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0264950697
D64906 allows PT_LOAD to have overlapping p_offset ranges. In the default R RX RW RW layout + -z noseparate-code case, we do not tail pad segments when transiting to another segment. This can save at most 3*maxPageSize bytes. a) Before D64906, we tail pad R, RX and the first RW. b) With -z separate-code, we tail pad R and RX, but not the first RW (RELRO). In some cases, b) saves one file page. In some cases, b) wastes one virtual memory page. The waste is a concern on Fuchsia. Because it uses compressed binaries, it doesn't benefit from the saved file page. This patch adds -z separate-loadable-segments to restore the behavior before D64906. It can affect section addresses and can thus be used as a debugging mechanism (see PR43214 and ld.so partition bug in crbug.com/998712). Reviewed By: jakehehrlich, ruiu Differential Revision: https://reviews.llvm.org/D67481 llvm-svn: 372807
43 lines
1.5 KiB
ArmAsm
43 lines
1.5 KiB
ArmAsm
# REQUIRES: x86
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# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
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## -z noseparate-code is the default: text segment is not tail padded.
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# RUN: ld.lld %t.o -o %t
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# RUN: llvm-readobj -l %t | FileCheck %s --check-prefixes=CHECK,NOPAD
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# RUN: ld.lld %t.o -z noseparate-code -o %t
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# RUN: llvm-readobj -l %t | FileCheck %s --check-prefixes=CHECK,NOPAD
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## -z separate-code pads the tail of text segment with traps.
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# RUN: ld.lld %t.o -z separate-code -o %t
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# RUN: llvm-readobj -l %t | FileCheck %s --check-prefixes=CHECK,PAD
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# RUN: od -Ax -x -N16 -j0x1ff0 %t | FileCheck %s --check-prefix=FILL
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## -z separate-loadable-segments pads all segments, including the text segment.
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# RUN: ld.lld %t.o -z separate-loadable-segments -o %t
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# RUN: llvm-readobj -l %t | FileCheck %s --check-prefixes=CHECK,PAD
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# RUN: od -Ax -x -N16 -j0x1ff0 %t | FileCheck %s --check-prefix=FILL
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# RUN: ld.lld %t.o -z separate-code -z noseparate-code -o %t
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# RUN: llvm-readobj -l %t | FileCheck %s --check-prefixes=CHECK,NOPAD
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# CHECK: ProgramHeader {
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# CHECK: Type: PT_LOAD
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# PAD: Offset: 0x1000
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# NOPAD: Offset: 0x120
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# CHECK-NEXT: VirtualAddress:
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# CHECK-NEXT: PhysicalAddress:
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# PAD-NEXT: FileSize: 4096
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# NOPAD-NEXT: FileSize: 1
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# CHECK-NEXT: MemSize:
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# CHECK-NEXT: Flags [
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# CHECK-NEXT: PF_R
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# CHECK-NEXT: PF_X
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# CHECK-NEXT: ]
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## Check that executable page is filled with traps at its end.
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# FILL: 001ff0 cccc cccc cccc cccc cccc cccc cccc cccc
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.globl _start
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_start:
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nop
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