[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>

1 files changed, 11 insertions, 1 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/run.c b/arch/powerpc/platforms/cell/spufs/run.c
index 57626600b1a4..6625ed2a7fdd 100644
--- 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);