diff --git a/kernel/events/core.c b/kernel/events/core.c index b2bc67791f84..bcb09e011e9e 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6277,41 +6277,6 @@ unlock: } EXPORT_SYMBOL_GPL(perf_event_update_userpage); -static vm_fault_t perf_mmap_fault(struct vm_fault *vmf) -{ - struct perf_event *event = vmf->vma->vm_file->private_data; - struct perf_buffer *rb; - vm_fault_t ret = VM_FAULT_SIGBUS; - - if (vmf->flags & FAULT_FLAG_MKWRITE) { - if (vmf->pgoff == 0) - ret = 0; - return ret; - } - - rcu_read_lock(); - rb = rcu_dereference(event->rb); - if (!rb) - goto unlock; - - if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE)) - goto unlock; - - vmf->page = perf_mmap_to_page(rb, vmf->pgoff); - if (!vmf->page) - goto unlock; - - get_page(vmf->page); - vmf->page->mapping = vmf->vma->vm_file->f_mapping; - vmf->page->index = vmf->pgoff; - - ret = 0; -unlock: - rcu_read_unlock(); - - return ret; -} - static void ring_buffer_attach(struct perf_event *event, struct perf_buffer *rb) { @@ -6551,13 +6516,87 @@ out_put: ring_buffer_put(rb); /* could be last */ } +static vm_fault_t perf_mmap_pfn_mkwrite(struct vm_fault *vmf) +{ + /* The first page is the user control page, others are read-only. */ + return vmf->pgoff == 0 ? 0 : VM_FAULT_SIGBUS; +} + static const struct vm_operations_struct perf_mmap_vmops = { .open = perf_mmap_open, .close = perf_mmap_close, /* non mergeable */ - .fault = perf_mmap_fault, - .page_mkwrite = perf_mmap_fault, + .pfn_mkwrite = perf_mmap_pfn_mkwrite, }; +static int map_range(struct perf_buffer *rb, struct vm_area_struct *vma) +{ + unsigned long nr_pages = vma_pages(vma); + int err = 0; + unsigned long pagenum; + + /* + * We map this as a VM_PFNMAP VMA. + * + * This is not ideal as this is designed broadly for mappings of PFNs + * referencing memory-mapped I/O ranges or non-system RAM i.e. for which + * !pfn_valid(pfn). + * + * We are mapping kernel-allocated memory (memory we manage ourselves) + * which would more ideally be mapped using vm_insert_page() or a + * similar mechanism, that is as a VM_MIXEDMAP mapping. + * + * However this won't work here, because: + * + * 1. It uses vma->vm_page_prot, but this field has not been completely + * setup at the point of the f_op->mmp() hook, so we are unable to + * indicate that this should be mapped CoW in order that the + * mkwrite() hook can be invoked to make the first page R/W and the + * rest R/O as desired. + * + * 2. Anything other than a VM_PFNMAP of valid PFNs will result in + * vm_normal_page() returning a struct page * pointer, which means + * vm_ops->page_mkwrite() will be invoked rather than + * vm_ops->pfn_mkwrite(), and this means we have to set page->mapping + * to work around retry logic in the fault handler, however this + * field is no longer allowed to be used within struct page. + * + * 3. Having a struct page * made available in the fault logic also + * means that the page gets put on the rmap and becomes + * inappropriately accessible and subject to map and ref counting. + * + * Ideally we would have a mechanism that could explicitly express our + * desires, but this is not currently the case, so we instead use + * VM_PFNMAP. + * + * We manage the lifetime of these mappings with internal refcounts (see + * perf_mmap_open() and perf_mmap_close()) so we ensure the lifetime of + * this mapping is maintained correctly. + */ + for (pagenum = 0; pagenum < nr_pages; pagenum++) { + unsigned long va = vma->vm_start + PAGE_SIZE * pagenum; + struct page *page = perf_mmap_to_page(rb, vma->vm_pgoff + pagenum); + + if (page == NULL) { + err = -EINVAL; + break; + } + + /* Map readonly, perf_mmap_pfn_mkwrite() called on write fault. */ + err = remap_pfn_range(vma, va, page_to_pfn(page), PAGE_SIZE, + vm_get_page_prot(vma->vm_flags & ~VM_SHARED)); + if (err) + break; + } + +#ifdef CONFIG_MMU + /* Clear any partial mappings on error. */ + if (err) + zap_page_range_single(vma, vma->vm_start, nr_pages * PAGE_SIZE, NULL); +#endif + + return err; +} + static int perf_mmap(struct file *file, struct vm_area_struct *vma) { struct perf_event *event = file->private_data; @@ -6682,6 +6721,8 @@ again: goto again; } + /* We need the rb to map pages. */ + rb = event->rb; goto unlock; } @@ -6776,6 +6817,9 @@ aux_unlock: vm_flags_set(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP); vma->vm_ops = &perf_mmap_vmops; + if (!ret) + ret = map_range(rb, vma); + if (event->pmu->event_mapped) event->pmu->event_mapped(event, vma->vm_mm); diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 4f46f688d0d4..180509132d4b 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -643,7 +643,6 @@ static void rb_free_aux_page(struct perf_buffer *rb, int idx) struct page *page = virt_to_page(rb->aux_pages[idx]); ClearPagePrivate(page); - page->mapping = NULL; __free_page(page); } @@ -819,7 +818,6 @@ static void perf_mmap_free_page(void *addr) { struct page *page = virt_to_page(addr); - page->mapping = NULL; __free_page(page); } @@ -890,28 +888,13 @@ __perf_mmap_to_page(struct perf_buffer *rb, unsigned long pgoff) 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 perf_buffer *rb; - void *base; - int i, nr; rb = container_of(work, struct perf_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); + vfree(rb->user_page); kfree(rb); }