From patchwork Mon Jun 15 08:47:30 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Liebler X-Patchwork-Id: 7176 Received: (qmail 123959 invoked by alias); 15 Jun 2015 08:47:49 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 123948 invoked by uid 89); 15 Jun 2015 08:47:48 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.7 required=5.0 tests=AWL, BAYES_00, RCVD_IN_DNSWL_LOW, RP_MATCHES_RCVD, SPF_HELO_PASS, SPF_PASS autolearn=ham version=3.3.2 X-HELO: plane.gmane.org To: libc-alpha@sourceware.org From: Stefan Liebler Subject: Re: [PATCH][BZ #18508] S390: Fix "backtrace() returns infinitely deep stack frames with makecontext()". Date: Mon, 15 Jun 2015 10:47:30 +0200 Lines: 169 Message-ID: References: <557AA306.4090208@redhat.com> <87eglhvsst.fsf@igel.home> Mime-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 In-Reply-To: <87eglhvsst.fsf@igel.home> On 06/12/2015 05:40 PM, Andreas Schwab wrote: > Stefan Liebler writes: > >> Is there a way to load the correct libgcc_s.so on all architectures? > > #include > dlopen(LIBGCC_S_SO, ...) > > Andreas. > Thanks. Here is the patch with the enhanced tst-makecontext testcase. It calls _Unwind_Backtrace within cf() function, which is called in a makecontext context and check if the callback function is not called infinitely times. Tested on s390/s390x before and after this patch. Before: Test fails; After: Test succeeds. Ok to commit? Bye Stefan --- 2015-06-15 Stefan Liebler [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. diff --git a/stdlib/Makefile b/stdlib/Makefile index 3300dd2..7fc5a80 100644 --- a/stdlib/Makefile +++ b/stdlib/Makefile @@ -164,3 +164,5 @@ $(objpfx)tst-setcontext3.out: tst-setcontext3.sh $(objpfx)tst-setcontext3 '$(run-program-env)' '$(test-program-prefix-after-env)' \ $(common-objpfx)stdlib/; \ $(evaluate-test) + +$(objpfx)tst-makecontext: $(libdl) diff --git a/stdlib/tst-makecontext.c b/stdlib/tst-makecontext.c index 29a588e..8170e8a 100644 --- a/stdlib/tst-makecontext.c +++ b/stdlib/tst-makecontext.c @@ -19,23 +19,62 @@ #include #include #include +#include +#include +#include +#include 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 + /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. */ } diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S b/sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S index e1f9347..8d36ea2 100644 --- a/sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S +++ b/sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S @@ -17,6 +17,14 @@ #include +/* We do not want .eh_frame info for __makecontext_ret to stop unwinding + if backtrace() was called within a context created by makecontext. + (there is also no .eh_frame info for _start or thread_start) */ +#undef cfi_startproc +#define cfi_startproc +#undef cfi_endproc +#define cfi_endproc + ENTRY(__makecontext_ret) basr %r14,%r7 ltr %r8,%r8 /* Check whether uc_link is 0. */ diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/__makecontext_ret.S b/sysdeps/unix/sysv/linux/s390/s390-64/__makecontext_ret.S index 11a3cd3..64619f1 100644 --- a/sysdeps/unix/sysv/linux/s390/s390-64/__makecontext_ret.S +++ b/sysdeps/unix/sysv/linux/s390/s390-64/__makecontext_ret.S @@ -17,6 +17,14 @@ #include +/* We do not want .eh_frame info for __makecontext_ret to stop unwinding + if backtrace() was called within a context created by makecontext. + (there is also no .eh_frame info for _start or thread_start) */ +#undef cfi_startproc +#define cfi_startproc +#undef cfi_endproc +#define cfi_endproc + ENTRY(__makecontext_ret) basr %r14,%r7 ltgr %r8,%r8 /* Check whether uc_link is 0. */