[Qemu-devel] [PATCH] PPC32 Trace Exception and Trap instruction

[Jason Wessel <jason.wessel@windriver.com>]

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Please add this patch to CVS. 

The patch has two purposes:

1) The NIP needs to be updated for a tw instruction. 
    I found that when executing protected mode traps
    the PC was always set to the begining of the code
    generation block instead of the instruction the trap
    occurred on.

    The usual PPC breakpoint instruction is:
    7d 82 10 08 twge    r2,r2  (Trap when rA >= rB)

2) Single stepping was fixed up earlier in the year
    for using a debugger connected to the QEMU
    gdb stub.  Now it is enabled for connecting a
    runtime single stepping with the trace trap so you
    can use ptrace() or even debug KGDB.

signed-off-by: jason.wessel@windriver.com

Thanks,
Jason.

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Index: qemu/target-ppc/helper.c
===================================================================
--- qemu.orig/target-ppc/helper.c
+++ qemu/target-ppc/helper.c
@@ -1113,8 +1113,6 @@ void do_interrupt (CPUState *env)
         }
         goto store_next;
     case EXCP_TRACE: /* 0x0D00 */
-        /* XXX: TODO */
-        cpu_abort(env, "Trace exception is not implemented yet !\n");
         goto store_next;
     case EXCP_PERF: /* 0x0F00 */
         /* XXX: TODO */
Index: qemu/target-ppc/translate.c
===================================================================
--- qemu.orig/target-ppc/translate.c
+++ qemu/target-ppc/translate.c
@@ -1956,6 +1956,8 @@ GEN_HANDLER(tw, 0x1F, 0x04, 0xFF, 0x0000
 {
     gen_op_load_gpr_T0(rA(ctx->opcode));
     gen_op_load_gpr_T1(rB(ctx->opcode));
+    /* Update the nip since this might generate a trap exception */
+    gen_op_update_nip(ctx->nip);
     gen_op_tw(TO(ctx->opcode));
 }