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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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