--- /dev/null
+/*
+ * Performance events ring-buffer code:
+ *
+ * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
+ * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
+ * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
+ * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
+ *
+ * For licensing details see kernel-base/COPYING
+ */
+
+#include <linux/perf_event.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/circ_buf.h>
+#include <linux/poll.h>
+
+#include "internal.h"
+
+static void perf_output_wakeup(struct perf_output_handle *handle)
+{
+ atomic_set(&handle->rb->poll, POLLIN);
+
+ handle->event->pending_wakeup = 1;
+ irq_work_queue(&handle->event->pending);
+}
+
+/*
+ * We need to ensure a later event_id doesn't publish a head when a former
+ * event isn't done writing. However since we need to deal with NMIs we
+ * cannot fully serialize things.
+ *
+ * We only publish the head (and generate a wakeup) when the outer-most
+ * event completes.
+ */
+static void perf_output_get_handle(struct perf_output_handle *handle)
+{
+ struct ring_buffer *rb = handle->rb;
+
+ preempt_disable();
+ local_inc(&rb->nest);
+ handle->wakeup = local_read(&rb->wakeup);
+}
+
+static void perf_output_put_handle(struct perf_output_handle *handle)
+{
+ struct ring_buffer *rb = handle->rb;
+ unsigned long head;
+
+again:
+ head = local_read(&rb->head);
+
+ /*
+ * IRQ/NMI can happen here, which means we can miss a head update.
+ */
+
+ if (!local_dec_and_test(&rb->nest))
+ goto out;
+
+ /*
+ * Since the mmap() consumer (userspace) can run on a different CPU:
+ *
+ * kernel user
+ *
+ * if (LOAD ->data_tail) { LOAD ->data_head
+ * (A) smp_rmb() (C)
+ * STORE $data LOAD $data
+ * smp_wmb() (B) smp_mb() (D)
+ * STORE ->data_head STORE ->data_tail
+ * }
+ *
+ * Where A pairs with D, and B pairs with C.
+ *
+ * In our case (A) is a control dependency that separates the load of
+ * the ->data_tail and the stores of $data. In case ->data_tail
+ * indicates there is no room in the buffer to store $data we do not.
+ *
+ * D needs to be a full barrier since it separates the data READ
+ * from the tail WRITE.
+ *
+ * For B a WMB is sufficient since it separates two WRITEs, and for C
+ * an RMB is sufficient since it separates two READs.
+ *
+ * See perf_output_begin().
+ */
+ smp_wmb(); /* B, matches C */
+ rb->user_page->data_head = head;
+
+ /*
+ * Now check if we missed an update -- rely on previous implied
+ * compiler barriers to force a re-read.
+ */
+ if (unlikely(head != local_read(&rb->head))) {
+ local_inc(&rb->nest);
+ goto again;
+ }
+
+ if (handle->wakeup != local_read(&rb->wakeup))
+ perf_output_wakeup(handle);
+
+out:
+ preempt_enable();
+}
+
+int perf_output_begin(struct perf_output_handle *handle,
+ struct perf_event *event, unsigned int size)
+{
+ struct ring_buffer *rb;
+ unsigned long tail, offset, head;
+ int have_lost, page_shift;
+ struct {
+ struct perf_event_header header;
+ u64 id;
+ u64 lost;
+ } lost_event;
+
+ rcu_read_lock();
+ /*
+ * For inherited events we send all the output towards the parent.
+ */
+ if (event->parent)
+ event = event->parent;
+
+ rb = rcu_dereference(event->rb);
+ if (unlikely(!rb))
+ goto out;
+
+ if (unlikely(!rb->nr_pages))
+ goto out;
+
+ handle->rb = rb;
+ handle->event = event;
+
+ have_lost = local_read(&rb->lost);
+ if (unlikely(have_lost)) {
+ size += sizeof(lost_event);
+ if (event->attr.sample_id_all)
+ size += event->id_header_size;
+ }
+
+ perf_output_get_handle(handle);
+
+ do {
+ tail = ACCESS_ONCE(rb->user_page->data_tail);
+ offset = head = local_read(&rb->head);
+ if (!rb->overwrite &&
+ unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size))
+ goto fail;
+
+ /*
+ * The above forms a control dependency barrier separating the
+ * @tail load above from the data stores below. Since the @tail
+ * load is required to compute the branch to fail below.
+ *
+ * A, matches D; the full memory barrier userspace SHOULD issue
+ * after reading the data and before storing the new tail
+ * position.
+ *
+ * See perf_output_put_handle().
+ */
+
+ head += size;
+ } while (local_cmpxchg(&rb->head, offset, head) != offset);
+
+ /*
+ * We rely on the implied barrier() by local_cmpxchg() to ensure
+ * none of the data stores below can be lifted up by the compiler.
+ */
+
+ if (unlikely(head - local_read(&rb->wakeup) > rb->watermark))
+ local_add(rb->watermark, &rb->wakeup);
+
+ page_shift = PAGE_SHIFT + page_order(rb);
+
+ handle->page = (offset >> page_shift) & (rb->nr_pages - 1);
+ offset &= (1UL << page_shift) - 1;
+ handle->addr = rb->data_pages[handle->page] + offset;
+ handle->size = (1UL << page_shift) - offset;
+
+ if (unlikely(have_lost)) {
+ struct perf_sample_data sample_data;
+
+ lost_event.header.size = sizeof(lost_event);
+ lost_event.header.type = PERF_RECORD_LOST;
+ lost_event.header.misc = 0;
+ lost_event.id = event->id;
+ lost_event.lost = local_xchg(&rb->lost, 0);
+
+ perf_event_header__init_id(&lost_event.header,
+ &sample_data, event);
+ perf_output_put(handle, lost_event);
+ perf_event__output_id_sample(event, handle, &sample_data);
+ }
+
+ return 0;
+
+fail:
+ local_inc(&rb->lost);
+ perf_output_put_handle(handle);
+out:
+ rcu_read_unlock();
+
+ return -ENOSPC;
+}
+
+unsigned int perf_output_copy(struct perf_output_handle *handle,
+ const void *buf, unsigned int len)
+{
+ return __output_copy(handle, buf, len);
+}
+
+unsigned int perf_output_skip(struct perf_output_handle *handle,
+ unsigned int len)
+{
+ return __output_skip(handle, NULL, len);
+}
+
+void perf_output_end(struct perf_output_handle *handle)
+{
+ perf_output_put_handle(handle);
+ rcu_read_unlock();
+}
+
+static void
+ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
+{
+ long max_size = perf_data_size(rb);
+
+ if (watermark)
+ rb->watermark = min(max_size, watermark);
+
+ if (!rb->watermark)
+ rb->watermark = max_size / 2;
+
+ if (flags & RING_BUFFER_WRITABLE)
+ rb->overwrite = 0;
+ else
+ rb->overwrite = 1;
+
+ atomic_set(&rb->refcount, 1);
+
+ INIT_LIST_HEAD(&rb->event_list);
+ spin_lock_init(&rb->event_lock);
+}
+
+/*
+ * This is called before hardware starts writing to the AUX area to
+ * obtain an output handle and make sure there's room in the buffer.
+ * When the capture completes, call perf_aux_output_end() to commit
+ * the recorded data to the buffer.
+ *
+ * The ordering is similar to that of perf_output_{begin,end}, with
+ * the exception of (B), which should be taken care of by the pmu
+ * driver, since ordering rules will differ depending on hardware.
+ */
+void *perf_aux_output_begin(struct perf_output_handle *handle,
+ struct perf_event *event)
+{
+ struct perf_event *output_event = event;
+ unsigned long aux_head, aux_tail;
+ struct ring_buffer *rb;
+
+ if (output_event->parent)
+ output_event = output_event->parent;
+
+ /*
+ * Since this will typically be open across pmu::add/pmu::del, we
+ * grab ring_buffer's refcount instead of holding rcu read lock
+ * to make sure it doesn't disappear under us.
+ */
+ rb = ring_buffer_get(output_event);
+ if (!rb)
+ return NULL;
+
+ if (!rb_has_aux(rb) || !atomic_inc_not_zero(&rb->aux_refcount))
+ goto err;
+
+ /*
+ * Nesting is not supported for AUX area, make sure nested
+ * writers are caught early
+ */
+ if (WARN_ON_ONCE(local_xchg(&rb->aux_nest, 1)))
+ goto err_put;
+
+ aux_head = local_read(&rb->aux_head);
+
+ handle->rb = rb;
+ handle->event = event;
+ handle->head = aux_head;
+ handle->size = 0;
+
+ /*
+ * In overwrite mode, AUX data stores do not depend on aux_tail,
+ * therefore (A) control dependency barrier does not exist. The
+ * (B) <-> (C) ordering is still observed by the pmu driver.
+ */
+ if (!rb->aux_overwrite) {
+ aux_tail = ACCESS_ONCE(rb->user_page->aux_tail);
+ handle->wakeup = local_read(&rb->aux_wakeup) + rb->aux_watermark;
+ if (aux_head - aux_tail < perf_aux_size(rb))
+ handle->size = CIRC_SPACE(aux_head, aux_tail, perf_aux_size(rb));
+
+ /*
+ * handle->size computation depends on aux_tail load; this forms a
+ * control dependency barrier separating aux_tail load from aux data
+ * store that will be enabled on successful return
+ */
+ if (!handle->size) { /* A, matches D */
+ event->pending_disable = 1;
+ perf_output_wakeup(handle);
+ local_set(&rb->aux_nest, 0);
+ goto err_put;
+ }
+ }
+
+ return handle->rb->aux_priv;
+
+err_put:
+ rb_free_aux(rb);
+
+err:
+ ring_buffer_put(rb);
+ handle->event = NULL;
+
+ return NULL;
+}
+
+/*
+ * Commit the data written by hardware into the ring buffer by adjusting
+ * aux_head and posting a PERF_RECORD_AUX into the perf buffer. It is the
+ * pmu driver's responsibility to observe ordering rules of the hardware,
+ * so that all the data is externally visible before this is called.
+ */
+void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size,
+ bool truncated)
+{
+ struct ring_buffer *rb = handle->rb;
+ unsigned long aux_head;
+ u64 flags = 0;
+
+ if (truncated)
+ flags |= PERF_AUX_FLAG_TRUNCATED;
+
+ /* in overwrite mode, driver provides aux_head via handle */
+ if (rb->aux_overwrite) {
+ flags |= PERF_AUX_FLAG_OVERWRITE;
+
+ aux_head = handle->head;
+ local_set(&rb->aux_head, aux_head);
+ } else {
+ aux_head = local_read(&rb->aux_head);
+ local_add(size, &rb->aux_head);
+ }
+
+ if (size || flags) {
+ /*
+ * Only send RECORD_AUX if we have something useful to communicate
+ */
+
+ perf_event_aux_event(handle->event, aux_head, size, flags);
+ }
+
+ aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
+
+ if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
+ perf_output_wakeup(handle);
+ local_add(rb->aux_watermark, &rb->aux_wakeup);
+ }
+ handle->event = NULL;
+
+ local_set(&rb->aux_nest, 0);
+ rb_free_aux(rb);
+ ring_buffer_put(rb);
+}
+
+/*
+ * Skip over a given number of bytes in the AUX buffer, due to, for example,
+ * hardware's alignment constraints.
+ */
+int perf_aux_output_skip(struct perf_output_handle *handle, unsigned long size)
+{
+ struct ring_buffer *rb = handle->rb;
+ unsigned long aux_head;
+
+ if (size > handle->size)
+ return -ENOSPC;
+
+ local_add(size, &rb->aux_head);
+
+ aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
+ if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
+ perf_output_wakeup(handle);
+ local_add(rb->aux_watermark, &rb->aux_wakeup);
+ handle->wakeup = local_read(&rb->aux_wakeup) +
+ rb->aux_watermark;
+ }
+
+ handle->head = aux_head;
+ handle->size -= size;
+
+ return 0;
+}
+
+void *perf_get_aux(struct perf_output_handle *handle)
+{
+ /* this is only valid between perf_aux_output_begin and *_end */
+ if (!handle->event)
+ return NULL;
+
+ return handle->rb->aux_priv;
+}
+
+#define PERF_AUX_GFP (GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_NORETRY)
+
+static struct page *rb_alloc_aux_page(int node, int order)
+{
+ struct page *page;
+
+ if (order > MAX_ORDER)
+ order = MAX_ORDER;
+
+ do {
+ page = alloc_pages_node(node, PERF_AUX_GFP, order);
+ } while (!page && order--);
+
+ if (page && order) {
+ /*
+ * Communicate the allocation size to the driver
+ */
+ split_page(page, order);
+ SetPagePrivate(page);
+ set_page_private(page, order);
+ }
+
+ return page;
+}
+
+static void rb_free_aux_page(struct ring_buffer *rb, int idx)
+{
+ struct page *page = virt_to_page(rb->aux_pages[idx]);
+
+ ClearPagePrivate(page);
+ page->mapping = NULL;
+ __free_page(page);
+}
+
+int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
+ pgoff_t pgoff, int nr_pages, long watermark, int flags)
+{
+ bool overwrite = !(flags & RING_BUFFER_WRITABLE);
+ int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
+ int ret = -ENOMEM, max_order = 0;
+
+ if (!has_aux(event))
+ return -ENOTSUPP;
+
+ if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) {
+ /*
+ * We need to start with the max_order that fits in nr_pages,
+ * not the other way around, hence ilog2() and not get_order.
+ */
+ max_order = ilog2(nr_pages);
+
+ /*
+ * PMU requests more than one contiguous chunks of memory
+ * for SW double buffering
+ */
+ if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_SW_DOUBLEBUF) &&
+ !overwrite) {
+ if (!max_order)
+ return -EINVAL;
+
+ max_order--;
+ }
+ }
+
+ rb->aux_pages = kzalloc_node(nr_pages * sizeof(void *), GFP_KERNEL, node);
+ if (!rb->aux_pages)
+ return -ENOMEM;
+
+ rb->free_aux = event->pmu->free_aux;
+ for (rb->aux_nr_pages = 0; rb->aux_nr_pages < nr_pages;) {
+ struct page *page;
+ int last, order;
+
+ order = min(max_order, ilog2(nr_pages - rb->aux_nr_pages));
+ page = rb_alloc_aux_page(node, order);
+ if (!page)
+ goto out;
+
+ for (last = rb->aux_nr_pages + (1 << page_private(page));
+ last > rb->aux_nr_pages; rb->aux_nr_pages++)
+ rb->aux_pages[rb->aux_nr_pages] = page_address(page++);
+ }
+
+ /*
+ * In overwrite mode, PMUs that don't support SG may not handle more
+ * than one contiguous allocation, since they rely on PMI to do double
+ * buffering. In this case, the entire buffer has to be one contiguous
+ * chunk.
+ */
+ if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) &&
+ overwrite) {
+ struct page *page = virt_to_page(rb->aux_pages[0]);
+
+ if (page_private(page) != max_order)
+ goto out;
+ }
+
+ rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages,
+ overwrite);
+ if (!rb->aux_priv)
+ goto out;
+
+ ret = 0;
+
+ /*
+ * aux_pages (and pmu driver's private data, aux_priv) will be
+ * referenced in both producer's and consumer's contexts, thus
+ * we keep a refcount here to make sure either of the two can
+ * reference them safely.
+ */
+ atomic_set(&rb->aux_refcount, 1);
+
+ rb->aux_overwrite = overwrite;
+ rb->aux_watermark = watermark;
+
+ if (!rb->aux_watermark && !rb->aux_overwrite)
+ rb->aux_watermark = nr_pages << (PAGE_SHIFT - 1);
+
+out:
+ if (!ret)
+ rb->aux_pgoff = pgoff;
+ else
+ rb_free_aux(rb);
+
+ return ret;
+}
+
+static void __rb_free_aux(struct ring_buffer *rb)
+{
+ int pg;
+
+ if (rb->aux_priv) {
+ rb->free_aux(rb->aux_priv);
+ rb->free_aux = NULL;
+ rb->aux_priv = NULL;
+ }
+
+ for (pg = 0; pg < rb->aux_nr_pages; pg++)
+ rb_free_aux_page(rb, pg);
+
+ kfree(rb->aux_pages);
+ rb->aux_nr_pages = 0;
+}
+
+void rb_free_aux(struct ring_buffer *rb)
+{
+ if (atomic_dec_and_test(&rb->aux_refcount))
+ __rb_free_aux(rb);
+}
+
+#ifndef CONFIG_PERF_USE_VMALLOC
+
+/*
+ * Back perf_mmap() with regular GFP_KERNEL-0 pages.
+ */
+
+static struct page *
+__perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
+{
+ if (pgoff > rb->nr_pages)
+ return NULL;
+
+ if (pgoff == 0)
+ return virt_to_page(rb->user_page);
+
+ return virt_to_page(rb->data_pages[pgoff - 1]);
+}
+
+static void *perf_mmap_alloc_page(int cpu)
+{
+ struct page *page;
+ int node;
+
+ node = (cpu == -1) ? cpu : cpu_to_node(cpu);
+ page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
+ if (!page)
+ return NULL;
+
+ return page_address(page);
+}
+
+struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
+{
+ struct ring_buffer *rb;
+ unsigned long size;
+ int i;
+
+ size = sizeof(struct ring_buffer);
+ size += nr_pages * sizeof(void *);
+
+ rb = kzalloc(size, GFP_KERNEL);
+ if (!rb)
+ goto fail;
+
+ rb->user_page = perf_mmap_alloc_page(cpu);
+ if (!rb->user_page)
+ goto fail_user_page;
+
+ for (i = 0; i < nr_pages; i++) {
+ rb->data_pages[i] = perf_mmap_alloc_page(cpu);
+ if (!rb->data_pages[i])
+ goto fail_data_pages;
+ }
+
+ rb->nr_pages = nr_pages;
+
+ ring_buffer_init(rb, watermark, flags);
+
+ return rb;
+
+fail_data_pages:
+ for (i--; i >= 0; i--)
+ free_page((unsigned long)rb->data_pages[i]);
+
+ free_page((unsigned long)rb->user_page);
+
+fail_user_page:
+ kfree(rb);
+
+fail:
+ return NULL;
+}
+
+static void perf_mmap_free_page(unsigned long addr)
+{
+ struct page *page = virt_to_page((void *)addr);
+
+ page->mapping = NULL;
+ __free_page(page);
+}
+
+void rb_free(struct ring_buffer *rb)
+{
+ int i;
+
+ perf_mmap_free_page((unsigned long)rb->user_page);
+ for (i = 0; i < rb->nr_pages; i++)
+ perf_mmap_free_page((unsigned long)rb->data_pages[i]);
+ kfree(rb);
+}
+
+#else
+static int data_page_nr(struct ring_buffer *rb)
+{
+ return rb->nr_pages << page_order(rb);
+}
+
+static struct page *
+__perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
+{
+ /* The '>' counts in the user page. */
+ if (pgoff > data_page_nr(rb))
+ return NULL;
+
+ return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
+}
+
+static void perf_mmap_unmark_page(void *addr)
+{
+ struct page *page = vmalloc_to_page(addr);
+
+ page->mapping = NULL;
+}
+
+static void rb_free_work(struct work_struct *work)
+{
+ struct ring_buffer *rb;
+ void *base;
+ int i, nr;
+
+ rb = container_of(work, struct ring_buffer, work);
+ nr = data_page_nr(rb);
+
+ base = rb->user_page;
+ /* The '<=' counts in the user page. */
+ for (i = 0; i <= nr; i++)
+ perf_mmap_unmark_page(base + (i * PAGE_SIZE));
+
+ vfree(base);
+ kfree(rb);
+}
+
+void rb_free(struct ring_buffer *rb)
+{
+ schedule_work(&rb->work);
+}
+
+struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
+{
+ struct ring_buffer *rb;
+ unsigned long size;
+ void *all_buf;
+
+ size = sizeof(struct ring_buffer);
+ size += sizeof(void *);
+
+ rb = kzalloc(size, GFP_KERNEL);
+ if (!rb)
+ goto fail;
+
+ INIT_WORK(&rb->work, rb_free_work);
+
+ all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
+ if (!all_buf)
+ goto fail_all_buf;
+
+ rb->user_page = all_buf;
+ rb->data_pages[0] = all_buf + PAGE_SIZE;
+ rb->page_order = ilog2(nr_pages);
+ rb->nr_pages = !!nr_pages;
+
+ ring_buffer_init(rb, watermark, flags);
+
+ return rb;
+
+fail_all_buf:
+ kfree(rb);
+
+fail:
+ return NULL;
+}
+
+#endif
+
+struct page *
+perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
+{
+ if (rb->aux_nr_pages) {
+ /* above AUX space */
+ if (pgoff > rb->aux_pgoff + rb->aux_nr_pages)
+ return NULL;
+
+ /* AUX space */
+ if (pgoff >= rb->aux_pgoff)
+ return virt_to_page(rb->aux_pages[pgoff - rb->aux_pgoff]);
+ }
+
+ return __perf_mmap_to_page(rb, pgoff);
+}
Code Review / kvmfornfv.git / blobdiff