From b2117ae840bd913cdc45baaec9b72f530cca2726 Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Thu, 4 Oct 2018 18:21:47 +0100 Subject: [PATCH] ANDROID: ion: flush cache before exporting non-cached buffers The memory allocated from the page pool might be in the CPU cache, as the zeroing can have been done through cache. e.g GFP_ZERO, or if the buffer was used as cached memory previously. To map this memory as non-cached, we need to flush the CPU cache first, to avoid any memory corruption when the corresponding dirty cache line gets evicted. A proper fix would be to flush the cache using the Linux DMA API. The problem is that the buffer can be used without a device attached, which is not covered since the introduction of: commit 1dccb598df54 ("arm64: simplify dma_get_ops") This patch is then a dirty fix, calling directly cache flush function, to cover the export of non-cached to an ION client. It ensures that the cache line is actually cleaned before the memory is used as non-cached. Change-Id: I9179c2f644a29ae71820c4ae63c880195f55e45d Signed-off-by: Vincent Donnefort --- .../staging/android/ion/heaps/ion_cma_heap.c | 3 +++ .../ion/heaps/ion_system_contig_heap.c | 2 ++ .../android/ion/heaps/ion_system_heap.c | 3 +++ drivers/staging/android/ion/ion_buffer.c | 19 +++++++++++++++++++ include/linux/ion.h | 15 +++++++++++++++ 5 files changed, 42 insertions(+) diff --git a/drivers/staging/android/ion/heaps/ion_cma_heap.c b/drivers/staging/android/ion/heaps/ion_cma_heap.c index 9584972b5005..6ba7fd84c9ee 100644 --- a/drivers/staging/android/ion/heaps/ion_cma_heap.c +++ b/drivers/staging/android/ion/heaps/ion_cma_heap.c @@ -70,6 +70,9 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer, buffer->priv_virt = pages; buffer->sg_table = table; + + ion_buffer_prep_noncached(buffer); + return 0; free_mem: diff --git a/drivers/staging/android/ion/heaps/ion_system_contig_heap.c b/drivers/staging/android/ion/heaps/ion_system_contig_heap.c index 36e8769f3ef7..ce854565b563 100644 --- a/drivers/staging/android/ion/heaps/ion_system_contig_heap.c +++ b/drivers/staging/android/ion/heaps/ion_system_contig_heap.c @@ -50,6 +50,8 @@ static int ion_system_contig_heap_allocate(struct ion_heap *heap, buffer->sg_table = table; + ion_buffer_prep_noncached(buffer); + return 0; free_table: diff --git a/drivers/staging/android/ion/heaps/ion_system_heap.c b/drivers/staging/android/ion/heaps/ion_system_heap.c index 054324784ab9..6052b843cdeb 100644 --- a/drivers/staging/android/ion/heaps/ion_system_heap.c +++ b/drivers/staging/android/ion/heaps/ion_system_heap.c @@ -141,6 +141,9 @@ static int ion_system_heap_allocate(struct ion_heap *heap, } buffer->sg_table = table; + + ion_buffer_prep_noncached(buffer); + return 0; free_table: diff --git a/drivers/staging/android/ion/ion_buffer.c b/drivers/staging/android/ion/ion_buffer.c index 4157f5d040f2..eaca61f1663c 100644 --- a/drivers/staging/android/ion/ion_buffer.c +++ b/drivers/staging/android/ion/ion_buffer.c @@ -9,6 +9,7 @@ #include #include #include +#include #include "ion_private.h" @@ -196,6 +197,24 @@ int ion_buffer_zero(struct ion_buffer *buffer) } EXPORT_SYMBOL_GPL(ion_buffer_zero); +void ion_buffer_prep_noncached(struct ion_buffer *buffer) +{ + struct scatterlist *sg; + struct sg_table *table; + int i; + + if (WARN_ONCE(!buffer || !buffer->sg_table, + "%s needs a buffer and a sg_table", __func__) || + buffer->flags & ION_FLAG_CACHED) + return; + + table = buffer->sg_table; + + for_each_sg(table->sgl, sg, table->orig_nents, i) + arch_dma_prep_coherent(sg_page(sg), sg->length); +} +EXPORT_SYMBOL_GPL(ion_buffer_prep_noncached); + void ion_buffer_release(struct ion_buffer *buffer) { if (buffer->kmap_cnt > 0) { diff --git a/include/linux/ion.h b/include/linux/ion.h index 88622fb8f9ea..0fdc1e1d4c29 100644 --- a/include/linux/ion.h +++ b/include/linux/ion.h @@ -279,6 +279,19 @@ int ion_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer, */ int ion_buffer_zero(struct ion_buffer *buffer); +/** + * ion_buffer_prep_noncached - flush cache before non-cached mapping + * + * @buffer: ion_buffer to flush + * + * The memory allocated by the heap could be in the CPU cache. To map + * this memory as non-cached, we need to flush the associated cache + * first. Without the flush, it is possible for stale dirty cache lines + * to be evicted after the ION client started writing into this buffer, + * leading to data corruption. + */ +void ion_buffer_prep_noncached(struct ion_buffer *buffer); + /** * ion_alloc - Allocates an ion buffer of given size from given heap * @@ -358,6 +371,8 @@ static inline int ion_buffer_zero(struct ion_buffer *buffer) return -EINVAL; } +static inline void ion_buffer_prep_noncached(struct ion_buffer *buffer) {} + static inline struct dma_buf *ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) {