On Mon, Jul 11, 2022 at 5:36 PM Yonghong Song <yhs@xxxxxx> wrote: > > > > On 7/6/22 10:28 AM, James Hilliard wrote: > > The current bpf_helper_defs.h helpers are llvm specific and don't work > > correctly with gcc. > > > > GCC appears to required kernel helper funcs to have the following > > attribute set: __attribute__((kernel_helper(NUM))) > > > > Generate gcc compatible headers based on the format in bpf-helpers.h. > > > > This adds conditional blocks for GCC while leaving clang codepaths > > unchanged, for example: > > #if __GNUC__ && !__clang__ > > void *bpf_map_lookup_elem(void *map, const void *key) __attribute__((kernel_helper(1))); > > #else > > static void *(*bpf_map_lookup_elem)(void *map, const void *key) = (void *) 1; > > #endif > > It does look like that gcc kernel_helper attribute is better than > '(void *) 1' style. The original clang uses '(void *) 1' style is > just for simplicity. Isn't the original style going to be needed for backwards compatibility with older clang versions for a while? > > Do you mind to help implement similar attribute in clang so we > don't need "#if" here? That's well outside my area of expertise unfortunately. > > > > > #if __GNUC__ && !__clang__ > > long bpf_map_update_elem(void *map, const void *key, const void *value, __u64 flags) __attribute__((kernel_helper(2))); > > #else > > static long (*bpf_map_update_elem)(void *map, const void *key, const void *value, __u64 flags) = (void *) 2; > > #endif > > > > See: > > https://github.com/gcc-mirror/gcc/blob/releases/gcc-12.1.0/gcc/config/bpf/bpf-helpers.h#L24-L27 > > > > This fixes the following build error: > > error: indirect call in function, which are not supported by eBPF > > > > Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx> > > --- > > Changes v1 -> v2: > > - more details in commit log > > --- > > scripts/bpf_doc.py | 43 ++++++++++++++++++++++++++----------------- > > 1 file changed, 26 insertions(+), 17 deletions(-) > > > [...]
