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Philippe Waroquiers a65f68357f Factorize killing the children in linux-ptrace.c, and fix a 'process leak'.
Running the gdb testsuite under Valgrind started to fail after 100+ tests,
due to out of memory caused by lingering processes.

The lingering processes are caused by the combination
of a limitation in Valgrind signal handling when using PTRACE_TRACEME
and a (minor) bug in GDB.

The Valgrind limitation is : when a process is ptraced and raises
a signal, Valgrind will replace the raised signal by SIGSTOP as other
signals are masked by Valgrind when executing a system call.
Removing this limitation seems far to be trivial, valgrind signal
handling is very complex.

Due to this valgrind limitation, GDB linux_ptrace_test_ret_to_nx gets
a SIGSTOP signal instead of the expected SIGTRAP or SIGSEGV.
In such a case, linux_ptrace_test_ret_to_nx does an early return, but
does not kill the child (running under valgrind), child stays in a STOP-ped
state.
These lingering processes then eat the available system memory,
till launching a new process starts to fail.

This patch fixes the GDB minor bug by killing the child in case
linux_ptrace_test_ret_to_nx does an early return.

nat/linux-ptrace.c has 3 different logics to kill a child process.
So, this patch factorizes killing a child in the function kill_child.

The 3 different logics are:
* linux_ptrace_test_ret_to_nx is calling both kill (child, SIGKILL)
  and ptrace (PTRACE_KILL, child, ...), and then is calling once
  waitpid.
* linux_check_ptrace_features is calling ptrace (PTRACE_KILL, child, ...)
  + my_waitpid in a loop, as long as the waitpid status was WIFSTOPPED.
* linux_test_for_tracefork is calling once ptrace (PTRACE_KILL, child, ...)
  + my_waitpid.

The linux ptrace documentation indicates that PTRACE_KILL is deprecated,
and tells to not use it, as it might return success but not kill the tracee.
The documentation indicates to send SIGKILL directly.

I suspect that linux_ptrace_test_ret_to_nx calls both kill and ptrace just
to be sure ...
I suspect that linux_check_ptrace_features calls ptrace in a loop
to bypass the PTRACE_KILL limitation.
And it looks like linux_test_for_tracefork does not handle the PTRACE_KILL
limitation.
Also, 2 of the 3 logics are calling my_waitpid, which seems better,
as this is protecting the waitpid syscall against EINTR.

So, the logic in kill_child is just using kill (child, SIGKILL)
+ my_waitpid, and then does a few verifications to see everything worked
accordingly to the plan.

Tested on Debian/x86_64.

2018-12-16  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* nat/linux-ptrace.c (kill_child): New function.
	(linux_ptrace_test_ret_to_nx): Use kill_child instead of local code.
	Add a call to kill_child in case of early return after fork.
	(linux_check_ptrace_features): Use kill_child instead of local code.
	(linux_test_for_tracefork): Likewise.
2018-12-16 21:24:29 +01:00
bfd Automatic date update in version.in 2018-12-16 00:01:06 +00:00
binutils elf: Add PT_GNU_PROPERTY segment type 2018-12-14 04:55:34 -08:00
config Fix a typo in iconv.m4. 2018-11-09 16:08:10 +00:00
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etc Bump to autoconf 2.69 and automake 1.15.1 2018-06-19 16:55:06 -04:00
gas elf: Add PT_GNU_PROPERTY segment type 2018-12-14 04:55:34 -08:00
gdb Factorize killing the children in linux-ptrace.c, and fix a 'process leak'. 2018-12-16 21:24:29 +01:00
gold [GOLD] icf_safe_so_test 2018-12-08 13:24:14 +10:30
gprof Fix typo setting user_specified variable when parsing -Z option. 2018-10-01 17:18:20 +01:00
include elf: Add PT_GNU_PROPERTY segment type 2018-12-14 04:55:34 -08:00
intl Fix a typo in iconv.m4. 2018-11-09 16:08:10 +00:00
ld elf: Add PT_GNU_PROPERTY segment type 2018-12-14 04:55:34 -08:00
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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,
see libg++/README, etc.  That'll give you info about this
package -- supported targets, how to use it, how to report bugs, etc.

It is now possible to automatically configure and build a variety of
tools with one command.  To build all of the tools contained herein,
run the ``configure'' script here, e.g.:

	./configure 
	make

To install them (by default in /usr/local/bin, /usr/local/lib, etc),
then do:
	make install

(If the configure script can't determine your type of computer, give it
the name as an argument, for instance ``./configure sun4''.  You can
use the script ``config.sub'' to test whether a name is recognized; if
it is, config.sub translates it to a triplet specifying CPU, vendor,
and OS.)

If you have more than one compiler on your system, it is often best to
explicitly set CC in the environment before running configure, and to
also set CC when running make.  For example (assuming sh/bash/ksh):

	CC=gcc ./configure
	make

A similar example using csh:

	setenv CC gcc
	./configure
	make

Much of the code and documentation enclosed is copyright by
the Free Software Foundation, Inc.  See the file COPYING or
COPYING.LIB in the various directories, for a description of the
GNU General Public License terms under which you can copy the files.

REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info
on where and how to report problems.