[PATCH v7 13/15] dma-direct: Allocate memory from restricted DMA pool if available

[Claire Chang <tientzu@xxxxxxxxxxxx>]

The restricted DMA pool is preferred if available.

The restricted DMA pools provide a basic level of protection against the
DMA overwriting buffer contents at unexpected times. However, to protect
against general data leakage and system memory corruption, the system
needs to provide a way to lock down the memory access, e.g., MPU.

Note that since coherent allocation needs remapping, one must set up
another device coherent pool by shared-dma-pool and use
dma_alloc_from_dev_coherent instead for atomic coherent allocation.

Signed-off-by: Claire Chang <tientzu@xxxxxxxxxxxx>
---
 kernel/dma/direct.c | 38 +++++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index eb4098323bbc..0d521f78c7b9 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -78,6 +78,10 @@ static bool dma_coherent_ok(struct device *dev, phys_addr_t 
phys, size_t size)
 static void __dma_direct_free_pages(struct device *dev, struct page *page,
                                    size_t size)
 {
+#ifdef CONFIG_DMA_RESTRICTED_POOL
+       if (swiotlb_free(dev, page, size))
+               return;
+#endif
        dma_free_contiguous(dev, page, size);
 }
 
@@ -92,7 +96,17 @@ static struct page *__dma_direct_alloc_pages(struct device 
*dev, size_t size,
 
        gfp |= dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
                                           &phys_limit);
-       page = dma_alloc_contiguous(dev, size, gfp);
+
+#ifdef CONFIG_DMA_RESTRICTED_POOL
+       page = swiotlb_alloc(dev, size);
+       if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
+               __dma_direct_free_pages(dev, page, size);
+               page = NULL;
+       }
+#endif
+
+       if (!page)
+               page = dma_alloc_contiguous(dev, size, gfp);
        if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
                dma_free_contiguous(dev, page, size);
                page = NULL;
@@ -148,7 +162,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
                gfp |= __GFP_NOWARN;
 
        if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
-           !force_dma_unencrypted(dev)) {
+           !force_dma_unencrypted(dev) && !is_dev_swiotlb_force(dev)) {
                page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO);
                if (!page)
                        return NULL;
@@ -161,18 +175,23 @@ void *dma_direct_alloc(struct device *dev, size_t size,
        }
 
        if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
-           !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
-           !dev_is_dma_coherent(dev))
+           !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && !dev_is_dma_coherent(dev) &&
+           !is_dev_swiotlb_force(dev))
                return arch_dma_alloc(dev, size, dma_handle, gfp, attrs);
 
        /*
         * Remapping or decrypting memory may block. If either is required and
         * we can't block, allocate the memory from the atomic pools.
+        * If restricted DMA (i.e., is_dev_swiotlb_force) is required, one must
+        * set up another device coherent pool by shared-dma-pool and use
+        * dma_alloc_from_dev_coherent instead.
         */
        if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
            !gfpflags_allow_blocking(gfp) &&
            (force_dma_unencrypted(dev) ||
-            (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && 
!dev_is_dma_coherent(dev))))
+            (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
+             !dev_is_dma_coherent(dev))) &&
+           !is_dev_swiotlb_force(dev))
                return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
 
        /* we always manually zero the memory once we are done */
@@ -253,15 +272,15 @@ void dma_direct_free(struct device *dev, size_t size,
        unsigned int page_order = get_order(size);
 
        if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
-           !force_dma_unencrypted(dev)) {
+           !force_dma_unencrypted(dev) && !is_dev_swiotlb_force(dev)) {
                /* cpu_addr is a struct page cookie, not a kernel address */
                dma_free_contiguous(dev, cpu_addr, size);
                return;
        }
 
        if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
-           !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
-           !dev_is_dma_coherent(dev)) {
+           !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && !dev_is_dma_coherent(dev) &&
+           !is_dev_swiotlb_force(dev)) {
                arch_dma_free(dev, size, cpu_addr, dma_addr, attrs);
                return;
        }
@@ -289,7 +308,8 @@ struct page *dma_direct_alloc_pages(struct device *dev, 
size_t size,
        void *ret;
 
        if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
-           force_dma_unencrypted(dev) && !gfpflags_allow_blocking(gfp))
+           force_dma_unencrypted(dev) && !gfpflags_allow_blocking(gfp) &&
+           !is_dev_swiotlb_force(dev))
                return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
 
        page = __dma_direct_alloc_pages(dev, size, gfp);
-- 
2.31.1.751.gd2f1c929bd-goog