[PATCH v5] dma-debug: New interfaces to debug dma mapping errors

Shuah Khan
2012-10-08T17:08:13Z

Add dma-debug interface debug_dma_mapping_error() to debug drivers that fail
to check dma mapping errors on addresses returned by dma_map_single() and
dma_map_page() interfaces. This interface clears a flag set by
debug_dma_map_page() to indicate that dma_mapping_error() has been called by
the driver. When driver does unmap, debug_dma_unmap() checks the flag and if
this flag is still set, prints warning message that includes call trace that
leads up to the unmap. This interface can be called from dma_mapping_error()
routines to enable dma mapping error check debugging.

Tested: Intel iommu and swiotlb (iommu=soft) on x86-64 with
CONFIG_DMA_API_DEBUG enabled and disabled.

Signed-off-by: Shuah Khan <shuah.khan@hp.com>
---
Documentation/DMA-API.txt | 12 ++++++
arch/x86/include/asm/dma-mapping.h | 1 +
include/linux/dma-debug.h | 7 ++++
lib/dma-debug.c | 71 ++++++++++++++++++++++++++++++++++--
4 files changed, 87 insertions(+), 4 deletions(-)

diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 66bd97a..78a6c56 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -678,3 +678,15 @@ out of dma_debug_entries. These entries are preallocated at boot. The number
of preallocated entries is defined per architecture. If it is too low for you
boot with 'dma_debug_entries=<your_desired_number>' to overwrite the
architectural default.
+
+void debug_dmap_mapping_error(struct device *dev, dma_addr_t dma_addr);
+
+dma-debug interface debug_dma_mapping_error() to debug drivers that fail
+to check dma mapping errors on addresses returned by dma_map_single() and
+dma_map_page() interfaces. This interface clears a flag set by
+debug_dma_map_page() to indicate that dma_mapping_error() has been called by
+the driver. When driver does unmap, debug_dma_unmap() checks the flag and if
+this flag is still set, prints warning message that includes call trace that
+leads up to the unmap. This interface can be called from dma_mapping_error()
+routines to enable dma mapping error check debugging.
+
diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
index f7b4c79..808dae6 100644
--- a/arch/x86/include/asm/dma-mapping.h
+++ b/arch/x86/include/asm/dma-mapping.h
@@ -47,6 +47,7 @@ static inline struct dma_map_ops *get_dma_ops(struct device *dev)
static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
{
struct dma_map_ops *ops = get_dma_ops(dev);
+ debug_dma_mapping_error(dev, dma_addr);
if (ops->mapping_error)
return ops->mapping_error(dev, dma_addr);

diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
index 171ad8a..fc0e34c 100644
--- a/include/linux/dma-debug.h
+++ b/include/linux/dma-debug.h
@@ -39,6 +39,8 @@ extern void debug_dma_map_page(struct device *dev, struct page *page,
int direction, dma_addr_t dma_addr,
bool map_single);

+extern void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
+
extern void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
size_t size, int direction, bool map_single);

@@ -105,6 +107,11 @@ static inline void debug_dma_map_page(struct device *dev, struct page *page,
{
}

+static inline void debug_dma_mapping_error(struct device *dev,
+ dma_addr_t dma_addr)
+{
+}
+
static inline void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
size_t size, int direction,
bool map_single)
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index b9087bf..94aa94e 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -45,6 +45,12 @@ enum {
dma_debug_coherent,
};

+enum map_err_types {
+ MAP_ERR_CHECK_NOT_APPLICABLE,
+ MAP_ERR_NOT_CHECKED,
+ MAP_ERR_CHECKED,
+};
+
#define DMA_DEBUG_STACKTRACE_ENTRIES 5

struct dma_debug_entry {
@@ -57,6 +63,7 @@ struct dma_debug_entry {
int direction;
int sg_call_ents;
int sg_mapped_ents;
+ enum map_err_types map_err_type;
#ifdef CONFIG_STACKTRACE
struct stack_trace stacktrace;
unsigned long st_entries[DMA_DEBUG_STACKTRACE_ENTRIES];
@@ -114,6 +121,12 @@ static struct device_driver *current_driver __read_mostly;

static DEFINE_RWLOCK(driver_name_lock);

+static const char *const maperr2str[] = {
+ [MAP_ERR_CHECK_NOT_APPLICABLE] = "dma map error check not applicable",
+ [MAP_ERR_NOT_CHECKED] = "dma map error not checked",
+ [MAP_ERR_CHECKED] = "dma map error checked",
+};
+
static const char *type2name[4] = { "single", "page",
"scather-gather", "coherent" };

@@ -376,11 +389,12 @@ 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\n",
+ "%s idx %d P=%Lx D=%Lx L=%Lx %s %s\n",
type2name[entry->type], idx,
(unsigned long long)entry->paddr,
entry->dev_addr, entry->size,
- dir2name[entry->direction]);
+ dir2name[entry->direction],
+ maperr2str[entry->map_err_type]);
}
}

@@ -838,13 +852,28 @@ static __init int dma_debug_entries_cmdline(char *str)
__setup("dma_debug=", dma_debug_cmdline);
__setup("dma_debug_entries=", dma_debug_entries_cmdline);

+/* Calling dma_mapping_error() from dma-debug api will result in calling
+ debug_dma_mapping_error() - need internal mapping error routine to
+ avoid debug checks */
+#ifndef DMA_ERROR_CODE
+#define DMA_ERROR_CODE 0
+#endif
+static inline int has_mapping_error(struct device *dev, dma_addr_t dma_addr)
+{
+ const struct dma_map_ops *ops = get_dma_ops(dev);
+ if (ops->mapping_error)
+ return ops->mapping_error(dev, dma_addr);
+
+ return (dma_addr == DMA_ERROR_CODE);
+}
+
static void check_unmap(struct dma_debug_entry *ref)
{
struct dma_debug_entry *entry;
struct hash_bucket *bucket;
unsigned long flags;

- if (dma_mapping_error(ref->dev, ref->dev_addr)) {
+ if (unlikely(has_mapping_error(ref->dev, ref->dev_addr))) {
err_printk(ref->dev, NULL, "DMA-API: device driver tries "
"to free an invalid DMA memory address\n");
return;
@@ -910,6 +939,15 @@ static void check_unmap(struct dma_debug_entry *ref)
dir2name[ref->direction]);
}

+ if (entry->map_err_type == MAP_ERR_NOT_CHECKED) {
+ err_printk(ref->dev, entry,
+ "DMA-API: device driver failed to check map error"
+ "[device address=0x%016llx] [size=%llu bytes] "
+ "[mapped as %s]",
+ ref->dev_addr, ref->size,
+ type2name[entry->type]);
+ }
+
hash_bucket_del(entry);
dma_entry_free(entry);

@@ -1017,7 +1055,7 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
if (unlikely(global_disable))
return;

- if (unlikely(dma_mapping_error(dev, dma_addr)))
+ if (unlikely(has_mapping_error(dev, dma_addr)))
return;

entry = dma_entry_alloc();
@@ -1030,6 +1068,7 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
entry->dev_addr = dma_addr;
entry->size = size;
entry->direction = direction;
+ entry->map_err_type = MAP_ERR_NOT_CHECKED;

if (map_single)
entry->type = dma_debug_single;
@@ -1045,6 +1084,30 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
}
EXPORT_SYMBOL(debug_dma_map_page);

+void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
+{
+ struct dma_debug_entry ref;
+ struct dma_debug_entry *entry;
+ struct hash_bucket *bucket;
+ unsigned long flags;
+
+ if (unlikely(global_disable))
+ return;
+
+ ref.dev = dev;
+ ref.dev_addr = dma_addr;
+ bucket = get_hash_bucket(&ref, &flags);
+ entry = bucket_find_exact(bucket, &ref);
+
+ if (!entry)
+ goto out;
+
+ entry->map_err_type = MAP_ERR_CHECKED;
+out:
+ put_hash_bucket(bucket, &flags);
+}
+EXPORT_SYMBOL(debug_dma_mapping_error);
+
void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
size_t size, int direction, bool map_single)
{
--
1.7.9.5