Warn users about mismatched PID namespaces

Linux supports multiple "PID namespaces".  Processes in different PID
namespaces have different views of the system process list.  Sometimes,
a single process can appear in more than one PID namespace, but with a
different PID in each.  When GDB and its target are in different PID
namespaces, various features can break due to the mismatch between
what the target believes its PID to be and what GDB believes its PID
to be.  The most visible broken functionality is thread enumeration
silently failing.

This patch explicitly warns users against trying to debug across PID
namespaces.

The patch introduced no new failures in my test suite run on an x86_64
installation of Ubuntu 14.10.  It doesn't include a test: writing an
automated test that exercises this code would be very involved because
CLONE_NEWNS requires CAP_SYS_ADMIN; the easier way to reproduce the
problem is to start a new lxc container.

gdb/
2014-11-11  Daniel Colascione  <dancol@dancol.org>

	Warn about cross-PID-namespace debugging.
	* nat/linux-procfs.h (linux_proc_pid_get_ns): New prototype.
	* nat/linux-procfs.c (linux_proc_pid_get_ns): New function.
	* linux-thread-db.c (check_pid_namespace_match): New function.
	(thread_db_inferior_created): Call it.
More fixes for invalid memory accesses, uncovered by valgrind and binary fuzzers.

	PR binutils/17512
	* coffcode.h (coff_slurp_line_table): Initialise the parts of the
	line number cache that would not be initialised by the copy from
	the new line number table.
	(coff_classify_symbol): Allow for _bfd_coff_internal_syment_name
	returning NULL.
	* coffgen.c (coff_get_normalized_symbols): Get the external
	symbols before allocating space for the internal symbols, in case
	the get fails.
	* elf.c (_bfd_elf_slurp_version_tables): Only allocate a verref
	array if one is needed.  Likewise with the verdef array.
	* peXXigen.c (_bfd_XXi_swap_sym_in): Replace abort()'s with error
	messages.
	(_bfd_XXi_swap_aux_in): Make sure that all fields of the aux
	structure are initialised.
	(pe_print_edata): Avoid reading off the end of the data buffer.
Prevent a buffer overrun whilst displaying corrupt ARM tags.

	PR binutils/17531
	* readelf.c (display_arm_attribute): Avoid reading off the end of
	the buffer when processing a Tag_nodefaults.
[PATCH] treate -specs as both cflags & ldflags

  ld/testsuite/
    * lib/ld-lib.exp (run_ld_link_exec_tests): Append board_cflags if gcc driver
    used as link tool.
    (run_cc_link_exec_tests): Likewise.
Updated French and Ukranian translations supplied by the Translation Project.

	* po/uk.po: Updated Ukranian translation.

	* po/fr.po: Updated French translation.
oops - missed the French translation.
	* avrtiny.sc: Apply avr.sc fixes.
Fix invalid memory accesses for more corrupt binary files.

	PR binutils/17531
	* binutils/readelf.c (dynamic_nent): Change type to size_t.
	(slurp_rela_relocs): Use size_t type for nrelas.
	(slurp_rel_relocs): Likewise.
	(get_program_headers): Improve out of memory error message.
	(get_32bit_section_headers): Likewise.
	(get_32bit_section_headers): Likewise.
	(get_64bit_section_headers): Likewise.
	(get_32bit_elf_symbols): Likewise.
	(get_64bit_elf_symbols): Likewise.
	(process_section_groups): Likewise.
	(get_32bit_dynamic_section): Likewise.
	(get_64bit_dynamic_section): Likewise.
	(process_dynamic_section): Likewise.
	(process_version_sections): Likewise.
	(get_symbol_index_type): Likewise.
	(process_mips_specific): Likewise.
	(process_corefile_note_segment): Likewise.
	(process_version_sections): Use size_t type for total.
	(get_dynamic_data): Change type of number parameter to size_t.
	Improve out of memory error messages.
	(process_symbol_table): Change type of nbuckets and nchains to
	size_t.  Skip processing of sections headers if there are none.
	Improve out of memory error messages.
daily update
Fix x86 non-ELF build breakage

	PR ld/17482
	* config/tc-i386.c (output_insn): Don't test x86_elf_abi when
	not ELF.
Fix z80-coff build breakage

	* config/tc-z80.c (parse_exp_not_indexed, parse_exp): Warning fixes.
Throw away dodgy coff line number info earlier

	PR 17521
	* coffcode.h (coff_slurp_line_table): Drop line number info
	not preceded by a valid function entry.  Revert last change.
add a default method for gdbarch_skip_permanent_breakpoint

breakpoint.c uses gdbarch_breakpoint_from_pc to determine whether a
breakpoint location points at a permanent breakpoint:

 static int
 bp_loc_is_permanent (struct bp_location *loc)
 {
 ...
   addr = loc->address;
   bpoint = gdbarch_breakpoint_from_pc (loc->gdbarch, &addr, &len);
 ...
  if (target_read_memory (loc->address, target_mem, len) == 0
      && memcmp (target_mem, bpoint, len) == 0)
    retval = 1;
 ...

So I think we should default the gdbarch_skip_permanent_breakpoint
hook to advancing the PC by the length of the breakpoint instruction,
as determined by gdbarch_breakpoint_from_pc.  I believe that simple
implementation does the right thing for most architectures.  If
there's an oddball architecture where that doesn't work, then it
should override the hook, just like it should be overriding the hook
if there was no default anyway.

The only two implementation of skip_permanent_breakpoint are
i386_skip_permanent_breakpoint, for x86, and
hppa_skip_permanent_breakpoint, for PA-RISC/HP-UX

The x86 implementation is trivial, and can clearly be replaced by the
new default.

I don't know about the HP-UX one though, I know almost nothing about
PA.  It may well be advancing the PC ends up being equivalent.
Otherwise, it must be that "jump $pc_after_bp" doesn't work either...

Tested on x86_64 Fedora 20 native and gdbserver.

gdb/
2014-11-12  Pedro Alves  <palves@redhat.com>

	* arch-utils.c (default_skip_permanent_breakpoint): New function.
	* arch-utils.h (default_skip_permanent_breakpoint): New
	declaration.
	* gdbarch.sh (skip_permanent_breakpoint): Now an 'f' function.
	Install default_skip_permanent_breakpoint as default method.
	* i386-tdep.c (i386_skip_permanent_breakpoint): Delete function.
	(i386_gdbarch_init): Don't install it.
	* infrun.c (resume): Assume there's always a
	gdbarch_skip_permanent_breakpoint implementation.
	* gdbarch.h, gdbarch.c: Regenerate.
make "permanent breakpoints" per location and disableable

"permanent"-ness is currently a property of the breakpoint.  But, it
should actually be an implementation detail of a _location_.  Consider
this bit in infrun.c:

  /* Normally, by the time we reach `resume', the breakpoints are either
     removed or inserted, as appropriate.  The exception is if we're sitting
     at a permanent breakpoint; we need to step over it, but permanent
     breakpoints can't be removed.  So we have to test for it here.  */
  if (breakpoint_here_p (aspace, pc) == permanent_breakpoint_here)
    {
      if (gdbarch_skip_permanent_breakpoint_p (gdbarch))
	gdbarch_skip_permanent_breakpoint (gdbarch, regcache);
      else
	error (_("\
The program is stopped at a permanent breakpoint, but GDB does not know\n\
how to step past a permanent breakpoint on this architecture.  Try using\n\
a command like `return' or `jump' to continue execution."));
    }

This will wrongly skip a non-breakpoint instruction if we have a
multiple location breakpoint where the whole breakpoint was set to
"permanent" because one of the locations happened to be permanent,
even if the one GDB is resuming from is not.

Related, because the permanent breakpoints are only marked as such in
init_breakpoint_sal, we currently miss marking momentary breakpoints
as permanent.  A test added by a following patch trips on that.
Making permanent-ness be per-location, and marking locations as such
in add_location_to_breakpoint, the natural place to do this, fixes
this issue...

... and then exposes a latent issue with mark_breakpoints_out.  It's
clearing the inserted flag of permanent breakpoints.  This results in
assertions failing like this:

 Breakpoint 1, main () at testsuite/gdb.base/callexit.c:32
 32        return 0;
 (gdb) call callexit()
 [Inferior 1 (process 15849) exited normally]
 gdb/breakpoint.c:12854: internal-error: allegedly permanent breakpoint is not actually inserted
 A problem internal to GDB has been detected,
 further debugging may prove unreliable.

The call dummy breakpoint, which is a momentary breakpoint, is set on
top of a manually inserted breakpoint instruction, and so is now
rightfully marked as a permanent breakpoint.  See "Write a legitimate
instruction at the point where the infcall breakpoint is going to be
inserted." comment in infcall.c.

Re. make_breakpoint_permanent.  That's only called by solib-pa64.c.
Permanent breakpoints were actually originally invented for HP-UX [1].
I believe that that call (the only one in the tree) is unnecessary
nowadays, given that nowadays the core breakpoints code analyzes the
instruction under the breakpoint to automatically detect whether it's
setting a breakpoint on top of a breakpoint instruction in the
program.  I know close to nothing about HP-PA/HP-UX, though.

[1] https://sourceware.org/ml/gdb-patches/1999-q3/msg00245.html, and
    https://sourceware.org/ml/gdb-patches/1999-q3/msg00242.html

In addition to the per-location issue, "permanent breakpoints" are
currently always displayed as enabled=='n':

 (gdb) b main
 Breakpoint 3 at 0x40053c: file ../../../src/gdb/testsuite/gdb.arch/i386-permbkpt.S, line 29.
 (gdb) info breakpoints
 Num     Type           Disp Enb Address            What
 3       breakpoint     keep n   0x000000000040053c ../../../src/gdb/testsuite/gdb.arch/i386-permbkpt.S:29

But OTOH they're always enabled; there's no way to disable them...

In turn, this means that if one adds commands to such a breakpoint,
they're _always_ run:

 (gdb) start
 Starting program: /home/pedro/gdb/mygit/build/gdb/testsuite/gdb.arch/i386-permbkpt
 ...
 Temporary breakpoint 1, main () at ../../../src/gdb/testsuite/gdb.arch/i386-permbkpt.S:29
 29              int3
 (gdb) b main
 Breakpoint 2 at 0x40053c: file ../../../src/gdb/testsuite/gdb.arch/i386-permbkpt.S, line 29.
 (gdb) info breakpoints
 Num     Type           Disp Enb Address            What
 2       breakpoint     keep n   0x000000000040053c ../../../src/gdb/testsuite/gdb.arch/i386-permbkpt.S:29
 (gdb) commands
 Type commands for breakpoint(s) 2, one per line.
 End with a line saying just "end".
 >echo "hello!"
 >end
 (gdb) disable 2
 (gdb) start
 The program being debugged has been started already.
 Start it from the beginning? (y or n) y
 Temporary breakpoint 3 at 0x40053c: file ../../../src/gdb/testsuite/gdb.arch/i386-permbkpt.S, line 29.
 Starting program: /home/pedro/gdb/mygit/build/gdb/testsuite/gdb.arch/i386-permbkpt

 Breakpoint 2, main () at ../../../src/gdb/testsuite/gdb.arch/i386-permbkpt.S:29
 29              int3
 "hello!"(gdb)

IMO, one should be able to disable such a breakpoint, and GDB should
then behave just like if the user hadn't created the breakpoint in the
first place (that is, report a SIGTRAP).

By making permanent-ness a property of the location, and eliminating
the bp_permanent enum enable_state state ends up fixing that as well.

No tests are added for these changes yet; they'll be added in a follow
up patch, as skipping permanent breakpoints is currently broken and
trips on an assertion in infrun.

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/ChangeLog:
2014-11-12  Pedro Alves  <palves@redhat.com>

	Mark locations as permanent, not the whole breakpoint.
	* breakpoint.c (remove_breakpoint_1, remove_breakpoint): Adjust.
	(mark_breakpoints_out): Don't mark permanent breakpoints as
	uninserted.
	(breakpoint_init_inferior): Use mark_breakpoints_out.
	(breakpoint_here_p): Adjust.
	(bpstat_stop_status, describe_other_breakpoints): Remove handling
	of permanent breakpoints.
	(make_breakpoint_permanent): Mark each location as permanent,
	instead of marking the breakpoint.
	(add_location_to_breakpoint): If the location is permanent, mark
	it as such, and as inserted.
	(init_breakpoint_sal): Don't make the breakpoint permanent here.
	(bp_location_compare, update_global_location_list): Adjust.
	(update_breakpoint_locations): Don't make the breakpoint permanent
	here.
	(disable_breakpoint, enable_breakpoint_disp): Don't skip permanent
	breakpoints.
	* breakpoint.h (enum enable_state) <bp_permanent>: Delete field.
	(struct bp_location) <permanent>: New field.
	* guile/scm-breakpoint.c (bpscm_enable_state_to_string): Remove
	reference to bp_permanent.
fix skipping permanent breakpoints

The gdb.arch/i386-bp_permanent.exp test is currently failing an
assertion recently added:

 (gdb) stepi
 ../../src/gdb/infrun.c:2237: internal-error: resume: Assertion `sig != GDB_SIGNAL_0' failed.
 A problem internal to GDB has been detected,
 further debugging may prove unreliable.
 Quit this debugging session? (y or n)
 FAIL: gdb.arch/i386-bp_permanent.exp: Single stepping past permanent breakpoint. (GDB internal error)

The assertion expects that the only reason we currently need to step a
breakpoint instruction is when we have a signal to deliver.  But when
stepping a permanent breakpoint (with or without a signal) we also
reach this code.

The assertion is correct and the permanent breakpoints skipping code
is wrong.

Consider the case of the user doing "step/stepi" when stopped at a
permanent breakpoint.  GDB's `resume' calls the
gdbarch_skip_permanent_breakpoint hook and then happily continues
stepping:

  /* Normally, by the time we reach `resume', the breakpoints are either
     removed or inserted, as appropriate.  The exception is if we're sitting
     at a permanent breakpoint; we need to step over it, but permanent
     breakpoints can't be removed.  So we have to test for it here.  */
  if (breakpoint_here_p (aspace, pc) == permanent_breakpoint_here)
    {
      gdbarch_skip_permanent_breakpoint (gdbarch, regcache);
    }

But since gdbarch_skip_permanent_breakpoint already advanced the PC
manually, this ends up executing the instruction that is _after_ the
breakpoint instruction.  The user-visible result is that a single-step
steps two instructions.

The gdb.arch/i386-bp_permanent.exp test is actually ensuring that
that's indeed how things work.  It runs to an int3 instruction, does
"stepi", and checks that "leave" was executed with that "stepi".  Like
this:

 (gdb) b *0x0804848c
 Breakpoint 2 at 0x804848c
 (gdb) c
 Continuing.

 Breakpoint 2, 0x0804848c in standard ()
 (gdb) disassemble
 Dump of assembler code for function standard:
    0x08048488 <+0>:     push   %ebp
    0x08048489 <+1>:     mov    %esp,%ebp
    0x0804848b <+3>:     push   %edi
 => 0x0804848c <+4>:     int3
    0x0804848d <+5>:     leave
    0x0804848e <+6>:     ret
    0x0804848f <+7>:     nop
 (gdb) si
 0x0804848e in standard ()
 (gdb) disassemble
 Dump of assembler code for function standard:
    0x08048488 <+0>:     push   %ebp
    0x08048489 <+1>:     mov    %esp,%ebp
    0x0804848b <+3>:     push   %edi
    0x0804848c <+4>:     int3
    0x0804848d <+5>:     leave
 => 0x0804848e <+6>:     ret
    0x0804848f <+7>:     nop
 End of assembler dump.
 (gdb)

One would instead expect that a stepi at 0x0804848c stops at
0x0804848d, _before_ the "leave" is executed.  This commit changes GDB
this way.  Care is taken to make stepping into a signal handler when
the step starts at a permanent breakpoint instruction work correctly.

The patch adjusts gdb.arch/i386-bp_permanent.exp in this direction,
and also makes it work on x86_64 (currently it only works on i*86).

The patch also adds a new gdb.base/bp-permanent.exp test that
exercises many different code paths related to stepping permanent
breakpoints, including the stepping with signals cases.  The test uses
"hack/trick" to make it work on all (or most) platforms -- it doesn't
really hard code a breakpoint instruction.

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/
2014-11-12  Pedro Alves  <palves@redhat.com>

	* infrun.c (resume): Clear the thread's 'stepped_breakpoint' flag.
	Rewrite stepping over a permanent breakpoint.
	(thread_still_needs_step_over, proceed): Don't set
	stepping_over_breakpoint for permanent breakpoints.
	(handle_signal_stop): Don't clear stepped_breakpoint.  Also pull
	single-step breakpoints out of the target on hardware step
	targets.
	(process_event_stop_test): If stepping a permanent breakpoint
	doesn't hit the step-resume breakpoint, delete the step-resume
	breakpoint.
	(switch_back_to_stepped_thread): Also check if the stepped thread
	has advanced already on hardware step targets.
	(currently_stepping): Return true if the thread stepped a
	breakpoint.

gdb/testsuite/
2014-11-12  Pedro Alves  <palves@redhat.com>

	* gdb.arch/i386-bp_permanent.c: New file.
	* gdb.arch/i386-bp_permanent.exp: Don't skip on x86_64.
	(srcfile): Set to i386-bp_permanent.c.
	(top level): Adjust to work in both 32-bit and 64-bit modes.  Test
	that stepi does not execute the 'leave' instruction, instead of
	testing it does execute.
	* gdb.base/bp-permanent.c: New file.
	* gdb.base/bp-permanent.exp: New file.
Garbage collect the infwait_state global

No longer used since the non-continuable watchpoints handling rework.

gdb/
2014-11-12  Pedro Alves  <palves@redhat.com>

	* infrun.c (enum infwait_states, infwait_state): Delete.
GDBserver: ctrl-c after leader has exited

The target->request_interrupt callback implements the handling for
ctrl-c.  User types ctrl-c in GDB, GDB sends a \003 to the remote
target, and the remote targets stops the program with a SIGINT, just
like if the user typed ctrl-c in GDBserver's terminal.

The trouble is that using kill_lwp(signal_pid, SIGINT) sends the
SIGINT directly to the program's main thread.  If that thread has
exited already, then that kill won't do anything.

Instead, send the SIGINT to the process group, just like GDB
does (see inf-ptrace.c:inf_ptrace_stop).

gdb.threads/leader-exit.exp is extended to cover the scenario.  It
fails against GDBserver before the patch.

Tested on x86_64 Fedora 20, native and GDBserver.

gdb/gdbserver/
2014-11-12  Pedro Alves  <palves@redhat.com>

	* linux-low.c (linux_request_interrupt): Always send a SIGINT to
	the process group instead of to a specific LWP.

gdb/testsuite/
2014-11-12  Pedro Alves  <palves@redhat.com>

	* gdb.threads/leader-exit.exp: Test sending ctrl-c works after the
	leader has exited.
GDBserver: don't resume all threads if the Hc thread disapears

There's code in linux_wait_1 that resumes all threads if the Hc thread
disappears.  It's the wrong thing to do, as GDB has told GDBserver to
resume only one thread, because e.g., the user has scheduler-locking
enabled, or because GDB was stepping the program over a breakpoint.
Resuming all threads behind GDB's back can't be good in either case.

The right thing to do is to detect that that the (only) resumed thread
is gone, and let GDB know about it.  The Linux backend is already
doing that nowadays, since:

 commit fa96cb382c12b099675c5cc238aaa7352a3fd3d7
 Author:     Pedro Alves <palves@redhat.com>
 AuthorDate: Thu Feb 27 14:30:08 2014 +0000

     Teach GDBserver's Linux backend about no unwaited-for children (TARGET_WAITKIND_NO_RESUMED).

The backend detects that all resumed threads have disappeared, and
returns TARGET_WAITKIND_NO_RESUMED to the core of GDBserver, which
then reports an error to GDB.

There's no need to frob the passed in ptid to wait for the continue
thread either -- linux_wait_for_event only returns events for resumed
threads.

The badness (of resuming threads) can actually be observed in the
testsuite, if we force-disable vCont support in GDBserver -- before
the patch, gdb.threads/no-unwaited-for-left.exp hangs if we disable
vCont:

 (gdb) continue
 Continuing.
 FAIL: gdb.threads/no-unwaited-for-left.exp: continue to breakpoint: break-here (timeout)
 ... more cascading timeouts ....

After the patch, gdb.threads/no-unwaited-for-left.exp behaves the same
with or without vCont support:

 (gdb) continue
 Continuing.
 [New Thread 32226]
 [Switching to Thread 32226]

 Breakpoint 2, thread_a (arg=0x0) at /home/pedro/gdb/mygit/build/../src/gdb/testsuite/gdb.threads/no-unwaited-for-left.c:28
 28	  return 0; /* break-here */
 (gdb) PASS: gdb.threads/no-unwaited-for-left.exp: continue to breakpoint: break-here
...
 continue
 Continuing.
 warning: Remote failure reply: E.No unwaited-for children left.

 [Thread 32222] #1 stopped.
 (gdb) FAIL: gdb.threads/no-unwaited-for-left.exp: continue stops when the main thread exits

Overall, this is also good for getting rid of a RSP detail from the backend.

gdb/gdbserver/
2014-11-12  Pedro Alves  <palves@redhat.com>

	* linux-low.c (linux_wait_1): Don't force a wait for the Hc
	thread, and don't resume all threads if the Hc thread has exited.
GDBserver: clean up 'cont_thread' handling

As no place in the backends check cont_thread anymore, we can stop
setting and clearing it in places that resume the target and wait for
events.  Instead simply clear it whenever a new GDB connects.

gdb/gdbserver/
2014-11-12  Pedro Alves  <palves@redhat.com>

	* server.c (cont_thread): Update comment.
	(start_inferior, attach_inferior): No longer clear cont_thread.
	(handle_v_cont): No longer set cont_thread.
	(captured_main): Clear cont_thread each time a GDB connects.
Fix more memory faults uncovered by fuzzing various executables.

	PR binutils/17512
	* dwarf.c (read_and_display_attr_value): Check that we do not read
	past end.
	(display_debug_pubnames_worker): Add range checks.
	(process_debug_info): Check for invalid pointer sizes.
	(display_loc_list): Likewise.
	(display_loc_list_dwo): Likewise.
	(display_debug_ranges): Likewise.
	(display_debug_aranges): Check for invalid address size.
	(read_cie): Add range checks.  Replace call strchr with while loop.
	* objdump.c (dump_dwarf): Replace abort with a warning message.
	(print_section_stabs): Improve range checks.
	* rdcoff.c (coff_get_slot): Use long for indx parameter type.
	Add check for an excesively large index.
	* rddbg.c (read_section_stabs_debugging_info): Zero terminate the
	string table.  Avoid walking off the end of the stabs data.
	* stabs.c (parse_stab_string): Add check for a NULL name.

	PR binutils/17512
	* coffcode.h (coff_slurp_line_table): Set the line number of
	corrupt entries to -1.
	(coff_slurp_symbol_table): Alway initialise the value of the
	symbol.
	* coffgen.c (coff_print_symbol): Check that the combined pointer
	is valid.
	(coff_print_symbol): Do not print negative line numbers.
	* peXXigen.c (pe_print_idata): Add range checking displaying
	member names.