Initialize target description early in IPA

Initialize target description early in IPA

Target descriptions are allocated lazily, that is fine in GDBserver,
but it is not safe to call malloc in gdb_collect in IPA, because we
can set a fast tracepoint in malloc, and when the tracepoint is hit,
gdb_collect/malloc is called, deadlock or memory corruption may be
triggered.

 #0  0xf7cfc200 in malloc ()
 #1  0xf7efdc07 in operator new(unsigned int) ()
 #2  0xf7ef7636 in allocate_target_description() ()
 #3  0xf7efcbe1 in i386_create_target_description(unsigned long long, bool) ()
 #4  0xf7efb474 in i386_linux_read_description(unsigned long long) ()
 #5  0xf7efb190 in get_ipa_tdesc(int) ()
 #6  0xf7ef9baa in gdb_collect ()

The fix is to initialize all target descriptions earlier, when the
IPA is loaded.  In order to guarantee malloc is not called in IPA
in gdb_collect, I change the test to set a breakpoint on malloc, if
IPA gdb_collect calls malloc, program will hit the breakpoint, and
test fail.

continue
Continuing.

Thread 1 "" hit Breakpoint 5, 0xf7cfc200 in malloc ()
(gdb) FAIL: gdb.trace/ftrace.exp: advance through tracing

gdb/gdbserver:

2017-12-07  Yao Qi  <yao.qi@linaro.org>

	* linux-aarch64-ipa.c (initialize_low_tracepoint): Call
	aarch64_linux_read_description.
	* linux-amd64-ipa.c (idx2mask): New array.
	(get_ipa_tdesc): Move idx2mask out.
	(initialize_low_tracepoint): Initialize target descriptions.
	* linux-i386-ipa.c (idx2mask): New array.
	(get_ipa_tdesc): Move idx2mask out.
	(initialize_low_tracepoint): Initialize target descriptions.

gdb/testsuite:

2017-12-07  Yao Qi  <yao.qi@linaro.org>

	* gdb.trace/ftrace.exp (run_trace_experiment): Set breakpoint on
	malloc and catch syscall.