[Xen-devel] [PATCH 4/9] xen: arm: turn vtimer traps for cp32/64 and sysreg into #undef

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

We have allowed EL1 to access these registers directly for some time
(at least since 4.3.0). They were only ever trapped to support very
early models which had a buggy hypervisor timer, requiring us to use
the phys timer for Xen itself.

In the interests of minimising the patch for the security update just
remove the call to vtimer_emulate and inject an #undef exception. In
practice we will never see any of these traps.

Handle CNTPCT_EL0 explicitly for consistency with CNTPCT on 32-bit.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 xen/arch/arm/traps.c |   37 ++++++++++++-------------------------
 1 file changed, 12 insertions(+), 25 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 353e38e..46ed21d 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1478,13 +1478,8 @@ static void do_cp15_32(struct cpu_user_regs *regs,
         break;
     case HSR_CPREG32(CNTP_CTL):
     case HSR_CPREG32(CNTP_TVAL):
-        if ( !vtimer_emulate(regs, hsr) )
-        {
-            dprintk(XENLOG_ERR,
-                    "failed emulation of 32-bit vtimer CP register access\n");
-            domain_crash_synchronous();
-        }
-        break;
+        goto undef_cp15_32;
+
     case HSR_CPREG32(ACTLR):
         if ( cp32.read )
            *r = v->arch.actlr;
@@ -1526,6 +1521,7 @@ static void do_cp15_32(struct cpu_user_regs *regs,
         gdprintk(XENLOG_ERR, "unhandled 32-bit CP15 access %#x\n",
                  hsr.bits & HSR_CP32_REGS_MASK);
 #endif
+ undef_cp15_32:
         inject_undef_exception(regs, hsr.len);
         return;
     }
@@ -1544,13 +1540,8 @@ static void do_cp15_64(struct cpu_user_regs *regs,
     switch ( hsr.bits & HSR_CP64_REGS_MASK )
     {
     case HSR_CPREG64(CNTPCT):
-        if ( !vtimer_emulate(regs, hsr) )
-        {
-            dprintk(XENLOG_ERR,
-                    "failed emulation of 64-bit vtimer CP register access\n");
-            domain_crash_synchronous();
-        }
-        break;
+        goto undef_cp15_64;
+
     default:
         {
 #ifndef NDEBUG
@@ -1563,6 +1554,7 @@ static void do_cp15_64(struct cpu_user_regs *regs,
             gdprintk(XENLOG_ERR, "unhandled 64-bit CP15 access %#x\n",
                      hsr.bits & HSR_CP64_REGS_MASK);
 #endif
+ undef_cp15_64:
             inject_undef_exception(regs, hsr.len);
             return;
         }
@@ -1729,18 +1721,13 @@ static void do_sysreg(struct cpu_user_regs *regs,
         break;
     case HSR_SYSREG_CNTP_CTL_EL0:
     case HSR_SYSREG_CNTP_TVAL_EL0:
-        if ( !vtimer_emulate(regs, hsr) )
-        {
-            dprintk(XENLOG_ERR,
-                    "failed emulation of 64-bit vtimer sysreg access\n");
-            domain_crash_synchronous();
-        }
-        break;
+    case HSR_SYSREG_CNTPCT_EL0:
+        goto undef_sysreg;
     default:
  bad_sysreg:
         {
-            struct hsr_sysreg sysreg = hsr.sysreg;
 #ifndef NDEBUG
+            struct hsr_sysreg sysreg = hsr.sysreg;
 
             gdprintk(XENLOG_ERR,
                      "%s %d, %d, c%d, c%d, %d %s x%d @ 0x%"PRIregister"\n",
@@ -1753,7 +1740,8 @@ static void do_sysreg(struct cpu_user_regs *regs,
             gdprintk(XENLOG_ERR, "unhandled 64-bit sysreg access %#x\n",
                      hsr.bits & HSR_SYSREG_REGS_MASK);
 #endif
-            inject_undef_exception(regs, sysreg.len);
+ undef_sysreg:
+            inject_undef_exception(regs, hsr.len);
             return;
         }
     }
@@ -1925,8 +1913,7 @@ asmlinkage void do_trap_hypervisor(struct cpu_user_regs 
*regs)
         do_cp15_32(regs, hsr);
         break;
     case HSR_EC_CP15_64:
-        if ( !is_32bit_domain(current->domain) )
-            goto bad_trap;
+        BUG_ON(!psr_mode_is_32bit(regs->cpsr));
         do_cp15_64(regs, hsr);
         break;
     case HSR_EC_CP14_32:
-- 
1.7.10.4


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