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bpf: Clarify data_len param in bpf_snprintf and bpf_seq_printf comments

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Since the data_len in these two functions is a byte len of the preceding
u64 *data array, it must always be a multiple of 8. If this isn't the
case both helpers error out, so let's make the requirement explicit so
users don't need to infer it.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210917182911.2426606-10-davemarchevsky@fb.com
This commit is contained in:
Dave Marchevsky 2021-09-17 11:29:11 -07:00 committed by Alexei Starovoitov
parent 7606729fe2
commit a42effb0b2
2 changed files with 6 additions and 4 deletions
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5
include/uapi/linux/bpf.h
View file

@ -4046,7 +4046,7 @@ union bpf_attr {
* arguments. The *data* are a **u64** array and corresponding format string
* values are stored in the 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.
* The *data_len* is the size of *data* in bytes - must be a multiple of 8.
*
* Formats **%s**, **%p{i,I}{4,6}** requires to read kernel memory.
* Reading kernel memory may fail due to either invalid address or
@ -4751,7 +4751,8 @@ union bpf_attr {
* 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.
* array. The *data_len* is the size of *data* in bytes - must be
* a multiple of 8.
*
* Formats **%s** and **%p{i,I}{4,6}** require to read kernel
* memory. Reading kernel memory may fail due to either invalid

5
tools/include/uapi/linux/bpf.h
View file

@ -4046,7 +4046,7 @@ union bpf_attr {
* arguments. The *data* are a **u64** array and corresponding format string
* values are stored in the 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.
* The *data_len* is the size of *data* in bytes - must be a multiple of 8.
*
* Formats **%s**, **%p{i,I}{4,6}** requires to read kernel memory.
* Reading kernel memory may fail due to either invalid address or
@ -4751,7 +4751,8 @@ union bpf_attr {
* 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.
* array. The *data_len* is the size of *data* in bytes - must be
* a multiple of 8.
*
* Formats **%s** and **%p{i,I}{4,6}** require to read kernel
* memory. Reading kernel memory may fail due to either invalid