[Xen-devel] [PATCH v2] xen/arm: Add some useful debug in coprocessor trapping

[Julien Grall <julien.grall@xxxxxxxxxx>]

XSA-93 adds a couple of new functions to trap coprocessor registers. They
unconditionally inject an undefined instruction to guest.

When debugging an OS at early stage, it may be hard to know why the guest
received an UNDEFINED. Add some debug message to help the developer when Xen
is built in debug mode.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

---
    Changes in v2:
        - Make the patch compile with debug=n
        - Fix typo in the commit message
        - Drop spurious change
---
 xen/arch/arm/traps.c            |   20 ++++++++++++++++++++
 xen/include/asm-arm/processor.h |   11 +++++++++++
 2 files changed, 31 insertions(+)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 7f77c56..069b9f3 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1546,23 +1546,43 @@ bad_cp:
 
 static void do_cp14_dbg(struct cpu_user_regs *regs, union hsr hsr)
 {
+#ifndef NDEBUG
+    struct hsr_cp64 cp64 = hsr.cp64;
+#endif
+
     if ( !check_conditional_instr(regs, hsr) )
     {
         advance_pc(regs, hsr);
         return;
     }
 
+#ifndef NDEBUG
+    gdprintk(XENLOG_ERR,
+             "%s p14, %d, r%d, r%d, cr%d @ 0x%"PRIregister"\n",
+             cp64.read ? "mrrc" : "mcrr",
+             cp64.op1, cp64.reg1, cp64.reg2, cp64.crm, regs->pc);
+    gdprintk(XENLOG_ERR, "unhandled 64-bit CP14 access %#x\n",
+             hsr.bits & HSR_CP64_REGS_MASK);
+#endif
     inject_undef32_exception(regs);
 }
 
 static void do_cp(struct cpu_user_regs *regs, union hsr hsr)
 {
+#ifndef NDEBUG
+    struct hsr_cp cp = hsr.cp;
+#endif
+
     if ( !check_conditional_instr(regs, hsr) )
     {
         advance_pc(regs, hsr);
         return;
     }
 
+#ifndef NDEBUG
+    ASSERT(!cp.tas); /* We don't trap SIMD instruction */
+    gdprintk(XENLOG_ERR, "unhandled CP%d access\n", cp.coproc);
+#endif
     inject_undef32_exception(regs);
 }
 
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index ebc683d..3be86f1 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -295,6 +295,17 @@ union hsr {
         unsigned long ec:6;     /* Exception Class */
     } cp64; /* HSR_EC_CP15_64, HSR_EC_CP14_64 */
 
+     struct hsr_cp {
+        unsigned long coproc:4; /* Number of coproc accessed */
+        unsigned long sbz0p:1;
+        unsigned long tas:1;    /* Trapped Advanced SIMD */
+        unsigned long res0:14;
+        unsigned long cc:4;     /* Condition Code */
+        unsigned long ccvalid:1;/* CC Valid */
+        unsigned long len:1;    /* Instruction length */
+        unsigned long ec:6;     /* Exception Class */
+    } cp; /* HSR_EC_CP */
+
 #ifdef CONFIG_ARM_64
     struct hsr_sysreg {
         unsigned long read:1;   /* Direction */
-- 
1.7.10.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel