1 files changed, 222 insertions, 0 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
new file mode 100644
index 000000000..2d56ce501
--- /dev/null
+++ b/kernel/trace/bpf_trace.c
@@ -0,0 +1,222 @@
+/* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com
+ *
+ * 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/kernel.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include <linux/uaccess.h>
+#include <linux/ctype.h>
+#include "trace.h"
+
+static DEFINE_PER_CPU(int, bpf_prog_active);
+
+/**
+ * trace_call_bpf - invoke BPF program
+ * @prog: BPF program
+ * @ctx: opaque context pointer
+ *
+ * kprobe handlers execute BPF programs via this helper.
+ * Can be used from static tracepoints in the future.
+ *
+ * Return: BPF programs always return an integer which is interpreted by
+ * kprobe handler as:
+ * 0 - return from kprobe (event is filtered out)
+ * 1 - store kprobe event into ring buffer
+ * Other values are reserved and currently alias to 1
+ */
+unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
+{
+	unsigned int ret;
+
+	if (in_nmi()) /* not supported yet */
+		return 1;
+
+	preempt_disable();
+
+	if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
+		/*
+		 * since some bpf program is already running on this cpu,
+		 * don't call into another bpf program (same or different)
+		 * and don't send kprobe event into ring-buffer,
+		 * so return zero here
+		 */
+		ret = 0;
+		goto out;
+	}
+
+	rcu_read_lock();
+	ret = BPF_PROG_RUN(prog, ctx);
+	rcu_read_unlock();
+
+ out:
+	__this_cpu_dec(bpf_prog_active);
+	preempt_enable();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(trace_call_bpf);
+
+static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	void *dst = (void *) (long) r1;
+	int size = (int) r2;
+	void *unsafe_ptr = (void *) (long) r3;
+
+	return probe_kernel_read(dst, unsafe_ptr, size);
+}
+
+static const struct bpf_func_proto bpf_probe_read_proto = {
+	.func		= bpf_probe_read,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_STACK,
+	.arg2_type	= ARG_CONST_STACK_SIZE,
+	.arg3_type	= ARG_ANYTHING,
+};
+
+static u64 bpf_ktime_get_ns(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	/* NMI safe access to clock monotonic */
+	return ktime_get_mono_fast_ns();
+}
+
+static const struct bpf_func_proto bpf_ktime_get_ns_proto = {
+	.func		= bpf_ktime_get_ns,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+};
+
+/*
+ * limited trace_printk()
+ * only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed
+ */
+static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
+{
+	char *fmt = (char *) (long) r1;
+	int mod[3] = {};
+	int fmt_cnt = 0;
+	int i;
+
+	/*
+	 * bpf_check()->check_func_arg()->check_stack_boundary()
+	 * guarantees that fmt points to bpf program stack,
+	 * fmt_size bytes of it were initialized and fmt_size > 0
+	 */
+	if (fmt[--fmt_size] != 0)
+		return -EINVAL;
+
+	/* check format string for allowed specifiers */
+	for (i = 0; i < fmt_size; i++) {
+		if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
+			return -EINVAL;
+
+		if (fmt[i] != '%')
+			continue;
+
+		if (fmt_cnt >= 3)
+			return -EINVAL;
+
+		/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
+		i++;
+		if (fmt[i] == 'l') {
+			mod[fmt_cnt]++;
+			i++;
+		} else if (fmt[i] == 'p') {
+			mod[fmt_cnt]++;
+			i++;
+			if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
+				return -EINVAL;
+			fmt_cnt++;
+			continue;
+		}
+
+		if (fmt[i] == 'l') {
+			mod[fmt_cnt]++;
+			i++;
+		}
+
+		if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
+			return -EINVAL;
+		fmt_cnt++;
+	}
+
+	return __trace_printk(1/* fake ip will not be printed */, fmt,
+			      mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3,
+			      mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4,
+			      mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5);
+}
+
+static const struct bpf_func_proto bpf_trace_printk_proto = {
+	.func		= bpf_trace_printk,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_STACK,
+	.arg2_type	= ARG_CONST_STACK_SIZE,
+};
+
+static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
+{
+	switch (func_id) {
+	case BPF_FUNC_map_lookup_elem:
+		return &bpf_map_lookup_elem_proto;
+	case BPF_FUNC_map_update_elem:
+		return &bpf_map_update_elem_proto;
+	case BPF_FUNC_map_delete_elem:
+		return &bpf_map_delete_elem_proto;
+	case BPF_FUNC_probe_read:
+		return &bpf_probe_read_proto;
+	case BPF_FUNC_ktime_get_ns:
+		return &bpf_ktime_get_ns_proto;
+
+	case BPF_FUNC_trace_printk:
+		/*
+		 * this program might be calling bpf_trace_printk,
+		 * so allocate per-cpu printk buffers
+		 */
+		trace_printk_init_buffers();
+
+		return &bpf_trace_printk_proto;
+	default:
+		return NULL;
+	}
+}
+
+/* bpf+kprobe programs can access fields of 'struct pt_regs' */
+static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type)
+{
+	/* check bounds */
+	if (off < 0 || off >= sizeof(struct pt_regs))
+		return false;
+
+	/* only read is allowed */
+	if (type != BPF_READ)
+		return false;
+
+	/* disallow misaligned access */
+	if (off % size != 0)
+		return false;
+
+	return true;
+}
+
+static struct bpf_verifier_ops kprobe_prog_ops = {
+	.get_func_proto  = kprobe_prog_func_proto,
+	.is_valid_access = kprobe_prog_is_valid_access,
+};
+
+static struct bpf_prog_type_list kprobe_tl = {
+	.ops	= &kprobe_prog_ops,
+	.type	= BPF_PROG_TYPE_KPROBE,
+};
+
+static int __init register_kprobe_prog_ops(void)
+{
+	bpf_register_prog_type(&kprobe_tl);
+	return 0;
+}
+late_initcall(register_kprobe_prog_ops);