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[Qemu-devel] [PATCH] target-openrisc: Fix exception handling status regi

From: Stafford Horne
Subject: [Qemu-devel] [PATCH] target-openrisc: Fix exception handling status registers
Date: Sat, 14 Jan 2017 07:00:28 +0900

I am working on testing instruction emulation patches for the linux
kernel. During testing I found these 2 issues:

 - sets DSX (delay slot exception) but never clears it
 - EEAR for illegal insns should point to the bad exception (as per
   openrisc spec) but its not

This patch fixes these two issues by clearing the DSX flag when not in a
delay slot and by setting EEAR to exception PC when handling illegal
instruction exceptions.

After this patch the openrisc kernel with latest patches boots great on
qemu and instruction emulation works.

Cc: address@hidden
Cc: address@hidden
Signed-off-by: Stafford Horne <address@hidden>
 target/openrisc/interrupt.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/target/openrisc/interrupt.c b/target/openrisc/interrupt.c
index 5fe3f11..e1b0142 100644
--- a/target/openrisc/interrupt.c
+++ b/target/openrisc/interrupt.c
@@ -38,10 +38,17 @@ void openrisc_cpu_do_interrupt(CPUState *cs)
         env->flags &= ~D_FLAG;
         env->sr |= SR_DSX;
         env->epcr -= 4;
+    } else {
+        env->sr &= ~SR_DSX;
     if (cs->exception_index == EXCP_SYSCALL) {
         env->epcr += 4;
+    /* When we have an illegal instruction the error effective address
+       shall be set to the illegal instruction address.  */
+    if (cs->exception_index == EXCP_ILLEGAL) {
+        env->eear = env->pc;
+    }
     /* For machine-state changed between user-mode and supervisor mode,
        we need flush TLB when we enter&exit EXCP.  */

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