6d2d3bd0a6
Change the default to facilitate GC for metadata section usage, so that they don't need SHF_LINK_ORDER or SHF_GROUP just to drop the unhelpful rule (if they want to be unconditionally retained, use SHF_GNU_RETAIN (`__attribute__((retain))`) or linker script `KEEP`). The dropped SHF_GROUP special case makes the behavior of -z start-stop-gc and -z nostart-stop-gc closer to GNU ld>=2.37 (https://sourceware.org/PR27451). However, we default to -z start-stop-gc (which actually matches more closely to GNU ld before 2015-10 https://sourceware.org/PR19167), which is different from modern GNU ld (which has the unhelpful rule to work around glibc). As a compensation, we special case `__libc_` sections as a workaround for glibc<2.34 (https://sourceware.org/PR27492). Since -z start-stop-gc as the default actually matches the traditional GNU ld behavior, there isn't much to be aware of. There was a systemd usage which has been fixed by https://github.com/systemd/systemd/pull/19144
81 lines
2.6 KiB
ArmAsm
81 lines
2.6 KiB
ArmAsm
# REQUIRES: x86
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## Test -r --gc-sections.
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# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
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## By default all regular sections are discarded. We currently don't track
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## usage of group signature symbols and will retain them and their associated
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## STT_SECTION symbols.
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# RUN: ld.lld -r --gc-sections --print-gc-sections %t.o -o %t
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# RUN: llvm-readelf -S -s %t | FileCheck %s
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# CHECK: [ 1] .group
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# CHECK-NEXT: [ 2] .note.GNU-stack
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# CHECK: Symbol table '.symtab' contains 3 entries:
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# CHECK-NEXT: Num:
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# CHECK-NEXT: 0:
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# CHECK-NEXT: 1: {{.*}} NOTYPE LOCAL DEFAULT 1 group
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# CHECK-NEXT: 2: {{.*}} SECTION LOCAL DEFAULT 1
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## -u keeps .text.bar alive. Other group members are kept alive as well.
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# RUN: ld.lld -r --gc-sections -u bar %t.o -o - | llvm-readelf -Ss - | \
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# RUN: FileCheck %s --check-prefix=KEEP_GROUP
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## -e, --init and --fini are similar.
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# RUN: ld.lld -r --gc-sections -e bar %t.o -o - | llvm-readelf -Ss - | \
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# RUN: FileCheck %s --check-prefix=KEEP_GROUP
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# RUN: ld.lld -r --gc-sections --init=bar %t.o -o - | llvm-readelf -Ss - | \
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# RUN: FileCheck %s --check-prefix=KEEP_GROUP
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# RUN: ld.lld -r --gc-sections --fini=bar %t.o -o - | llvm-readelf -Ss - | \
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# RUN: FileCheck %s --check-prefix=KEEP_GROUP
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# KEEP_GROUP: [ 1] .group
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# KEEP_GROUP-NEXT: [ 2] .text.bar
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# KEEP_GROUP-NEXT: [ 3] .text.foo
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# KEEP_GROUP-NEXT: [ 4] .note.GNU-stack
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# KEEP_GROUP: Symbol table '.symtab' contains 7 entries:
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# KEEP_GROUP: 4: {{.*}} SECTION
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# KEEP_GROUP-NEXT: 5: {{.*}} 2 bar
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# KEEP_GROUP-NEXT: 6: {{.*}} 3 foo
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## If .text is retained, its referenced qux and .fred are retained as well.
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## fred_und is used (by .fred) and thus emitted.
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## Note, GNU ld does not retain qux.
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# RUN: ld.lld -r --gc-sections -z nostart-stop-gc -e _start %t.o -o %tstart.ro
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# RUN: llvm-readelf -Ss %tstart.ro | FileCheck %s --check-prefix=KEEP_START
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# KEEP_START: [ 1] .text
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# KEEP_START-NEXT: [ 2] .rela.text
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# KEEP_START-NEXT: [ 3] qux
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# KEEP_START-NEXT: [ 4] .group
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# KEEP_START-NEXT: [ 5] .fred
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# KEEP_START-NEXT: [ 6] .rela.fred
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# KEEP_START-NEXT: [ 7] .note.GNU-stack
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# KEEP_START: Symbol table '.symtab' contains 10 entries:
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# KEEP_START: 5: {{.*}} SECTION
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# KEEP_START-NEXT: 6: {{.*}} 1 _start
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# KEEP_START-NEXT: 7: {{.*}} 5 fred
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# KEEP_START-NEXT: 8: {{.*}} UND __start_qux
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# KEEP_START-NEXT: 9: {{.*}} UND fred_und
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.section qux,"a",@progbits
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.byte 0
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.text
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.globl _start, bar, foo, fred
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_start:
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call fred
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.quad __start_qux
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.section .text.bar,"axG",@progbits,group,comdat
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bar:
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.byte 1
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.section .text.foo,"axG",@progbits,group,comdat
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foo:
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.byte 2
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.section .fred,"ax",@progbits
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fred:
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call fred_und
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