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




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