5a58e98c20
Close #57618: currently we align the end of PT_GNU_RELRO to a common-page-size boundary, but do not align the end of the associated PT_LOAD. This is benign when runtime_page_size >= common-page-size. However, when runtime_page_size < common-page-size, it is possible that `alignUp(end(PT_LOAD), page_size) < alignDown(end(PT_GNU_RELRO), page_size)`. In this case, rtld's mprotect call for PT_GNU_RELRO will apply to unmapped regions and lead to an error, e.g. ``` error while loading shared libraries: cannot apply additional memory protection after relocation: Cannot allocate memory ``` To fix the issue, add a padding section .relro_padding like mold, which is contained in the PT_GNU_RELRO segment and the associated PT_LOAD segment. The section also prevents strip from corrupting PT_LOAD program headers. .relro_padding has the largest `sortRank` among RELRO sections. Therefore, it is naturally placed at the end of `PT_GNU_RELRO` segment in the absence of `PHDRS`/`SECTIONS` commands. In the presence of `SECTIONS` commands, we place .relro_padding immediately before a symbol assignment using DATA_SEGMENT_RELRO_END (see also https://reviews.llvm.org/D124656), if present. DATA_SEGMENT_RELRO_END is changed to align to max-page-size instead of common-page-size. Some edge cases worth mentioning: * ppc64-toc-addis-nop.s: when PHDRS is present, do not append .relro_padding * avoid-empty-program-headers.s: when the only RELRO section is .tbss, it is not part of PT_LOAD segment, therefore we do not append .relro_padding. --- Close #65002: GNU ld from 2.39 onwards aligns the end of PT_GNU_RELRO to a max-page-size boundary (https://sourceware.org/PR28824) so that the last page is protected even if runtime_page_size > common-page-size. In my opinion, losing protection for the last page when the runtime page size is larger than common-page-size is not really an issue. Double mapping a page of up to max-common-page for the protection could cause undesired VM waste. Internally we had users complaining about 2MiB max-page-size applying to shared objects. Therefore, the end of .relro_padding is padded to a common-page-size boundary. Users who are really anxious can set common-page-size to match their runtime page size. --- 17 tests need updating as there are lots of change detectors.
53 lines
1.2 KiB
ArmAsm
53 lines
1.2 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/1.s -o %t/1.o
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# RUN: llvm-mc -filetype=obj -triple=x86_64 %t/2.s -o %t/2.o
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# RUN: llvm-mc -filetype=obj -triple=x86_64 %t/3.s -o %t/3.o
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# RUN: ld.lld -shared -soname=3 --version-script=%t/3.ver %t/3.o -o %t/3.so
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# RUN: ld.lld -Map=%t/1.map %t/1.o %t/2.o %t/3.so -o %t/1
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# RUN: FileCheck %s --input-file=%t/1.map
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## Both TUs reference func/copy which need a canonical PLT entry/copy relocation.
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## Test we print func/copy just once.
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# CHECK: {{ }}.plt
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# CHECK-NEXT: <internal>:(.plt)
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# CHECK-NEXT: func@v1{{$}}
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# CHECK-NEXT: .dynamic
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# CHECK: .bss.rel.ro
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# CHECK-NEXT: <internal>:(.bss.rel.ro)
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## Ideally this is displayed as copy@v2.
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# CHECK-NEXT: copy{{$}}
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# CHECK-NEXT: .relro_padding
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#--- 1.s
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.global _start
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_start:
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.symver func, func@@@v1
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mov $copy, %eax
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mov $func - ., %eax
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#--- 2.s
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.symver func, func@@@v1
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mov $copy, %eax
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mov $func - ., %eax
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#--- 3.s
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.globl func
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.symver func, func@v1, remove
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.type func, @function
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func:
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ret
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.section .rodata,"a"
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.globl copy
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.type copy, @object
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copy:
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.byte 1
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.size copy, 1
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#--- 3.ver
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v1 { func; };
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v2 { copy; };
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