On Sun, 2024-08-04 at 20:55 +0200, Uros Bizjak wrote: [...] > Found by GCC's named address space checks. Please provide some additional details. I assume that the definition of __percpu was changed from __attribute__((btf_type_tag(percpu))) to __attribute__((address_space(??)), is that correct? What is the motivation for this patch? Currently __percpu is defined as a type tag and is used only by BPF verifier, where it seems to be relevant only for structure fields and function parameters. This patch only changes local variables. > There were no changes in the resulting object files. > > [1] https://sparse.docs.kernel.org/en/latest/annotations.html#address-space-name > > Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx> > Cc: Alexei Starovoitov <ast@xxxxxxxxxx> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx> > Cc: Andrii Nakryiko <andrii@xxxxxxxxxx> > Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx> > Cc: Eduard Zingerman <eddyz87@xxxxxxxxx> > Cc: Song Liu <song@xxxxxxxxxx> > Cc: Yonghong Song <yonghong.song@xxxxxxxxx> > Cc: John Fastabend <john.fastabend@xxxxxxxxx> > Cc: KP Singh <kpsingh@xxxxxxxxxx> > Cc: Stanislav Fomichev <sdf@xxxxxxxxxxx> > Cc: Hao Luo <haoluo@xxxxxxxxxx> > Cc: Jiri Olsa <jolsa@xxxxxxxxxx> > --- > kernel/bpf/arraymap.c | 8 ++++---- > kernel/bpf/hashtab.c | 8 ++++---- > kernel/bpf/helpers.c | 4 ++-- > kernel/bpf/memalloc.c | 12 ++++++------ > 4 files changed, 16 insertions(+), 16 deletions(-) > > diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c > index 188e3c2effb2..544ca433275e 100644 > --- a/kernel/bpf/arraymap.c > +++ b/kernel/bpf/arraymap.c > @@ -600,7 +600,7 @@ static void *bpf_array_map_seq_start(struct seq_file *seq, loff_t *pos) > array = container_of(map, struct bpf_array, map); > index = info->index & array->index_mask; > if (info->percpu_value_buf) > - return array->pptrs[index]; > + return array->ptrs[index]; I disagree with this change. One might say that indeed the address space is cast away here, however, value returned by this function is only used in functions bpf_array_map_seq_{next,show,stop}(), where it is guarded by the same 'if (info->percpu_value_buf)' condition to identify if per_cpu_ptr() is necessary. > return array_map_elem_ptr(array, index); > } > > @@ -619,7 +619,7 @@ static void *bpf_array_map_seq_next(struct seq_file *seq, void *v, loff_t *pos) > array = container_of(map, struct bpf_array, map); > index = info->index & array->index_mask; > if (info->percpu_value_buf) > - return array->pptrs[index]; > + return array->ptrs[index]; Same as above. > return array_map_elem_ptr(array, index); > } > > @@ -632,7 +632,7 @@ static int __bpf_array_map_seq_show(struct seq_file *seq, void *v) > struct bpf_iter_meta meta; > struct bpf_prog *prog; > int off = 0, cpu = 0; > - void __percpu **pptr; > + void * __percpu *pptr; Should this be 'void __percpu *pptr;? The value comes from array->pptrs[*] field, which has the above type for elements. > u32 size; > > meta.seq = seq; > @@ -648,7 +648,7 @@ static int __bpf_array_map_seq_show(struct seq_file *seq, void *v) > if (!info->percpu_value_buf) { > ctx.value = v; > } else { > - pptr = v; > + pptr = (void __percpu *)(uintptr_t)v; > size = array->elem_size; > for_each_possible_cpu(cpu) { > copy_map_value_long(map, info->percpu_value_buf + off, > diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c > index be1f64c20125..a49212bbda09 100644 > --- a/kernel/bpf/hashtab.c > +++ b/kernel/bpf/hashtab.c > @@ -1049,14 +1049,14 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key, > pptr = htab_elem_get_ptr(l_new, key_size); > } else { > /* alloc_percpu zero-fills */ > - pptr = bpf_mem_cache_alloc(&htab->pcpu_ma); > - if (!pptr) { > + void *ptr = bpf_mem_cache_alloc(&htab->pcpu_ma); > + if (!ptr) { Why adding an intermediate variable here? Is casting bpf_mem_cache_alloc() result to percpu not sufficient? It looks like bpf_mem_cache_alloc() returns a percpu pointer, should it be declared as such? > bpf_mem_cache_free(&htab->ma, l_new); > l_new = ERR_PTR(-ENOMEM); > goto dec_count; > } > - l_new->ptr_to_pptr = pptr; > - pptr = *(void **)pptr; > + l_new->ptr_to_pptr = ptr; > + pptr = *(void __percpu **)ptr; > } > > pcpu_init_value(htab, pptr, value, onallcpus); [...] > diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c > index dec892ded031..b3858a76e0b3 100644 > --- a/kernel/bpf/memalloc.c > +++ b/kernel/bpf/memalloc.c > @@ -138,8 +138,8 @@ static struct llist_node notrace *__llist_del_first(struct llist_head *head) > static void *__alloc(struct bpf_mem_cache *c, int node, gfp_t flags) > { > if (c->percpu_size) { > - void **obj = kmalloc_node(c->percpu_size, flags, node); > - void *pptr = __alloc_percpu_gfp(c->unit_size, 8, flags); > + void __percpu **obj = kmalloc_node(c->percpu_size, flags, node); Why __percpu is needed for obj? kmalloc_node is defined as 'alloc_hooks(kmalloc_node_noprof(__VA_ARGS__))', alloc_hooks(X) is a macro and it produces result of type typeof(X), kmalloc_node_noprof() returns void*, not __percpu void*. Do I miss something? > + void __percpu *pptr = __alloc_percpu_gfp(c->unit_size, 8, flags); > > if (!obj || !pptr) { > free_percpu(pptr); [...]
