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.
34 lines
1.3 KiB
ArmAsm
34 lines
1.3 KiB
ArmAsm
// REQUIRES: arm
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// RUN: llvm-mc -filetype=obj -triple=armv7-pc-linux %s -o %t.o
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// RUN: ld.lld %t.o -o %t.so -shared
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// RUN: llvm-readelf -l %t.so | FileCheck --implicit-check-not=LOAD %s
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// RUN: echo ".section .foo,\"ax\"; \
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// RUN: bx lr" > %t.s
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// RUN: llvm-mc -filetype=obj -triple=armv7-pc-linux %t.s -o %t2.o
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// RUN: ld.lld %t.o %t2.o -o %t.so -shared
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// RUN: llvm-readelf -l %t.so | FileCheck --check-prefix=DIFF --implicit-check-not=LOAD %s
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// CHECK: LOAD 0x000000 0x00000000 0x00000000 0x0016d 0x0016d R 0x10000
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// CHECK: LOAD 0x000170 0x00010170 0x00010170 0x{{.*}} 0x{{.*}} R E 0x10000
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// CHECK: LOAD 0x000174 0x00020174 0x00020174 0x{{.*}} 0x{{.*}} E 0x10000
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// CHECK: LOAD 0x000178 0x00030178 0x00030178 0x00038 0x00e88 RW 0x10000
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// CHECK: 01 .dynsym .gnu.hash .hash .dynstr
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// CHECK: 02 .text
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// CHECK: 03 .foo
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// CHECK: 04 .dynamic
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// DIFF: LOAD 0x000000 0x00000000 0x00000000 0x0014d 0x0014d R 0x10000
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// DIFF: LOAD 0x000150 0x00010150 0x00010150 0x0000c 0x0000c R E 0x10000
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// DIFF: LOAD 0x00015c 0x0002015c 0x0002015c 0x00038 0x00ea4 RW 0x10000
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// DIFF: 01 .dynsym .gnu.hash .hash .dynstr
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// DIFF: 02 .text .foo
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// DIFF: 03 .dynamic
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bx lr
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.section .foo,"axy"
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bx lr
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