------- Comment From brueck...@de.ibm.com 2016-02-26 10:59 EDT------- Problem fix is now upstream:
commit 1b17cb796f5d40ffa239c6926385abd83a77a49b Author: Martin Schwidefsky <schwidef...@de.ibm.com> Date: Fri Feb 19 15:29:05 2016 +0100 s390/fpu: signals vs. floating point control register git commit 904818e2f229f3d94ec95f6932a6358c81e73d78 "s390/kernel: introduce fpu-internal.h with fpu helper functions" introduced the fpregs_store / fp_regs_load helper. These function fail to save and restore the floating pointer control registers. The effect is that the FPC is not correctly handled on signal delivery and signal return. Cc: sta...@vger.kernel.org # 4.4 Signed-off-by: Martin Schwidefsky <schwidef...@de.ibm.com> -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1548414 Title: Floating-point exception handler receives empty Data-Exception Code in Floating Point Control register Status in linux package in Ubuntu: Fix Committed Status in linux source package in Xenial: Fix Committed Bug description: == Comment: #0 - Alexander Efremkin <a.efrem...@ru.ibm.com> - 2016-02-17 12:18:14 == With a C program sets FPE handler and triggers an FPE exception, it expects that machine-dependent context data, which is passed to the handler, will contain sensible values. In this scenario, however, FPC register was zero and contained no DXC (Data-Exception Code) indication: #include <stdio.h> #include <string.h> #include <signal.h> void trapFunction() { asm volatile ("lhi %r1,0\n\t" "cit %r1,0,8\n\t"); } static void sigFPE_handler(int signal, siginfo_t *info, void *context) { ucontext_t *uc = context; mcontext_t mc = uc->uc_mcontext; fpregset_t fpregs = mc.fpregs; unsigned int fpc = fpregs.fpc; printf("received signal!\n"); printf("fpc: %08x\n", fpc ); } int main() { struct sigaction action; memset(&action, '\0', sizeof(action)); printf("registering signal handler\n"); action.sa_flags |= SA_SIGINFO; action.sa_sigaction = sigFPE_handler; if (sigaction(SIGFPE, &action, NULL)) printf("error calling sigaction\n"); printf("firing trap\n"); trapFunction(); return 0; } This program prints "fpc: 00000000", but the expected output is "fpc: 0000ff00".. The IBM Java team has encountered test failures around the use of trap instructions; Linux on z Distribution Test reproduced the issue on the following system: z13 LPAR Ubuntu 16.04 Kernel 4.4.0-4-generic gcc (Ubuntu 5.3.1-8ubuntu2) 5.3.1 20160205 libc6 2.21-0ubuntu5 Also, similar issue has been found during test of SIMD (vector) instructions, FPC contents was also zero, whereas it expected at least an exception mask and vector-defined DXC. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1548414/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
