perf_event: Provide vmalloc() based mmap() backing
Some architectures such as Sparc, ARM and MIPS (basically everything with flush_dcache_page()) need to deal with dcache aliases by carefully placing pages in both kernel and user maps. These architectures typically have to use vmalloc_user() for this. However, on other architectures, vmalloc() is not needed and has the downsides of being more restricted and slower than regular allocations. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: David Miller <davem@davemloft.net> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Paul Mackerras <paulus@samba.org> LKML-Reference: <1254830228.21044.272.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
Ingo Molnar
parent
e13dbd7d75
commit
906010b213
@ -26,6 +26,7 @@ config SPARC
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select RTC_CLASS
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select RTC_DRV_M48T59
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select HAVE_PERF_EVENTS
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select PERF_USE_VMALLOC
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select HAVE_DMA_ATTRS
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select HAVE_DMA_API_DEBUG
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@ -48,6 +49,7 @@ config SPARC64
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select RTC_DRV_SUN4V
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select RTC_DRV_STARFIRE
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select HAVE_PERF_EVENTS
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select PERF_USE_VMALLOC
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config ARCH_DEFCONFIG
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string
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@ -442,6 +442,7 @@ enum perf_callchain_context {
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#include <linux/hrtimer.h>
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#include <linux/fs.h>
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#include <linux/pid_namespace.h>
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#include <linux/workqueue.h>
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#include <asm/atomic.h>
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#define PERF_MAX_STACK_DEPTH 255
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@ -513,6 +514,10 @@ struct file;
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struct perf_mmap_data {
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struct rcu_head rcu_head;
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#ifdef CONFIG_PERF_USE_VMALLOC
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struct work_struct work;
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#endif
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int data_order;
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int nr_pages; /* nr of data pages */
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int writable; /* are we writable */
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int nr_locked; /* nr pages mlocked */
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18
init/Kconfig
18
init/Kconfig
@ -921,6 +921,11 @@ config HAVE_PERF_EVENTS
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help
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See tools/perf/design.txt for details.
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config PERF_USE_VMALLOC
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bool
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help
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See tools/perf/design.txt for details
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menu "Kernel Performance Events And Counters"
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config PERF_EVENTS
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@ -976,6 +981,19 @@ config PERF_COUNTERS
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Say N if unsure.
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config DEBUG_PERF_USE_VMALLOC
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default n
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bool "Debug: use vmalloc to back perf mmap() buffers"
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depends on PERF_EVENTS && DEBUG_KERNEL
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select PERF_USE_VMALLOC
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help
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Use vmalloc memory to back perf mmap() buffers.
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Mostly useful for debugging the vmalloc code on platforms
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that don't require it.
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Say N if unsure.
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endmenu
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config VM_EVENT_COUNTERS
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@ -20,6 +20,7 @@
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#include <linux/percpu.h>
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#include <linux/ptrace.h>
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#include <linux/vmstat.h>
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#include <linux/vmalloc.h>
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#include <linux/hardirq.h>
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#include <linux/rculist.h>
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#include <linux/uaccess.h>
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@ -2091,49 +2092,31 @@ unlock:
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rcu_read_unlock();
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}
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static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
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static unsigned long perf_data_size(struct perf_mmap_data *data)
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{
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struct perf_event *event = vma->vm_file->private_data;
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struct perf_mmap_data *data;
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int ret = VM_FAULT_SIGBUS;
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if (vmf->flags & FAULT_FLAG_MKWRITE) {
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if (vmf->pgoff == 0)
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ret = 0;
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return ret;
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}
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rcu_read_lock();
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data = rcu_dereference(event->data);
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if (!data)
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goto unlock;
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if (vmf->pgoff == 0) {
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vmf->page = virt_to_page(data->user_page);
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} else {
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int nr = vmf->pgoff - 1;
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if ((unsigned)nr > data->nr_pages)
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goto unlock;
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if (vmf->flags & FAULT_FLAG_WRITE)
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goto unlock;
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vmf->page = virt_to_page(data->data_pages[nr]);
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}
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get_page(vmf->page);
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vmf->page->mapping = vma->vm_file->f_mapping;
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vmf->page->index = vmf->pgoff;
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ret = 0;
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unlock:
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rcu_read_unlock();
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return ret;
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return data->nr_pages << (PAGE_SHIFT + data->data_order);
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}
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static int perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
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#ifndef CONFIG_PERF_USE_VMALLOC
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/*
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* Back perf_mmap() with regular GFP_KERNEL-0 pages.
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*/
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static struct page *
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perf_mmap_to_page(struct perf_mmap_data *data, unsigned long pgoff)
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{
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if (pgoff > data->nr_pages)
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return NULL;
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if (pgoff == 0)
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return virt_to_page(data->user_page);
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return virt_to_page(data->data_pages[pgoff - 1]);
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}
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static struct perf_mmap_data *
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perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
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{
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struct perf_mmap_data *data;
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unsigned long size;
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@ -2158,19 +2141,10 @@ static int perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
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goto fail_data_pages;
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}
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data->data_order = 0;
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data->nr_pages = nr_pages;
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atomic_set(&data->lock, -1);
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if (event->attr.watermark) {
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data->watermark = min_t(long, PAGE_SIZE * nr_pages,
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event->attr.wakeup_watermark);
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}
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if (!data->watermark)
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data->watermark = max(PAGE_SIZE, PAGE_SIZE * nr_pages / 4);
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rcu_assign_pointer(event->data, data);
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return 0;
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return data;
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fail_data_pages:
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for (i--; i >= 0; i--)
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@ -2182,7 +2156,7 @@ fail_user_page:
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kfree(data);
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fail:
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return -ENOMEM;
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return NULL;
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}
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static void perf_mmap_free_page(unsigned long addr)
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@ -2193,28 +2167,169 @@ static void perf_mmap_free_page(unsigned long addr)
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__free_page(page);
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}
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static void __perf_mmap_data_free(struct rcu_head *rcu_head)
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static void perf_mmap_data_free(struct perf_mmap_data *data)
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{
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struct perf_mmap_data *data;
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int i;
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data = container_of(rcu_head, struct perf_mmap_data, rcu_head);
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perf_mmap_free_page((unsigned long)data->user_page);
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for (i = 0; i < data->nr_pages; i++)
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perf_mmap_free_page((unsigned long)data->data_pages[i]);
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}
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#else
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/*
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* Back perf_mmap() with vmalloc memory.
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*
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* Required for architectures that have d-cache aliasing issues.
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*/
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static struct page *
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perf_mmap_to_page(struct perf_mmap_data *data, unsigned long pgoff)
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{
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if (pgoff > (1UL << data->data_order))
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return NULL;
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return vmalloc_to_page((void *)data->user_page + pgoff * PAGE_SIZE);
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}
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static void perf_mmap_unmark_page(void *addr)
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{
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struct page *page = vmalloc_to_page(addr);
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page->mapping = NULL;
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}
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static void perf_mmap_data_free_work(struct work_struct *work)
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{
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struct perf_mmap_data *data;
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void *base;
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int i, nr;
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data = container_of(work, struct perf_mmap_data, work);
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nr = 1 << data->data_order;
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base = data->user_page;
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for (i = 0; i < nr + 1; i++)
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perf_mmap_unmark_page(base + (i * PAGE_SIZE));
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vfree(base);
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}
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static void perf_mmap_data_free(struct perf_mmap_data *data)
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{
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schedule_work(&data->work);
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}
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static struct perf_mmap_data *
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perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
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{
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struct perf_mmap_data *data;
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unsigned long size;
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void *all_buf;
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WARN_ON(atomic_read(&event->mmap_count));
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size = sizeof(struct perf_mmap_data);
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size += sizeof(void *);
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data = kzalloc(size, GFP_KERNEL);
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if (!data)
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goto fail;
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INIT_WORK(&data->work, perf_mmap_data_free_work);
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all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
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if (!all_buf)
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goto fail_all_buf;
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data->user_page = all_buf;
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data->data_pages[0] = all_buf + PAGE_SIZE;
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data->data_order = ilog2(nr_pages);
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data->nr_pages = 1;
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return data;
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fail_all_buf:
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kfree(data);
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fail:
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return NULL;
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}
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#endif
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static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
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{
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struct perf_event *event = vma->vm_file->private_data;
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struct perf_mmap_data *data;
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int ret = VM_FAULT_SIGBUS;
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if (vmf->flags & FAULT_FLAG_MKWRITE) {
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if (vmf->pgoff == 0)
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ret = 0;
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return ret;
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}
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rcu_read_lock();
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data = rcu_dereference(event->data);
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if (!data)
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goto unlock;
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if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE))
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goto unlock;
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vmf->page = perf_mmap_to_page(data, vmf->pgoff);
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if (!vmf->page)
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goto unlock;
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get_page(vmf->page);
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vmf->page->mapping = vma->vm_file->f_mapping;
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vmf->page->index = vmf->pgoff;
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ret = 0;
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unlock:
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rcu_read_unlock();
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return ret;
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}
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static void
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perf_mmap_data_init(struct perf_event *event, struct perf_mmap_data *data)
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{
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long max_size = perf_data_size(data);
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atomic_set(&data->lock, -1);
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if (event->attr.watermark) {
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data->watermark = min_t(long, max_size,
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event->attr.wakeup_watermark);
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}
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if (!data->watermark)
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data->watermark = max_t(long, PAGE_SIZE, max_size / 2);
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rcu_assign_pointer(event->data, data);
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}
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static void perf_mmap_data_free_rcu(struct rcu_head *rcu_head)
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{
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struct perf_mmap_data *data;
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data = container_of(rcu_head, struct perf_mmap_data, rcu_head);
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perf_mmap_data_free(data);
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kfree(data);
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}
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static void perf_mmap_data_free(struct perf_event *event)
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static void perf_mmap_data_release(struct perf_event *event)
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{
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struct perf_mmap_data *data = event->data;
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WARN_ON(atomic_read(&event->mmap_count));
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rcu_assign_pointer(event->data, NULL);
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call_rcu(&data->rcu_head, __perf_mmap_data_free);
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call_rcu(&data->rcu_head, perf_mmap_data_free_rcu);
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}
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static void perf_mmap_open(struct vm_area_struct *vma)
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@ -2230,11 +2345,12 @@ static void perf_mmap_close(struct vm_area_struct *vma)
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WARN_ON_ONCE(event->ctx->parent_ctx);
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if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
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unsigned long size = perf_data_size(event->data);
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struct user_struct *user = current_user();
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atomic_long_sub(event->data->nr_pages + 1, &user->locked_vm);
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atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);
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vma->vm_mm->locked_vm -= event->data->nr_locked;
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perf_mmap_data_free(event);
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perf_mmap_data_release(event);
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mutex_unlock(&event->mmap_mutex);
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}
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}
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@ -2252,6 +2368,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
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unsigned long user_locked, user_lock_limit;
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struct user_struct *user = current_user();
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unsigned long locked, lock_limit;
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struct perf_mmap_data *data;
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unsigned long vma_size;
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unsigned long nr_pages;
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long user_extra, extra;
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@ -2314,10 +2431,15 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
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}
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WARN_ON(event->data);
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ret = perf_mmap_data_alloc(event, nr_pages);
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if (ret)
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data = perf_mmap_data_alloc(event, nr_pages);
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ret = -ENOMEM;
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if (!data)
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goto unlock;
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ret = 0;
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perf_mmap_data_init(event, data);
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atomic_set(&event->mmap_count, 1);
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atomic_long_add(user_extra, &user->locked_vm);
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vma->vm_mm->locked_vm += extra;
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@ -2505,7 +2627,7 @@ static bool perf_output_space(struct perf_mmap_data *data, unsigned long tail,
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if (!data->writable)
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return true;
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mask = (data->nr_pages << PAGE_SHIFT) - 1;
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mask = perf_data_size(data) - 1;
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offset = (offset - tail) & mask;
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head = (head - tail) & mask;
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@ -2610,7 +2732,7 @@ void perf_output_copy(struct perf_output_handle *handle,
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const void *buf, unsigned int len)
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{
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unsigned int pages_mask;
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unsigned int offset;
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unsigned long offset;
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unsigned int size;
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void **pages;
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@ -2619,12 +2741,14 @@ void perf_output_copy(struct perf_output_handle *handle,
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pages = handle->data->data_pages;
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do {
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unsigned int page_offset;
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unsigned long page_offset;
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unsigned long page_size;
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int nr;
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nr = (offset >> PAGE_SHIFT) & pages_mask;
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page_offset = offset & (PAGE_SIZE - 1);
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size = min_t(unsigned int, PAGE_SIZE - page_offset, len);
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page_size = 1UL << (handle->data->data_order + PAGE_SHIFT);
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page_offset = offset & (page_size - 1);
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size = min_t(unsigned int, page_size - page_offset, len);
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memcpy(pages[nr] + page_offset, buf, size);
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@ -455,3 +455,6 @@ will need at least this:
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If your architecture does have hardware capabilities, you can override the
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weak stub hw_perf_event_init() to register hardware counters.
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Architectures that have d-cache aliassing issues, such as Sparc and ARM,
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should select PERF_USE_VMALLOC in order to avoid these for perf mmap().
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