On 2021-04-22 09:15, Claire Chang wrote:
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.
Signed-off-by: Claire Chang tientzu@chromium.org
kernel/dma/direct.c | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-)
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 7a27f0510fcc..29523d2a9845 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);@@ -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)) {@@ -161,8 +175,8 @@ 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);
/*
@@ -172,7 +186,9 @@ void *dma_direct_alloc(struct device *dev, size_t size, 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 +269,15 @@ 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)) {@@ -289,7 +305,8 @@ 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))
Wait, this seems broken for non-coherent devices - in that case we need to return a non-cacheable address, but we can't simply fall through into the remapping path below in GFP_ATOMIC context. That's why we need the atomic pool concept in the first place :/
Unless I've overlooked something, we're still using the regular cacheable linear map address of the dma_io_tlb_mem buffer, no?
Robin.
page = __dma_direct_alloc_pages(dev, size, gfp);