bpf: Add a bpf_snprintf helper

[linux-block.git] / tools / include / uapi / linux / bpf.h

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index df164a44bb4136049f15af95a35c445436e75490..ec6d85a817449ecf11942c5119f120e52ecf1fb7 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4708,6 +4708,33 @@ union bpf_attr {
  *     Return
  *             The number of traversed map elements for success, **-EINVAL** for
  *             invalid **flags**.
+ *
+ * long bpf_snprintf(char *str, u32 str_size, const char *fmt, u64 *data, u32 data_len)
+ *     Description
+ *             Outputs a string into the **str** buffer of size **str_size**
+ *             based on a format string stored in a read-only map pointed by
+ *             **fmt**.
+ *
+ *             Each format specifier in **fmt** corresponds to one u64 element
+ *             in the **data** array. For strings and pointers where pointees
+ *             are accessed, only the pointer values are stored in the *data*
+ *             array. The *data_len* is the size of *data* in bytes.
+ *
+ *             Formats **%s** and **%p{i,I}{4,6}** require to read kernel
+ *             memory. Reading kernel memory may fail due to either invalid
+ *             address or valid address but requiring a major memory fault. If
+ *             reading kernel memory fails, the string for **%s** will be an
+ *             empty string, and the ip address for **%p{i,I}{4,6}** will be 0.
+ *             Not returning error to bpf program is consistent with what
+ *             **bpf_trace_printk**\ () does for now.
+ *
+ *     Return
+ *             The strictly positive length of the formatted string, including
+ *             the trailing zero character. If the return value is greater than
+ *             **str_size**, **str** contains a truncated string, guaranteed to
+ *             be zero-terminated except when **str_size** is 0.
+ *
+ *             Or **-EBUSY** if the per-CPU memory copy buffer is busy.
  */
 #define __BPF_FUNC_MAPPER(FN)          \
        FN(unspec),                     \
@@ -4875,6 +4902,7 @@ union bpf_attr {
        FN(sock_from_file),             \
        FN(check_mtu),                  \
        FN(for_each_map_elem),          \
+       FN(snprintf),                   \
        /* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper