From 3a76f8f489428bada97c9dea2145448a3e0f7135 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Mon, 12 Jul 2021 18:03:22 +0100 Subject: Avoid letting exceptions escape gdb_bfd_iovec_fileio_close (PR gdb/28080) Before PR gdb/28080 was fixed by the previous patch, GDB was crashing like this: (gdb) detach Detaching from program: target:/any/program, process 3671843 Detaching from process 3671843 Ending remote debugging. [Inferior 1 (process 3671843) detached] In main terminate called after throwing an instance of 'gdb_exception_error' Aborted (core dumped) Here's the exception above being thrown: (top-gdb) bt #0 throw_error (error=TARGET_CLOSE_ERROR, fmt=0x555556035588 "Remote connection closed") at src/gdbsupport/common-exceptions.cc:222 #1 0x0000555555bbaa46 in remote_target::readchar (this=0x555556a11040, timeout=10000) at src/gdb/remote.c:9440 #2 0x0000555555bbb9e5 in remote_target::getpkt_or_notif_sane_1 (this=0x555556a11040, buf=0x555556a11058, forever=0, expecting_notif=0, is_notif=0x0) at src/gdb/remote.c:9928 #3 0x0000555555bbbda9 in remote_target::getpkt_sane (this=0x555556a11040, buf=0x555556a11058, forever=0) at src/gdb/remote.c:10030 #4 0x0000555555bc0e75 in remote_target::remote_hostio_send_command (this=0x555556a11040, command_bytes=13, which_packet=14, remote_errno=0x7fffffffcfd0, attachment=0x0, attachment_len=0x0) at src/gdb/remote.c:12137 #5 0x0000555555bc1b6c in remote_target::remote_hostio_close (this=0x555556a11040, fd=8, remote_errno=0x7fffffffcfd0) at src/gdb/remote.c:12455 #6 0x0000555555bc1bb4 in remote_target::fileio_close (During symbol reading: .debug_line address at offset 0x64f417 is 0 [in module build/gdb/gdb] this=0x555556a11040, fd=8, remote_errno=0x7fffffffcfd0) at src/gdb/remote.c:12462 #7 0x0000555555c9274c in target_fileio_close (fd=3, target_errno=0x7fffffffcfd0) at src/gdb/target.c:3365 #8 0x000055555595a19d in gdb_bfd_iovec_fileio_close (abfd=0x555556b9f8a0, stream=0x555556b11530) at src/gdb/gdb_bfd.c:439 #9 0x0000555555e09e3f in opncls_bclose (abfd=0x555556b9f8a0) at src/bfd/opncls.c:599 #10 0x0000555555e0a2c7 in bfd_close_all_done (abfd=0x555556b9f8a0) at src/bfd/opncls.c:847 #11 0x0000555555e0a27a in bfd_close (abfd=0x555556b9f8a0) at src/bfd/opncls.c:814 #12 0x000055555595a9d3 in gdb_bfd_close_or_warn (abfd=0x555556b9f8a0) at src/gdb/gdb_bfd.c:626 #13 0x000055555595ad29 in gdb_bfd_unref (abfd=0x555556b9f8a0) at src/gdb/gdb_bfd.c:715 #14 0x0000555555ae4730 in objfile::~objfile (this=0x555556515540, __in_chrg=) at src/gdb/objfiles.c:573 #15 0x0000555555ae955a in std::_Sp_counted_ptr::_M_dispose (this=0x555556c20db0) at /usr/include/c++/9/bits/shared_ptr_base.h:377 #16 0x000055555572b7c8 in std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release (this=0x555556c20db0) at /usr/include/c++/9/bits/shared_ptr_base.h:155 #17 0x00005555557263c3 in std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count (this=0x555556bf0588, __in_chrg=) at /usr/include/c++/9/bits/shared_ptr_base.h:730 #18 0x0000555555ae745e in std::__shared_ptr::~__shared_ptr (this=0x555556bf0580, __in_chrg=) at /usr/include/c++/9/bits/shared_ptr_base.h:1169 #19 0x0000555555ae747e in std::shared_ptr::~shared_ptr (this=0x555556bf0580, __in_chrg=) at /usr/include/c++/9/bits/shared_ptr.h:103 #20 0x0000555555b1c1dc in __gnu_cxx::new_allocator > >::destroy > (this=0x5555564cdd60, __p=0x555556bf0580) at /usr/include/c++/9/ext/new_allocator.h:153 #21 0x0000555555b1bb1d in std::allocator_traits > > >::destroy > (__a=..., __p=0x555556bf0580) at /usr/include/c++/9/bits/alloc_traits.h:497 #22 0x0000555555b1b73e in std::__cxx11::list, std::allocator > >::_M_erase (this=0x5555564cdd60, __position=std::shared_ptr (expired, weak count 1) = {get() = 0x555556515540}) at /usr/include/c++/9/bits/stl_list.h:1921 #23 0x0000555555b1afeb in std::__cxx11::list, std::allocator > >::erase (this=0x5555564cdd60, __position=std::shared_ptr (expired, weak count 1) = {get() = 0x555556515540}) at /usr/include/c++/9/bits/list.tcc:158 #24 0x0000555555b19576 in program_space::remove_objfile (this=0x5555564cdd20, objfile=0x555556515540) at src/gdb/progspace.c:210 #25 0x0000555555ae4502 in objfile::unlink (this=0x555556515540) at src/gdb/objfiles.c:487 #26 0x0000555555ae5a12 in objfile_purge_solibs () at src/gdb/objfiles.c:875 #27 0x0000555555c09686 in no_shared_libraries (ignored=0x0, from_tty=1) at src/gdb/solib.c:1236 #28 0x00005555559e3f5f in detach_command (args=0x0, from_tty=1) at src/gdb/infcmd.c:2769 Note frame #14: #14 0x0000555555ae4730 in objfile::~objfile (this=0x555556515540, __in_chrg=) at src/gdb/objfiles.c:573 That's a dtor, thus noexcept. That's the reason for the std::terminate. The previous patch fixed things such that the exception above isn't thrown anymore. However, it's possible that e.g., the remote connection drops just while a user types "nosharedlibrary", or some other reason that leads to objfile::~objfile, and then we end up the same std::terminate problem. Also notice that frames #9-#11 are BFD frames: #9 0x0000555555e09e3f in opncls_bclose (abfd=0x555556bc27e0) at src/bfd/opncls.c:599 #10 0x0000555555e0a2c7 in bfd_close_all_done (abfd=0x555556bc27e0) at src/bfd/opncls.c:847 #11 0x0000555555e0a27a in bfd_close (abfd=0x555556bc27e0) at src/bfd/opncls.c:814 BFD is written in C and thus throwing exceptions over such frames may either not clean up properly, or, may abort if bfd is not compiled with -fasynchronous-unwind-tables (x86-64 defaults that on, but not all GCC ports do). Thus frame #8 seems like a good place to swallow exceptions. More so since in this spot we already ignore target_fileio_close return errors. That's what this commit does. Without the previous fix, we'd see: (gdb) detach Detaching from program: target:/any/program, process 2197701 Ending remote debugging. [Inferior 1 (process 2197701) detached] warning: cannot close "target:/lib64/ld-linux-x86-64.so.2": Remote connection closed Note it prints a warning, which would still be a regression compared to GDB 10, if it weren't for the previous fix. gdb/ChangeLog: yyyy-mm-dd Pedro Alves PR gdb/28080 * gdb_bfd.c (gdb_bfd_close_warning): New. (gdb_bfd_iovec_fileio_close): Wrap target_fileio_close in try/catch and print warning on exception. (gdb_bfd_close_or_warn): Use gdb_bfd_close_warning. Change-Id: Ic7a26ddba0a4444e3377b0e7c1c89934a84545d7 --- gdb/gdb_bfd.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c index 3312197acd5..312442a466e 100644 --- a/gdb/gdb_bfd.c +++ b/gdb/gdb_bfd.c @@ -423,6 +423,15 @@ gdb_bfd_iovec_fileio_pread (struct bfd *abfd, void *stream, void *buf, return pos; } +/* Warn that it wasn't possible to close a bfd for file NAME, because + of REASON. */ + +static void +gdb_bfd_close_warning (const char *name, const char *reason) +{ + warning (_("cannot close \"%s\": %s"), name, reason); +} + /* Wrapper for target_fileio_close suitable for passing as the CLOSE_FUNC argument to gdb_bfd_openr_iovec. */ @@ -436,7 +445,16 @@ gdb_bfd_iovec_fileio_close (struct bfd *abfd, void *stream) /* Ignore errors on close. These may happen with remote targets if the connection has already been torn down. */ - target_fileio_close (fd, &target_errno); + try + { + target_fileio_close (fd, &target_errno); + } + catch (const gdb_exception &ex) + { + /* Also avoid crossing exceptions over bfd. */ + gdb_bfd_close_warning (bfd_get_filename (abfd), + ex.message->c_str ()); + } /* Zero means success. */ return 0; @@ -626,8 +644,8 @@ gdb_bfd_close_or_warn (struct bfd *abfd) ret = bfd_close (abfd); if (!ret) - warning (_("cannot close \"%s\": %s"), - name, bfd_errmsg (bfd_get_error ())); + gdb_bfd_close_warning (name, + bfd_errmsg (bfd_get_error ())); return ret; } -- cgit v1.2.1