linux-kernel - Re: [PATCH v3 3/3] remoteproc: Add coredump debugfs entry

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Date:   Thu, 21 May 2020 15:26:32 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Rishabh Bhatnagar <rishabhb@...eaurora.org>
Cc:     linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        bjorn.andersson@...aro.org, tsoni@...eaurora.org,
        psodagud@...eaurora.org, sidgup@...eaurora.org
Subject: Re: [PATCH v3 3/3] remoteproc: Add coredump debugfs entry

On Thu, May 14, 2020 at 01:07:36PM -0700, Rishabh Bhatnagar wrote:
> Add coredump debugfs entry to configure the type of dump that will
> be collected during recovery. User can select between default or
> inline coredump functionality. Also coredump collection can be
> disabled through this interface.
> This functionality can be configured differently for different
> remote processors.
> 
> Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
> ---
>  drivers/remoteproc/remoteproc_debugfs.c | 86 +++++++++++++++++++++++++++++++++
>  1 file changed, 86 insertions(+)
> 
> diff --git a/drivers/remoteproc/remoteproc_debugfs.c b/drivers/remoteproc/remoteproc_debugfs.c
> index 732770e..2f611de 100644
> --- a/drivers/remoteproc/remoteproc_debugfs.c
> +++ b/drivers/remoteproc/remoteproc_debugfs.c
> @@ -28,6 +28,90 @@
>  static struct dentry *rproc_dbg;
>  
>  /*
> + * A coredump-configuration-to-string lookup table, for exposing a
> + * human readable configuration via debugfs. Always keep in sync with
> + * enum rproc_coredump_mechanism
> + */
> +static const char * const rproc_coredump_str[] = {
> +	[COREDUMP_DEFAULT]	= "default",
> +	[COREDUMP_INLINE]	= "inline",
> +	[COREDUMP_DISABLED]	= "disabled",
> +};
> +
> +/* Expose the current coredump configuration via debugfs */
> +static ssize_t rproc_coredump_read(struct file *filp, char __user *userbuf,
> +				    size_t count, loff_t *ppos)
> +{
> +	struct rproc *rproc = filp->private_data;
> +	const char *buf = rproc_coredump_str[rproc->dump_conf];
> +
> +	return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf));
> +}
> +
> +/*
> + * By writing to the 'coredump' debugfs entry, we control the behavior of the
> + * coredump mechanism dynamically. The default value of this entry is "default".
> + *
> + * The 'coredump' debugfs entry supports these commands:
> + *
> + * default:	This is the default coredump mechanism. When the remoteproc
> + *		crashes the entire coredump will be copied to a separate buffer
> + *		and exposed to userspace.
> + *
> + * inline:	The coredump will not be copied to a separate buffer and the
> + *		recovery process will have to wait until data is read by
> + *		userspace. But this avoid usage of extra memory.
> + *
> + * disabled:	This will disable coredump. Recovery will proceed without
> + *		collecting any dump.
> + */
> +static ssize_t rproc_coredump_write(struct file *filp,
> +				     const char __user *user_buf, size_t count,
> +				     loff_t *ppos)
> +{
> +	struct rproc *rproc = filp->private_data;
> +	int ret, err = 0;
> +	char buf[20];
> +
> +	if (count > sizeof(buf))
> +		return -EINVAL;
> +
> +	ret = copy_from_user(buf, user_buf, count);
> +	if (ret)
> +		return -EFAULT;
> +
> +	/* remove end of line */
> +	if (buf[count - 1] == '\n')
> +		buf[count - 1] = '\0';
> +
> +	if (rproc->state == RPROC_CRASHED) {
> +		dev_err(&rproc->dev, "can't change coredump configuration\n");
> +		err = -EBUSY;
> +		goto out;
> +	}
> +
> +	if (!strncmp(buf, "disable", count))
> +		rproc->dump_conf = COREDUMP_DISABLED;
> +	else if (!strncmp(buf, "inline", count))
> +		rproc->dump_conf = COREDUMP_INLINE;
> +	else if (!strncmp(buf, "default", count))
> +		rproc->dump_conf = COREDUMP_DEFAULT;
> +	else {
> +		dev_err(&rproc->dev, "Invalid coredump configuration\n");
> +		err = -EINVAL;
> +	}
> +out:
> +	return err ? err : count;
> +}
> +
> +static const struct file_operations rproc_coredump_fops = {
> +	.read = rproc_coredump_read,
> +	.write = rproc_coredump_write,
> +	.open = simple_open,
> +	.llseek = generic_file_llseek,
> +};
> +
> +/*
>   * Some remote processors may support dumping trace logs into a shared
>   * memory buffer. We expose this trace buffer using debugfs, so users
>   * can easily tell what's going on remotely.
> @@ -337,6 +421,8 @@ void rproc_create_debug_dir(struct rproc *rproc)
>  			    rproc, &rproc_rsc_table_fops);
>  	debugfs_create_file("carveout_memories", 0400, rproc->dbg_dir,
>  			    rproc, &rproc_carveouts_fops);
> +	debugfs_create_file("coredump", 0600, rproc->dbg_dir,
> +			    rproc, &rproc_coredump_fops);

Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>

>  }
>  
>  void __init rproc_init_debugfs(void)
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project