ec29538af2
* GNU ld places non-SHF_ALLOC sections after SHF_ALLOC sections. This has the advantage that the file offsets of a non-SHF_ALLOC cannot be contained in a PT_LOAD. This patch matches the behavior. * For non-SHF_ALLOC non-orphan sections, GNU ld may assign non-zero sh_addr and treat them similar to SHT_NOBITS (not advance location counter). This is an alternative approach to what we have done in D85100. By placing non-SHF_ALLOC sections at the end, we can drop special cases in createSection and findOrphanPos added by D85100. Different from GNU ld, we set sh_addr to 0 for non-SHF_ALLOC sections. 0 arguably is better because non-SHF_ALLOC sections don't appear in the memory image. ELF spec says: > sh_addr - If the section will appear in the memory image of a process, this > member gives the address at which the section's first byte should > reside. Otherwise, the member contains 0. D85100 appeared to take a detour. If we take a combined view on D85100 and this patch, the overall complexity slightly increases (one more 3-line loop) and compatibility with GNU ld improves. The behavior we don't want to match is the special treatment of .symtab .shstrtab .strtab: they can be matched in LLD but not in GNU ld. Reviewed By: jhenderson, psmith Differential Revision: https://reviews.llvm.org/D85867
91 lines
4.2 KiB
ArmAsm
91 lines
4.2 KiB
ArmAsm
# REQUIRES: x86
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# RUN: split-file %s %t
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# RUN: llvm-mc -filetype=obj -triple=x86_64 %t/main.s -o %t.o
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## Non-SHF_ALLOC sections are placed after all SHF_ALLOC sections. They will
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## thus not be contained in a PT_LOAD segment. data2 has a PT_LOAD segment,
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## even if it is preceded by a non-SHF_ALLOC section. Non-SHF_ALLOC orphan
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## sections have zero addresses.
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## NOTE: GNU ld assigns non-zero addresses to non-SHF_ALLOC non-orphan sections.
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# RUN: ld.lld -T %t/a.lds %t.o -o %ta
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# RUN: llvm-readelf -S -l %ta | FileCheck %s
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# CHECK: [Nr] Name Type Address Off Size ES Flg Lk
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# CHECK-NEXT: [ 0] NULL 0000000000000000 000000 000000 00 0
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# CHECK-NEXT: [ 1] .bss NOBITS 0000000000000000 001000 000001 00 WA 0
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# CHECK-NEXT: [ 2] data1 PROGBITS 0000000000000001 001001 000001 00 WA 0
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# CHECK-NEXT: [ 3] data3 PROGBITS 0000000000000002 001002 000001 00 WA 0
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# CHECK-NEXT: [ 4] other1 PROGBITS 0000000000000000 001008 000001 00 0
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# CHECK-NEXT: [ 5] 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: [ 6] other3 PROGBITS 0000000000000000 001020 000001 00 0
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# CHECK-NEXT: [ 7] .symtab SYMTAB 0000000000000000 001028 000030 18 9
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# CHECK-NEXT: [ 8] .shstrtab STRTAB 0000000000000000 001058 00004d 00 0
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# CHECK-NEXT: [ 9] .strtab STRTAB 0000000000000000 0010a5 000008 00 0
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# CHECK-NEXT: [10] data2 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: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
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# CHECK-NEXT: LOAD 0x001000 0x0000000000000000 0x0000000000000000 0x000004 0x000004 RW 0x1000
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# CHECK-NEXT: LOAD 0x001004 0x0000000000000004 0x0000000000000004 0x000001 0x000001 R E 0x1000
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# CHECK-NEXT: GNU_STACK 0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 RW 0
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# RUN: ld.lld -T %t/b.lds %t.o -o %tb
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# RUN: llvm-readelf -S -l %tb | FileCheck %s --check-prefix=CHECK1
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# CHECK1: [Nr] Name Type Address Off Size ES Flg Lk
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# CHECK1-NEXT: [ 0] NULL 0000000000000000 000000 000000 00 0
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# CHECK1-NEXT: [ 1] .text PROGBITS 00000000000000b0 0000b0 000001 00 AX 0
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# CHECK1-NEXT: [ 2] .bss NOBITS 00000000000000b1 0000b1 000001 00 WA 0
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# CHECK1-NEXT: [ 3] data1 PROGBITS 00000000000000b2 0000b2 000001 00 WA 0
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# CHECK1-NEXT: [ 4] data3 PROGBITS 00000000000000b3 0000b3 000001 00 WA 0
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# CHECK1-NEXT: [ 5] other1 PROGBITS 0000000000000000 0000b8 000001 00 0
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# CHECK1-NEXT: [ 6] other2 PROGBITS 0000000000000000 0000c0 000001 00 0
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# CHECK1-NEXT: [ 7] other3 PROGBITS 0000000000000000 0000d0 000001 00 0
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# CHECK1-NEXT: [ 8] .symtab SYMTAB 0000000000000000 0000d8 000030 18 10
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# CHECK1-NEXT: [ 9] .shstrtab STRTAB 0000000000000000 000108 00004d 00 0
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# CHECK1-NEXT: [10] .strtab STRTAB 0000000000000000 000155 000008 00 0
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# CHECK1-NEXT: [11] data2 PROGBITS 00000000000000b4 0000b4 000001 00 WA 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
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#--- a.lds
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SECTIONS {
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.bss : { *(.bss) }
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data1 : { *(data1) }
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other1 : { *(other1) }
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other2 : { *(other2) }
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data2 : { *(data2) }
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.text : { *(.text) }
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/DISCARD/ : { *(.comment) }
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}
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#--- b.lds
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PHDRS {
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text PT_LOAD FILEHDR PHDRS;
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foo 0x60000000 FLAGS (0);
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}
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SECTIONS {
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. = SIZEOF_HEADERS;
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.text : { *(.text) } : text
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.bss : { *(.bss) } : text
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data1 : { *(data1) } : text
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other1 : { *(other1) } : foo
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other2 : { *(other2) } : foo
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data2 : { *(data1) } : text
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/DISCARD/ : { *(.comment) }
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}
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#--- main.s
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.globl _start
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_start: nop
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.section data1,"aw"; .byte 0
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.section data2,"aw"; .byte 0
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.section data3,"aw"; .byte 0
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.bss; .byte 0
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.section other1; .p2align 2; .byte 0
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.section other2; .p2align 3; .byte 0
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.section other3; .p2align 4; .byte 0
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