[src/trunk]: src/sys/arch/arm/vfp PR port-arm/55790

[rin <rin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/17456fbc7d62
branches:  trunk
changeset: 1021475:17456fbc7d62
user:      rin <rin%NetBSD.org@localhost>
date:      Tue Jun 01 00:30:22 2021 +0000

description:
PR port-arm/55790

Fix KASSERT failure with floating-point exception in userland.

Consider the case in which curlwp owns enabled FPU in vfp_handler().
If FPE is raised, we must skip pcu_load(9) rather than just falling
through. Otherwise, KASSERT fires in vfp_state_load(), since curlwp
already owns enabled FPU.

No regression for ATF is introduced.

diffstat:

 sys/arch/arm/vfp/vfp_init.c |  23 ++++++++++++++++-------
 1 files changed, 16 insertions(+), 7 deletions(-)

diffs (64 lines):

diff -r b577e0cd9d7c -r 17456fbc7d62 sys/arch/arm/vfp/vfp_init.c
--- a/sys/arch/arm/vfp/vfp_init.c       Tue Jun 01 00:13:19 2021 +0000
+++ b/sys/arch/arm/vfp/vfp_init.c       Tue Jun 01 00:30:22 2021 +0000
@@ -1,4 +1,4 @@
-/*      $NetBSD: vfp_init.c,v 1.73 2021/06/01 00:13:19 rin Exp $ */
+/*      $NetBSD: vfp_init.c,v 1.74 2021/06/01 00:30:22 rin Exp $ */
 
 /*
  * Copyright (c) 2008 ARM Ltd
@@ -32,7 +32,7 @@
 #include "opt_cputypes.h"
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfp_init.c,v 1.73 2021/06/01 00:13:19 rin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfp_init.c,v 1.74 2021/06/01 00:30:22 rin Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -423,6 +423,7 @@
 vfp_handler(u_int address, u_int insn, trapframe_t *frame, int fault_code)
 {
        struct cpu_info * const ci = curcpu();
+       uint32_t fpexc;
 
        /* This shouldn't ever happen.  */
        if (fault_code != FAULT_USER &&
@@ -436,12 +437,19 @@
 
        /* 
         * If we already own the FPU and it's enabled (and no exception), raise
-        * SIGILL.  If there is an exception, drop through to raise a SIGFPE.
+        * SIGILL.  If there is an exception, raise SIGFPE.
         */
-       if (curlwp->l_pcu_cpu[PCU_FPU] == ci
-           && (armreg_fpexc_read() & (VFP_FPEXC_EX|VFP_FPEXC_EN)) == VFP_FPEXC_EN) {
+       if (curlwp->l_pcu_cpu[PCU_FPU] == ci) {
                KASSERT(ci->ci_pcu_curlwp[PCU_FPU] == curlwp);
-               return 1;
+
+               fpexc = armreg_fpexc_read();
+               if (fpexc & VFP_FPEXC_EN) {
+                       if ((fpexc & VFP_FPEXC_EX) == 0) {
+                               return 1;       /* SIGILL */
+                       } else {
+                               goto fpe;       /* SIGFPE; skip pcu_load(9) */
+                       }
+               }
        }
 
        /*
@@ -449,11 +457,12 @@
         */
        pcu_load(&arm_vfp_ops);
 
-       uint32_t fpexc = armreg_fpexc_read();
+       fpexc = armreg_fpexc_read();
        if (fpexc & VFP_FPEXC_EX) {
                ksiginfo_t ksi;
                KASSERT(fpexc & VFP_FPEXC_EN);
 
+fpe:
                curcpu()->ci_vfp_evs[2].ev_count++;
 
                /*