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.
55 lines
1.9 KiB
ArmAsm
55 lines
1.9 KiB
ArmAsm
// REQUIRES: x86
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// Reserve space for copy relocations of read-only symbols in .bss.rel.ro
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// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
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// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/relocation-copy-relro.s -o %t2.o
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// RUN: ld.lld -shared %t2.o -soname=so -o %t.so
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// RUN: ld.lld %t.o %t.so -o %t3
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// RUN: llvm-readobj -S -l -r %t3 | FileCheck %s
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/// Due to -z rodynamic, The only RELRO section is .bss.rel.ro. Test that we
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/// still append the .relro_padding section.
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// RUN: ld.lld -z rodynamic %t.o %t.so -o %t4
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// RUN: llvm-readelf -S -l %t4 | FileCheck %s --check-prefix=CHECK2
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// CHECK: Name: .bss.rel.ro
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// CHECK-NEXT: Type: SHT_NOBITS (0x8)
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// CHECK-NEXT: Flags [ (0x3)
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// CHECK-NEXT: SHF_ALLOC (0x2)
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// CHECK-NEXT: SHF_WRITE (0x1)
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// CHECK-NEXT: ]
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// CHECK-NEXT: Address: 0x202368
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// CHECK-NEXT: Offset: 0x368
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// CHECK-NEXT: Size: 8
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// CHECK: Type: PT_GNU_RELRO (0x6474E552)
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// CHECK-NEXT: Offset: 0x2A8
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// CHECK-NEXT: VirtualAddress: 0x2022A8
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// CHECK-NEXT: PhysicalAddress: 0x2022A8
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// CHECK-NEXT: FileSize: 192
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// CHECK-NEXT: MemSize: 3416
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// CHECK: 0x202368 R_X86_64_COPY a 0x0
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// CHECK: 0x20236C R_X86_64_COPY b 0x0
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// CHECK2: LOAD 0x000356 0x0000000000202356 0x0000000000202356 0x000000 0x000caa RW 0x1000
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// CHECK2: DYNAMIC 0x000258 0x0000000000200258 0x0000000000200258 0x0000b0 0x0000b0 R 0x8
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// CHECK2: GNU_RELRO 0x000356 0x0000000000202356 0x0000000000202356 0x000000 0x000caa R 0x1
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// CHECK2: Section to Segment mapping:
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// CHECK2-NEXT: Segment Sections...
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// CHECK2-NEXT: 00
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// CHECK2-NEXT: 01 .dynsym .gnu.hash .hash .dynamic .dynstr .rela.dyn
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// CHECK2-NEXT: 02 .text
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// CHECK2-NEXT: 03 .bss.rel.ro .relro_padding
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// CHECK2-NEXT: 04 .dynamic
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// CHECK2-NEXT: 05 .bss.rel.ro .relro_padding
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// CHECK2-NEXT: 06
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.text
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.global _start
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_start:
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movl $1, a
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movl $2, b
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