Date: Tue, 12 Mar 2019 16:34:47 -0700 From: Mark Millard <marklmi@yahoo.com> To: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, FreeBSD Toolchain <freebsd-toolchain@freebsd.org> Subject: Re: powerpc64 head -r345044: WITH_LLVM_LIBUNWIND= based buildworld leads to thrown C++ exceptions segmentation faulting Message-ID: <3B37B7B0-DCB0-4984-AABD-4C3448DA7D56@yahoo.com> In-Reply-To: <EBF75BC7-DD49-4FBA-86DD-F3F848BB5280@yahoo.com> References: <36A485AF-E786-4BDB-8DD8-863BAB38D359@yahoo.com> <EBF75BC7-DD49-4FBA-86DD-F3F848BB5280@yahoo.com>
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[The unoptimized code is more revealing so I switch to
presenting it and what it lead me to: more detail on
r2 being mishandled.]
> On 2019-Mar-12, at 14:05, Mark Millard <marklmi at yahoo.com> wrote:
>=20
> [I got some libunwind debug output from the a.out run. This
> and a disassembly of main suggest an instruction pointer
> address is too large by 0x4 for jumping to the code that
> would call __cxa_begin_catch .]
>=20
>> On 2019-Mar-12, at 12:20, Mark Millard <marklmi@yahoo.com> wrote:
>>=20
>> [I sometimes experiment with building powerpc64 (and 32-bit) via
>> more modern toolchains, here a amd64->powerpc64 cross build via
>> system-clang (so 8.0.0).]
>>=20
>> buildworld with WITH_LLVM_LIBUNWIND=3D completes for powerpc64
>> (but not 32-bit powerpc). However, for a system installed
>> from such for pwoerpc64, the following program (for example)
>> gets a segmentation fault:
>>=20
>> # more ~/c_tests/exception_test.cpp=20
>> #include <exception>
>>=20
>> int main(void)
>> {
>> try { throw std::exception(); }
>> catch (std::exception& e) {}
>> return 0;
>> }
>>=20
>> (Note: the same a.out works under a WITHOUT_LLVM_LIBUNWIND=3D
>> environment, that was patched for DW_CFA_remember_state and
>> DW_CFA_restore_state handling, with the system built via
>> devel/powerpc64-xtoolchain-gcc related materials. So the
>> failure is on the system library does of things for the
>> WITH_LLVM_LIBUNWIND=3D context.)
>>=20
>> Unfortunately:
>>=20
>> A) devel/gdb makes extensive use of thrown C++ exceptions
>> and so does not work for a powerpc64 system based on
>> WITH_LLVM_LIBUNWIND=3D .
>>=20
>> B) The world built is not using dwarf-2 so /usr/libexec/gdb
>> is not handy/useful.
>>=20
>> C) CFLAGS+=3D-gdwarf-2 leads to system-clang having an Abort
>> trap during buildworld's compile of gcrt1.s . (Reference
>> material later, below.)
>>=20
>> D) lldb crashes in llvm_unreachable in
>> lldb::RegisterContextSP FreeBSDThread::GetRegisterContext()
>> on powerpc64. (Reference material later, below.)
>>=20
>> So I've not managed to check the backtrace for the
>> segmentation fault in the short example.
>>=20
>>=20
>>=20
>> For reference . . .
>>=20
>>=20
>> For (C) ( -gdwarf-2 use ):
>>=20
>> QUOTES
>> (gdb) bt
>> #0 thr_kill () at thr_kill.S:3
>> #1 0x000000000474afcf in __raise (s=3D6) at =
/usr/src/lib/libc/gen/raise.c:52
>> #2 0x00000000046cd386 in abort () at =
/usr/src/lib/libc/stdlib/abort.c:79
>> #3 0x00000000047394ba in __assert (func=3D<optimized out>, =
file=3D<optimized out>, line=3D<optimized out>, failedexpr=3D<optimized =
out>) at /usr/src/lib/libc/gen/assert.c:51
>> #4 0x000000000429aa9f in resetRootFile () at =
/usr/src/contrib/llvm/include/llvm/MC/MCDwarf.h:316
>> #5 parseDirectiveFile () at =
/usr/src/contrib/llvm/lib/MC/MCParser/AsmParser.cpp:3377
>> #6 parseStatement () at =
/usr/src/contrib/llvm/lib/MC/MCParser/AsmParser.cpp:2023
>> #7 0x000000000428cc12 in Run () at =
/usr/src/contrib/llvm/lib/MC/MCParser/AsmParser.cpp:884
>> #8 0x000000000163c649 in ExecuteAssembler () at =
/usr/src/contrib/llvm/tools/clang/tools/driver/cc1as_main.cpp:503
>> #9 cc1as_main () at =
/usr/src/contrib/llvm/tools/clang/tools/driver/cc1as_main.cpp:589
>> #10 0x0000000001643d10 in ExecuteCC1Tool () at =
/usr/src/contrib/llvm/tools/clang/tools/driver/driver.cpp:312
>> #11 main () at =
/usr/src/contrib/llvm/tools/clang/tools/driver/driver.cpp:382
>>=20
>> void resetRootFile() {
>> assert(Header.MCDwarfFiles.empty());
>> Header.RootFile.Name.clear();
>> Header.resetMD5Usage();
>> Header.HasSource =3D false;
>> }
>>=20
>> --- lib/csu__L ---
>> cc: error: unable to execute command: Abort trap (core dumped)
>> cc: error: clang integrated assembler command failed due to signal =
(use -v to see invocation)
>> FreeBSD clang version 8.0.0 (branches/release_80 355677) (based on =
LLVM 8.0.0)
>> Target: powerpc64-unknown-freebsd13.0
>> Thread model: posix
>> InstalledDir: /usr/bin
>> cc: note: diagnostic msg: PLEASE submit a bug report to =
https://bugs.freebsd.org/submit/ and include the crash backtrace, =
preprocessed source, and associated run script.
>> cc: note: diagnostic msg: Error generating preprocessed source(s) - =
no preprocessable inputs.
>> *** [gcrt1.o] Error code 254
>>=20
>> make[5]: stopped in /usr/src/lib/csu/powerpc64
>> .ERROR_TARGET=3D'gcrt1.o'
>> =
.ERROR_META_FILE=3D'/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.power=
pc64/usr/src/powerpc.powerpc64/lib/csu/powerpc64/gcrt1.o.meta'
>> .MAKE.LEVEL=3D'5'
>> MAKEFILE=3D''
>> .MAKE.MODE=3D'meta missing-filemon=3Dyes missing-meta=3Dyes =
silent=3Dyes verbose'
>> _ERROR_CMD=3D'cc -gdwarf-2 -target powerpc64-unknown-freebsd13.0 =
--sysroot=3D/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr=
/src/powerpc.powerpc64/tmp =
-B/usr/local/powerpc64-unknown-freebsd13.0/bin/ -O2 -pipe =
-I/usr/src/lib/csu/common -I/usr/src/lib/libc/include -mlongcall =
-DCRT_IRELOC_SUPPRESS -std=3Dgnu99 -Wsystem-headers -Wall =
-Wno-format-y2k -W -Wno-unused-parameter -Wstrict-prototypes =
-Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual =
-Wwrite-strings -Wswitch -Wshadow -Wunused-parameter -Wcast-align =
-Wchar-subscripts -Winline -Wnested-externs -Wredundant-decls =
-Wold-style-definition -Wno-pointer-sign -Wthread-safety -Wno-empty-body =
-Wno-string-plus-int -Wno-unused-const-variable -Qunused-arguments -c =
-o gcrt1.o gcrt1.s;'
>> .CURDIR=3D'/usr/src/lib/csu/powerpc64'
>> .MAKE=3D'make'
>> =
.OBJDIR=3D'/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/=
src/powerpc.powerpc64/lib/csu/powerpc64'
>> .TARGETS=3D'all'
>> =
DESTDIR=3D'/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/=
src/powerpc.powerpc64/tmp'
>> LD_LIBRARY_PATH=3D''
>> MACHINE=3D'powerpc'
>> MACHINE_ARCH=3D'powerpc64'
>> MAKEOBJDIRPREFIX=3D''
>> MAKESYSPATH=3D'/usr/src/share/mk'
>> MAKE_VERSION=3D'20181221'
>> =
PATH=3D'/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src=
/powerpc.powerpc64/tmp/usr/sbin:/usr/obj/powerpc64vtsc_clang_altbinutils/p=
owerpc.powerpc64/usr/src/powerpc.powerpc64/tmp/usr/bin:/usr/obj/powerpc64v=
tsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp/lega=
cy/usr/sbin:/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr=
/src/powerpc.powerpc64/tmp/legacy/usr/bin:/usr/obj/powerpc64vtsc_clang_alt=
binutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp/legacy/bin::/sbin=
:/bin:/usr/sbin:/usr/bin'
>> SRCTOP=3D'/usr/src'
>> =
OBJTOP=3D'/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/s=
rc/powerpc.powerpc64'
>> .MAKE.MAKEFILES=3D'/usr/src/share/mk/sys.mk =
/usr/src/share/mk/local.sys.env.mk /usr/src/share/mk/src.sys.env.mk =
/root/src.configs/src.conf.powerpc64-clang_altbinutils-bootstrap.amd64-hos=
t /usr/src/share/mk/bsd.mkopt.mk /usr/src/share/mk/src.sys.obj.mk =
/usr/src/share/mk/auto.obj.mk /usr/src/share/mk/bsd.suffixes.mk =
/root/src.configs/make.conf /usr/src/share/mk/local.sys.mk =
/usr/src/share/mk/src.sys.mk /dev/null =
/usr/src/lib/csu/powerpc64/Makefile /usr/src/share/mk/bsd.lib.mk =
/usr/src/share/mk/bsd.init.mk /usr/src/share/mk/bsd.opts.mk =
/usr/src/share/mk/bsd.cpu.mk /usr/src/share/mk/local.init.mk =
/usr/src/share/mk/src.init.mk /usr/src/lib/csu/powerpc64/../Makefile.inc =
/usr/src/share/mk/src.opts.mk /usr/src/share/mk/bsd.own.mk =
/usr/src/share/mk/bsd.compiler.mk /usr/src/share/mk/bsd.linker.mk =
/usr/src/lib/csu/powerpc64/../../Makefile.inc =
/usr/src/share/mk/bsd.libnames.mk /usr/src/share/mk/src.libnames.mk =
/usr/src/share/mk/bsd.symver.mk /usr/src/share/mk/bsd.nls.mk =
/usr/src/share/mk/bsd.confs.mk /usr/src/share/mk/bsd.files.mk =
/usr/src/share/mk/bsd.dirs.mk /usr/src/share/mk/bsd.incs.mk =
/usr/src/share/mk/bsd.links.mk /usr/src/share/mk/bsd.dep.mk =
/usr/src/share/mk/bsd.clang-analyze.mk /usr/src/share/mk/bsd.obj.mk =
/usr/src/share/mk/bsd.subdir.mk /usr/src/share/mk/bsd.sys.mk'
>> .PATH=3D'. /usr/src/lib/csu/powerpc64 /usr/src/lib/csu/common'
>> 1 error
>> END QUOTES
>>=20
>>=20
>> For (D) (lldb):
>>=20
>> QUOTES
>> CPU not supported
>> UNREACHABLE executed at =
/usr/src/contrib/llvm/tools/lldb/source/Plugins/Process/FreeBSD/FreeBSDThr=
ead.cpp:192!
>> Abort trap (core dumped)
>>=20
>> (gdb) bt
>> #0 0x0000000813715208 in .__sys_thr_kill () at thr_kill.S:3
>> #1 0x00000008137147cc in __raise (s=3D<optimized out>) at =
/usr/src/lib/libc/gen/raise.c:52
>> #2 0x000000081366b5d8 in abort () at =
/usr/src/lib/libc/stdlib/abort.c:79
>> #3 0x0000000011df6fb8 in llvm::llvm_unreachable_internal () at =
/usr/src/contrib/llvm/lib/Support/ErrorHandling.cpp:222
>> #4 0x00000000103aaaf8 in FreeBSDThread::GetRegisterContext () at =
/usr/src/contrib/llvm/tools/lldb/source/Plugins/Process/FreeBSD/FreeBSDThr=
ead.cpp:192
>> #5 0x00000000105807d4 in lldb_private::Thread::SetupForResume () at =
/usr/src/contrib/llvm/tools/lldb/source/Target/Thread.cpp:613
>> #6 0x0000000010571bc8 in lldb_private::ThreadList::WillResume () at =
/usr/src/contrib/llvm/tools/lldb/source/Target/ThreadList.cpp:541
>> #7 0x00000000105da23c in lldb_private::Process::PrivateResume () at =
/usr/src/contrib/llvm/tools/lldb/source/Target/Process.cpp:3281
>> #8 0x00000000105a00c8 in lldb_private::Target::Launch () at =
/usr/src/contrib/llvm/tools/lldb/source/Target/Target.cpp:2922
>> #9 0x000000001073f550 in CommandObjectProcessLaunch::DoExecute () at =
/usr/src/contrib/llvm/tools/lldb/source/Commands/CommandObjectProcess.cpp:=
221
>> #10 0x00000000106c36c4 in lldb_private::CommandObjectParsed::Execute =
() at =
/usr/src/contrib/llvm/tools/lldb/source/Interpreter/CommandObject.cpp:975
>> #11 0x00000000106d8b44 in =
lldb_private::CommandInterpreter::HandleCommand () at =
/usr/src/contrib/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp=
:1761
>> #12 0x00000000106da0a0 in =
lldb_private::CommandInterpreter::IOHandlerInputComplete () at =
/usr/src/contrib/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp=
:2801
>> #13 0x00000000107c0a08 in lldb_private::IOHandlerEditline::Run () at =
/usr/src/contrib/llvm/tools/lldb/source/Core/IOHandler.cpp:558
>> #14 0x0000000010346e5c in lldb_private::Debugger::ExecuteIOHandlers =
() at /usr/src/contrib/llvm/tools/lldb/source/Core/Debugger.cpp:988
>> #15 0x00000000106c8ddc in =
lldb_private::CommandInterpreter::RunCommandInterpreter () at =
/usr/src/contrib/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp=
:3003
>> #16 0x000000001034feb4 in lldb::SBDebugger::RunCommandInterpreter () =
at /usr/src/contrib/llvm/tools/lldb/source/API/SBDebugger.cpp:935
>> #17 0x00000000101de878 in Driver::MainLoop () at =
/usr/src/contrib/llvm/tools/lldb/tools/driver/Driver.cpp:756
>> #18 0x00000000101a0088 in main () at =
/usr/src/contrib/llvm/tools/lldb/tools/driver/Driver.cpp:936
>>=20
>> lldb::RegisterContextSP FreeBSDThread::GetRegisterContext() {
>> if (!m_reg_context_sp) {
>> m_posix_thread =3D nullptr;
>>=20
>> RegisterInfoInterface *reg_interface =3D nullptr;
>> const ArchSpec &target_arch =3D =
GetProcess()->GetTarget().GetArchitecture();
>>=20
>> switch (target_arch.GetMachine()) {
>> case llvm::Triple::aarch64:
>> reg_interface =3D new RegisterInfoPOSIX_arm64(target_arch);
>> break;
>> case llvm::Triple::arm:
>> reg_interface =3D new RegisterInfoPOSIX_arm(target_arch);
>> break;
>> case llvm::Triple::ppc:
>> #ifndef __powerpc64__
>> reg_interface =3D new =
RegisterContextFreeBSD_powerpc32(target_arch);
>> break;
>> #endif
>> case llvm::Triple::ppc64:
>> reg_interface =3D new =
RegisterContextFreeBSD_powerpc64(target_arch);
>> break;
>> case llvm::Triple::mips64:
>> reg_interface =3D new RegisterContextFreeBSD_mips64(target_arch);
>> break;
>> case llvm::Triple::x86:
>> reg_interface =3D new RegisterContextFreeBSD_i386(target_arch);
>> break;
>> case llvm::Triple::x86_64:
>> reg_interface =3D new RegisterContextFreeBSD_x86_64(target_arch);
>> break;
>> default:
>> llvm_unreachable("CPU not supported");
>> }
>> END QUOTES.
>=20
>=20
>=20
> I ran into libunwind having LIBUNWIND_PRINT_UNWINDING and
> LIBUNWIND_PRINT_APIS so I can report for the segmentation
> fault:
>=20
> # export LIBUNWIND_PRINT_UNWINDING=3D""
> # export LIBUNWIND_PRINT_APIS=3D""
> # ./a.out
> . . .
Using unoptimized code instead:
# c++ -g exception_test.cpp
libunwind: __register_frame_info(0x137d6610, 0x13ae3150)
libunwind: __register_frame_info(0x137d6610, 0x13ae3150)
libunwind: __deregister_frame_info(0x137d6610)
libunwind: __deregister_frame_info(0x137d6610)
# ./a.out
libunwind: _Unwind_RaiseException(ex_obj=3D0x810043060)
libunwind: unw_init_local(cursor=3D0x3fffffffffffcb48, =
context=3D0x3fffffffffffd0e0)
libunwind: unw_step(cursor=3D0x3fffffffffffcb48)
libunwind: unw_get_proc_info(cursor=3D0x3fffffffffffcb48, =
&info=3D0x3fffffffffffd830)
libunwind: unw_get_proc_name(cursor=3D0x3fffffffffffcb48, =
&buf=3D0x3fffffffffffd628, bufLen=3D512)
libunwind: unw_get_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-1, =
&value=3D0x3fffffffffffd618)
libunwind: unwind_phase1(ex_ojb=3D0x810043060): pc=3D0x81019d954, =
start_ip=3D0x81019d860, func=3D.anonymous., lsda=3D0x0, personality=3D0x0
libunwind: unw_step(cursor=3D0x3fffffffffffcb48)
libunwind: unw_get_proc_info(cursor=3D0x3fffffffffffcb48, =
&info=3D0x3fffffffffffd830)
libunwind: unw_get_proc_name(cursor=3D0x3fffffffffffcb48, =
&buf=3D0x3fffffffffffd628, bufLen=3D512)
libunwind: unw_get_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-1, =
&value=3D0x3fffffffffffd618)
libunwind: unwind_phase1(ex_ojb=3D0x810043060): pc=3D0x10000dac, =
start_ip=3D0x10000d64, func=3D.anonymous., lsda=3D0x10000fe0, =
personality=3D0x8101b5360
libunwind: unwind_phase1(ex_ojb=3D0x810043060): calling personality =
function 0x8101b5360
libunwind: unw_get_proc_info(cursor=3D0x3fffffffffffcb48, =
&info=3D0x3fffffffffffc950)
libunwind: _Unwind_GetLanguageSpecificData(context=3D0x3fffffffffffcb48) =
=3D> 0x10000fe0
libunwind: unw_get_proc_info(cursor=3D0x3fffffffffffcb48, =
&info=3D0x3fffffffffffc890)
libunwind: _Unwind_GetRegionStart(context=3D0x3fffffffffffcb48) =3D> =
0x10000d64
libunwind: unw_get_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-1, =
&value=3D0x3fffffffffffc8c8)
libunwind: _Unwind_GetIP(context=3D0x3fffffffffffcb48) =3D> 0x10000dac
libunwind: unw_get_proc_info(cursor=3D0x3fffffffffffcb48, =
&info=3D0x3fffffffffffc880)
libunwind: _Unwind_GetRegionStart(context=3D0x3fffffffffffcb48) =3D> =
0x10000d64
libunwind: unw_get_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-2, =
&value=3D0x3fffffffffffd828)
libunwind: unwind_phase1(ex_ojb=3D0x810043060): _URC_HANDLER_FOUND
libunwind: unw_init_local(cursor=3D0x3fffffffffffcb48, =
context=3D0x3fffffffffffd0e0)
libunwind: unwind_phase2(ex_ojb=3D0x810043060)
libunwind: unw_step(cursor=3D0x3fffffffffffcb48)
libunwind: unw_get_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-2, =
&value=3D0x3fffffffffffca58)
libunwind: unw_get_proc_info(cursor=3D0x3fffffffffffcb48, =
&info=3D0x3fffffffffffca10)
libunwind: unw_get_proc_name(cursor=3D0x3fffffffffffcb48, =
&buf=3D0x3fffffffffffc810, bufLen=3D512)
libunwind: unwind_phase2(ex_ojb=3D0x810043060): start_ip=3D0x81019d860, =
func=3D.anonymous., sp=3D0x3fffffffffffd8e0, lsda=3D0x0, personality=3D0x0=
libunwind: unw_step(cursor=3D0x3fffffffffffcb48)
libunwind: unw_get_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-2, =
&value=3D0x3fffffffffffca58)
libunwind: unw_get_proc_info(cursor=3D0x3fffffffffffcb48, =
&info=3D0x3fffffffffffca10)
libunwind: unw_get_proc_name(cursor=3D0x3fffffffffffcb48, =
&buf=3D0x3fffffffffffc810, bufLen=3D512)
libunwind: unwind_phase2(ex_ojb=3D0x810043060): start_ip=3D0x10000d64, =
func=3D.anonymous., sp=3D0x3fffffffffffd980, lsda=3D0x10000fe0, =
personality=3D0x8101b5360
libunwind: unw_get_proc_info(cursor=3D0x3fffffffffffcb48, =
&info=3D0x3fffffffffffc610)
libunwind: _Unwind_GetLanguageSpecificData(context=3D0x3fffffffffffcb48) =
=3D> 0x10000fe0
libunwind: _Unwind_SetIP(context=3D0x3fffffffffffcb48, value=3D0x10000db4)=
libunwind: unw_set_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-1, =
value=3D0x10000db4)
libunwind: _Unwind_SetGR(context=3D0x3fffffffffffcb48, reg=3D3, =
value=3D0x810043060)
libunwind: unw_set_reg(cursor=3D0x3fffffffffffcb48, regNum=3D3, =
value=3D0x810043060)
libunwind: _Unwind_SetGR(context=3D0x3fffffffffffcb48, reg=3D4, =
value=3D0x1)
libunwind: unw_set_reg(cursor=3D0x3fffffffffffcb48, regNum=3D4, =
value=3D0x1)
libunwind: unwind_phase2(ex_ojb=3D0x810043060): _URC_INSTALL_CONTEXT
libunwind: unw_get_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-1, =
&value=3D0x3fffffffffffc810)
libunwind: unw_get_reg(cursor=3D0x3fffffffffffcb48, regNum=3D-2, =
&value=3D0x3fffffffffffca58)
libunwind: unwind_phase2(ex_ojb=3D0x810043060): re-entering user code =
with ip=3D0x10000db4, sp=3D0x3fffffffffffd980
libunwind: unw_resume(cursor=3D0x3fffffffffffcb48)
Segmentation fault (core dumped)
The below shows that the 0x10000db4 in this case seems right --and
also that the code sequence does not set r2. Apparently the
throw handling was supposed to set it so the optimized code
skips setting it. (Later below it seems r2 should have been
set by something but was not correctly set.)
(gdb) disass main
Dump of assembler code for function main():
0x0000000010000d64 <+0>: mflr r0
0x0000000010000d68 <+4>: std r31,-8(r1)
0x0000000010000d6c <+8>: std r0,16(r1)
0x0000000010000d70 <+12>: stdu r1,-160(r1)
0x0000000010000d74 <+16>: mr r31,r1
0x0000000010000d78 <+20>: li r3,0
0x0000000010000d7c <+24>: stw r3,148(r31)
0x0000000010000d80 <+28>: li r3,8
0x0000000010000d84 <+32>: bl 0x100007a0 =
<00000018.plt_call.__cxa_allocate_exception@@CXXABI_1.3>
0x0000000010000d88 <+36>: ld r2,40(r1)
0x0000000010000d8c <+40>: std r3,112(r31)
0x0000000010000d90 <+44>: bl 0x10000e00 =
<std::exception::exception()>
0x0000000010000d94 <+48>: nop
0x0000000010000d98 <+52>: ld r4,-32728(r2)
0x0000000010000d9c <+56>: nop
0x0000000010000da0 <+60>: ld r5,-32720(r2)
0x0000000010000da4 <+64>: ld r3,112(r31)
0x0000000010000da8 <+68>: bl 0x10000800 =
<00000018.plt_call.__cxa_throw@@CXXABI_1.3>
0x0000000010000dac <+72>: ld r2,40(r1)
0x0000000010000db0 <+76>: b 0x10000df4 <main()+144>
0x0000000010000db4 <+80>: mr r5,r4
0x0000000010000db8 <+84>: std r3,136(r31)
0x0000000010000dbc <+88>: stw r5,132(r31)
0x0000000010000dc0 <+92>: b 0x10000dc4 <main()+96>
0x0000000010000dc4 <+96>: ld r3,136(r31)
0x0000000010000dc8 <+100>: bl 0x100007c0 =
<00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3>
0x0000000010000dcc <+104>: ld r2,40(r1)
0x0000000010000dd0 <+108>: std r3,120(r31)
0x0000000010000dd4 <+112>: bl 0x100007e0 =
<00000018.plt_call.__cxa_end_catch@@CXXABI_1.3>
0x0000000010000dd8 <+116>: ld r2,40(r1)
0x0000000010000ddc <+120>: li r3,0
0x0000000010000de0 <+124>: addi r1,r1,160
0x0000000010000de4 <+128>: ld r0,16(r1)
0x0000000010000de8 <+132>: ld r31,-8(r1)
0x0000000010000dec <+136>: mtlr r0
0x0000000010000df0 <+140>: blr
0x0000000010000df4 <+144>: .long 0x0
0x0000000010000df8 <+148>: .long 0x0
0x0000000010000dfc <+152>: .long 0x0
End of assembler dump.
Notably lr seems to be: 0x10000dcc which
is just after:
bl 0x100007c0 <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3>
Note also the pc, r12, and ctr all having the failure
address: 0x81042b900 .
#0 0x000000081042b900 in ?? () from /lib/libc.so.7
(gdb) x/32i 0x000000081042b8F0
0x81042b8f0 <getfsstat@got.plt>: .long 0x8
0x81042b8f4 <getfsstat@got.plt+4>: vmrglh v1,v30,v7
0x81042b8f8: .long 0x8
0x81042b8fc: vsubeuqm v1,v30,v7,v17
=3D> 0x81042b900: .long 0x8
0x81042b904: vpmsumw v1,v30,v7
0x81042b908 <_citrus_bcs_skip_ws_len@got.plt>: .long 0x8
0x81042b90c <_citrus_bcs_skip_ws_len@got.plt+4>: .long 0x103e3c92
0x81042b910: .long 0x8
0x81042b914: .long 0x103e3c9b
0x81042b918: .long 0x8
(gdb) info reg
r0 0x810563d10 34633825552
r1 0x3fffffffffffd980 4611686018427378048
r2 0x0 0
r3 0x810043060 34628448352
r4 0x1 1
r5 0x1 1
r6 0x8103d9490 34632209552
r7 0x0 0
r8 0x29 41
r9 0x4e 78
r10 0x3fffffffffffc8f8 4611686018427373816
r11 0x81056c28c 34633859724
r12 0x81042b900 34632546560
r13 0x81005f020 34628562976
r14 0x0 0
r15 0x0 0
r16 0x0 0
r17 0x0 0
r18 0x0 0
r19 0x0 0
r20 0x0 0
r21 0x0 0
r22 0x0 0
r23 0x0 0
r24 0x0 0
r25 0x0 0
r26 0x0 0
r27 0x0 0
r28 0x1 1
r29 0x3fffffffffffdb78 4611686018427378552
r30 0x3fffffffffffdb88 4611686018427378568
r31 0x3fffffffffffd980 4611686018427378048
pc 0x81042b900 0x81042b900
msr <unavailable>
cr 0x28000802 671090690
lr 0x10000dcc 0x10000dcc <main()+104>
ctr 0x81042b900 34632546560
xer 0x0 0
fpscr 0x0 0
vscr <unavailable>
vrsave <unavailable>
And the following shows how r12 and ctr were filled in by
code that expected r2 to be correct:
(gdb) x/32i 0x100007c0
0x100007c0 <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3>: =
std r2,40(r1)
0x100007c4 <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3+4>: =
ld r12,-32608(r2)
0x100007c8 <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3+8>: =
mtctr r12
0x100007cc <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3+12>: =
ld r11,-32592(r2)
0x100007d0 <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3+16>: =
ld r2,-32600(r2)
0x100007d4 <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3+20>: =
bctr
0x100007d8 <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3+24>: =
.long 0x0
0x100007dc <00000018.plt_call.__cxa_begin_catch@@CXXABI_1.3+28>: =
.long 0x0
. . .
Overall: r2 seem to be mishandled in the exception handling.
Note on the gdb use:
The above devel/gdb activity was executed from a
devel/powerpc64-xtoolchain-gcc built world that was based on
WITHOUT_LLVM_LIBUNWIND=3D and and my patched libgcc_s material.
This means it suffered from mismatches with the clang/libunwind
world (that I chroot to):
QUOTE
warning: .dynamic section for "/usr/lib/libc++.so.1" is not at the =
expected address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/libcxxrt.so.1" is not at the =
expected address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/libm.so.5" is not at the expected =
address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/libc.so.7" is not at the expected =
address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/libgcc_s.so.1" is not at the =
expected address (wrong library or version mismatch?)
warning: .dynamic section for "/libexec/ld-elf.so.1" is not at the =
expected address (wrong library or version mismatch?)
END QUOTE
But any thrown exceptions the gdb may have used worked in my
patched WITHOUT_LLVM_LIBUNWIND=3D environment. This gdb is not
limited to dwarf-2.
The material from the a.out is not misinterpreted even if
library code details might be.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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