Message-ID: <alpine.DEB.2.20.1703140954310.2394@mgerlach-VirtualBox>
Date:   Tue, 14 Mar 2017 09:55:37 -0700 (PDT)
From:   matthew.gerlach@...ux.intel.com
To:     "Li, Yi" <yi1.li@...ux.intel.com>
cc:     ming.lei@...onical.com, mcgrof@...nel.org,
        gregkh@...uxfoundation.org, atull@...nsource.altera.com,
        moritz.fischer@...us.com, linux-kernel@...r.kernel.org,
        linux-fpga@...r.kernel.org
Subject: Re: [RFC 1/2] firmware class: Add stream_firmware API.



On Tue, 14 Mar 2017, Li, Yi wrote:

> hi Matthew,
>
Hi Yi,

>
> On 3/13/2017 4:09 PM, matthew.gerlach@...ux.intel.com wrote:
>> 
>> 
>> On Fri, 10 Mar 2017, Li, Yi wrote:
>> 
>>> Hi Matthew
>>> 
>> Hi Yi,
>> 
>> 
>>> 
>>> On 3/10/2017 11:44 AM, matthew.gerlach@...ux.intel.com wrote:
>>>> 
>>>> 
>>>> On Thu, 9 Mar 2017, yi1.li@...ux.intel.com wrote:
>>>> 
>>>>> From: Yi Li <yi1.li@...ux.intel.com>
>>>> 
>>>> 
>>>> Hi Yi,
>>>> 
>>>> Just one question below.
>>>> 
>>>> Matthew Gerlach
>>>> 
>>>> 
>>>>> Add function to load firmware in multiple chucks instead of
>>>>> 
>>>>> loading the whole big firmware file at once.
>>>>> 
>>>>> Signed-off-by: Yi Li <yi1.li@...ux.intel.com>
>>>>> ---
>>>>> drivers/base/firmware_class.c | 128 
>>>>> ++++++++++++++++++++++++++++++++++++++++++
>>>>> include/linux/firmware.h      |   2 +
>>>>> 2 files changed, 130 insertions(+)
>>>>> 
>>>>> diff --git a/drivers/base/firmware_class.c 
>>>>> b/drivers/base/firmware_class.c
>>>>> index ac350c5..44fddff 100644
>>>>> --- a/drivers/base/firmware_class.c
>>>>> +++ b/drivers/base/firmware_class.c
>>>>> @@ -436,6 +436,62 @@ fw_get_filesystem_firmware(struct device *device, 
>>>>> struct firmware_buf *buf)
>>>>>     return rc;
>>>>> }
>>>>> 
>>>>> +static int
>>>>> +fw_stream_filesystem_firmware(struct device *device, struct 
>>>>> firmware_buf *buf,
>>>>> +            size_t offset, size_t length)
>>>>> +{
>>>>> +    int i, len;
>>>>> +    char *path;
>>>>> +    int rc = 0;
>>>>> +    struct file *file;
>>>>> +
>>>>> +    buf->size = 0;
>>>>> +
>>>>> +    path = __getname();
>>>>> +    if (!path)
>>>>> +        return -ENOMEM;
>>>>> +
>>>>> +    for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
>>>>> +        /* skip the unset customized path */
>>>>> +        if (!fw_path[i][0])
>>>>> +            continue;
>>>>> +
>>>>> +        len = snprintf(path, PATH_MAX, "%s/%s",
>>>>> +                   fw_path[i], buf->fw_id);
>>>> 
>>>> I'm probably being paranoid, but is it safe to assume the length of the 
>>>> buffer returned by __getname() is at least PATH_MAX?  It seems like
>>>> the length should be pagesize.
>>> 
>>> The size should be the maximum number of char of the string be produced, 
>>> not the input size.
>>> According to 
>>> https://www.gnu.org/software/libc/manual/html_node/Formatted-Output-Functions.html
>>> Function:/int/*snprintf*/(char *s, size_tsize, const char *template, …)
>>> /The|snprintf|function is similar to|sprintf|, except that thesizeargument 
>>> specifies the maximum number of characters to produce. The trailing null 
>>> character is counted towards this limit, so you should allocate at 
>>> leastsizecharacters for the strings. Ifsizeis zero, nothing, not even the 
>>> null byte, shall be written andsmay be a null pointer.
>>> The return value is the number of characters which would be generated for 
>>> the given input, excluding the trailing null. If this value is greater 
>>> than or equal tosize, not all characters from the result have been stored 
>>> ins
>>> 
>> 
>> I am familiar with the functionality of snprintf versus sprintf. In the
>> snprintf call above, you are saying that memory pointed to by the variable 
>> path, has at least PATH_MAX number of bytes.  My question is how can you 
>> know that the memory returned by __getname() has PATH_MAX number of bytes?
>> 
>> 
>
> Ah, now I understand the concerns.
>
> The __getname() will allocate an buffer object from names_cachep
> extern struct kmem_cache <http://lxr.free-electrons.com/ident?i=kmem_cache> 
> *names_cachep <http://lxr.free-electrons.com/ident?i=names_cachep>;
> #define __getname <http://lxr.free-electrons.com/ident?i=__getname>() 
> kmem_cache_alloc 
> <http://lxr.free-electrons.com/ident?i=kmem_cache_alloc>(names_cachep 
> <http://lxr.free-electrons.com/ident?i=names_cachep>, GFP_KERNEL 
> <http://lxr.free-electrons.com/ident?i=GFP_KERNEL>)
>
> names_cachep is created in fs/dcaches.c vfs_caches_init function with object 
> size equal to PATH_MAX.
> names_cachep <http://lxr.free-electrons.com/ident?i=names_cachep> = 
> kmem_cache_create 
> <http://lxr.free-electrons.com/ident?i=kmem_cache_create>(/"names_cache"/, 
> PATH_MAX <http://lxr.free-electrons.com/ident?i=PATH_MAX>, 
> 0,SLAB_HWCACHE_ALIGN 
> <http://lxr.free-electrons.com/ident?i=SLAB_HWCACHE_ALIGN>|SLAB_PANIC 
> <http://lxr.free-electrons.com/ident?i=SLAB_PANIC>, NULL 
> <http://lxr.free-electrons.com/ident?i=NULL>);
>
> so __getname() should allocate buffer with size of PATH_MAX.
>
> The code is borrowed from fw_get_filesystem_firmware function, which should 
> be reviewed and safe to use. :)

Thanks for following up. I am no longer paranoid.

Matthew Gerlach
>
> Thanks,
> Yi
>
>
>>>> 
>>>>> +        if (len >= PATH_MAX) {
>>>>> +            rc = -ENAMETOOLONG;
>>>>> +            break;
>>>>> +        }
>>>>> +
>>>>> +        if (!path || !*path)
>>>>> +            continue;
>>>>> +
>>>>> +        if (!buf->data) {
>>>>> +            buf->data = vmalloc(length);
>>>>> +            if (!buf->data) {
>>>>> +                rc = -ENOMEM;
>>>>> +                break;
>>>>> +            }
>>>>> +        }
>>>>> +
>>>>> +        file = filp_open(path, O_RDONLY, 0);
>>>>> +        if (IS_ERR(file))
>>>>> +            continue;
>>>>> +
>>>>> +        buf->size = kernel_read(file, offset, (char *) buf->data,
>>>>> +                    length);
>>>>> +        fput(file);
>>>>> +        break;
>>>>> +    }
>>>>> +
>>>>> +    __putname(path);
>>>>> +
>>>>> +    if (rc)
>>>>> +        dev_err(device, "loading %s failed with error %d\n",
>>>>> +             path, rc);
>>>>> +    return rc;
>>>>> +}
>>>>> +
>>>>> /* firmware holds the ownership of pages */
>>>>> static void firmware_free_data(const struct firmware *fw)
>>>>> {
>>>>> @@ -1267,6 +1323,78 @@ request_firmware(const struct firmware 
>>>>> **firmware_p, const char *name,
>>>>> }
>>>>> EXPORT_SYMBOL(request_firmware);
>>>>> 
>>>>> +static int
>>>>> +_stream_firmware(const struct firmware **firmware_p, const char *name,
>>>>> +          struct device *device, void *buf, size_t size,
>>>>> +          unsigned int opt_flags, size_t offset, size_t length)
>>>>> +{
>>>>> +    int ret;
>>>>> +    struct firmware *fw = NULL;
>>>>> +    struct firmware_buf *fbuf;
>>>>> +
>>>>> +    if ((!firmware_p) || (!name || name[0] == '\0')) {
>>>>> +        dev_err(device, "invalid firmware pointer or file name\n");
>>>>> +        return -EINVAL;
>>>>> +    }
>>>>> +
>>>>> +    if (!*firmware_p) {
>>>>> +        ret = _request_firmware_prepare(&fw, name, device, buf, size);
>>>>> +        if (ret <= 0) {
>>>>> +            dev_err(device, "%s: _request_firmware_prepare failed 
>>>>> %d\n",
>>>>> +                __func__, ret);
>>>>> +        }
>>>>> +    } else {
>>>>> +        fw = (struct firmware *) *firmware_p;
>>>>> +    }
>>>>> +
>>>>> +    fbuf = (struct firmware_buf *) fw->priv;
>>>>> +    ret = fw_stream_filesystem_firmware(device, fbuf, offset, length);
>>>>> +    fw->size = fbuf->size;
>>>>> +    fw->data = fbuf->data;
>>>>> +    *firmware_p = fw;
>>>>> +
>>>>> +    if (ret)
>>>>> +        dev_err(device, "streaming with error %d\n", ret);
>>>>> +    return ret;
>>>>> +}
>>>>> +
>>>>> +/**
>>>>> + * stream_firmware: - send firmware request and wait for it
>>>>> + * @firmware_p: pointer to firmware image
>>>>> + * @name: name of firmware file
>>>>> + * @device: device for which firmware is being loaded
>>>>> + * @offset: offset of the file to read from
>>>>> + * @length: length in bytes to read
>>>>> + *
>>>>> + *      @firmware_p will be used to return a firmware image by the name
>>>>> + *      of @name for device @device.
>>>>> + *
>>>>> + *      Should be called from user context where sleeping is allowed.
>>>>> + *
>>>>> + *      @name will be used as $FIRMWARE in the uevent environment and
>>>>> + *      should be distinctive enough not to be confused with any other
>>>>> + *      firmware image for this or any other device.
>>>>> + *
>>>>> + *    Caller must hold the reference count of @device.
>>>>> + *
>>>>> + *    The function can be called safely inside device's suspend and
>>>>> + *    resume callback.
>>>>> + **/
>>>>> +int
>>>>> +stream_firmware(const struct firmware **firmware_p, const char *name,
>>>>> +         struct device *device, size_t offset, size_t length)
>>>>> +{
>>>>> +    size_t ret;
>>>>> +
>>>>> +    /* Need to pin this module until return */
>>>>> +    __module_get(THIS_MODULE);
>>>>> +    ret = _stream_firmware(firmware_p, name, device, NULL, 0,
>>>>> +                FW_OPT_UEVENT | FW_OPT_NO_WARN, offset, length);
>>>>> +    module_put(THIS_MODULE);
>>>>> +    return ret;
>>>>> +}
>>>>> +EXPORT_SYMBOL(stream_firmware);
>>>>> +
>>>>> /**
>>>>>  * request_firmware_direct: - load firmware directly without usermode 
>>>>> helper
>>>>>  * @firmware_p: pointer to firmware image
>>>>> diff --git a/include/linux/firmware.h b/include/linux/firmware.h
>>>>> index b1f9f0c..accd7f6 100644
>>>>> --- a/include/linux/firmware.h
>>>>> +++ b/include/linux/firmware.h
>>>>> @@ -41,6 +41,8 @@ struct builtin_fw {
>>>>> #if defined(CONFIG_FW_LOADER) || (defined(CONFIG_FW_LOADER_MODULE) && 
>>>>> defined(MODULE))
>>>>> int request_firmware(const struct firmware **fw, const char *name,
>>>>>              struct device *device);
>>>>> +int stream_firmware(const struct firmware **fw, const char *name,
>>>>> +            struct device *device, size_t offset, size_t length);
>>>>> int request_firmware_nowait(
>>>>>     struct module *module, bool uevent,
>>>>>     const char *name, struct device *device, gfp_t gfp, void *context,
>>>>> -- 
>>>>> 2.7.4
>>>>> 
>>>>> -- 
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>>> 
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>
>

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