From patchwork Tue Jun 9 15:42:22 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Liebler X-Patchwork-Id: 7088 Received: (qmail 16191 invoked by alias); 9 Jun 2015 15:42:43 -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 16092 invoked by uid 89); 9 Jun 2015 15:42:42 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.5 required=5.0 tests=AWL, BAYES_00, RCVD_IN_DNSWL_LOW, SPF_HELO_PASS, SPF_PASS, T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: plane.gmane.org To: libc-alpha@sourceware.org From: Stefan Liebler Subject: [PATCH][BZ #18508] S390: Fix "backtrace() returns infinitely deep stack frames with makecontext()". Date: Tue, 09 Jun 2015 17:42:22 +0200 Lines: 86 Message-ID: Mime-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 Hi, 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. Ok to commit? Bye Stefan --- 2015-06-09 Stefan Liebler [BZ #18508] * 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/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. */