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clang-p2996/lld/test/ELF/map-file.s
Fangrui Song 5a58e98c20 [ELF] Align the end of PT_GNU_RELRO associated PT_LOAD to a common-page-size boundary (#66042) 
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.
2023-09-14 10:33:11 -07:00

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# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t1.o
# RUN: llvm-mc -filetype=obj -triple=x86_64 %p/Inputs/map-file2.s -o %t2.o
# RUN: echo '.global bah; bah:' | llvm-mc -filetype=obj -triple=x86_64 - -o %t3.o
# RUN: echo '.global baz; baz: ret' | llvm-mc -filetype=obj -triple=x86_64 - -o %t4.o
# RUN: llvm-mc -filetype=obj -triple=x86_64 %p/Inputs/map-file5.s -o %t5.o
# RUN: echo '.global hey; hey: ret' | llvm-mc -filetype=obj -triple=x86_64 - -o %t6.o
# RUN: echo '.reloc ., R_X86_64_RELATIVE, 0' | llvm-mc -filetype=obj -triple=x86_64 - -o %t7.o
# RUN: ld.lld -shared %t5.o -o %t5.so -soname dso
# RUN: rm -f %t4.a
# RUN: llvm-ar rc %t4.a %t4.o
# RUN: rm -f %t6.a
# RUN: llvm-ar rcT %t6.a %t6.o
# RUN: ld.lld %t1.o %t2.o %t3.o %t4.a %t5.so %t6.a -o %t -M | FileCheck --match-full-lines --strict-whitespace %s
# RUN: ld.lld %t1.o %t2.o %t3.o %t4.a %t5.so %t6.a -o %t --print-map | FileCheck --match-full-lines -strict-whitespace %s
# RUN: ld.lld %t1.o %t2.o %t3.o %t4.a %t5.so %t6.a -o %t -Map=%t.map
# RUN: FileCheck -match-full-lines -strict-whitespace %s < %t.map
## A relocation error does not suppress the output.
# RUN: not ld.lld %t1.o %t2.o %t3.o %t4.a %t5.so %t6.a %t7.o -o /dev/null -M | FileCheck --strict-whitespace --check-prefix=CHECK2 %s
.global _start
_start:
.cfi_startproc
.cfi_endproc
.quad sharedFoo
.quad sharedBar
.byte 0xe8
.long sharedFunc1 - .
.byte 0xe8
.long sharedFunc2 - .
.byte 0xe8
.long baz - .
.long hey - .
.global _Z1fi
_Z1fi:
.cfi_startproc
nop
.cfi_endproc
.weak bar
bar:
.long bar - .
.long zed - .
local:
.comm common,4,16
.global abs
abs = 0xAB5
labs = 0x1AB5
## 0123456789abcdef 0123456789abcdef
# CHECK: VMA LMA Size Align Out In Symbol
# CHECK-NEXT: 200200 200200 78 8 .dynsym
# CHECK-NEXT: 200200 200200 78 8 <internal>:(.dynsym)
# CHECK-NEXT: 200278 200278 2c 8 .gnu.hash
# CHECK-NEXT: 200278 200278 2c 8 <internal>:(.gnu.hash)
# CHECK-NEXT: 2002a4 2002a4 30 4 .hash
# CHECK-NEXT: 2002a4 2002a4 30 4 <internal>:(.hash)
# CHECK-NEXT: 2002d4 2002d4 31 1 .dynstr
# CHECK-NEXT: 2002d4 2002d4 31 1 <internal>:(.dynstr)
# CHECK-NEXT: 200308 200308 30 8 .rela.dyn
# CHECK-NEXT: 200308 200308 30 8 <internal>:(.rela.dyn)
# CHECK-NEXT: 200338 200338 30 8 .rela.plt
# CHECK-NEXT: 200338 200338 30 8 <internal>:(.rela.plt)
# CHECK-NEXT: 200368 200368 5c 8 .eh_frame
# CHECK-NEXT: 200368 200368 40 1 {{.*}}{{/|\\}}map-file.s.tmp1.o:(.eh_frame+0x0)
# CHECK-NEXT: 2003a8 2003a8 18 1 {{.*}}{{/|\\}}map-file.s.tmp2.o:(.eh_frame+0x18)
# CHECK-NEXT: 2013c4 2013c4 35 4 .text
# CHECK-NEXT: 2013c4 2013c4 2c 4 {{.*}}{{/|\\}}map-file.s.tmp1.o:(.text)
# CHECK-NEXT: 2013c4 2013c4 0 1 _start
# CHECK-NEXT: 2013e7 2013e7 0 1 f(int)
# CHECK-NEXT: 2013f0 2013f0 0 1 local
# CHECK-NEXT: 2013f0 2013f0 2 4 {{.*}}{{/|\\}}map-file.s.tmp2.o:(.text)
# CHECK-NEXT: 2013f0 2013f0 0 1 foo
# CHECK-NEXT: 2013f1 2013f1 0 1 bar
# CHECK-NEXT: 2013f2 2013f2 0 1 {{.*}}{{/|\\}}map-file.s.tmp2.o:(.text.zed)
# CHECK-NEXT: 2013f2 2013f2 0 1 zed
# CHECK-NEXT: 2013f4 2013f4 0 4 {{.*}}{{/|\\}}map-file.s.tmp3.o:(.text)
# CHECK-NEXT: 2013f4 2013f4 0 1 bah
# CHECK-NEXT: 2013f4 2013f4 1 4 {{.*}}{{/|\\}}map-file.s.tmp4.a(map-file.s.tmp4.o):(.text)
# CHECK-NEXT: 2013f4 2013f4 0 1 baz
# CHECK-NEXT: 2013f8 2013f8 1 4 {{.*}}{{/|\\}}map-file.s.tmp6.a({{.*}}{{/|\\}}map-file.s.tmp6.o):(.text)
# CHECK-NEXT: 2013f8 2013f8 0 1 hey
# CHECK-NEXT: 201400 201400 30 16 .plt
# CHECK-NEXT: 201400 201400 30 16 <internal>:(.plt)
# CHECK-NEXT: 201410 201410 0 1 sharedFunc1
# CHECK-NEXT: 201420 201420 0 1 sharedFunc2
# CHECK-NEXT: 202430 202430 100 8 .dynamic
# CHECK-NEXT: 202430 202430 100 8 <internal>:(.dynamic)
# CHECK-NEXT: 202530 202530 ad0 1 .relro_padding
# CHECK-NEXT: 202530 202530 0 1 <internal>:(.relro_padding)
# CHECK-NEXT: 203530 203530 28 8 .got.plt
# CHECK-NEXT: 203530 203530 28 8 <internal>:(.got.plt)
# CHECK-NEXT: 203560 203560 10 16 .bss
# CHECK-NEXT: 203560 203560 4 16 {{.*}}{{/|\\}}map-file.s.tmp1.o:(COMMON)
# CHECK-NEXT: 203560 203560 4 1 common
# CHECK-NEXT: 203564 203564 4 1 <internal>:(.bss)
# CHECK-NEXT: 203564 203564 4 1 sharedFoo
# CHECK-NEXT: 203568 203568 8 1 <internal>:(.bss)
# CHECK-NEXT: 203568 203568 8 1 sharedBar
# CHECK-NEXT: 0 0 8 1 .comment
# CHECK-NEXT: 0 0 8 1 <internal>:(.comment)
# CHECK-NEXT: 0 0 1b0 8 .symtab
# CHECK-NEXT: 0 0 1b0 8 <internal>:(.symtab)
# CHECK-NEXT: 0 0 93 1 .shstrtab
# CHECK-NEXT: 0 0 93 1 <internal>:(.shstrtab)
# CHECK-NEXT: 0 0 71 1 .strtab
# CHECK-NEXT: 0 0 71 1 <internal>:(.strtab)
# CHECK2: VMA LMA Size Align Out In Symbol
# CHECK2-NEXT: 200200 200200 78 8 .dynsym
# CHECK2-NEXT: 200200 200200 78 8 <internal>:(.dynsym)
# CHECK2-NEXT: 200278 200278 2c 8 .gnu.hash
# CHECK2-NEXT: 200278 200278 2c 8 <internal>:(.gnu.hash)
# RUN: not ld.lld %t1.o %t2.o %t3.o %t4.a -o /dev/null -Map=/ 2>&1 \
# RUN: | FileCheck --check-prefix=FAIL %s
# FAIL: cannot open map file /
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