Bug 14663 – shared library test - link_linkdep - segfaults on FreeBSD 10

Running the druntime unit tests with the current dmd/druntime master (post 2.067) on FreeBSD 10 results in Testing link Testing load Testing linkD Testing linkDR Testing loadDR Testing host Testing finalize Testing link_linkdep Makefile:28: recipe for target 'obj/freebsd/64/link_linkdep.done' failed gmake[1]: *** [obj/freebsd/64/link_linkdep.done] Segmentation fault gmake[1]: Leaving directory '/usr/home/jmdavis/Programming/github/druntime/test/shared' posix.mak:206: recipe for target 'test/shared/.run' failed gmake: *** [test/shared/.run] Error 2 I don't know if FreeBSD 9 has the same problem, but clearly FreeBSD 8 does not, because that's what the autotester is running, and it's passing. So, something changed in either FreeBSD 9 or 10 to make it so that this test doesn't work anymore. I'll see if I can figure something out, but I'm not at all familiar with how the shared library code works or what exactly is being tested.

issue# 14776 is likely related to this one, but I don't know if they're the same bug or not. issue# 14776 is only triggered without -release and stops the unit tests before they get to the link_linkdep test which this bug report is for.

Can't reproduce the issue using dmd/druntime master and FBSD 10.

Oh wait, it happens only when using gcc, both in debug and release builds.

It dies in the runtime linker itself before _start and before library initialization. It's hard to find out b/c the runtime linker neither has symbols nor debug information. From a ktrace/utrace dump it seems that it happens shortly after relocation the symbols in liblinkdep.so https://github.com/freebsd/freebsd/blob/d16fdde7e16c8c6a2133a2385b83ce0955e576b1/libexec/rtld-elf/rtld.c#L2622. Seems there is something wrong with linking segments. When linked with clang it's: Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flags Align LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x00000000000006ec 0x00000000000006ec R E 200000 LOAD 0x00000000000006f0 0x00000000002006f0 0x00000000002006f0 0x00000000000002a8 0x00000000000002a8 RW 200000 DYNAMIC 0x0000000000000760 0x0000000000200760 0x0000000000200760 0x00000000000001d0 0x00000000000001d0 RW 8 GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 RW 8 Section to Segment mapping: Segment Sections... 00 .hash .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .text .fini .eh_frame 01 .ctors .dtors .jcr .data.rel.ro .dynamic .got .got.plt .data .minfo 02 .dynamic 03 When linked with gcc it becomes: Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flags Align LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000200aa8 0x0000000000200ac0 RWE 200000 DYNAMIC 0x0000000000200830 0x0000000000200830 0x0000000000200830 0x0000000000000210 0x0000000000000210 RW 8 GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 RW 10 Section to Segment mapping: Segment Sections... 00 .hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .text .fini .eh_frame .init_array .fini_array .ctors .dtors .jcr .data.rel.ro .dynamic .got .got.plt .data .minfo .bss 01 .dynamic 02 For some reason the readonly segment get's merged with the writeable segment. We had something similar already as issue 13117.

(In reply to Martin Nowak from comment #3) > Oh wait, it happens only when using gcc, both in debug and release builds. I wasn't aware that you could use anything other than gcc. dmd spits out errors if gcc isn't available for it to use.

(In reply to Jonathan M Davis from comment #6) > I wasn't aware that you could use anything other than gcc. dmd spits out > errors if gcc isn't available for it to use. I just fixed dmd's makefile, simply set CC. https://github.com/D-Programming-Language/dmd/pull/4837

Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/c011a559128e0c069140df4f7b3afd670403b081 fix Issue 14663 - shared library test - link_linkdep - segfaults on FreeBSD 10 - the .ctors.d_dso_ctor and .dtors.d_dso_dtor sections are merged into .ctors/.dtors or .init_array/.fini_array depending on the linker script - those sections need to be writeable b/c they can contain relocations (in PIC code) - merging readonly with writeable sections cause the gcc49 linker on FBSD10 to collapse the readonly and writeable segments https://github.com/D-Programming-Language/dmd/commit/8dad102881c0183256b9440d348a71b387c4b378 Merge pull request #4838 from MartinNowak/fix14776 fix Issue 14663 - shared library test - link_linkdep - segfaults on FreeBSD 10

All of the druntime tests now pass on my FreeBSD 10 box. Thanks!

Commits pushed to dmd-cxx at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/c011a559128e0c069140df4f7b3afd670403b081 fix Issue 14663 - shared library test - link_linkdep - segfaults on FreeBSD 10 https://github.com/dlang/dmd/commit/8dad102881c0183256b9440d348a71b387c4b378 Merge pull request #4838 from MartinNowak/fix14776