The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().
struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).
It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.
To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
For more information, see '[PATCH v4 00/38] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread:
https://lore.kernel.org/dri-devel/20200512085710.14688-1-m.szyprowski@xxxxxxxxxxx/T/
---
drivers/staging/android/ion/ion.c | 25 +++++++--------
drivers/staging/android/ion/ion_heap.c | 44 ++++++++-------------------
drivers/staging/android/ion/ion_system_heap.c | 2 +-
3 files changed, 25 insertions(+), 46 deletions(-)
diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index 38b51ea..2db041d 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -147,14 +147,14 @@ static struct sg_table *dup_sg_table(struct sg_table *table)
if (!new_table)
return ERR_PTR(-ENOMEM);
- ret = sg_alloc_table(new_table, table->nents, GFP_KERNEL);
+ ret = sg_alloc_table(new_table, table->orig_nents, GFP_KERNEL);
if (ret) {
kfree(new_table);
return ERR_PTR(-ENOMEM);
}
new_sg = new_table->sgl;
- for_each_sg(table->sgl, sg, table->nents, i) {
+ for_each_sgtable_sg(table, sg, i) {
memcpy(new_sg, sg, sizeof(*sg));
new_sg->dma_address = 0;
new_sg = sg_next(new_sg);
@@ -224,12 +224,13 @@ static struct sg_table *ion_map_dma_buf(struct dma_buf_attachment *attachment,
{
struct ion_dma_buf_attachment *a = attachment->priv;
struct sg_table *table;
+ int ret;
table = a->table;
- if (!dma_map_sg(attachment->dev, table->sgl, table->nents,
- direction))
- return ERR_PTR(-ENOMEM);
+ ret = dma_map_sgtable(attachment->dev, table, direction);
+ if (ret)
+ return ERR_PTR(ret);
return table;
}
@@ -238,7 +239,7 @@ static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment,
struct sg_table *table,
enum dma_data_direction direction)
{
- dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction);
+ dma_unmap_sgtable(attachment->dev, table, direction);
}
static int ion_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
@@ -296,10 +297,8 @@ static int ion_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
}
mutex_lock(&buffer->lock);
- list_for_each_entry(a, &buffer->attachments, list) {
- dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents,
- direction);
- }
+ list_for_each_entry(a, &buffer->attachments, list)
+ dma_sync_sgtable_for_cpu(a->dev, a->table, direction);
unlock:
mutex_unlock(&buffer->lock);
@@ -319,10 +318,8 @@ static int ion_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
}
mutex_lock(&buffer->lock);
- list_for_each_entry(a, &buffer->attachments, list) {
- dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents,
- direction);
- }
+ list_for_each_entry(a, &buffer->attachments, list)
+ dma_sync_sgtable_for_device(a->dev, a->table, direction);
mutex_unlock(&buffer->lock);
return 0;
diff --git a/drivers/staging/android/ion/ion_heap.c b/drivers/staging/android/ion/ion_heap.c
index 9c23b23..79f2794 100644
--- a/drivers/staging/android/ion/ion_heap.c
+++ b/drivers/staging/android/ion/ion_heap.c
@@ -20,8 +20,7 @@
void *ion_heap_map_kernel(struct ion_heap *heap,
struct ion_buffer *buffer)
{
- struct scatterlist *sg;
- int i, j;
+ struct sg_page_iter piter;
void *vaddr;
pgprot_t pgprot;
struct sg_table *table = buffer->sg_table;
@@ -38,14 +37,11 @@ void *ion_heap_map_kernel(struct ion_heap *heap,
else
pgprot = pgprot_writecombine(PAGE_KERNEL);
- for_each_sg(table->sgl, sg, table->nents, i) {
- int npages_this_entry = PAGE_ALIGN(sg->length) / PAGE_SIZE;
- struct page *page = sg_page(sg);
-
- BUG_ON(i >= npages);
- for (j = 0; j < npages_this_entry; j++)
- *(tmp++) = page++;
+ for_each_sgtable_page(table, &piter, 0) {
+ BUG_ON(tmp - pages >= npages);
+ *tmp++ = sg_page_iter_page(&piter);
}
+
vaddr = vmap(pages, npages, VM_MAP, pgprot);
vfree(pages);
@@ -64,32 +60,19 @@ void ion_heap_unmap_kernel(struct ion_heap *heap,
int ion_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer,
struct vm_area_struct *vma)
{
+ struct sg_page_iter piter;
struct sg_table *table = buffer->sg_table;
unsigned long addr = vma->vm_start;
- unsigned long offset = vma->vm_pgoff * PAGE_SIZE;
- struct scatterlist *sg;
- int i;
int ret;
- for_each_sg(table->sgl, sg, table->nents, i) {
- struct page *page = sg_page(sg);
- unsigned long remainder = vma->vm_end - addr;
- unsigned long len = sg->length;
+ for_each_sgtable_page(table, &piter, vma->vm_pgoff) {
+ struct page *page = sg_page_iter_page(&piter);
- if (offset >= sg->length) {
- offset -= sg->length;
- continue;
- } else if (offset) {
- page += offset / PAGE_SIZE;
- len = sg->length - offset;
- offset = 0;
- }
- len = min(len, remainder);
- ret = remap_pfn_range(vma, addr, page_to_pfn(page), len,
+ ret = remap_pfn_range(vma, addr, page_to_pfn(page), PAGE_SIZE,
vma->vm_page_prot);
if (ret)
return ret;
- addr += len;
+ addr += PAGE_SIZE;
if (addr >= vma->vm_end)
return 0;
}
@@ -109,15 +92,14 @@ static int ion_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)
return 0;
}
-static int ion_heap_sglist_zero(struct scatterlist *sgl, unsigned int nents,
- pgprot_t pgprot)
+static int ion_heap_sglist_zero(struct sg_table *sgt, pgprot_t pgprot)
{
int p = 0;
int ret = 0;
struct sg_page_iter piter;
struct page *pages[32];
- for_each_sg_page(sgl, &piter, nents, 0) {
+ for_each_sgtable_page(sgt, &piter, 0) {
pages[p++] = sg_page_iter_page(&piter);
if (p == ARRAY_SIZE(pages)) {
ret = ion_heap_clear_pages(pages, p, pgprot);
@@ -142,7 +124,7 @@ int ion_heap_buffer_zero(struct ion_buffer *buffer)
else
pgprot = pgprot_writecombine(PAGE_KERNEL);
- return ion_heap_sglist_zero(table->sgl, table->nents, pgprot);
+ return ion_heap_sglist_zero(table, pgprot);
}
void ion_heap_freelist_add(struct ion_heap *heap, struct ion_buffer *buffer)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
index b83a1d1..eac0632 100644
--- a/drivers/staging/android/ion/ion_system_heap.c
+++ b/drivers/staging/android/ion/ion_system_heap.c
@@ -162,7 +162,7 @@ static void ion_system_heap_free(struct ion_buffer *buffer)
if (!(buffer->private_flags & ION_PRIV_FLAG_SHRINKER_FREE))
ion_heap_buffer_zero(buffer);
- for_each_sg(table->sgl, sg, table->nents, i)
+ for_each_sgtable_sg(table, sg, i)
free_buffer_page(sys_heap, buffer, sg_page(sg));
sg_free_table(table);
kfree(table);
--
1.9.1
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