[llvm-bugs] [Bug 38074] New: Error static linking when clang++/lld 6.0.0 using Arch Linux

via llvm-bugs llvm-bugs at lists.llvm.org
Thu Jul 5 13:23:26 PDT 2018 

https://bugs.llvm.org/show_bug.cgi?id=38074

            Bug ID: 38074
           Summary: Error static linking when clang++/lld 6.0.0 using Arch
                    Linux
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: ELF
          Assignee: unassignedbugs at nondot.org
          Reporter: wink at saville.com
                CC: llvm-bugs at lists.llvm.org

See [1] for a conversation on cfe-dev.

My executive summary at [2] is: In _dl_get_origin lld is linking a call to
mempcpy which I'd call "thunking code" as it returns in rax the address of the
code that should be called instead of the address of the next available address
of the destination buffer. And specifically, since rax is pointing at code,
when a zero is stored to try to terminate the string we seg fault.


The following (github [3]) code:

$ cat main.cpp 
#include <iostream>

int main(int argc, char *argv[]) {
  for (int i=0; i < argc; i++) {
    std::cout << "argv[" << i << "]: " << argv[i] << std::endl;
  }
}


Compiles successfully:

$ clang++ -fuse-ld=lld  -o main-lld -static -pthread main.cpp
-Wl,--reproduce=main-lld-repro.tar
$

But the resulting binary seg faults when run:

$ ./main-lld 1 2 3
Segmentation fault (core dumped)


If I compile using gold and then run, all is well:

$ clang++ -fuse-ld=gold  -o main-gold -static -pthread main.cpp                 
$ ./main-gold 4 5   
argv[0]: ./main-gold
argv[1]: 4
argv[2]: 5


Rui and Peter are unable to reproduce this on their older systems, so I've
prepared a docker image [4] which can be used to test.

For example:

wink at wink-desktop:~/
$ mkdir xx && cd xx
wink at wink-desktop:~/xx
$ docker run --name lld-bug -v `pwd`:`pwd` -w `pwd` --rm -it
winksaville/lld-static-link-bug:arch
Cloning into 'lld-bug'...
remote: Counting objects: 11, done.
remote: Compressing objects: 100% (8/8), done.
remote: Total 11 (delta 2), reused 11 (delta 2), pack-reused 0
Unpacking objects: 100% (11/11), done.
clang++ -fuse-ld=gold -g -o main-gold -v -static -pthread main.cpp
clang version 6.0.0 (tags/RELEASE_600/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/sbin
Found candidate GCC installation: /usr/lib/gcc/x86_64-pc-linux-gnu/8.1.1
Found candidate GCC installation: /usr/lib64/gcc/x86_64-pc-linux-gnu/8.1.1
Found candidate GCC installation:
/usr/sbin/../lib/gcc/x86_64-pc-linux-gnu/8.1.1
Found candidate GCC installation:
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1
Selected GCC installation: /usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
 "/usr/bin/clang-6.0" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all
-disable-free -disable-llvm-verifier -discard-value-names -main-file-name
main.cpp -static-define -mrelocation-model pic -pic-level 2 -pic-is-pie
-mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose
-mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64
-dwarf-column-info -debug-info-kind=limited -dwarf-version=4
-debugger-tuning=gdb -v -resource-dir /usr/lib/clang/6.0.0 -internal-isystem
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1
-internal-isystem
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1/x86_64-pc-linux-gnu
-internal-isystem
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1/backward
-internal-isystem /usr/local/include -internal-isystem
/usr/lib/clang/6.0.0/include -internal-externc-isystem /include
-internal-externc-isystem /usr/include -fdeprecated-macro
-fdebug-compilation-dir /home/wink/xx/lld-bug -ferror-limit 19 -fmessage-length
186 -pthread -stack-protector 2 -fobjc-runtime=gcc -fcxx-exceptions
-fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o
/tmp/main-395c1b.o -x c++ main.cpp
clang -cc1 version 6.0.0 based upon LLVM 6.0.0 default target
x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1

/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1/x86_64-pc-linux-gnu

/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1/backward
 /usr/local/include
 /usr/lib/clang/6.0.0/include
 /usr/include
End of search list.
 "/usr/sbin/ld.gold" -m elf_x86_64 -static -o main-gold
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../lib64/crt1.o
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../lib64/crti.o
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/crtbeginT.o
-L/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1
-L/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../lib64
-L/usr/bin/../lib64 -L/lib/../lib64 -L/usr/lib/../lib64
-L/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../.. -L/usr/bin/../lib
-L/lib -L/usr/lib /tmp/main-395c1b.o -lstdc++ -lm --start-group -lgcc -lgcc_eh
-lpthread -lc --end-group
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/crtend.o
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../lib64/crtn.o
./main-gold 4 5 6
argv[0]: ./main-gold
argv[1]: 4
argv[2]: 5
argv[3]: 6
clang++ -fuse-ld=lld  -g -o main-lld  -v -static -pthread main.cpp
-Wl,--reproduce=main-lld-repro
clang version 6.0.0 (tags/RELEASE_600/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/sbin
Found candidate GCC installation: /usr/lib/gcc/x86_64-pc-linux-gnu/8.1.1
Found candidate GCC installation: /usr/lib64/gcc/x86_64-pc-linux-gnu/8.1.1
Found candidate GCC installation:
/usr/sbin/../lib/gcc/x86_64-pc-linux-gnu/8.1.1
Found candidate GCC installation:
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1
Selected GCC installation: /usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
 "/usr/bin/clang-6.0" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all
-disable-free -disable-llvm-verifier -discard-value-names -main-file-name
main.cpp -static-define -mrelocation-model pic -pic-level 2 -pic-is-pie
-mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose
-mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64
-dwarf-column-info -debug-info-kind=limited -dwarf-version=4
-debugger-tuning=gdb -v -resource-dir /usr/lib/clang/6.0.0 -internal-isystem
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1
-internal-isystem
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1/x86_64-pc-linux-gnu
-internal-isystem
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1/backward
-internal-isystem /usr/local/include -internal-isystem
/usr/lib/clang/6.0.0/include -internal-externc-isystem /include
-internal-externc-isystem /usr/include -fdeprecated-macro
-fdebug-compilation-dir /home/wink/xx/lld-bug -ferror-limit 19 -fmessage-length
186 -pthread -stack-protector 2 -fobjc-runtime=gcc -fcxx-exceptions
-fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o
/tmp/main-96773c.o -x c++ main.cpp
clang -cc1 version 6.0.0 based upon LLVM 6.0.0 default target
x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1

/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1/x86_64-pc-linux-gnu

/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../include/c++/8.1.1/backward
 /usr/local/include
 /usr/lib/clang/6.0.0/include
 /usr/include
End of search list.
 "/usr/sbin/ld.lld" -m elf_x86_64 -static -o main-lld
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../lib64/crt1.o
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../lib64/crti.o
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/crtbeginT.o
-L/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1
-L/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../lib64
-L/usr/bin/../lib64 -L/lib/../lib64 -L/usr/lib/../lib64
-L/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../.. -L/usr/bin/../lib
-L/lib -L/usr/lib /tmp/main-96773c.o --reproduce=main-lld-repro -lstdc++ -lm
--start-group -lgcc -lgcc_eh -lpthread -lc --end-group
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/crtend.o
/usr/sbin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.1/../../../../lib64/crtn.o
./main-lld 1 2 3
make: *** [Makefile:3: run-lld] Segmentation fault (core dumped)



And below I run the docker image interactively and use gdb:

wink at wink-desktop:~/xx
$ docker run --privileged --name lld-bug -v `pwd`:`pwd` -w `pwd` --rm -it
--entrypoint='/usr/bin/bash' winksaville/lld-static-link-bug:arch
[root at db1cc49aeeeb xx]# cd lld-bug/
[root at db1cc49aeeeb lld-bug]# gdb -q --args ./main-lld 1 2 3
Reading symbols from ./main-lld...done.
(gdb) r
Starting program: /home/wink/xx/lld-bug/main-lld 1 2 3

Program received signal SIGSEGV, Segmentation fault.
0x0000000000384256 in _dl_get_origin ()
(gdb) bt
#0  0x0000000000384256 in _dl_get_origin ()
#1  0x00000000003838bf in _dl_non_dynamic_init ()
#2  0x00000000002ef141 in __libc_init_first ()
#3  0x00000000002eee37 in __libc_start_main ()
#4  0x000000000025302a in _start ()
(gdb) i r 
rax            0x364ca0 3558560
rbx            0x7fffffffdb70   140737488345968
rcx            0x3ae460 3859552
rdx            0x364c60 3558496
rsi            0x7fffffffdb70   140737488345968
rdi            0x3ae460 3859552
rbp            0x16     0x16
rsp            0x7fffffffdb70   0x7fffffffdb70
r8             0x3      3
r9             0x0      0
r10            0xfffffffffffff000       -4096
r11            0x0      0
r12            0x3ae460 3859552
r13            0x0      0
r14            0x3994f8 3773688
r15            0x0      0
rip            0x384256 0x384256 <_dl_get_origin+342>
eflags         0x10202  [ IF RF ]
cs             0x33     51
ss             0x2b     43
ds             0x0      0
es             0x0      0
fs             0x0      0
gs             0x0      0
(gdb) disassemble $rax
Dump of assembler code for function __mempcpy_avx_unaligned_erms:
   0x0000000000364ca0 <+0>:     mov    %rdi,%rax
   0x0000000000364ca3 <+3>:     add    %rdx,%rax
   0x0000000000364ca6 <+6>:     jmp    0x364cb3
<__memmove_avx_unaligned_erms+3>
End of assembler dump.
(gdb) 




[1]:
http://clang-developers.42468.n3.nabble.com/Static-linking-a-program-td4061003.html
[2]:
http://clang-developers.42468.n3.nabble.com/Static-linking-a-program-tc4061003.html#a4061103
[3]: https://github.com/winksaville/explore-cpp-lld-static-link-bug
[4]: https://github.com/winksaville/Dockerfile-lld-static-link-bug

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