
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# CHECK-NEXT: [ 6] .intvec3_out PROGBITS 00000000803fe060 001060 000004 00 AX 0 0 1
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# CHECK-NEXT: [ 7] .text PROGBITS 00000000803fe064 001064 000000 00 AX 0 0 4
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# CHECK-NEXT: [ 8] .comment PROGBITS 0000000000000000 {{.*}} {{.*}} 01 MS 0 0 1
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# CHECK-NEXT: [ 9] .symtab SYMTAB 0000000000000000 {{.*}} {{.*}} 18 11 1 8
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# CHECK-NEXT: [10] .shstrtab STRTAB 0000000000000000 {{.*}} {{.*}} 00 0 0 1
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# CHECK-NEXT: [11] .strtab STRTAB 0000000000000000 {{.*}} {{.*}} 00 0 0 1
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#--- a.s

‎lld/test/ELF/linkerscript/sections-nonalloc.s

Lines changed: 14 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -16,15 +16,15 @@
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# CHECK-NEXT: [ 2] data1 PROGBITS 0000000000000001 001001 000001 00 WA 0
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# CHECK-NEXT: [ 3] other1 PROGBITS 0000000000000000 001008 000001 00 0
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# CHECK-NEXT: [ 4] other2 PROGBITS 0000000000000000 001010 000001 00 0
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## Orphan placement places other3, .symtab, .shstrtab and .strtab after other2.
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# CHECK-NEXT: [ 5] other3 PROGBITS 0000000000000000 001020 000001 00 0
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# CHECK-NEXT: [ 6] .symtab SYMTAB 0000000000000000 001028 000030 18 8
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# CHECK-NEXT: [ 7] .shstrtab STRTAB 0000000000000000 001058 00004d 00 0
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# CHECK-NEXT: [ 8] .strtab STRTAB 0000000000000000 0010a5 000008 00 0
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# CHECK-NEXT: [ 9] data2 PROGBITS 0000000000000002 001002 000001 00 WA 0
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# CHECK-NEXT: [ 5] data2 PROGBITS 0000000000000002 001002 000001 00 WA 0
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## max{sortRank(data1),sortRank(data2)} <= sortRank(data3). data3 is placed after the latter.
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# CHECK-NEXT: [10] data3 PROGBITS 0000000000000003 001003 000001 00 WA 0
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# CHECK-NEXT: [11] .text PROGBITS 0000000000000004 001004 000001 00 AX 0
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# CHECK-NEXT: [ 6] data3 PROGBITS 0000000000000003 001003 000001 00 WA 0
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# CHECK-NEXT: [ 7] .text PROGBITS 0000000000000004 001004 000001 00 AX 0
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## Non-alloc orphan sections other3, .symtab, .shstrtab and .strtab are placed at the end.
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# CHECK-NEXT: [ 8] other3 PROGBITS 0000000000000000 001020 000001 00 0
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# CHECK-NEXT: [ 9] .symtab SYMTAB 0000000000000000 001028 000030 18 11
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# CHECK-NEXT: [10] .shstrtab STRTAB 0000000000000000 001058 00004d 00 0
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# CHECK-NEXT: [11] .strtab STRTAB 0000000000000000 0010a5 000008 00 0
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# CHECK: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
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# CHECK-NEXT: LOAD 0x001000 0x0000000000000000 0x0000000000000000 0x000004 0x000004 RW 0x1000
@@ -41,12 +41,12 @@
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# CHECK1-NEXT: [ 3] data1 PROGBITS 00000000000000b2 0000b2 000001 00 WA 0
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# CHECK1-NEXT: [ 4] other1 PROGBITS 0000000000000000 0000b8 000001 00 0
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# CHECK1-NEXT: [ 5] other2 PROGBITS 0000000000000000 0000c0 000001 00 0
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# CHECK1-NEXT: [ 6] other3 PROGBITS 0000000000000000 0000d0 000001 00 0
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# CHECK1-NEXT: [ 7] .symtab SYMTAB 0000000000000000 0000d8 000030 18 9
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# CHECK1-NEXT: [ 8] .shstrtab STRTAB 0000000000000000 000108 00004d 00 0
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# CHECK1-NEXT: [ 9] .strtab STRTAB 0000000000000000 000155 000008 00 0
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# CHECK1-NEXT: [10] data2 PROGBITS 00000000000000b3 0000b3 000001 00 WA 0
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# CHECK1-NEXT: [11] data3 PROGBITS 00000000000000b4 0000b4 000001 00 WA 0
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# CHECK1-NEXT: [ 6] data2 PROGBITS 00000000000000b3 0000b3 000001 00 WA 0
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# CHECK1-NEXT: [ 7] data3 PROGBITS 00000000000000b4 0000b4 000001 00 WA 0
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# CHECK1-NEXT: [ 8] other3 PROGBITS 0000000000000000 0000d0 000001 00 0
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# CHECK1-NEXT: [ 9] .symtab SYMTAB 0000000000000000 0000d8 000030 18 11
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# CHECK1-NEXT: [10] .shstrtab STRTAB 0000000000000000 000108 00004d 00 0
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# CHECK1-NEXT: [11] .strtab STRTAB 0000000000000000 000155 000008 00 0
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# CHECK1: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
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# CHECK1-NEXT: LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x0000b5 0x0000b5 RWE 0x1000
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# CHECK1-NEXT: 0x60000000 0x0000b8 0x0000000000000000 0x0000000000000000 0x000009 0x000001 0x8

‎lld/test/ELF/linkerscript/sections.s

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Original file line numberDiff line numberDiff line change
@@ -79,8 +79,8 @@
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# SEP-BY-NONALLOC: [ 1] .text PROGBITS 0000000000000000 001000 00000e 00 AX
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# SEP-BY-NONALLOC-NEXT: [ 2] .data PROGBITS 000000000000000e 00100e 000020 00 WA
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# SEP-BY-NONALLOC-NEXT: [ 3] .comment PROGBITS 0000000000000000 001031 000008 01 MS
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# SEP-BY-NONALLOC: [ 7] other PROGBITS 000000000000002e 00102e 000003 00 WA
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# SEP-BY-NONALLOC-NEXT: [ 8] .bss NOBITS 0000000000000031 001031 000002 00 WA
82+
# SEP-BY-NONALLOC: [ 4] other PROGBITS 000000000000002e 00102e 000003 00 WA
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# SEP-BY-NONALLOC-NEXT: [ 5] .bss NOBITS 0000000000000031 001031 000002 00 WA
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8585
# SEP-BY-NONALLOC: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
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# SEP-BY-NONALLOC-NEXT: LOAD 0x001000 0x0000000000000000 0x0000000000000000 0x00000e 0x00000e R E 0x1000

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