Date: Thu, 13 Oct 2016 21:31:43 -0700
From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: Ohad Ben-Cohen <ohad@wizery.com>, linux-remoteproc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] remoteproc: Use fixed length field for firmware name
Message-ID: <20161014043143.GA8247@tuxbot>
References: <1476193185-32107-1-git-send-email-matt.redfearn@imgtec.com>
 <1476193185-32107-2-git-send-email-matt.redfearn@imgtec.com>
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On Tue 11 Oct 06:39 PDT 2016, Matt Redfearn wrote:

> Storage of the firmware name was inconsistent, either storing a pointer
> to a name stored with unknown ownership, or a variable length tacked
> onto the end of the struct proc allocated in rproc_alloc.
> 

Instead of using a statically sized array for "firmware", just keep it
a pointer to a local copy of the firmware name.

> In preparation for allowing the firmware of an already allocated struct
> rproc to be changed, the easiest way to allow reallocation of the name
> is to switch to a fixed length buffer held as part of the struct rproc.
> That way we can either copy the provided firmware name into it, or print
> into it based on a name template. A new function,
> rproc_set_firmware_name() is introduced for this purpose, and that logic
> removed from rproc_alloc().
> 
> Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
> ---
> 
>  drivers/remoteproc/remoteproc_core.c | 64 +++++++++++++++++++++++-------------
>  include/linux/remoteproc.h           |  4 ++-
>  2 files changed, 45 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index fe0539ed9cb5..48cd9d5afb69 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1309,6 +1309,42 @@ static void rproc_type_release(struct device *dev)
>  	kfree(rproc);
>  }
>  
> +/**
> + * rproc_set_firmware_name() - helper to create a valid firmare name
> + * @rproc: remote processor
> + * @firmware: name of firmware file, can be NULL
> + *
> + * If the caller didn't pass in a firmware name then construct a default name,
> + * otherwise the provided name is copied into the firmware field of struct
> + * rproc. If the name is too long to fit, -EINVAL is returned.
> + *
> + * Returns 0 on success and an appropriate error code otherwise.
> + */
> +static int rproc_set_firmware_name(struct rproc *rproc, const char *firmware)

That would turn this function into something like:

char *p, *template = "rproc-%s-fw";

if (!firmware) {
	name_len = strlen(name) + strlen(template) - 2 + 1;
	p = kmalloc(name_len, GFP_KERNEL);
	if (!p)
		return -ENOMEM;

	sprintf(p, template, firmware);
} else {
	p = kstrdup(firmware, GFP_KERNEL);
	if (!p)
		return -ENOMEM;
}

kfree(rproc->firmware);
rproc->firmware = p;

Like your version this leaves the firmware name unchanged in the case of
an error.

> +{
> +	char *cp, *template = "rproc-%s-fw";
> +	int name_len;
> +
> +	if (firmware) {
> +		name_len = strlen(firmware);
> +		cp = memchr(firmware, '\n', name_len);

Let's just require the caller to pass us a valid name.

> +		if (cp)
> +			name_len = cp - firmware;
> +
> +		if (name_len > RPROC_MAX_FIRMWARE_NAME_LEN)
> +			return -EINVAL;
> +
> +		strncpy(rproc->firmware, firmware, name_len);
> +		rproc->firmware[name_len] = '\0';
> +	} else {
> +		snprintf(rproc->firmware, RPROC_MAX_FIRMWARE_NAME_LEN,
> +			 template, rproc->name);
> +	}
> +
> +	dev_dbg(&rproc->dev, "Using firmware %s\n", rproc->firmware);
> +	return 0;
> +}

PS. Don't forget to free the string in rproc_type_release()

Regards,
Bjorn

> +
>  static struct device_type rproc_type = {
>  	.name		= "remoteproc",
>  	.release	= rproc_type_release,
> @@ -1342,35 +1378,14 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
>  				const char *firmware, int len)
>  {
>  	struct rproc *rproc;
> -	char *p, *template = "rproc-%s-fw";
> -	int name_len = 0;
>  
>  	if (!dev || !name || !ops)
>  		return NULL;
>  
> -	if (!firmware)
> -		/*
> -		 * Make room for default firmware name (minus %s plus '\0').
> -		 * If the caller didn't pass in a firmware name then
> -		 * construct a default name.  We're already glomming 'len'
> -		 * bytes onto the end of the struct rproc allocation, so do
> -		 * a few more for the default firmware name (but only if
> -		 * the caller doesn't pass one).
> -		 */
> -		name_len = strlen(name) + strlen(template) - 2 + 1;
> -
> -	rproc = kzalloc(sizeof(struct rproc) + len + name_len, GFP_KERNEL);
> +	rproc = kzalloc(sizeof(struct rproc) + len, GFP_KERNEL);
>  	if (!rproc)
>  		return NULL;
>  
> -	if (!firmware) {
> -		p = (char *)rproc + sizeof(struct rproc) + len;
> -		snprintf(p, name_len, template, name);
> -	} else {
> -		p = (char *)firmware;
> -	}
> -
> -	rproc->firmware = p;
>  	rproc->name = name;
>  	rproc->ops = ops;
>  	rproc->priv = &rproc[1];
> @@ -1389,6 +1404,11 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
>  
>  	dev_set_name(&rproc->dev, "remoteproc%d", rproc->index);
>  
> +	if (rproc_set_firmware_name(rproc, firmware)) {
> +		put_device(&rproc->dev);
> +		return NULL;
> +	}
> +
>  	atomic_set(&rproc->power, 0);
>  
>  	/* Set ELF as the default fw_ops handler */
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index 1c457a8dd5a6..7a6f9ad55011 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -42,6 +42,8 @@
>  #include <linux/idr.h>
>  #include <linux/of.h>
>  
> +#define RPROC_MAX_FIRMWARE_NAME_LEN 128
> +
>  /**
>   * struct resource_table - firmware resource table header
>   * @ver: version number
> @@ -416,7 +418,7 @@ struct rproc {
>  	struct list_head node;
>  	struct iommu_domain *domain;
>  	const char *name;
> -	const char *firmware;
> +	char firmware[RPROC_MAX_FIRMWARE_NAME_LEN];
>  	void *priv;
>  	const struct rproc_ops *ops;
>  	struct device dev;
> -- 
> 2.7.4
>