Fix signal handlers regression (RH BZ 1542149, Pedro Alves).
This commit is contained in:
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commit e379cee61f3890e535e995828e8846b020ef2a32
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Author: Pedro Alves <palves@redhat.com>
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Date: Fri Jan 5 18:26:18 2018 +0000
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Fix regression: cannot start with LD_PRELOAD=libSegFault.so (PR gdb/18653#c7)
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At https://sourceware.org/bugzilla/show_bug.cgi?id=18653#c7, Andrew
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reports that the fix for PR gdb/18653 made GDB useless if you preload
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libSegFault.so, because GDB internal-errors on startup:
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$ LD_PRELOAD=libSegFault.so gdb
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src/gdb/common/signals-state-save-restore.c:64: internal-error: unexpected signal handler
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A problem internal to GDB has been detected,
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further debugging may prove unreliable.
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Aborted (core dumped)
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$
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The internal error comes from the code saving the signal dispositions
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inherited from gdb's parent:
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(top-gdb) bt
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#0 0x000000000056b001 in internal_error(char const*, int, char const*, ...) (file=0xaf5f38 "src/gdb/common/signals-state-save-restore.c", line=64, fmt=0xaf5f18 "unexpected signal handler") at src/gdb/common/errors.c:54
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#1 0x00000000005752c9 in save_original_signals_state() () at src/gdb/common/signals-state-save-restore.c:64
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#2 0x00000000007425de in captured_main_1(captured_main_args*) (context=0x7fffffffd860)
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at src/gdb/main.c:509
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#3 0x0000000000743622 in captured_main(void*) (data=0x7fffffffd860) at src/gdb/main.c:1145
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During symbol reading, cannot get low and high bounds for subprogram DIE at 24065.
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#4 0x00000000007436f9 in gdb_main(captured_main_args*) (args=0x7fffffffd860) at src/gdb/main.c:1171
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#5 0x0000000000413acd in main(int, char**) (argc=1, argv=0x7fffffffd968) at src/gdb/gdb.c:32
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This commit downgrades the internal error to a warning. You'll get
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instead:
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~~~
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$ LD_PRELOAD=libSegFault.so gdb
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warning: Found custom handler for signal 11 (Segmentation fault) preinstalled.
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Some signal dispositions inherited from the environment (SIG_DFL/SIG_IGN)
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won't be propagated to spawned programs.
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GNU gdb (GDB) 8.0.50.20171213-git
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Copyright (C) 2017 Free Software Foundation, Inc.
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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This is free software: you are free to change and redistribute it.
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There is NO WARRANTY, to the extent permitted by law. Type "show copying"
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and "show warranty" for details.
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This GDB was configured as "x86_64-pc-linux-gnu".
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Type "show configuration" for configuration details.
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For bug reporting instructions, please see:
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<http://www.gnu.org/software/gdb/bugs/>.
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Find the GDB manual and other documentation resources online at:
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<http://www.gnu.org/software/gdb/documentation/>.
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For help, type "help".
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Type "apropos word" to search for commands related to "word"...
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(gdb)
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~~~
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This also moves the location where save_original_signals_state is
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called a bit further below (to after option processing), so that "-q"
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disables the warning:
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~~~
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$ LD_PRELOAD=libSegFault.so gdb -q
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(gdb)
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~~~
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New testcase included.
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gdb/ChangeLog:
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2018-01-05 Pedro Alves <palves@redhat.com>
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PR gdb/18653
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* common/signals-state-save-restore.c
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(save_original_signals_state): New parameter 'quiet'. Warn if we
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find a custom handler preinstalled, instead of internal erroring.
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But only warn if !quiet.
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* common/signals-state-save-restore.h
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(save_original_signals_state): New parameter 'quiet'.
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* main.c (captured_main_1): Move save_original_signals_state call
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after option handling, and pass QUIET.
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gdb/gdbserver/ChangeLog:
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2018-01-05 Pedro Alves <palves@redhat.com>
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PR gdb/18653
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* server.c (captured_main): Pass quiet=false to
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save_original_signals_state.
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gdb/testsuite/ChangeLog:
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2018-01-05 Pedro Alves <palves@redhat.com>
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PR gdb/18653
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* gdb.base/libsegfault.exp: New.
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### a/gdb/ChangeLog
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### b/gdb/ChangeLog
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## -1,3 +1,15 @@
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+2018-01-05 Pedro Alves <palves@redhat.com>
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+
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+ PR gdb/18653
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+ * common/signals-state-save-restore.c
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+ (save_original_signals_state): New parameter 'quiet'. Warn if we
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+ find a custom handler preinstalled, instead of internal erroring.
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+ But only warn if !quiet.
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+ * common/signals-state-save-restore.h
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+ (save_original_signals_state): New parameter 'quiet'.
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+ * main.c (captured_main_1): Move save_original_signals_state call
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+ after option handling, and pass QUIET.
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+
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2018-01-05 Pedro Alves <palves@redhat.com>
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* spu-tdep.c (spu_catch_start): Pass
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--- a/gdb/common/signals-state-save-restore.c
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+++ b/gdb/common/signals-state-save-restore.c
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@@ -35,7 +35,7 @@ static sigset_t original_signal_mask;
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/* See signals-state-save-restore.h. */
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void
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-save_original_signals_state (void)
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+save_original_signals_state (bool quiet)
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{
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#ifdef HAVE_SIGACTION
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int i;
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@@ -45,6 +45,8 @@ save_original_signals_state (void)
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if (res == -1)
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perror_with_name (("sigprocmask"));
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+ bool found_preinstalled = false;
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+
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for (i = 1; i < NSIG; i++)
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{
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struct sigaction *oldact = &original_signal_actions[i];
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@@ -59,9 +61,31 @@ save_original_signals_state (void)
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perror_with_name (("sigaction"));
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/* If we find a custom signal handler already installed, then
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- this function was called too late. */
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- if (oldact->sa_handler != SIG_DFL && oldact->sa_handler != SIG_IGN)
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- internal_error (__FILE__, __LINE__, _("unexpected signal handler"));
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+ this function was called too late. This is a warning instead
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+ of an internal error because this can also happen if you
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+ LD_PRELOAD a library that installs a signal handler early via
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+ __attribute__((constructor)), like libSegFault.so. */
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+ if (!quiet
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+ && oldact->sa_handler != SIG_DFL
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+ && oldact->sa_handler != SIG_IGN)
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+ {
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+ found_preinstalled = true;
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+
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+ /* Use raw fprintf here because we're being called in early
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+ startup, because GDB's filtered streams are are
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+ created. */
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+ fprintf (stderr,
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+ _("warning: Found custom handler for signal "
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+ "%d (%s) preinstalled.\n"), i,
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+ strsignal (i));
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+ }
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+ }
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+
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+ if (found_preinstalled)
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+ {
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+ fprintf (stderr, _("\
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+Some signal dispositions inherited from the environment (SIG_DFL/SIG_IGN)\n\
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+won't be propagated to spawned programs.\n"));
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}
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#endif
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}
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--- a/gdb/common/signals-state-save-restore.h
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+++ b/gdb/common/signals-state-save-restore.h
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@@ -28,9 +28,10 @@
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back to what was originally inherited from gdb/gdbserver's parent,
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just before execing the target program to debug. */
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-/* Save the signal state of all signals. */
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+/* Save the signal state of all signals. If !QUIET, warn if we detect
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+ a custom signal handler preinstalled. */
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-extern void save_original_signals_state (void);
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+extern void save_original_signals_state (bool quiet);
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/* Restore the signal state of all signals. */
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### a/gdb/gdbserver/ChangeLog
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### b/gdb/gdbserver/ChangeLog
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## -1,3 +1,9 @@
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+2018-01-05 Pedro Alves <palves@redhat.com>
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+
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+ PR gdb/18653
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+ * server.c (captured_main): Pass quiet=false to
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+ save_original_signals_state.
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+
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2018-01-01 Joel Brobecker <brobecker@adacore.com>
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* gdbreplay.c (gdbreplay_version): Update copyright year in
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--- a/gdb/gdbserver/server.c
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+++ b/gdb/gdbserver/server.c
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@@ -3712,7 +3712,7 @@ captured_main (int argc, char *argv[])
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opened by remote_prepare. */
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notice_open_fds ();
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- save_original_signals_state ();
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+ save_original_signals_state (false);
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/* We need to know whether the remote connection is stdio before
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starting the inferior. Inferiors created in this scenario have
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--- a/gdb/main.c
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+++ b/gdb/main.c
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@@ -506,7 +506,6 @@ captured_main_1 (struct captured_main_args *context)
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bfd_init ();
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notice_open_fds ();
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- save_original_signals_state ();
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saved_command_line = (char *) xstrdup ("");
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@@ -849,6 +848,8 @@ captured_main_1 (struct captured_main_args *context)
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quiet = 1;
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}
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+ save_original_signals_state (quiet);
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+
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/* Try to set up an alternate signal stack for SIGSEGV handlers. */
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setup_alternate_signal_stack ();
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### a/gdb/testsuite/ChangeLog
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### b/gdb/testsuite/ChangeLog
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## -1,3 +1,8 @@
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+2018-01-05 Pedro Alves <palves@redhat.com>
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+
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+ PR gdb/18653
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+ * gdb.base/libsegfault.exp: New.
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+
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2018-01-05 Joel Brobecker <brobecker@adacore.com>
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PR gdb/22670
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--- /dev/null
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+++ b/gdb/testsuite/gdb.base/libsegfault.exp
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@@ -0,0 +1,84 @@
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+# Copyright 2017-2018 Free Software Foundation, Inc.
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+
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+# This program is free software; you can redistribute it and/or modify
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+# it under the terms of the GNU General Public License as published by
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+# the Free Software Foundation; either version 3 of the License, or
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+# (at your option) any later version.
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+#
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+# This program is distributed in the hope that it will be useful,
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+# but WITHOUT ANY WARRANTY; without even the implied warranty of
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+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+# GNU General Public License for more details.
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+#
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+# You should have received a copy of the GNU General Public License
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+# along with this program. If not, see <http://www.gnu.org/licenses/>.
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+
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+# This file is part of the gdb testsuite.
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+
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+# Test that GDB tolerates being started with libSegFault.so preloaded
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+# with LD_PRELOAD, and that GDB warns about a custom SIGSEGV custom
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+# handler. See PR gdb/18653
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+# <https://sourceware.org/bugzilla/show_bug.cgi?id=18653#c7>.
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+
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+# We cannot expect remote hosts to see environment variables set on
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+# the local machine.
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+if { [is_remote host] } {
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+ unsupported "can't set environment variables on remote host"
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+ return -1
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+}
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+
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+# Spawn GDB with LIB preloaded with LD_PRELOAD. CMDLINE_OPTS are
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+# command line options passed to GDB.
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+
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+proc gdb_spawn_with_ld_preload {lib cmdline_opts} {
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+ global env
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+
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+ save_vars { env(LD_PRELOAD) } {
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+ if { ![info exists env(LD_PRELOAD) ]
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+ || $env(LD_PRELOAD) == "" } {
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+ set env(LD_PRELOAD) "$lib"
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+ } else {
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+ append env(LD_PRELOAD) ":$lib"
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+ }
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+
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+ gdb_spawn_with_cmdline_opts $cmdline_opts
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+ }
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+}
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+
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+proc test_libsegfault {} {
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+ global gdb_prompt
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+
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+ set libsegfault "libSegFault.so"
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+
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+ # When started normally, if libSegFault.so is preloaded, GDB
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+ # should warn about not being able to propagate the signal
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+ # disposition of SIGSEGV.
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+ gdb_exit
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+ gdb_spawn_with_ld_preload $libsegfault ""
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+
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+ set test "gdb emits custom handler warning"
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+ gdb_test_multiple "" $test {
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+ -re "cannot be preloaded.*\r\n$gdb_prompt $" {
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+ # Glibc 2.22 outputs:
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+ # ERROR: ld.so: object 'libSegFault.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
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+ untested "cannot preload libSegFault.so"
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+ return
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+ }
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+ -re "Found custom handler.*won't be propagated.*\r\n$gdb_prompt $" {
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+ pass $test
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+ }
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+ }
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+
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+ # "-q" should disable the warning, though.
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+ gdb_exit
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+ gdb_spawn_with_ld_preload $libsegfault "-q"
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+
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+ set test "quiet suppresses custom handler warning"
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+ gdb_test_multiple "" $test {
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+ -re "^$gdb_prompt $" {
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+ pass $test
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+ }
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+ }
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+}
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+
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+test_libsegfault
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13
gdb.spec
13
gdb.spec
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@ -26,7 +26,7 @@ Version: 8.0.1
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# The release always contains a leading reserved number, start it at 1.
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# `upstream' is not a part of `name' to stay fully rpm dependencies compatible for the testing.
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Release: 35%{?dist}
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Release: 36%{?dist}
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License: GPLv3+ and GPLv3+ with exceptions and GPLv2+ and GPLv2+ with exceptions and GPL+ and LGPLv2+ and LGPLv3+ and BSD and Public Domain and GFDL
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Group: Development/Debuggers
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@ -741,6 +741,9 @@ Patch1262: gdb-rhbz1228556-bpt-inlined-func-name-2of2.patch
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# PR83906) (Pedro Alves).
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Patch1263: gdb-random-libstdcpp-prettyprinters-fail.patch
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# Fix signal handlers regression (RH BZ 1542149, Pedro Alves).
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Patch1270: gdb-rhbz1542149-spawn-default-signal-handlers-regression.patch
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%if 0%{!?rhel:1} || 0%{?rhel} > 6
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# RL_STATE_FEDORA_GDB would not be found for:
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# Patch642: gdb-readline62-ask-more-rh.patch
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@ -1154,6 +1157,7 @@ done
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%patch1261 -p1
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%patch1262 -p1
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%patch1263 -p1
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%patch1270 -p1
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%patch1075 -p1
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%if 0%{?rhel:1} && 0%{?rhel} <= 7
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@ -1736,10 +1740,13 @@ then
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fi
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%changelog
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* Thu Jan 25 2018 Sergio Durigan Junior <sergiodj@redhat.com> - 8.0.1-35.fc27
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* Tue Feb 6 2018 Jan Kratochvil <jan.kratochvil@redhat.com> - 8.0.1-36.fc26
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- Fix signal handlers regression (RH BZ 1542149, Pedro Alves).
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* Thu Jan 25 2018 Sergio Durigan Junior <sergiodj@redhat.com> - 8.0.1-35.fc26
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- Add %patch directive to the commit below.
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* Wed Jan 24 2018 Sergio Durigan Junior <sergiodj@fedoraproject.org> - 8.0.1-34.fc27
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* Wed Jan 24 2018 Sergio Durigan Junior <sergiodj@fedoraproject.org> - 8.0.1-34.fc26
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- Fix random 'FAIL: libstdc++-prettyprinters/80276.cc whatis p4' (GCC PR83906)
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(Pedro Alves).
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