On Sat, Feb 03, 2024 at 03:40:24PM +0100, Jiri Olsa wrote: > On Fri, Feb 02, 2024 at 03:09:05PM -0800, Manu Bretelle wrote: > > On Sun, Jan 28, 2024 at 06:24:05PM -0700, Daniel Xu wrote: > > > === Description === > > > > > > This is a bpf-treewide change that annotates all kfuncs as such inside > > > .BTF_ids. This annotation eventually allows us to automatically generate > > > kfunc prototypes from bpftool. > > > > > > We store this metadata inside a yet-unused flags field inside struct > > > btf_id_set8 (thanks Kumar!). pahole will be taught where to look. > > > > > > More details about the full chain of events are available in commit 3's > > > description. > > > > > > The accompanying pahole and bpftool changes can be viewed > > > here on these "frozen" branches [0][1]. > > > > > > [0]: https://github.com/danobi/pahole/tree/kfunc_btf-v3-mailed > > > [1]: https://github.com/danobi/linux/tree/kfunc_bpftool-mailed > > > > > > I hit a similar issue to [0] on master > > 943b043aeecc ("selftests/bpf: Fix bench runner SIGSEGV") > > when cross-compiling on x86_64 (LE) to s390x (BE). > > I do have CONFIG_DEBUG_INFO_BTF enable and the issue would not trigger if > > I disabled CONFIG_DEBUG_INFO_BTF (and with the fix mentioned in [0]). > > > > What seems to happen is that `tools/resolve_btfids` is ran in the context of the > > host endianess and if I printk before the WARN_ON: > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > > index ef380e546952..a9ed7a1a4936 100644 > > --- a/kernel/bpf/btf.c > > +++ b/kernel/bpf/btf.c > > @@ -8128,6 +8128,7 @@ int register_btf_kfunc_id_set(enum bpf_prog_type prog_type, > > * WARN() for initcall registrations that do not check errors. > > */ > > if (!(kset->set->flags & BTF_SET8_KFUNCS)) { > > + printk("Flag 0x%08X, expected 0x%08X\n", kset->set->flags, BTF_SET8_KFUNCS); > > WARN_ON(!kset->owner); > > return -EINVAL; > > } > > > > the boot logs would show: > > Flag 0x01000000, expected 0x00000001 > > > > The issue did not happen prior to > > 6f3189f38a3e ("bpf: treewide: Annotate BPF kfuncs in BTF") > > has only 0 was written before. > > > > It seems [1] will be addressing cross-compilation, but it did not fix it as is > > by just applying on top of master, so probably some of the changes will also need > > to be ported to `tools/include/linux/btf_ids.h`? > > the fix in [1] is fixing flags in set8's pairs, but not the global flags > > it looks like Viktor's fix should now also swap that as well? like in the > change below on top of Viktor's changes (untested) > > jirka > > > --- > diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c > index d01603ef6283..c44d57fec390 100644 > --- a/tools/bpf/resolve_btfids/main.c > +++ b/tools/bpf/resolve_btfids/main.c > @@ -706,6 +706,8 @@ static int sets_patch(struct object *obj) > * correctly translate everything. > */ > if (need_bswap) { > + set8->flags = bswap_32(set8->flags); > + > for (i = 0; i < cnt; i++) { > set8->pairs[i].flags = > bswap_32(set8->pairs[i].flags); > That should work. Here are a few tests I ran: $ md5sum /tmp/kbuild-s390x/vmlinux.* eb658e51e089f3c5b2c8909a29dc9997 /tmp/kbuild-s390x/vmlinux.a # plain vmlinux before running resolv_btfids (all 0s) ea907cd46a1a73b8276b5f2a82af00ca /tmp/kbuild-s390x/vmlinux.before_resolv # x86_64 resolv_btfids on master without Viktor's patch 980a40c3a3ff563d1c2d1ebdd5071a23 /tmp/kbuild-s390x/vmlinux.resolv_native # x86_64 resolv_btfids on master with Viktor's patch b986d19e242719ebea41c578235da662 /tmp/kbuild-s390x/vmlinux.resolv_native_patch_viktor # x86_64 resolv_btfids on master with Viktor's patch and your suggested patch 4edd8752ff01129945bd442689b1927b /tmp/kbuild-s390x/vmlinux.resolv_native_patch_viktor_patched # s390x resolv_btfids run with qemu-s390x-static 4edd8752ff01129945bd442689b1927b /tmp/kbuild-s390x/vmlinux.resolv_s390x and some hexdiff of those binaries: # difference between master's native build and s390x build.... has byte swapping for set8 and others diff -ruN <(xxd /tmp/kbuild-s390x/vmlinux.resolv_s390x) <(xxd /tmp/kbuild-s390x/vmlinux.resolv_native) > diff_s390x_native.diff https://gist.github.com/chantra/c3d58637a08a6f7340953dc155bb18cc # difference betwee Viktor's version and s390x build.... squinting my eyes I only see the global set8 is missing diff -ruN <(xxd /tmp/kbuild-s390x/vmlinux.resolv_s390x) <(xxd /tmp/kbuild-s390x/vmlinux.resolv_native_patch_viktor) > diff_s390x_native_viktor.diff https://gist.github.com/chantra/61cfff02b456ae72d3c0161ce1897097 Have a good weekend all! Manu
