Subject: spufs: add infrastructure to support spu profiling

In order for oprofile to find the location in an spu-elf
binary where an event counter triggered, we need a way
to identify the binary in the first place.

Unfortunately, that binary itself can be embedded in a
powerpc ELF binary. Since we can assume it is mapped into
the effective address space of the running process,
have that one write the pointer value into a new spufs
file.

When a context switch occurs, pass the user value to
the profiler so that can look at the mapped file (with
some care).

Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>

Index: linus-2.6/arch/powerpc/platforms/cell/spufs/file.c
===================================================================
--- linus-2.6.orig/arch/powerpc/platforms/cell/spufs/file.c
+++ linus-2.6/arch/powerpc/platforms/cell/spufs/file.c
@@ -1344,6 +1344,21 @@ static u64 spufs_id_get(void *data)
 }
 DEFINE_SIMPLE_ATTRIBUTE(spufs_id_ops, spufs_id_get, 0, "0x%llx\n")
 
+static u64 spufs_object_id_get(void *data)
+{
+	struct spu_context *ctx = data;
+	return ctx->object_id;
+}
+
+static void spufs_object_id_set(void *data, u64 id)
+{
+	struct spu_context *ctx = data;
+	ctx->object_id = id;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(spufs_object_id_ops, spufs_object_id_get,
+		spufs_object_id_set, "0x%llx\n");
+
 struct tree_descr spufs_dir_contents[] = {
 	{ "mem",  &spufs_mem_fops,  0666, },
 	{ "regs", &spufs_regs_fops,  0666, },
@@ -1368,5 +1383,6 @@ struct tree_descr spufs_dir_contents[] =
 	{ "event_mask", &spufs_event_mask_ops, 0666, },
 	{ "srr0", &spufs_srr0_ops, 0666, },
 	{ "phys-id", &spufs_id_ops, 0666, },
+	{ "object-id", &spufs_object_id_ops, 0666, },
 	{},
 };
Index: linus-2.6/arch/powerpc/platforms/cell/spufs/spufs.h
===================================================================
--- linus-2.6.orig/arch/powerpc/platforms/cell/spufs/spufs.h
+++ linus-2.6/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -48,6 +48,7 @@ struct spu_context {
 	struct address_space *cntl; 	   /* 'control' area mappings. */
 	struct address_space *signal1; 	   /* 'signal1' area mappings. */
 	struct address_space *signal2; 	   /* 'signal2' area mappings. */
+	u64 object_id;		   /* user space pointer for oprofile */
 
 	enum { SPU_STATE_RUNNABLE, SPU_STATE_SAVED } state;
 	struct rw_semaphore state_sema;
Index: linus-2.6/arch/powerpc/platforms/cell/spufs/sched.c
===================================================================
--- linus-2.6.orig/arch/powerpc/platforms/cell/spufs/sched.c
+++ linus-2.6/arch/powerpc/platforms/cell/spufs/sched.c
@@ -36,6 +36,7 @@
 #include <linux/unistd.h>
 #include <linux/numa.h>
 #include <linux/mutex.h>
+#include <linux/notifier.h>
 
 #include <asm/io.h>
 #include <asm/mmu_context.h>
@@ -75,6 +76,25 @@ static inline void mm_needs_global_tlbie
 	__cpus_setall(&mm->cpu_vm_mask, nr);
 }
 
+static BLOCKING_NOTIFIER_HEAD(spu_switch_notifier);
+
+static void spu_switch_notify(struct spu *spu, struct spu_context *ctx)
+{
+	blocking_notifier_call_chain(&spu_switch_notifier,
+			    ctx ? ctx->object_id : 0, spu);
+}
+
+int spu_switch_event_register(struct notifier_block * n)
+{
+	return blocking_notifier_chain_register(&spu_switch_notifier, n);
+}
+
+int spu_switch_event_unregister(struct notifier_block * n)
+{
+	return blocking_notifier_chain_unregister(&spu_switch_notifier, n);
+}
+
+
 static inline void bind_context(struct spu *spu, struct spu_context *ctx)
 {
 	pr_debug("%s: pid=%d SPU=%d NODE=%d\n", __FUNCTION__, current->pid,
@@ -97,12 +117,14 @@ static inline void bind_context(struct s
 	spu_restore(&ctx->csa, spu);
 	spu->timestamp = jiffies;
 	spu_irq_setaffinity(spu, raw_smp_processor_id());
+	spu_switch_notify(spu, ctx);
 }
 
 static inline void unbind_context(struct spu *spu, struct spu_context *ctx)
 {
 	pr_debug("%s: unbind pid=%d SPU=%d NODE=%d\n", __FUNCTION__,
 		 spu->pid, spu->number, spu->node);
+	spu_switch_notify(spu, 0);
 	spu_unmap_mappings(ctx);
 	spu_save(&ctx->csa, spu);
 	spu->timestamp = jiffies;
Index: linus-2.6/include/asm-powerpc/spu.h
===================================================================
--- linus-2.6.orig/include/asm-powerpc/spu.h
+++ linus-2.6/include/asm-powerpc/spu.h
@@ -184,6 +184,24 @@ static inline void unregister_spu_syscal
 #endif /* MODULE */
 
 
+/*
+ * Notifier blocks:
+ *
+ * oprofile can get notified when a context switch is performed
+ * on an spe. The notifer function that gets called is passed
+ * a pointer to the SPU structure as well as the object-id that
+ * identifies the binary running on that SPU now.
+ *
+ * For a context save, the object-id that is passed is zero,
+ * identifying that the kernel will run from that moment on.
+ *
+ * For a context restore, the object-id is the value written
+ * to object-id spufs file from user space and the notifer
+ * function can assume that spu->ctx is valid.
+ */
+int spu_switch_event_register(struct notifier_block * n);
+int spu_switch_event_unregister(struct notifier_block * n);
+
 /* access to priv1 registers */
 void spu_int_mask_and(struct spu *spu, int class, u64 mask);
 void spu_int_mask_or(struct spu *spu, int class, u64 mask);