diff options
| -rw-r--r-- | include/linux/dma-debug.h | 6 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 12 | ||||
| -rw-r--r-- | lib/dma-debug.c | 193 | ||||
| -rw-r--r-- | mm/memory.c | 3 |
4 files changed, 199 insertions, 15 deletions
diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h index fc0e34c..fe8cb61 100644 --- a/include/linux/dma-debug.h +++ b/include/linux/dma-debug.h @@ -85,6 +85,8 @@ extern void debug_dma_sync_sg_for_device(struct device *dev, extern void debug_dma_dump_mappings(struct device *dev); +extern void debug_dma_assert_idle(struct page *page); + #else /* CONFIG_DMA_API_DEBUG */ static inline void dma_debug_add_bus(struct bus_type *bus) @@ -183,6 +185,10 @@ static inline void debug_dma_dump_mappings(struct device *dev) { } +static inline void debug_dma_assert_idle(struct page *page) +{ +} + #endif /* CONFIG_DMA_API_DEBUG */ #endif /* __DMA_DEBUG_H */ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 6982094..900b63c 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1584,8 +1584,16 @@ config DMA_API_DEBUG With this option you will be able to detect common bugs in device drivers like double-freeing of DMA mappings or freeing mappings that were never allocated. - This option causes a performance degredation. Use only if you want - to debug device drivers. If unsure, say N. + + This also attempts to catch cases where a page owned by DMA is + accessed by the cpu in a way that could cause data corruption. For + example, this enables cow_user_page() to check that the source page is + not undergoing DMA. + + This option causes a performance degradation. Use only if you want to + debug device drivers and dma interactions. + + If unsure, say N. source "samples/Kconfig" diff --git a/lib/dma-debug.c b/lib/dma-debug.c index d87a17a..c380838 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -53,11 +53,26 @@ enum map_err_types { #define DMA_DEBUG_STACKTRACE_ENTRIES 5 +/** + * struct dma_debug_entry - track a dma_map* or dma_alloc_coherent mapping + * @list: node on pre-allocated free_entries list + * @dev: 'dev' argument to dma_map_{page|single|sg} or dma_alloc_coherent + * @type: single, page, sg, coherent + * @pfn: page frame of the start address + * @offset: offset of mapping relative to pfn + * @size: length of the mapping + * @direction: enum dma_data_direction + * @sg_call_ents: 'nents' from dma_map_sg + * @sg_mapped_ents: 'mapped_ents' from dma_map_sg + * @map_err_type: track whether dma_mapping_error() was checked + * @stacktrace: support backtraces when a violation is detected + */ struct dma_debug_entry { struct list_head list; struct device *dev; int type; - phys_addr_t paddr; + unsigned long pfn; + size_t offset; u64 dev_addr; u64 size; int direction; @@ -372,6 +387,11 @@ static void hash_bucket_del(struct dma_debug_entry *entry) list_del(&entry->list); } +static unsigned long long phys_addr(struct dma_debug_entry *entry) +{ + return page_to_phys(pfn_to_page(entry->pfn)) + entry->offset; +} + /* * Dump mapping entries for debugging purposes */ @@ -389,9 +409,9 @@ void debug_dma_dump_mappings(struct device *dev) list_for_each_entry(entry, &bucket->list, list) { if (!dev || dev == entry->dev) { dev_info(entry->dev, - "%s idx %d P=%Lx D=%Lx L=%Lx %s %s\n", + "%s idx %d P=%Lx N=%lx D=%Lx L=%Lx %s %s\n", type2name[entry->type], idx, - (unsigned long long)entry->paddr, + phys_addr(entry), entry->pfn, entry->dev_addr, entry->size, dir2name[entry->direction], maperr2str[entry->map_err_type]); @@ -404,6 +424,133 @@ void debug_dma_dump_mappings(struct device *dev) EXPORT_SYMBOL(debug_dma_dump_mappings); /* + * For each page mapped (initial page in the case of + * dma_alloc_coherent/dma_map_{single|page}, or each page in a + * scatterlist) insert into this tree using the pfn as the key. At + * dma_unmap_{single|sg|page} or dma_free_coherent delete the entry. If + * the pfn already exists at insertion time add a tag as a reference + * count for the overlapping mappings. For now, the overlap tracking + * just ensures that 'unmaps' balance 'maps' before marking the pfn + * idle, but we should also be flagging overlaps as an API violation. + * + * Memory usage is mostly constrained by the maximum number of available + * dma-debug entries in that we need a free dma_debug_entry before + * inserting into the tree. In the case of dma_map_{single|page} and + * dma_alloc_coherent there is only one dma_debug_entry and one pfn to + * track per event. dma_map_sg(), on the other hand, + * consumes a single dma_debug_entry, but inserts 'nents' entries into + * the tree. + * + * At any time debug_dma_assert_idle() can be called to trigger a + * warning if the given page is in the active set. + */ +static RADIX_TREE(dma_active_pfn, GFP_NOWAIT); +static DEFINE_SPINLOCK(radix_lock); +#define ACTIVE_PFN_MAX_OVERLAP ((1 << RADIX_TREE_MAX_TAGS) - 1) + +static int active_pfn_read_overlap(unsigned long pfn) +{ + int overlap = 0, i; + + for (i = RADIX_TREE_MAX_TAGS - 1; i >= 0; i--) + if (radix_tree_tag_get(&dma_active_pfn, pfn, i)) + overlap |= 1 << i; + return overlap; +} + +static int active_pfn_set_overlap(unsigned long pfn, int overlap) +{ + int i; + + if (overlap > ACTIVE_PFN_MAX_OVERLAP || overlap < 0) + return 0; + + for (i = RADIX_TREE_MAX_TAGS - 1; i >= 0; i--) + if (overlap & 1 << i) + radix_tree_tag_set(&dma_active_pfn, pfn, i); + else + radix_tree_tag_clear(&dma_active_pfn, pfn, i); + + return overlap; +} + +static void active_pfn_inc_overlap(unsigned long pfn) +{ + int overlap = active_pfn_read_overlap(pfn); + + overlap = active_pfn_set_overlap(pfn, ++overlap); + + /* If we overflowed the overlap counter then we're potentially + * leaking dma-mappings. Otherwise, if maps and unmaps are + * balanced then this overflow may cause false negatives in + * debug_dma_assert_idle() as the pfn may be marked idle + * prematurely. + */ + WARN_ONCE(overlap == 0, + "DMA-API: exceeded %d overlapping mappings of pfn %lx\n", + ACTIVE_PFN_MAX_OVERLAP, pfn); +} + +static int active_pfn_dec_overlap(unsigned long pfn) +{ + int overlap = active_pfn_read_overlap(pfn); + + return active_pfn_set_overlap(pfn, --overlap); +} + +static int active_pfn_insert(struct dma_debug_entry *entry) +{ + unsigned long flags; + int rc; + + spin_lock_irqsave(&radix_lock, flags); + rc = radix_tree_insert(&dma_active_pfn, entry->pfn, entry); + if (rc == -EEXIST) + active_pfn_inc_overlap(entry->pfn); + spin_unlock_irqrestore(&radix_lock, flags); + + return rc; +} + +static void active_pfn_remove(struct dma_debug_entry *entry) +{ + unsigned long flags; + + spin_lock_irqsave(&radix_lock, flags); + if (active_pfn_dec_overlap(entry->pfn) == 0) + radix_tree_delete(&dma_active_pfn, entry->pfn); + spin_unlock_irqrestore(&radix_lock, flags); +} + +/** + * debug_dma_assert_idle() - assert that a page is not undergoing dma + * @page: page to lookup in the dma_active_pfn tree + * + * Place a call to this routine in cases where the cpu touching the page + * before the dma completes (page is dma_unmapped) will lead to data + * corruption. + */ +void debug_dma_assert_idle(struct page *page) +{ + unsigned long flags; + struct dma_debug_entry *entry; + + if (!page) + return; + + spin_lock_irqsave(&radix_lock, flags); + entry = radix_tree_lookup(&dma_active_pfn, page_to_pfn(page)); + spin_unlock_irqrestore(&radix_lock, flags); + + if (!entry) + return; + + err_printk(entry->dev, entry, + "DMA-API: cpu touching an active dma mapped page " + "[pfn=0x%lx]\n", entry->pfn); +} + +/* * Wrapper function for adding an entry to the hash. * This function takes care of locking itself. */ @@ -411,10 +558,21 @@ static void add_dma_entry(struct dma_debug_entry *entry) { struct hash_bucket *bucket; unsigned long flags; + int rc; bucket = get_hash_bucket(entry, &flags); hash_bucket_add(bucket, entry); put_hash_bucket(bucket, &flags); + + rc = active_pfn_insert(entry); + if (rc == -ENOMEM) { + pr_err("DMA-API: pfn tracking ENOMEM, dma-debug disabled\n"); + global_disable = true; + } + + /* TODO: report -EEXIST errors here as overlapping mappings are + * not supported by the DMA API + */ } static struct dma_debug_entry *__dma_entry_alloc(void) @@ -469,6 +627,8 @@ static void dma_entry_free(struct dma_debug_entry *entry) { unsigned long flags; + active_pfn_remove(entry); + /* * add to beginning of the list - this way the entries are * more likely cache hot when they are reallocated. @@ -895,15 +1055,15 @@ static void check_unmap(struct dma_debug_entry *ref) ref->dev_addr, ref->size, type2name[entry->type], type2name[ref->type]); } else if ((entry->type == dma_debug_coherent) && - (ref->paddr != entry->paddr)) { + (phys_addr(ref) != phys_addr(entry))) { err_printk(ref->dev, entry, "DMA-API: device driver frees " "DMA memory with different CPU address " "[device address=0x%016llx] [size=%llu bytes] " "[cpu alloc address=0x%016llx] " "[cpu free address=0x%016llx]", ref->dev_addr, ref->size, - (unsigned long long)entry->paddr, - (unsigned long long)ref->paddr); + phys_addr(entry), + phys_addr(ref)); } if (ref->sg_call_ents && ref->type == dma_debug_sg && @@ -1052,7 +1212,8 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset, entry->dev = dev; entry->type = dma_debug_page; - entry->paddr = page_to_phys(page) + offset; + entry->pfn = page_to_pfn(page); + entry->offset = offset, entry->dev_addr = dma_addr; entry->size = size; entry->direction = direction; @@ -1148,7 +1309,8 @@ void debug_dma_map_sg(struct device *dev, struct scatterlist *sg, entry->type = dma_debug_sg; entry->dev = dev; - entry->paddr = sg_phys(s); + entry->pfn = page_to_pfn(sg_page(s)); + entry->offset = s->offset, entry->size = sg_dma_len(s); entry->dev_addr = sg_dma_address(s); entry->direction = direction; @@ -1198,7 +1360,8 @@ void debug_dma_unmap_sg(struct device *dev, struct scatterlist *sglist, struct dma_debug_entry ref = { .type = dma_debug_sg, .dev = dev, - .paddr = sg_phys(s), + .pfn = page_to_pfn(sg_page(s)), + .offset = s->offset, .dev_addr = sg_dma_address(s), .size = sg_dma_len(s), .direction = dir, @@ -1233,7 +1396,8 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, entry->type = dma_debug_coherent; entry->dev = dev; - entry->paddr = virt_to_phys(virt); + entry->pfn = page_to_pfn(virt_to_page(virt)); + entry->offset = (size_t) virt & PAGE_MASK; entry->size = size; entry->dev_addr = dma_addr; entry->direction = DMA_BIDIRECTIONAL; @@ -1248,7 +1412,8 @@ void debug_dma_free_coherent(struct device *dev, size_t size, struct dma_debug_entry ref = { .type = dma_debug_coherent, .dev = dev, - .paddr = virt_to_phys(virt), + .pfn = page_to_pfn(virt_to_page(virt)), + .offset = (size_t) virt & PAGE_MASK, .dev_addr = addr, .size = size, .direction = DMA_BIDIRECTIONAL, @@ -1356,7 +1521,8 @@ void debug_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, struct dma_debug_entry ref = { .type = dma_debug_sg, .dev = dev, - .paddr = sg_phys(s), + .pfn = page_to_pfn(sg_page(s)), + .offset = s->offset, .dev_addr = sg_dma_address(s), .size = sg_dma_len(s), .direction = direction, @@ -1388,7 +1554,8 @@ void debug_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, struct dma_debug_entry ref = { .type = dma_debug_sg, .dev = dev, - .paddr = sg_phys(s), + .pfn = page_to_pfn(sg_page(s)), + .offset = s->offset, .dev_addr = sg_dma_address(s), .size = sg_dma_len(s), .direction = direction, diff --git a/mm/memory.c b/mm/memory.c index 6768ce9..e9c5504 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -59,6 +59,7 @@ #include <linux/gfp.h> #include <linux/migrate.h> #include <linux/string.h> +#include <linux/dma-debug.h> #include <asm/io.h> #include <asm/pgalloc.h> @@ -2559,6 +2560,8 @@ static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd, static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma) { + debug_dma_assert_idle(src); + /* * If the source page was a PFN mapping, we don't have * a "struct page" for it. We do a best-effort copy by |
