linux-kernel - Re: [PATCH v2 01/14] rasdaemon: Fix for parsing error when trace event's format file is larger than PAGE

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Message-ID: <20250110160244.00006635@huawei.com>
Date: Fri, 10 Jan 2025 16:02:44 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: <shiju.jose@...wei.com>
CC: <linux-edac@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
	<mchehab@...nel.org>, <dave.jiang@...el.com>, <dan.j.williams@...el.com>,
	<alison.schofield@...el.com>, <nifan.cxl@...il.com>,
	<vishal.l.verma@...el.com>, <ira.weiny@...el.com>, <dave@...olabs.net>,
	<linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>,
	<tanxiaofei@...wei.com>, <prime.zeng@...ilicon.com>
Subject: Re: [PATCH v2 01/14] rasdaemon: Fix for parsing error when trace
 event's format file is larger than PAGE_SIZE

On Fri, 10 Jan 2025 12:26:27 +0000
<shiju.jose@...wei.com> wrote:

> From: Shiju Jose <shiju.jose@...wei.com>
> 
> When a trace event's format file is larger than PAGE_SIZE (4096) then
> libtraceevent returns parsing failed when rasdaemon reads the fields.
> The reason found that tep_parse_event() call in the add_event_handler()
> internally fails in libtraceevent because of the incomplete format file
> data read. However libtraceevent did not return error in this stage,
> which is fixed in the following patch for libtraceevent.
> https://lore.kernel.org/all/20250109102338.6128644d@gandalf.local.home/
> 
> When rasdaemon reads a trace event format file,the maximum data size

space after that comma if spinning a v3.

> that can be read is limited to PAGE_SIZE by the seq_read() and
> seq_read_iter() functions in the kernel. This results in userspace
> receiving partial data if the format file is larger than PAGE_SIZE,
> requiring fix in the rasdaemon to read the complete data from the
> format file.
> 
> Add fix for reading trace event format files larger than PAGE_SIZE
> in add_event_handler().
> 
> Signed-off-by: Shiju Jose <shiju.jose@...wei.com>

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  ras-events.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/ras-events.c b/ras-events.c
> index 5d8118a..6692a31 100644
> --- a/ras-events.c
> +++ b/ras-events.c
> @@ -376,7 +376,7 @@ static int filter_ras_mc_event(struct ras_events *ras, char *group, char *event,
>  
>  static int get_pagesize(struct ras_events *ras, struct tep_handle *pevent)
>  {
> -	int fd, len, page_size = 4096;
> +	int fd, len, page_size = 8192;
>  	char buf[page_size];
>  
>  	fd = open_trace(ras, "events/header_page", O_RDONLY);
> @@ -827,7 +827,8 @@ static int add_event_handler(struct ras_events *ras, struct tep_handle *pevent,
>  			     unsigned int page_size, char *group, char *event,
>  			     tep_event_handler_func func, char *filter_str, int id)
>  {
> -	int fd, size, rc;
> +	int fd, rc;
> +	int size = 0;
>  	char *page, fname[MAX_PATH + 1];
>  	struct tep_event_filter *filter = NULL;
>  
> @@ -857,13 +858,17 @@ static int add_event_handler(struct ras_events *ras, struct tep_handle *pevent,
>  		return rc;
>  	}
>  
> -	size = read(fd, page, page_size);
> +	do {
> +		rc = read(fd, page + size, page_size);
> +		if (rc < 0) {
> +			log(TERM, LOG_ERR, "Can't get arch page size\n");
> +			free(page);
> +			close(fd);
> +			return size;
> +		}
> +		size += rc;
> +	} while (rc > 0);
>  	close(fd);
> -	if (size < 0) {
> -		log(TERM, LOG_ERR, "Can't get arch page size\n");
> -		free(page);
> -		return size;
> -	}
>  
>  	/* Registers the special event handlers */
>  	rc = tep_register_event_handler(pevent, -1, group, event, func, ras);