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Date: Thu, 2 Apr 2015 05:35:42 -0700
From: tip-bot for Alexei Starovoitov <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: acme@...hat.com, linux-kernel@...r.kernel.org, rostedt@...dmis.org,
daniel@...earbox.net, akpm@...ux-foundation.org,
davem@...emloft.net, acme@...radead.org, peterz@...radead.org,
ast@...mgrid.com, masami.hiramatsu.pt@...achi.com,
namhyung@...nel.org, torvalds@...ux-foundation.org, hpa@...or.com,
a.p.zijlstra@...llo.nl, tglx@...utronix.de, jolsa@...hat.com,
mingo@...nel.org
Subject: [tip:perf/core] tracing:
Allow BPF programs to call bpf_trace_printk()
Commit-ID: 9c959c863f8217a2ff3d7c296e8223654d240569
Gitweb: http://git.kernel.org/tip/9c959c863f8217a2ff3d7c296e8223654d240569
Author: Alexei Starovoitov <ast@...mgrid.com>
AuthorDate: Wed, 25 Mar 2015 12:49:22 -0700
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 2 Apr 2015 13:25:50 +0200
tracing: Allow BPF programs to call bpf_trace_printk()
Debugging of BPF programs needs some form of printk from the
program, so let programs call limited trace_printk() with %d %u
%x %p modifiers only.
Similar to kernel modules, during program load verifier checks
whether program is calling bpf_trace_printk() and if so, kernel
allocates trace_printk buffers and emits big 'this is debug
only' banner.
Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
Reviewed-by: Steven Rostedt <rostedt@...dmis.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnaldo Carvalho de Melo <acme@...radead.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: David S. Miller <davem@...emloft.net>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1427312966-8434-6-git-send-email-ast@plumgrid.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
include/uapi/linux/bpf.h | 1 +
kernel/trace/bpf_trace.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 79 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 238c688..cc47ef4 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -166,6 +166,7 @@ enum bpf_func_id {
BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
BPF_FUNC_probe_read, /* int bpf_probe_read(void *dst, int size, void *src) */
BPF_FUNC_ktime_get_ns, /* u64 bpf_ktime_get_ns(void) */
+ BPF_FUNC_trace_printk, /* int bpf_trace_printk(const char *fmt, int fmt_size, ...) */
__BPF_FUNC_MAX_ID,
};
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 8f57872..2d56ce5 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -10,6 +10,7 @@
#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);
@@ -90,6 +91,74 @@ static const struct bpf_func_proto bpf_ktime_get_ns_proto = {
.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) {
@@ -103,6 +172,15 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
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;
}
--
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