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S390: Fix "backtrace() returns infinitely deep stack frames with makecontext()" [BZ #18508].

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On s390/s390x backtrace(buffer, size) returns the series of called functions until
"makecontext_ret" and additional entries (up to "size") with "makecontext_ret".
GDB-backtrace is also warning:
"Backtrace stopped: previous frame identical to this frame (corrupt stack?)"

To reproduce this scenario you have to setup a new context with makecontext()
and activate it with setcontext(). See e.g. cf() function in testcase stdlib/tst-makecontext.c.
Or see bug in libgo "Bug 66303 - runtime.Caller() returns infinitely deep stack frames
on s390x " (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66303).

This patch omits the cfi_startproc/cfi_endproc directives in ENTRY/END macro of
__makecontext_ret. Thus no frame information is generated in .eh_frame and backtrace
stops after __makecontext_ret. There is also no .eh_frame info for _start or
thread_start functions.

ChangeLog:

	[BZ #18508]
	* stdlib/Makefile ($(objpfx)tst-makecontext3):
	Depend on $(libdl).
	* stdlib/tst-makecontext.c (cf): Test if _Unwind_Backtrace
	is not called infinitely times.
	(backtrace_helper): New function.
	(trace_arg): New struct.
	(st1): Enlarge stack size.
	* sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S:
	(__makecontext_ret): Omit cfi_startproc and cfi_endproc.
	* sysdeps/unix/sysv/linux/s390/s390-64/__makecontext_ret.S:
	Likewise.
This commit is contained in:
Stefan Liebler
2015-07-07 16:11:14 +02:00
committed by Andreas Krebbel
parent fa4eeac73d
commit 890b7a4b33
6 changed files with 78 additions and 5 deletions
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41
stdlib/tst-makecontext.c
View File

@ -19,23 +19,62 @@
#include <stdlib.h>
#include <stdio.h>
#include <ucontext.h>
#include <assert.h>
#include <unwind.h>
#include <dlfcn.h>
#include <gnu/lib-names.h>
ucontext_t ucp;
char st1[8192];
char st1[16384];
__thread int thr;
int somevar = -76;
long othervar = -78L;
struct trace_arg
{
int cnt, size;
};
static _Unwind_Reason_Code
backtrace_helper (struct _Unwind_Context *ctx, void *a)
{
struct trace_arg *arg = a;
if (++arg->cnt == arg->size)
return _URC_END_OF_STACK;
return _URC_NO_REASON;
}
void
cf (int i)
{
struct trace_arg arg = { .size = 100, .cnt = -1 };
void *handle;
_Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
if (i != othervar || thr != 94)
{
printf ("i %d thr %d\n", i, thr);
exit (1);
}
/* Test if callback function of _Unwind_Backtrace is not called infinitely
times. See Bug 18508 or gcc bug "Bug 66303 - runtime.Caller() returns
infinitely deep stack frames on s390x.".
The go runtime calls backtrace_full() in
<gcc-src>/libbacktrace/backtrace.c, which uses _Unwind_Backtrace(). */
handle = dlopen (LIBGCC_S_SO, RTLD_LAZY);
if (handle != NULL)
{
unwind_backtrace = dlsym (handle, "_Unwind_Backtrace");
if (unwind_backtrace != NULL)
{
unwind_backtrace (backtrace_helper, &arg);
assert (arg.cnt != -1 && arg.cnt < 100);
}
dlclose (handle);
}
/* Since uc_link below has been set to NULL, setcontext is supposed to
terminate the process normally after this function returns. */
}