07f8daf05e
Old: PT_LOAD(.data | PT_GNU_RELRO(.data.rel.ro .bss.rel.ro) | .bss) New: PT_LOAD(PT_GNU_RELRO(.data.rel.ro .bss.rel.ro) | .data .bss) The placement of | indicates page alignment caused by PT_GNU_RELRO. The new layout has simpler rules and saves space for many cases. Old size: roundup(.data) + roundup(.data.rel.ro) New size: roundup(.data.rel.ro + .bss.rel.ro) + .data Other advantages: * At runtime the 3 memory mappings decrease to 2. * start(PT_TLS) = start(PT_GNU_RELRO) = start(RW PT_LOAD). This simplifies binary manipulation tools. GNU strip before 2.31 discards PT_GNU_RELRO if its address is not equal to the start of its associated PT_LOAD. This has been fixed by https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f2731e0c374e5323ce4cdae2bcc7b7fe22da1a6f But with this change, we will be compatible with GNU strip before 2.31 * Before, .got.plt (non-relro by default) was placed before .got (relro by default), which made it impossible to have _GLOBAL_OFFSET_TABLE_ (start of .got.plt on x86-64) equal to the end of .got (R_GOT*_FROM_END) (https://bugs.llvm.org/show_bug.cgi?id=36555). With the new ordering, we can improve on this regard if we'd like to. Reviewers: ruiu, espindola, pcc Subscribers: emaste, arichardson, llvm-commits, joerg, jdoerfert Differential Revision: https://reviews.llvm.org/D56828 llvm-svn: 356117
37 lines
1.1 KiB
ArmAsm
37 lines
1.1 KiB
ArmAsm
# REQUIRES: x86
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# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
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# RUN: echo "SECTIONS { \
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# RUN: .text : { *(.text) } \
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# RUN: .rw1 : { *(.rw1) } \
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# RUN: .rw2 : { *(.rw2) } \
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# RUN: .rw3 : { *(.rw3) } \
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# RUN: }" > %t.script
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# RUN: ld.lld -o %t1 --script %t.script %t
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# RUN: llvm-objdump -section-headers %t1 | FileCheck %s
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## .jcr is a relro section and should be placed before other RW sections.
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## .bss is SHT_NOBITS section and should be last RW section, so some space
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## in ELF file could be saved.
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# CHECK: 0 00000000 0000000000000000
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# CHECK-NEXT: 1 .text 00000000 0000000000000000 TEXT
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# CHECK-NEXT: 2 .jcr 00000008 0000000000000000 DATA
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# CHECK-NEXT: 3 .rw1 00000008 0000000000000008 DATA
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# CHECK-NEXT: 4 .rw2 00000008 0000000000000010 DATA
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# CHECK-NEXT: 5 .rw3 00000008 0000000000000018 DATA
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# CHECK-NEXT: 6 .bss 00000008 0000000000000020 BSS
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.section .rw1, "aw"
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.quad 0
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.section .rw2, "aw"
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.quad 0
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.section .rw3, "aw"
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.quad 0
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.section .jcr, "aw"
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.quad 0
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.section .bss, "aw",@nobits
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.quad 0
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