+ Andrii Nakryiko This was a rather tricky series to get the recipients correct for and my script did not realize that "supporter" was a pseudonym for "maintainer" so you were missed off the original post. Appologies! More context in cover letter: https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@xxxxxxx/ On 14/10/2024 11:58, Ryan Roberts wrote: > To prepare for supporting boot-time page size selection, refactor code > to remove assumptions about PAGE_SIZE being compile-time constant. Code > intended to be equivalent when compile-time page size is active. > > Refactor "struct bpf_ringbuf" so that consumer_pos, producer_pos, > pending_pos and data are no longer embedded at (static) page offsets > within the struct. This can't work for boot-time page size because the > page size isn't known at compile-time. Instead, only define the meta > data in the struct, along with pointers to those values. At "struct > bpf_ringbuf" allocation time, the extra pages are allocated at the end > and the pointers are initialized to point to the correct locations. > > Additionally, only expose the __PAGE_SIZE enum to BTF for compile-time > page size builds. We don't know the page size at compile-time for > boot-time builds. NOTE: This may need some extra thought; perhaps > __PAGE_SIZE should be exposed as 0 in this case? And/or perhaps > __PAGE_SIZE_MIN/__PAGE_SIZE_MAX should be exposed? And there would need > to be a runtime mechanism for querying the page size (e.g. > getpagesize()). > > Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx> > --- > > ***NOTE*** > Any confused maintainers may want to read the cover note here for context: > https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@xxxxxxx/ > > kernel/bpf/core.c | 9 ++++++-- > kernel/bpf/ringbuf.c | 54 ++++++++++++++++++++++++-------------------- > 2 files changed, 37 insertions(+), 26 deletions(-) > > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > index 7ee62e38faf0e..485875aa78e63 100644 > --- a/kernel/bpf/core.c > +++ b/kernel/bpf/core.c > @@ -89,10 +89,15 @@ void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb, int k, uns > return NULL; > } > > -/* tell bpf programs that include vmlinux.h kernel's PAGE_SIZE */ > +/* > + * tell bpf programs that include vmlinux.h kernel's PAGE_SIZE. We can only do > + * this for compile-time PAGE_SIZE builds. > + */ > +#if PAGE_SIZE_MIN == PAGE_SIZE_MAX > enum page_size_enum { > __PAGE_SIZE = PAGE_SIZE > }; > +#endif > > struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flags) > { > @@ -100,7 +105,7 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flag > struct bpf_prog_aux *aux; > struct bpf_prog *fp; > > - size = round_up(size, __PAGE_SIZE); > + size = round_up(size, PAGE_SIZE); > fp = __vmalloc(size, gfp_flags); > if (fp == NULL) > return NULL; > diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c > index e20b90c361316..8e4093ddbc638 100644 > --- a/kernel/bpf/ringbuf.c > +++ b/kernel/bpf/ringbuf.c > @@ -14,9 +14,9 @@ > > #define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE) > > -/* non-mmap()'able part of bpf_ringbuf (everything up to consumer page) */ > +/* non-mmap()'able part of bpf_ringbuf (everything defined in struct) */ > #define RINGBUF_PGOFF \ > - (offsetof(struct bpf_ringbuf, consumer_pos) >> PAGE_SHIFT) > + (PAGE_ALIGN(sizeof(struct bpf_ringbuf)) >> PAGE_SHIFT) > /* consumer page and producer page */ > #define RINGBUF_POS_PAGES 2 > #define RINGBUF_NR_META_PAGES (RINGBUF_PGOFF + RINGBUF_POS_PAGES) > @@ -69,10 +69,10 @@ struct bpf_ringbuf { > * validate each sample to ensure that they're correctly formatted, and > * fully contained within the ring buffer. > */ > - unsigned long consumer_pos __aligned(PAGE_SIZE); > - unsigned long producer_pos __aligned(PAGE_SIZE); > - unsigned long pending_pos; > - char data[] __aligned(PAGE_SIZE); > + unsigned long *consumer_pos; > + unsigned long *producer_pos; > + unsigned long *pending_pos; > + char *data; > }; > > struct bpf_ringbuf_map { > @@ -134,9 +134,15 @@ static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node) > rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages, > VM_MAP | VM_USERMAP, PAGE_KERNEL); > if (rb) { > + void *base = rb; > + > kmemleak_not_leak(pages); > rb->pages = pages; > rb->nr_pages = nr_pages; > + rb->consumer_pos = (unsigned long *)(base + PAGE_SIZE * RINGBUF_PGOFF); > + rb->producer_pos = (unsigned long *)(base + PAGE_SIZE * (RINGBUF_PGOFF + 1)); > + rb->pending_pos = rb->producer_pos + 1; > + rb->data = base + PAGE_SIZE * nr_meta_pages; > return rb; > } > > @@ -179,9 +185,9 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node) > init_irq_work(&rb->work, bpf_ringbuf_notify); > > rb->mask = data_sz - 1; > - rb->consumer_pos = 0; > - rb->producer_pos = 0; > - rb->pending_pos = 0; > + *rb->consumer_pos = 0; > + *rb->producer_pos = 0; > + *rb->pending_pos = 0; > > return rb; > } > @@ -300,8 +306,8 @@ static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb) > { > unsigned long cons_pos, prod_pos; > > - cons_pos = smp_load_acquire(&rb->consumer_pos); > - prod_pos = smp_load_acquire(&rb->producer_pos); > + cons_pos = smp_load_acquire(rb->consumer_pos); > + prod_pos = smp_load_acquire(rb->producer_pos); > return prod_pos - cons_pos; > } > > @@ -418,7 +424,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) > if (len > ringbuf_total_data_sz(rb)) > return NULL; > > - cons_pos = smp_load_acquire(&rb->consumer_pos); > + cons_pos = smp_load_acquire(rb->consumer_pos); > > if (in_nmi()) { > if (!spin_trylock_irqsave(&rb->spinlock, flags)) > @@ -427,8 +433,8 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) > spin_lock_irqsave(&rb->spinlock, flags); > } > > - pend_pos = rb->pending_pos; > - prod_pos = rb->producer_pos; > + pend_pos = *rb->pending_pos; > + prod_pos = *rb->producer_pos; > new_prod_pos = prod_pos + len; > > while (pend_pos < prod_pos) { > @@ -440,7 +446,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) > tmp_size = round_up(tmp_size + BPF_RINGBUF_HDR_SZ, 8); > pend_pos += tmp_size; > } > - rb->pending_pos = pend_pos; > + *rb->pending_pos = pend_pos; > > /* check for out of ringbuf space: > * - by ensuring producer position doesn't advance more than > @@ -460,7 +466,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) > hdr->pg_off = pg_off; > > /* pairs with consumer's smp_load_acquire() */ > - smp_store_release(&rb->producer_pos, new_prod_pos); > + smp_store_release(rb->producer_pos, new_prod_pos); > > spin_unlock_irqrestore(&rb->spinlock, flags); > > @@ -506,7 +512,7 @@ static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard) > * new data availability > */ > rec_pos = (void *)hdr - (void *)rb->data; > - cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask; > + cons_pos = smp_load_acquire(rb->consumer_pos) & rb->mask; > > if (flags & BPF_RB_FORCE_WAKEUP) > irq_work_queue(&rb->work); > @@ -580,9 +586,9 @@ BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags) > case BPF_RB_RING_SIZE: > return ringbuf_total_data_sz(rb); > case BPF_RB_CONS_POS: > - return smp_load_acquire(&rb->consumer_pos); > + return smp_load_acquire(rb->consumer_pos); > case BPF_RB_PROD_POS: > - return smp_load_acquire(&rb->producer_pos); > + return smp_load_acquire(rb->producer_pos); > default: > return 0; > } > @@ -680,12 +686,12 @@ static int __bpf_user_ringbuf_peek(struct bpf_ringbuf *rb, void **sample, u32 *s > u64 cons_pos, prod_pos; > > /* Synchronizes with smp_store_release() in user-space producer. */ > - prod_pos = smp_load_acquire(&rb->producer_pos); > + prod_pos = smp_load_acquire(rb->producer_pos); > if (prod_pos % 8) > return -EINVAL; > > /* Synchronizes with smp_store_release() in __bpf_user_ringbuf_sample_release() */ > - cons_pos = smp_load_acquire(&rb->consumer_pos); > + cons_pos = smp_load_acquire(rb->consumer_pos); > if (cons_pos >= prod_pos) > return -ENODATA; > > @@ -715,7 +721,7 @@ static int __bpf_user_ringbuf_peek(struct bpf_ringbuf *rb, void **sample, u32 *s > * Update the consumer pos, and return -EAGAIN so the caller > * knows to skip this sample and try to read the next one. > */ > - smp_store_release(&rb->consumer_pos, cons_pos + total_len); > + smp_store_release(rb->consumer_pos, cons_pos + total_len); > return -EAGAIN; > } > > @@ -737,9 +743,9 @@ static void __bpf_user_ringbuf_sample_release(struct bpf_ringbuf *rb, size_t siz > * prevents another task from writing to consumer_pos after it was read > * by this task with smp_load_acquire() in __bpf_user_ringbuf_peek(). > */ > - consumer_pos = rb->consumer_pos; > + consumer_pos = *rb->consumer_pos; > /* Synchronizes with smp_load_acquire() in user-space producer. */ > - smp_store_release(&rb->consumer_pos, consumer_pos + rounded_size); > + smp_store_release(rb->consumer_pos, consumer_pos + rounded_size); > } > > BPF_CALL_4(bpf_user_ringbuf_drain, struct bpf_map *, map,
