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

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

[Jason Wessel]

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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));
 }
 

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

[Ely Soto]

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Excellent, I had encountered that bug earlier on when trying to debug 
using workbench.

Are you guys developing a BSP for qemu?
I have a partially working one.

Ely Soto




Jason Wessel <jason.wessel@windriver.com> 
Sent by: qemu-devel-bounces+soto.ely=orbital.com@nongnu.org
12/27/2006 11:05 AM
Please respond to
qemu-devel@nongnu.org


To
qemu-devel@nongnu.org
cc

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






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.
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));
 }
 
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Re: [Qemu-devel] [PATCH] PPC32 Trace Exception and Trap instruction

[Rob Landley]

On Wednesday 27 December 2006 11:24 am, Ely Soto wrote:
> Excellent, I had encountered that bug earlier on when trying to debug 
> using workbench.
> 
> Are you guys developing a BSP for qemu?
> I have a partially working one.

I'm poking at something like that.

http://landley.net/code/firmware
http://landley.net/hg/firmware

Of course I'm using a gcc 4.x toolchain, so I'm applying the gentoo patches to 
qemu 0.8.2 to build under that, and last I checked they weren't enough to get 
cvs to build under gcc 4.x, but I haven't poked at it recently...

Rob
-- 
"Perfection is reached, not when there is no longer anything to add, but
when there is no longer anything to take away." - Antoine de Saint-Exupery