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Pedro Alves 20db9c52a2 File I/O file handles after target closes
A future patch will propose making the remote target's target_ops be
heap-allocated (to make it possible to have multiple instances of
remote targets, for multiple simultaneous connections), and will
delete/destroy the remote target at target_close time.

That change trips on a latent problem, though.  File I/O handles
remain open even after the target is gone, with a dangling pointer to
a target that no longer exists.  This results in GDB crashing when it
calls the target_ops backend associated with the file handle:

 (gdb) Disconnect
 Ending remote debugging.
 * GDB crashes deferencing a dangling pointer

Backtrace:

   #0  0x00007f79338570a0 in main_arena () at /lib64/libc.so.6
   #1  0x0000000000858bfe in target_fileio_close(int, int*) (fd=1, target_errno=0x7ffe0499a4c8)
       at src/gdb/target.c:2980
   #2  0x00000000007088bd in gdb_bfd_iovec_fileio_close(bfd*, void*) (abfd=0x1a631b0, stream=0x223c9d0)
       at src/gdb/gdb_bfd.c:353
   #3  0x0000000000930906 in opncls_bclose (abfd=0x1a631b0) at src/bfd/opncls.c:528
   #4  0x0000000000930cf9 in bfd_close_all_done (abfd=0x1a631b0) at src/bfd/opncls.c:768
   #5  0x0000000000930cb3 in bfd_close (abfd=0x1a631b0) at src/bfd/opncls.c:735
   #6  0x0000000000708dc5 in gdb_bfd_close_or_warn(bfd*) (abfd=0x1a631b0) at src/gdb/gdb_bfd.c:511
   #7  0x00000000007091a2 in gdb_bfd_unref(bfd*) (abfd=0x1a631b0) at src/gdb/gdb_bfd.c:615
   #8  0x000000000079ed8e in objfile::~objfile() (this=0x2154730, __in_chrg=<optimized out>)
       at src/gdb/objfiles.c:682
   #9  0x000000000079fd1a in objfile_purge_solibs() () at src/gdb/objfiles.c:1065
   #10 0x00000000008162ca in no_shared_libraries(char const*, int) (ignored=0x0, from_tty=1)
       at src/gdb/solib.c:1251
   #11 0x000000000073b89b in disconnect_command(char const*, int) (args=0x0, from_tty=1)
       at src/gdb/infcmd.c:3035

This goes unnoticed in current master, because the current remote
target's target_ops is never destroyed nowadays, so we end up calling:

  remote_hostio_close -> remote_hostio_send_command

which gracefully fails with FILEIO_ENOSYS if remote_desc is NULL
(because the target is closed).

Fix this by invalidating a target's file I/O handles when the target
is closed.

With this change, remote_hostio_send_command no longer needs to handle the
case of being called with a closed remote target, originally added here:
<https://sourceware.org/ml/gdb-patches/2008-08/msg00359.html>.

gdb/ChangeLog:
2018-04-11  Pedro Alves  <palves@redhat.com>

	* target.c (fileio_fh_t::t): Add comment.
	(target_fileio_pwrite, target_fileio_pread, target_fileio_fstat)
	(target_fileio_close): Handle a NULL target.
	(invalidate_fileio_fh): New.
	(target_close): Call it.
	* remote.c (remote_hostio_send_command): No longer check whether
	remote_desc is open.
2018-04-11 11:40:05 +01:00
bfd Automatic date update in version.in 2018-04-11 00:00:15 +00:00
binutils Fix some strip test fails on nds32 and pru 2018-04-10 09:41:25 +09:30
config config: Sync with GCC 2018-04-05 15:22:13 -07:00
cpu
elfcpp PowerPC inline PLT call support 2018-04-09 17:25:20 +09:30
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gas Use dlsym to check if libdl is needed for plugin 2018-04-05 15:31:53 -07:00
gdb File I/O file handles after target closes 2018-04-11 11:40:05 +01:00
gold Regenerate some files 2018-04-10 00:20:19 +09:30
gprof Use dlsym to check if libdl is needed for plugin 2018-04-05 15:31:53 -07:00
include PowerPC inline PLT call support 2018-04-09 17:25:20 +09:30
intl
ld Silence nds32 pic warnings 2018-04-11 11:13:49 +09:30
libdecnumber
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opcodes i386: Clear vex instead of vex.evex 2018-04-04 04:36:44 -07:00
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		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
debuggers, etc., plus their support routines, definitions, and documentation.

If you are receiving this as part of a GDB release, see the file gdb/README.
If with a binutils release, see binutils/README;  if with a libg++ release,
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