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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - LLD produced executable with ld.bfd internal ldscript segfaults."
href="https://bugs.llvm.org/show_bug.cgi?id=35265">35265</a>
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<th>Summary</th>
<td>LLD produced executable with ld.bfd internal ldscript segfaults.
</td>
</tr>
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<th>Product</th>
<td>lld
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>ELF
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>peter.smith@linaro.org
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=19393" name="attach_19393" title="linker script output from ld.bfd --verbose with header/trailer removed.">attachment 19393</a> <a href="attachment.cgi?id=19393&action=edit" title="linker script output from ld.bfd --verbose with header/trailer removed.">[details]</a></span>
linker script output from ld.bfd --verbose with header/trailer removed.
I took the internal linker script that ld.bfd uses for an executable and fed it
into lld. The resultant executable segfaulted in the dynamic loader when
writing back the resolved address of a function into .got.plt. I found that I
could get the executable to run if I turned off relro with -zno-relro.
I've reproduced this problem on Ubuntu 16.04 x86_64, and on AArch64 via
qemu-aarch64. Also on Ubuntu 14.04 running on Armv7-a so I think that this is
likely to be a target independent problem with the way we handle relro.
To reproduce:
Any C program, including "int main(void) { return 0; }"
Extract the default linker-script for your target using ld.bfd --verbose
Edit out the header and trailer to leave just the SECTIONS command.
Link the program with lld
clang main.c -Wl,-script=main.script -fuse-ld=lld -o main.exe
./main.exe
Segmentation fault (core dumped)
To prevent the segfault add -Wl,-znorelro
I've attached the linker script that I used for x86_64 "GNU ld (GNU Binutils
for Ubuntu) 2.26.1"
I haven't investigated why -zrelro isn't working yet, nor have I tried a shared
library (obtain the script with "ld --verbose --shared").
The linker script contains: . = DATA_SEGMENT_RELRO_END (SIZEOF (.got.plt) >= 24
? 24 : 0, .);
so we may be missing some magic. The RELRO program header certainly looks very
different to the one produced by ld.bfd.</pre>
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