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| author | David Vernet <void@manifault.com> | 2023-02-01 20:30:14 +0300 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-02-02 02:25:14 +0300 |
| commit | 98e6ab7a04353c95b1f4bad345d156ded865fd96 (patch) | |
| tree | 05fdeb14c15c8074dce01875bba9532da3554521 /Documentation/bpf | |
| parent | 57e7c169cd6afa093d858b8edfb9bceaf2e1c93b (diff) | |
| download | linux-98e6ab7a04353c95b1f4bad345d156ded865fd96.tar.xz | |
bpf: Document usage of the new __bpf_kfunc macro
Now that the __bpf_kfunc macro has been added to linux/btf.h, include a
blurb about it in the kfuncs.rst file. In order for the macro to
successfully render with .. kernel-doc, we'll also need to add it to the
c_id_attributes array.
Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20230201173016.342758-3-void@manifault.com
Diffstat (limited to 'Documentation/bpf')
| -rw-r--r-- | Documentation/bpf/kfuncs.rst | 20 |
1 files changed, 17 insertions, 3 deletions
diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst index 1a683225d080..0bd07b39c2a4 100644 --- a/Documentation/bpf/kfuncs.rst +++ b/Documentation/bpf/kfuncs.rst @@ -41,7 +41,7 @@ An example is given below:: __diag_ignore_all("-Wmissing-prototypes", "Global kfuncs as their definitions will be in BTF"); - struct task_struct *bpf_find_get_task_by_vpid(pid_t nr) + __bpf_kfunc struct task_struct *bpf_find_get_task_by_vpid(pid_t nr) { return find_get_task_by_vpid(nr); } @@ -66,7 +66,7 @@ kfunc with a __tag, where tag may be one of the supported annotations. This annotation is used to indicate a memory and size pair in the argument list. An example is given below:: - void bpf_memzero(void *mem, int mem__sz) + __bpf_kfunc void bpf_memzero(void *mem, int mem__sz) { ... } @@ -86,7 +86,7 @@ safety of the program. An example is given below:: - void *bpf_obj_new(u32 local_type_id__k, ...) + __bpf_kfunc void *bpf_obj_new(u32 local_type_id__k, ...) { ... } @@ -125,6 +125,20 @@ flags on a set of kfuncs as follows:: This set encodes the BTF ID of each kfunc listed above, and encodes the flags along with it. Ofcourse, it is also allowed to specify no flags. +kfunc definitions should also always be annotated with the ``__bpf_kfunc`` +macro. This prevents issues such as the compiler inlining the kfunc if it's a +static kernel function, or the function being elided in an LTO build as it's +not used in the rest of the kernel. Developers should not manually add +annotations to their kfunc to prevent these issues. If an annotation is +required to prevent such an issue with your kfunc, it is a bug and should be +added to the definition of the macro so that other kfuncs are similarly +protected. An example is given below:: + + __bpf_kfunc struct task_struct *bpf_get_task_pid(s32 pid) + { + ... + } + 2.4.1 KF_ACQUIRE flag --------------------- |