[POWERPC] spufs: Add support for SPU single stepping

This patch adds support for SPU single stepping. The single
step bit is set in the SPU when the current process is
being single-stepped via ptrace. The spu then stops and
returns with a specific flag set and the syscall exit code
will generate the SIGTRAP.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/platforms/cell/spufs/run.c b/arch/powerpc/platforms/cell/spufs/run.c
index 57626600b1a4b5c7cb3d46d17ef214e5b5807d1d..6625ed2a7fddcbb3808deb3f4b163e3ca37326cb 100644 (file)
--- a/arch/powerpc/platforms/cell/spufs/run.c
+++ b/arch/powerpc/platforms/cell/spufs/run.c
@@ -142,8 +142,12 @@ static int spu_run_init(struct spu_context *ctx, u32 * npc)
                        runcntl = SPU_RUNCNTL_RUNNABLE;
                ctx->ops->runcntl_write(ctx, runcntl);
        } else {
+               unsigned long mode = SPU_PRIVCNTL_MODE_NORMAL;
                spu_start_tick(ctx);
                ctx->ops->npc_write(ctx, *npc);
+               if (test_thread_flag(TIF_SINGLESTEP))
+                       mode = SPU_PRIVCNTL_MODE_SINGLE_STEP;
+               out_be64(&ctx->spu->priv2->spu_privcntl_RW, mode);
                ctx->ops->runcntl_write(ctx, SPU_RUNCNTL_RUNNABLE);
        }
 
@@ -334,7 +338,8 @@ long spufs_run_spu(struct file *file, struct spu_context *ctx,
                ret = spu_process_events(ctx);
 
        } while (!ret && !(status & (SPU_STATUS_STOPPED_BY_STOP |
-                                     SPU_STATUS_STOPPED_BY_HALT)));
+                                     SPU_STATUS_STOPPED_BY_HALT |
+                                      SPU_STATUS_SINGLE_STEP)));
 
        ctx->ops->master_stop(ctx);
        ret = spu_run_fini(ctx, npc, &status);
@@ -344,10 +349,15 @@ out2:
        if ((ret == 0) ||
            ((ret == -ERESTARTSYS) &&
             ((status & SPU_STATUS_STOPPED_BY_HALT) ||
+             (status & SPU_STATUS_SINGLE_STEP) ||
              ((status & SPU_STATUS_STOPPED_BY_STOP) &&
               (status >> SPU_STOP_STATUS_SHIFT != 0x2104)))))
                ret = status;
 
+       /* Note: we don't need to force_sig SIGTRAP on single-step
+        * since we have TIF_SINGLESTEP set, thus the kernel will do
+        * it upon return from the syscall anyawy
+        */
        if ((status & SPU_STATUS_STOPPED_BY_STOP)
            && (status >> SPU_STOP_STATUS_SHIFT) == 0x3fff) {
                force_sig(SIGTRAP, current);