From 94dc51ad841ba5a019680f7fd48decf7f23e964e Mon Sep 17 00:00:00 2001 From: Stefan Liebler Date: Thu, 28 Apr 2016 10:30:09 +0200 Subject: [PATCH] S390: Fix "backtrace() returns infinitely deep stack frames with makecontext()" [BZ #18508]. 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 $(libdl). * stdlib/tst-makecontext.c (cf): Test if _Unwind_Backtrace is not called infinitely times. (backtrace_helper): New function. (trace_arg): New struct. (st1): Enlarge stack size. * sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S: (__makecontext_ret): Omit cfi_startproc and cfi_endproc. * sysdeps/unix/sysv/linux/s390/s390-64/__makecontext_ret.S: Likewise. (cherry picked from commit 890b7a4b33d482b5c768ab47d70758b80227e9bc) --- ChangeLog | 15 +++++++ NEWS | 4 +- stdlib/Makefile | 2 + stdlib/tst-makecontext.c | 41 ++++++++++++++++++- .../linux/s390/s390-32/__makecontext_ret.S | 8 ++++ .../linux/s390/s390-64/__makecontext_ret.S | 8 ++++ 6 files changed, 75 insertions(+), 3 deletions(-) diff --git a/ChangeLog b/ChangeLog index 16c99d65eb2..b36cd9e17a0 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,18 @@ +2016-04-28 Stefan Liebler + + [BZ #18508] + * stdlib/Makefile ($(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. + 2016-04-28 Stefan Liebler [BZ #18080] diff --git a/NEWS b/NEWS index 1d802661c96..c27c29ff5a1 100644 --- a/NEWS +++ b/NEWS @@ -9,8 +9,8 @@ Version 2.21.1 * The following bugs are resolved with this release: - 17269, 17905, 17949, 18007, 18032, 18080, 18240, 18287, 18694, 18887, - 18985, 19682. + 17269, 17905, 17949, 18007, 18032, 18080, 18240, 18287, 18508, 18694, + 18887, 18985, 19682. * A stack-based buffer overflow was found in libresolv when invoked from libnss_dns, allowing specially crafted DNS responses to seize control diff --git a/stdlib/Makefile b/stdlib/Makefile index c78fdb51ecc..501b1f2d0a6 100644 --- a/stdlib/Makefile +++ b/stdlib/Makefile @@ -157,3 +157,5 @@ tst-tls-atexit-lib.so-no-z-defs = yes $(objpfx)tst-tls-atexit: $(shared-thread-library) $(libdl) $(objpfx)tst-tls-atexit.out: $(objpfx)tst-tls-atexit-lib.so + +$(objpfx)tst-makecontext: $(libdl) diff --git a/stdlib/tst-makecontext.c b/stdlib/tst-makecontext.c index 29a588e5885..8170e8aeeda 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 e1f9347f42f..ad39bb84339 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 so that __makecontext_ret stops 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 11a3cd37bb3..8a8665c21c6 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 so that __makecontext_ret stops 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. */ -- 2.47.2