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Differential D41477

[LLD] [ELF] Result of subtracting two symbols should be absolute
Needs ReviewPublic

Authored by erickreyes on Dec 20 2017, 7:49 PM.

Details

Reviewers
ruiu
• espindola
Group Reviewers
lld
Summary

When two linker script symbols are subtracted, the result should be absolute.

This is the behavior of binutils' ld.

Diff Detail

Repository
rLLD LLVM Linker

Event Timeline

erickreyes created this revision.Dec 20 2017, 7:49 PM
Herald added subscribers: llvm-commits, emaste. · View Herald TranscriptDec 20 2017, 7:49 PM
erickreyes added reviewers: ruiu, • rafael.Dec 21 2017, 10:38 AM
ruiu added inline comments.Dec 25 2017, 11:42 PM
ELF/ScriptParser.cpp
153

Please add a comment saying that subtracting two symbol values should logically should yield an absolute value and that's actually what the bfd linker produces.

• espindola edited reviewers, added: • espindola; removed: • rafael.Mar 15 2018, 8:39 AM
Herald added a subscriber: arichardson. · View Herald TranscriptMar 15 2018, 8:39 AM

Revision Contents

PathSize
ELF/
2 lines
test/
ELF/
linkerscript/
6 lines

Diff 127824

ELF/ScriptParser.cpp

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} }
static ExprValue sub(ExprValue A, ExprValue B) { static ExprValue sub(ExprValue A, ExprValue B) {
ruiuUnsubmitted
Not Done
ReplyInline Actions

Please add a comment saying that subtracting two symbol values should logically should yield an absolute value and that's actually what the bfd linker produces.

ruiu: Please add a comment saying that subtracting two symbol values should logically should yield an…
if (!A.isAbsolute() && !B.isAbsolute())
return A.getValue() - B.getValue();
return {A.Sec, false, A.getSectionOffset() - B.getValue(), A.Loc}; return {A.Sec, false, A.getSectionOffset() - B.getValue(), A.Loc};
} }
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test/ELF/linkerscript/operators.s

# REQUIRES: x86 # REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
# RUN: echo "SECTIONS { \ # RUN: echo "SECTIONS { \
# RUN: _start = .; \
# RUN: plus = 1 + 2 + 3; \ # RUN: plus = 1 + 2 + 3; \
# RUN: minus = 5 - 1; \ # RUN: minus = 5 - 1; \
# RUN: div = 6 / 2; \ # RUN: div = 6 / 2; \
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# RUN: . = 0xfff0; \ # RUN: . = 0xfff0; \
# RUN: datasegmentalign = DATA_SEGMENT_ALIGN (0xffff, 0); \ # RUN: datasegmentalign = DATA_SEGMENT_ALIGN (0xffff, 0); \
# RUN: datasegmentalign2 = DATA_SEGMENT_ALIGN (0, 0); \ # RUN: datasegmentalign2 = DATA_SEGMENT_ALIGN (0, 0); \
# RUN: _end = .; \
# RUN: minus_rel = _end - 0x10; \
# RUN: minus_abs = _end - _start; \
# RUN: }" > %t.script # RUN: }" > %t.script
# RUN: ld.lld %t --script %t.script -o %t2 # RUN: ld.lld %t --script %t.script -o %t2
# RUN: llvm-objdump -t %t2 | FileCheck %s # RUN: llvm-objdump -t %t2 | FileCheck %s
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# CHECK: 00000000001000 *ABS* 00000000 commonpagesize # CHECK: 00000000001000 *ABS* 00000000 commonpagesize
# CHECK: 0000000000ffff *ABS* 00000000 datasegmentalign # CHECK: 0000000000ffff *ABS* 00000000 datasegmentalign
# CHECK: 0000000000fff0 *ABS* 00000000 datasegmentalign2 # CHECK: 0000000000fff0 *ABS* 00000000 datasegmentalign2
# CHECK: 0000000000ffe0 .text 00000000 minus_rel
# CHECK: 0000000000fff0 *ABS* 00000000 minus_abs
## Mailformed number error. ## Mailformed number error.
# RUN: echo "SECTIONS { . = 0x12Q41; }" > %t.script # RUN: echo "SECTIONS { . = 0x12Q41; }" > %t.script
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