[BZ,#18508] S390: Fix "backtrace() returns infinitely deep stack frames with makecontext()".
Commit Message
On 06/12/2015 11:14 AM, Florian Weimer wrote:
> On 06/09/2015 05:42 PM, Stefan Liebler wrote:
>
>> 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?)"
>
> Is it possible to extract a test case from the Go program, by calling
> makecontext and backtrace in the same way to Go run time does?
>
> I think this would be a useful addition to the glibc test suite.
>
Yes, i can make a testcase like stdlib/tst-makecontext.c or extend it -
see below.
Can i call _Unwind_Backtrace directly on all architectures? Or does it
exist on all architectures?
The diff below uses dlopen to load libgcc, but e.g. s390 needs
libgcc_s.so.1 and others like m68k needs libgcc_s.so.2.
Is there a way to load the correct libgcc_s.so on all architectures?
As an alternative i could use the glibc backtrace() method. But at least
for the x86_64 version and all others who simply includes it, this
testcase would not fail, because the backtrace_helper function has a
check, if the address has changed in two consecutively calls.
The go runtime hasn't such a check and would fail like reported by the
mentioned go-bug.
Any ideas?
Bye Stefan
terminate the process normally after this function returns. */
}
Comments
Stefan Liebler <stli@linux.vnet.ibm.com> writes:
> Is there a way to load the correct libgcc_s.so on all architectures?
#include <gnu/lib-names.h>
dlopen(LIBGCC_S_SO, ...)
Andreas.
@@ -19,23 +19,62 @@
#include <stdlib.h>
#include <stdio.h>
#include <ucontext.h>
+#include <assert.h>
+#include <unwind.h>
+#include <dlfcn.h>
ucontext_t ucp;
-char st1[8192];
+char st1[16384];
__thread int thr;
+struct trace_arg
+{
+ int cnt, size;
+};
+
int somevar = -76;
long othervar = -78L;
+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 = __libc_dlopen ("libgcc_s.so.1");
+ if (handle != NULL)
+ {
+ unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");
+ if (unwind_backtrace != NULL)
+ {
+ unwind_backtrace (backtrace_helper, &arg);
+ assert (arg.cnt != -1 && arg.cnt < 100);
+ }
+ __libc_dlclose (handle);
+ }
+
/* Since uc_link below has been set to NULL, setcontext is supposed to