* Using dlmope/dlopem with RTLD_GLOBAL
[not found] <14297fb9-70cb-42b1-a477-6fb68c03ff64@Spark>
@ 2023-02-13 9:23 ` Nima Hamidi
2023-02-13 10:29 ` Florian Weimer
0 siblings, 1 reply; 4+ messages in thread
From: Nima Hamidi @ 2023-02-13 9:23 UTC (permalink / raw)
To: libc-help
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Hello all,
I’m trying to dlmopen a shared library which in turn dlopen’s another shared library with RTLD_GLOBAL flag set. On some platforms, it works as I expect it, but on some other platforms it crashes. Here is the simplest example I could make to show that crash:
I create a docker container containing my example using:
////////////////////////////////////////////////////////////
docker run --rm -it ubuntu:devel bash
apt-get update
apt install g++-10
cd ~
cat >a.cpp <<EOF
// a.cpp
#include <iostream>
#include <dlfcn.h>
using namespace std;
int main () {
void * handle = nullptr;
bool mopen = true;
if (mopen) {
cout << "mopening libb.so" << endl;
handle = dlmopen(LM_ID_NEWLM, "libb.so", RTLD_NOW | RTLD_LOCAL);
} else {
cout << "opening libb.so" << endl;
handle = dlopen("libb.so", RTLD_NOW | RTLD_LOCAL);
}
void (*bfunc)();
*(void**)(&bfunc) = dlsym(handle, "bfunc");
bfunc();
return 0;
}
EOF
cat >b.cpp <<EOF
// b.cpp
#include <iostream>
#include <dlfcn.h>
using namespace std;
extern "C" void bfunc() {
cout << "bfunc in b.cpp is being called..." << endl;
void * handle = dlopen("libc.so", RTLD_NOW | RTLD_GLOBAL);
//void * handle = dlopen("libc.so", RTLD_NOW | RTLD_LOCAL);
void (*cfunc)();
*(void**)(&cfunc) = dlsym(handle, "cfunc");
cfunc();
}
EOF
cat >c.cpp <<EOF
// c.cpp
#include <iostream>
using namespace std;
extern "C" void cfunc() {
cout << "cfunc in c.cpp is being called..." << endl;
}
EOF
g++-10 a.cpp -o a -ldl -Wl,-rpath `pwd`
g++-10 b.cpp -o libb.so -shared -fPIC -ldl -Wl,-rpath `pwd`
g++-10 c.cpp -o libc.so -shared -fPIC
////////////////////////////////////////////////////////////
Finally, when I run LD_DEBUG=1 ./a, it crashes with the following log:
902: symbol=_ZNSt8ios_base4InitD1Ev; lookup in file=/root/libb.so [1]
902: symbol=_ZNSt8ios_base4InitD1Ev; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1]
902: symbol=__cxa_finalize; lookup in file=/root/libb.so [1]
902: symbol=__cxa_finalize; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1]
902: symbol=__cxa_finalize; lookup in file=/lib/aarch64-linux-gnu/libc.so.6 [1]
902: symbol=_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc; lookup in file=/root/libb.so [1]
902: symbol=_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1]
902: symbol=_ZNSolsEPFRSoS_E; lookup in file=/root/libb.so [1]
902: symbol=_ZNSolsEPFRSoS_E; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1]
902: symbol=__cxa_atexit; lookup in file=/root/libb.so [1]
902: symbol=__cxa_atexit; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1]
902: symbol=__cxa_atexit; lookup in file=/lib/aarch64-linux-gnu/libc.so.6 [1]
902: symbol=_ZNSt8ios_base4InitC1Ev; lookup in file=/root/libb.so [1]
902: symbol=_ZNSt8ios_base4InitC1Ev; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1]
902: symbol=__gmon_start__; lookup in file=/root/libb.so [1]
902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1]
902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libc.so.6 [1]
902: symbol=__gmon_start__; lookup in file=/lib/ld-linux-aarch64.so.1 [0]
902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libm.so.6 [1]
902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libgcc_s.so.1 [1]
902: symbol=__gmon_start__; lookup in file=/root/libc.so [1]
902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1]
902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libc.so.6 [1]
902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libm.so.6 [1]
902: symbol=__gmon_start__; lookup in file=/lib/ld-linux-aarch64.so.1 [0]
902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libgcc_s.so.1 [1]
Segmentation fault
The libc version that I’m using is 2.36 as outputted by
$ ldd --version
ldd (Ubuntu GLIBC 2.36-0ubuntu4) 2.36
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Written by Roland McGrath and Ulrich Drepper
The error won’t happen if I dlopen with RTLD_LOCAL in b.cpp rather than RTLD_GLOBAL. I would appreciate any help on what I’m doing wrong here.
Best,
Nima
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Using dlmope/dlopem with RTLD_GLOBAL
2023-02-13 9:23 ` Using dlmope/dlopem with RTLD_GLOBAL Nima Hamidi
@ 2023-02-13 10:29 ` Florian Weimer
2023-02-13 10:40 ` Nima Hamidi
0 siblings, 1 reply; 4+ messages in thread
From: Florian Weimer @ 2023-02-13 10:29 UTC (permalink / raw)
To: Nima Hamidi via Libc-help; +Cc: Nima Hamidi
* Nima Hamidi via Libc-help:
> The error won’t happen if I dlopen with RTLD_LOCAL in b.cpp rather
> than RTLD_GLOBAL. I would appreciate any help on what I’m doing wrong
> here.
I think I see what's going on. The add_to_global_resize function does
not take into account that the global scope does not exist yet when it
is called. Would you please file a bug in Bugzilla?
<https://sourceware.org/bugzilla/enter_bug.cgi?product=glibc&component=dynamic-link>
Thanks,
Florian
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Using dlmope/dlopem with RTLD_GLOBAL
2023-02-13 10:29 ` Florian Weimer
@ 2023-02-13 10:40 ` Nima Hamidi
2023-02-13 11:28 ` Nima Hamidi
0 siblings, 1 reply; 4+ messages in thread
From: Nima Hamidi @ 2023-02-13 10:40 UTC (permalink / raw)
To: Nima Hamidi via Libc-help, Florian Weimer
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Thanks for your quick response. Will do that once I can create an account on Bugzilla.
On Feb 13, 2023 at 4:30 AM -0600, Florian Weimer <fweimer@redhat.com>, wrote:
> * Nima Hamidi via Libc-help:
>
> > The error won’t happen if I dlopen with RTLD_LOCAL in b.cpp rather
> > than RTLD_GLOBAL. I would appreciate any help on what I’m doing wrong
> > here.
>
> I think I see what's going on. The add_to_global_resize function does
> not take into account that the global scope does not exist yet when it
> is called. Would you please file a bug in Bugzilla?
>
> <https://sourceware.org/bugzilla/enter_bug.cgi?product=glibc&component=dynamic-link>
>
> Thanks,
> Florian
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Using dlmope/dlopem with RTLD_GLOBAL
2023-02-13 10:40 ` Nima Hamidi
@ 2023-02-13 11:28 ` Nima Hamidi
0 siblings, 0 replies; 4+ messages in thread
From: Nima Hamidi @ 2023-02-13 11:28 UTC (permalink / raw)
To: Nima Hamidi via Libc-help, Florian Weimer
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FYI, filed the issue: https://sourceware.org/bugzilla/show_bug.cgi?id=30118
On Feb 13, 2023 at 4:40 AM -0600, Nima Hamidi <nimaa.hamidi@gmail.com>, wrote:
> Thanks for your quick response. Will do that once I can create an account on Bugzilla.
> On Feb 13, 2023 at 4:30 AM -0600, Florian Weimer <fweimer@redhat.com>, wrote:
> > * Nima Hamidi via Libc-help:
> >
> > > The error won’t happen if I dlopen with RTLD_LOCAL in b.cpp rather
> > > than RTLD_GLOBAL. I would appreciate any help on what I’m doing wrong
> > > here.
> >
> > I think I see what's going on. The add_to_global_resize function does
> > not take into account that the global scope does not exist yet when it
> > is called. Would you please file a bug in Bugzilla?
> >
> > <https://sourceware.org/bugzilla/enter_bug.cgi?product=glibc&component=dynamic-link>
> >
> > Thanks,
> > Florian
> >
^ permalink raw reply [flat|nested] 4+ messages in thread
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[not found] <14297fb9-70cb-42b1-a477-6fb68c03ff64@Spark>
2023-02-13 9:23 ` Using dlmope/dlopem with RTLD_GLOBAL Nima Hamidi
2023-02-13 10:29 ` Florian Weimer
2023-02-13 10:40 ` Nima Hamidi
2023-02-13 11:28 ` Nima Hamidi
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