On Mon, Jun 2, 2025 at 11:59 PM Song Liu <song@xxxxxxxxxx> wrote: > > Introduce a path iterator, which reliably walk a struct path toward > the root. This path iterator is based on path_walk_parent. A fixed > zero'ed root is passed to path_walk_parent(). Therefore, unless the > user terminates it earlier, the iterator will terminate at the real > root. > > Signed-off-by: Song Liu <song@xxxxxxxxxx> > --- > kernel/bpf/Makefile | 1 + > kernel/bpf/helpers.c | 3 +++ > kernel/bpf/path_iter.c | 58 ++++++++++++++++++++++++++++++++++++++++++ > kernel/bpf/verifier.c | 5 ++++ > 4 files changed, 67 insertions(+) > create mode 100644 kernel/bpf/path_iter.c > > diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile > index 3a335c50e6e3..454a650d934e 100644 > --- a/kernel/bpf/Makefile > +++ b/kernel/bpf/Makefile > @@ -56,6 +56,7 @@ obj-$(CONFIG_BPF_SYSCALL) += kmem_cache_iter.o > ifeq ($(CONFIG_DMA_SHARED_BUFFER),y) > obj-$(CONFIG_BPF_SYSCALL) += dmabuf_iter.o > endif > +obj-$(CONFIG_BPF_SYSCALL) += path_iter.o > > CFLAGS_REMOVE_percpu_freelist.o = $(CC_FLAGS_FTRACE) > CFLAGS_REMOVE_bpf_lru_list.o = $(CC_FLAGS_FTRACE) > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index b71e428ad936..b190c78e40f6 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -3397,6 +3397,9 @@ BTF_ID_FLAGS(func, bpf_iter_dmabuf_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPAB > BTF_ID_FLAGS(func, bpf_iter_dmabuf_destroy, KF_ITER_DESTROY | KF_SLEEPABLE) > #endif > BTF_ID_FLAGS(func, __bpf_trap) > +BTF_ID_FLAGS(func, bpf_iter_path_new, KF_ITER_NEW | KF_SLEEPABLE) > +BTF_ID_FLAGS(func, bpf_iter_path_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPABLE) > +BTF_ID_FLAGS(func, bpf_iter_path_destroy, KF_ITER_DESTROY | KF_SLEEPABLE) > BTF_KFUNCS_END(common_btf_ids) > > static const struct btf_kfunc_id_set common_kfunc_set = { > diff --git a/kernel/bpf/path_iter.c b/kernel/bpf/path_iter.c > new file mode 100644 > index 000000000000..0d972ec84beb > --- /dev/null > +++ b/kernel/bpf/path_iter.c I think Christian's preference was to keep everything in fs/bpf_fs_kfuncs.c Don't add a new file. Just add this iter there. > @@ -0,0 +1,58 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */ > +#include <linux/bpf.h> > +#include <linux/bpf_mem_alloc.h> > +#include <linux/namei.h> > +#include <linux/path.h> > + > +/* open-coded iterator */ > +struct bpf_iter_path { > + __u64 __opaque[3]; > +} __aligned(8); > + > +struct bpf_iter_path_kern { > + struct path path; > + __u64 flags; Why? flags is unused. Don't waste space for it.