ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 38 insertions, 0 deletions

diff --git a/samples/bpf/sampleip_kern.c b/samples/bpf/sampleip_kern.c
new file mode 100644
index 000000000..a3f8a3998
--- /dev/null
+++ b/samples/bpf/sampleip_kern.c
@@ -0,0 +1,38 @@
+/* Copyright 2016 Netflix, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <linux/ptrace.h>
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/bpf_perf_event.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#define MAX_IPS		8192
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, u64);
+	__type(value, u32);
+	__uint(max_entries, MAX_IPS);
+} ip_map SEC(".maps");
+
+SEC("perf_event")
+int do_sample(struct bpf_perf_event_data *ctx)
+{
+	u64 ip;
+	u32 *value, init_val = 1;
+
+	ip = PT_REGS_IP(&ctx->regs);
+	value = bpf_map_lookup_elem(&ip_map, &ip);
+	if (value)
+		*value += 1;
+	else
+		/* E2BIG not tested for this example only */
+		bpf_map_update_elem(&ip_map, &ip, &init_val, BPF_NOEXIST);
+
+	return 0;
+}
+char _license[] SEC("license") = "GPL";