a40f651a06
For an output section with no input section, GNU ld eliminates the
output section when there are only symbol assignments (e.g.
`.foo : { symbol = 42; }`) but not for `.foo : { . += 42; }`
(`SHF_ALLOC|SHF_WRITE`).
We choose to retain such an output section with a symbol assignment
(unless unreferenced `PROVIDE`). We copy the previous section flag (see
https://reviews.llvm.org/D37736) to hopefully make the current PT_LOAD
segment extend to the current output section:
* decrease the number of PT_LOAD segments
* If a new PT_LOAD segment is introduced without a page-size
alignment as a separator, there may be a run-time crash.
However, this `flags` copying behavior is not suitable for
`.foo : { . += 42; }` when `flags` contains `SHF_EXECINSTR`. The
executable bit is surprising
(https://discourse.llvm.org/t/lld-output-section-flag-assignment-behavior/74359).
I think we should drop SHF_EXECINSTR when copying `flags`. The risk is a
code section followed by `.foo : { symbol = 42; }` will be broken, which
I believe is unrelated as such uses are almost always related to data
sections.
For data-command-only output sections (e.g. `.foo : { QUAD(42) }`), we
keep allowing copyable SHF_WRITE.
Some tests are updated to drop the SHF_EXECINSTR flag. GNU ld doesn't
set SHF_EXECINSTR as well, though it sets SHF_WRITE for some tests while
we don't.
49 lines
2.2 KiB
Plaintext
49 lines
2.2 KiB
Plaintext
# REQUIRES: x86
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# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/insert-after.s -o %t1.o
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## Main linker script contains .text and .data sections. Here
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## we check that can use INSERT BEFORE to insert sections .foo.data
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## and .foo.text at the right places.
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# RUN: ld.lld %t1.o -o %t1 --script %p/Inputs/insert-after.script --script %s
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# RUN: llvm-readelf -S -l %t1 | FileCheck %s
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# CHECK: Name Type Address Off Size ES Flg
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# CHECK-NEXT: NULL
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# CHECK-NEXT: .foo.text PROGBITS 0000000000000000 001000 000008 00 AX 0
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# CHECK-NEXT: .text PROGBITS 0000000000000008 001008 000008 00 AX 0
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# CHECK-NEXT: .byte PROGBITS 0000000000000010 001010 000001 00 A 0
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# CHECK-NEXT: .foo.data PROGBITS 0000000000000011 001011 000008 00 WA 0
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# CHECK-NEXT: .data PROGBITS 0000000000000019 001019 000008 00 WA 0
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# CHECK: Type
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# CHECK-NEXT: LOAD {{.*}} R E
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# CHECK-NEXT: LOAD {{.*}} R
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# CHECK-NEXT: LOAD {{.*}} RW
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# CHECK-NEXT: GNU_STACK {{.*}} RW
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## There is no main linker script. INSERT BEFORE just reorders output sections,
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## without making more layout changes. Address/offset assignments are different
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## with a main linker script.
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# RUN: ld.lld --script %s %t1.o -o %t2
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# RUN: llvm-readelf -S -l %t2 | FileCheck --check-prefix=CHECK2 %s
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# CHECK2: Name Type Address Off Size ES Flg
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# CHECK2-NEXT: NULL
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# CHECK2-NEXT: .foo.text PROGBITS 000000000020{{.*}} [[#%x,]] 000008 00 AX
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# CHECK2-NEXT: .text PROGBITS [[#%x,]] [[#%x,]] 000008 00 AX
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# CHECK2-NEXT: .byte PROGBITS [[#%x,]] [[#%x,]] 000001 00 WA
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# CHECK2-NEXT: .foo.data PROGBITS [[#%x,]] [[#%x,]] 000008 00 WA
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# CHECK2-NEXT: .data PROGBITS [[#%x,]] [[#%x,]] 000008 00 WA
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# CHECK2: Type {{.*}} Flg Align
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# CHECK2-NEXT: PHDR {{.*}} R 0x8
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# CHECK2-NEXT: LOAD {{.*}} R 0x1000
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# CHECK2-NEXT: LOAD {{.*}} R E 0x1000
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# CHECK2-NEXT: LOAD {{.*}} RW 0x1000
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# CHECK2-NEXT: GNU_STACK {{.*}} RW 0
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SECTIONS { .byte : { BYTE(0) } } INSERT BEFORE .data;
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SECTIONS { .foo.data : { *(.foo.data) } } INSERT BEFORE .data;
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## The input section .foo.text is an orphan. It will be placed in .foo.text
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SECTIONS { .foo.text : {} } INSERT BEFORE .text;
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