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Re: [Tinycc-devel] Overflows in the dynamic linker on x86_64 when using
Re: [Tinycc-devel] Overflows in the dynamic linker on x86_64 when using a tcc-built shared library along with others
Mon, 2 Jul 2018 01:15:52 +0200 (CEST)
Alpine 2.20 (LSU 67 2015-01-07)
On Thu, 28 Jun 2018, Petr Skocik wrote:
Symbol `__dso_handle' causes overflow in R_X86_64_PC32 relocation
Symbol `fstatat' causes overflow in R_X86_64_PC32 relocation
Symbol `fstat' causes overflow in R_X86_64_PC32 relocation
Symbol `mknod' causes overflow in R_X86_64_PC32 relocation
Symbol `pthread_atfork' causes overflow in R_X86_64_PC32 relocation
Indeed. TCC doesn't link with crtbegin.o (or crtbeginS.o) coming from
GCC, and hence doesn't provide the hack symbol __dso_handle (which
pthread_atfork in glibc needs). This is another case of an
interdependency between glibc and compiler specifics.
I tried to make an MCVE (minimal, complete, verifiable example) and this one
should do it:
Thanks. There's a work around for the pthread_atfork problem: add this
definition to one source file for each shared library/executable that
contains a call to pthread_atfork:
void * __dso_handle __attribute((visibility("hidden"))) = &__dso_handle;
e.g. in your testcase, add it to liblib.c . Eventually we probably want
to create this symbol automatically from TCC on glibc systems, until then
you can use the above.
That fstat/fstatat/mknod have overflows as well might have multiple
reasons: on glibc systems all three functions have something in common:
they are defined in the libc_nonshared.a archive, which normally should
have been included via libc.so (a linker script, not a normal softlink to
the real shared lib). You can check with -vvv which should list that
library to be included. No matter what I can't reproduce that problem by
e.g. adding a call to fstatat into your reproducer for the dso_handle
problem, so if you can provide one for e.g. fstatat as well...
If this is a bad place to post such bug reports, please let me know.
(Should I post bug reports on
https://savannah.nongnu.org/bugs/?group=tinycc or elsewhere instead?)
Many people here don't have a bugzilla account there and so
don't monitor it; it seems better to write here.
- Re: [Tinycc-devel] Overflows in the dynamic linker on x86_64 when using a tcc-built shared library along with others,
Michael Matz <=