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[Qemu-arm] [PATCH v2 6/6] arm: fix aa64_generate_debug_exceptions to wor


From: Alex Bennée
Subject: [Qemu-arm] [PATCH v2 6/6] arm: fix aa64_generate_debug_exceptions to work with EL2
Date: Thu, 8 Nov 2018 16:33:29 +0000

The test was incomplete and incorrectly caused debug exceptions to be
generated when returning to EL2 after a failed attempt to single-step
an EL1 instruction. Fix this while cleaning up the function a little.

Signed-off-by: Alex Bennée <address@hidden>
---
 target/arm/cpu.h | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 1efff21a18..a6d8eb14f6 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -2764,23 +2764,33 @@ static inline bool arm_v7m_csselr_razwi(ARMCPU *cpu)
     return (cpu->clidr & R_V7M_CLIDR_CTYPE_ALL_MASK) != 0;
 }
 
+/* See AArch64.GenerateDebugExceptionsFrom() in ARM ARM pseudocode */
 static inline bool aa64_generate_debug_exceptions(CPUARMState *env)
 {
+    int cur_el = arm_current_el(env);
+    int debug_el;
+
     if (arm_is_secure(env)) {
         /* MDCR_EL3.SDD disables debug events from Secure state */
         if (extract32(env->cp15.mdcr_el3, 16, 1) != 0
-            || arm_current_el(env) == 3) {
+            || cur_el == 3) {
             return false;
         }
     }
 
-    if (arm_current_el(env) == arm_debug_target_el(env)) {
-        if ((extract32(env->cp15.mdscr_el1, 13, 1) == 0)
-            || (env->daif & PSTATE_D)) {
-            return false;
-        }
+    /*
+     * Same EL to same EL debug exceptions need MDSCR_KDE enabled
+     * while not masking the (D)ebug bit in DAIF.
+     */
+    debug_el = arm_debug_target_el(env);
+
+    if (cur_el == debug_el) {
+        return extract32(env->cp15.mdscr_el1, 13, 1)
+            && !(env->daif & PSTATE_D);
     }
-    return true;
+
+    /* Otherwise the debug target needs to be a higher EL */
+    return debug_el > cur_el;
 }
 
 static inline bool aa32_generate_debug_exceptions(CPUARMState *env)
@@ -2833,9 +2843,6 @@ static inline bool 
aa32_generate_debug_exceptions(CPUARMState *env)
  * since the pseudocode has it at all callsites except for the one in
  * CheckSoftwareStep(), where it is elided because both branches would
  * always return the same value.
- *
- * Parts of the pseudocode relating to EL2 and EL3 are omitted because we
- * don't yet implement those exception levels or their associated trap bits.
  */
 static inline bool arm_generate_debug_exceptions(CPUARMState *env)
 {
-- 
2.17.1




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