video: tegra: nvmap: Add support for zeroed pages

Add support to alloc zeroed pages for user space alloc requests. Also
define a config option to force userspace allocation requests to be
zeroed.

Change-Id: I75d3b2bc36e808f1470b423578ec4cba99e0f967
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/122549
Reviewed-by: Simone Willett <swillett@nvidia.com>
Tested-by: Simone Willett <swillett@nvidia.com>

3 files changed, 49 insertions, 4 deletions

diff --git a/drivers/video/tegra/Kconfig b/drivers/video/tegra/Kconfig
index b5540a5793b2..650c418ccb52 100644
--- a/drivers/video/tegra/Kconfig
+++ b/drivers/video/tegra/Kconfig
@@ -135,6 +135,15 @@ config NVMAP_VPR
 	  Say Y here to enable Video Protection Region(VPR) heap.
 	  if unsure, say N.
 
+config NVMAP_FORCE_ZEROED_USER_PAGES
+	bool "Only alloc zeroed pages for user space"
+	depends on TEGRA_NVMAP
+	help
+	  Say Y here to force zeroing of pages allocated for user space. This
+	  avoids leaking kernel secure data to user space. This can add
+	  significant overhead to allocation operations depending on the
+	  allocation size requested.
+
 config TEGRA_DSI
 	bool "Enable DSI panel."
 	default n
diff --git a/drivers/video/tegra/nvmap/nvmap_handle.c b/drivers/video/tegra/nvmap/nvmap_handle.c
index f12c058042dc..df54f1a1a8e9 100644
--- a/drivers/video/tegra/nvmap/nvmap_handle.c
+++ b/drivers/video/tegra/nvmap/nvmap_handle.c
@@ -36,6 +36,7 @@
 
 #include <asm/cacheflush.h>
 #include <asm/outercache.h>
+#include <asm/tlbflush.h>
 #include <asm/pgtable.h>
 
 #include <mach/iovmm.h>
@@ -555,6 +556,17 @@ static int handle_page_alloc(struct nvmap_client *client,
 	struct nvmap_page_pool *pool = NULL;
 	struct nvmap_share *share = nvmap_get_share_from_dev(h->dev);
 #endif
+	gfp_t gfp = GFP_NVMAP;
+	unsigned long kaddr, paddr;
+	pte_t **pte = NULL;
+
+	if (h->userflags & NVMAP_HANDLE_ZEROED_PAGES) {
+		gfp |= __GFP_ZERO;
+		prot = nvmap_pgprot(h, pgprot_kernel);
+		pte = nvmap_alloc_pte(client->dev, (void **)&kaddr);
+		if (IS_ERR(pte))
+			return -ENOMEM;
+	}
 
 	pages = altalloc(nr_page * sizeof(*pages));
 	if (!pages)
@@ -565,7 +577,7 @@ static int handle_page_alloc(struct nvmap_client *client,
 	h->pgalloc.area = NULL;
 	if (contiguous) {
 		struct page *page;
-		page = nvmap_alloc_pages_exact(GFP_NVMAP, size);
+		page = nvmap_alloc_pages_exact(gfp, size);
 		if (!page)
 			goto fail;
 
@@ -582,12 +594,29 @@ static int handle_page_alloc(struct nvmap_client *client,
 			pages[i] = nvmap_page_pool_alloc(pool);
 			if (!pages[i])
 				break;
+			if (h->userflags & NVMAP_HANDLE_ZEROED_PAGES) {
+				/*
+				 * Just memset low mem pages; they will for
+				 * sure have a virtual address. Otherwise, build
+				 * a mapping for the page in the kernel.
+				 */
+				if (!PageHighMem(pages[i])) {
+					memset(page_address(pages[i]), 0,
+					       PAGE_SIZE);
+				} else {
+					paddr = page_to_phys(pages[i]);
+					set_pte_at(&init_mm, kaddr, *pte,
+						   pfn_pte(__phys_to_pfn(paddr),
+							   prot));
+					flush_tlb_kernel_page(kaddr);
+					memset((char *)kaddr, 0, PAGE_SIZE);
+				}
+			}
 			page_index++;
 		}
 #endif
 		for (; i < nr_page; i++) {
-			pages[i] = nvmap_alloc_pages_exact(GFP_NVMAP,
-				PAGE_SIZE);
+			pages[i] = nvmap_alloc_pages_exact(gfp,	PAGE_SIZE);
 			if (!pages[i])
 				goto fail;
 		}
@@ -618,6 +647,8 @@ static int handle_page_alloc(struct nvmap_client *client,
 				nr_page - page_index);
 
 skip_attr_change:
+	if (h->userflags & NVMAP_HANDLE_ZEROED_PAGES)
+		nvmap_free_pte(client->dev, pte);
 	h->size = size;
 	h->pgalloc.pages = pages;
 	h->pgalloc.contig = contiguous;
@@ -625,6 +656,8 @@ skip_attr_change:
 	return 0;
 
 fail:
+	if (h->userflags & NVMAP_HANDLE_ZEROED_PAGES)
+		nvmap_free_pte(client->dev, pte);
 	while (i--) {
 		set_pages_array_wb(&pages[i], 1);
 		__free_page(pages[i]);
diff --git a/drivers/video/tegra/nvmap/nvmap_ioctl.c b/drivers/video/tegra/nvmap/nvmap_ioctl.c
index 5bfbbf60f8ff..bb15699ad855 100644
--- a/drivers/video/tegra/nvmap/nvmap_ioctl.c
+++ b/drivers/video/tegra/nvmap/nvmap_ioctl.c
@@ -3,7 +3,7 @@
  *
  * User-space interface to nvmap
  *
- * Copyright (c) 2011, NVIDIA Corporation.
+ * Copyright (c) 2011-2012, NVIDIA CORPORATION. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -175,6 +175,9 @@ int nvmap_ioctl_alloc(struct file *filp, void __user *arg)
 	/* user-space handles are aligned to page boundaries, to prevent
 	 * data leakage. */
 	op.align = max_t(size_t, op.align, PAGE_SIZE);
+#if defined(CONFIG_NVMAP_FORCE_ZEROED_USER_PAGES)
+	op.flags |= NVMAP_HANDLE_ZEROED_PAGES;
+#endif
 
 	return nvmap_alloc_handle_id(client, op.handle, op.heap_mask,
 				     op.align, op.flags);