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.
48 lines
2.2 KiB
Plaintext
48 lines
2.2 KiB
Plaintext
# REQUIRES: x86
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# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/insert-after.s -o %t1.o
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## Main linker script contains .text and .data sections. Here
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## we check that can use INSERT BEFORE to insert sections .foo.data
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## and .foo.text at the right places.
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# RUN: ld.lld %t1.o -o %t1 --script %p/Inputs/insert-after.script --script %s
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# RUN: llvm-readelf -S -l %t1 | FileCheck %s
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# CHECK: Name Type Address Off Size ES Flg
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# CHECK-NEXT: NULL
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# CHECK-NEXT: .foo.text PROGBITS 0000000000000000 001000 000008 00 AX
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# CHECK-NEXT: .text PROGBITS 0000000000000008 001008 000008 00 AX
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# CHECK-NEXT: .byte PROGBITS 0000000000000010 001010 000001 00 AX
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# CHECK-NEXT: .foo.data PROGBITS 0000000000000011 001011 000008 00 WA
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# CHECK-NEXT: .data PROGBITS 0000000000000019 001019 000008 00 WA
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# CHECK: Type
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# CHECK-NEXT: LOAD {{.*}} R E
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# CHECK-NEXT: LOAD {{.*}} RW
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# CHECK-NEXT: GNU_STACK {{.*}} RW
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## There is no main linker script. INSERT BEFORE just reorders output sections,
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## without making more layout changes. Address/offset assignments are different
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## with a main linker script.
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# RUN: ld.lld --script %s %t1.o -o %t2
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# RUN: llvm-readelf -S -l %t2 | FileCheck --check-prefix=CHECK2 %s
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# CHECK2: Name Type Address Off Size ES Flg
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# CHECK2-NEXT: NULL
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# CHECK2-NEXT: .foo.text PROGBITS 000000000020{{.*}} [[#%x,]] 000008 00 AX
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# CHECK2-NEXT: .text PROGBITS [[#%x,]] [[#%x,]] 000008 00 AX
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# CHECK2-NEXT: .byte PROGBITS [[#%x,]] [[#%x,]] 000001 00 WA
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# CHECK2-NEXT: .foo.data PROGBITS [[#%x,]] [[#%x,]] 000008 00 WA
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# CHECK2-NEXT: .data PROGBITS [[#%x,]] [[#%x,]] 000008 00 WA
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# CHECK2: Type {{.*}} Flg Align
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# CHECK2-NEXT: PHDR {{.*}} R 0x8
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# CHECK2-NEXT: LOAD {{.*}} R 0x1000
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# CHECK2-NEXT: LOAD {{.*}} R E 0x1000
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# CHECK2-NEXT: LOAD {{.*}} RW 0x1000
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# CHECK2-NEXT: GNU_STACK {{.*}} RW 0
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SECTIONS { .byte : { BYTE(0) } } INSERT BEFORE .data;
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SECTIONS { .foo.data : { *(.foo.data) } } INSERT BEFORE .data;
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## The input section .foo.text is an orphan. It will be placed in .foo.text
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SECTIONS { .foo.text : {} } INSERT BEFORE .text;
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