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
47 lines
1.1 KiB
ArmAsm
47 lines
1.1 KiB
ArmAsm
# REQUIRES: x86
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# LINK_ORDER cnamed sections are not kept alive by the __start_* reference.
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# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
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# RUN: ld.lld --gc-sections -z start-stop-gc -z nostart-stop-gc %t.o -o %t
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# RUN: llvm-objdump --section-headers -t %t | FileCheck %s
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## With -z start-stop-gc (default), non-SHF_LINK_ORDER C identifier name
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## sections are not retained by __start_/__stop_ references.
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# RUN: ld.lld --gc-sections %t.o -o %t
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# RUN: llvm-readelf -S -s %t | FileCheck %s --check-prefix=GC
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# RUN: ld.lld --gc-sections -z start-stop-gc %t.o -o %t1
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# RUN: llvm-readelf -S -s %t1 | FileCheck %s --check-prefix=GC
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# CHECK: Sections:
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# CHECK-NOT: yy
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# CHECK: xx {{.*}} DATA
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# CHECK-NOT: yy
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# CHECK: SYMBOL TABLE:
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# CHECK: xx 0000000000000000 .protected __start_xx
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# CHECK: w *UND* 0000000000000000 __start_yy
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# GC: Section Headers:
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# GC-NOT: xx
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# GC-NOT: yy
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# GC: WEAK DEFAULT UND __start_xx
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# GC: WEAK DEFAULT UND __start_yy
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.weak __start_xx
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.weak __start_yy
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.global _start
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_start:
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.quad __start_xx
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.quad __start_yy
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.section xx,"a"
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.quad 0
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.section .foo,"a"
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.quad 0
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.section yy,"ao",@progbits,.foo
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.quad 0
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