Re: [PATCH v3 bpf-next 2/7] bpf: add bpf_trace_vprintk helper

---
  include/linux/bpf.h            |  1 +
  include/uapi/linux/bpf.h       |  9 ++++++
  kernel/bpf/core.c              |  5 ++++
  kernel/bpf/helpers.c           |  2 ++
  kernel/trace/bpf_trace.c       | 52 +++++++++++++++++++++++++++++++++-
  tools/include/uapi/linux/bpf.h |  9 ++++++
  6 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index be8d57e6e78a..b6c45a6cbbba 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h

@@ -1088,6 +1088,7 @@ bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *f
  int bpf_prog_calc_tag(struct bpf_prog *fp);
  
  const struct bpf_func_proto *bpf_get_trace_printk_proto(void);
+const struct bpf_func_proto *bpf_get_trace_vprintk_proto(void);
  
  typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const void *src,
  					unsigned long off, unsigned long len);

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 791f31dd0abe..f171d4d33136 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h

@@ -4877,6 +4877,14 @@ union bpf_attr {
   *		Get the struct pt_regs associated with **task**.
   *	Return
   *		A pointer to struct pt_regs.
+ *
+ * u64 bpf_trace_vprintk(const char *fmt, u32 fmt_size, const void *data, u32 data_len)

+ *		to format. Arguments are to be used as in **bpf_seq_printf**\ () helper.
+ *	Return
+ *		The number of bytes written to the buffer, or a negative error
+ *		in case of failure.
   */

  	default:
  		return NULL;
  	}

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 10672ebc63b7..ea8358b0c748 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c

@@ -398,7 +398,7 @@ static const struct bpf_func_proto bpf_trace_printk_proto = {
  	.arg2_type	= ARG_CONST_SIZE,
  };
  
-const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
+static void __set_printk_clr_event(void)
  {
  	/*
  	 * This program might be calling bpf_trace_printk,

@@ -410,10 +410,58 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
  	 */
  	if (trace_set_clr_event("bpf_trace", "bpf_trace_printk", 1))
  		pr_warn_ratelimited("could not enable bpf_trace_printk events");
+}
  
+const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
+{
+	__set_printk_clr_event();
  	return &bpf_trace_printk_proto;
  }
  
+BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, data,
+	   u32, data_len)
+{
+	static char buf[BPF_TRACE_PRINTK_SIZE];
+	unsigned long flags;
+	int ret, num_args;
+	u32 *bin_args;
+
+	if (data_len & 7 || data_len > MAX_BPRINTF_VARARGS * 8 ||
+	    (data_len && !data))
+		return -EINVAL;
+	num_args = data_len / 8;
+
+	ret = bpf_bprintf_prepare(fmt, fmt_size, data, &bin_args, num_args);
+	if (ret < 0)
+		return ret;

+	raw_spin_lock_irqsave(&trace_printk_lock, flags);
+	ret = bstr_printf(buf, sizeof(buf), fmt, bin_args);
+
+	trace_bpf_trace_printk(buf);
+	raw_spin_unlock_irqrestore(&trace_printk_lock, flags);
+
+	bpf_bprintf_cleanup();
+
+	return ret;
+}