[PATCH v2 2/4] makedumpfile: use pointer arithmetics for dump_dmesg

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> When parsing the printk buffer for the old printk mechanism (> v3.5.0+ and
> < 5.10.0) a log entry is currently specified by the offset into the
> buffer where the entry starts. Change this to use a pointers instead.
> This is done in preparation for using the new cycle detection mechanism.
> 
> Signed-off-by: Philipp Rudo <prudo at redhat.com>
> ---
>  makedumpfile.c | 29 +++++++++++++----------------
>  1 file changed, 13 insertions(+), 16 deletions(-)
> 
> diff --git a/makedumpfile.c b/makedumpfile.c
> index 7ed9756..9a05c96 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -5482,13 +5482,10 @@ dump_log_entry(char *logptr, int fp, const char *file_name)
>   * get log record by index; idx must point to valid message.
>   */
>  static char *
> -log_from_idx(unsigned int idx, char *logbuf)
> +log_from_ptr(char *logptr, char *logbuf)
>  {
> -	char *logptr;
>  	unsigned int msglen;
> 
> -	logptr = logbuf + idx;
> -
>  	/*
>  	 * A length == 0 record is the end of buffer marker.
>  	 * Wrap around and return the message at the start of
> @@ -5502,14 +5499,13 @@ log_from_idx(unsigned int idx, char *logbuf)
>  	return logptr;
>  }
> 
> -static long
> -log_next(unsigned int idx, char *logbuf)
> +static void *
> +log_next(void *_logptr, void *_logbuf)
>  {
> -	char *logptr;
> +	char *logptr = _logptr;
> +	char *logbuf = _logbuf;
>  	unsigned int msglen;
> 
> -	logptr = logbuf + idx;
> -

I added the following change to the log_from_ptr() and log_next() because of
- assigning to the argument (possible but unusual)
- the unnecessary local variables

--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -5494,16 +5494,14 @@ log_from_ptr(char *logptr, char *logbuf)
 
        msglen = USHORT(logptr + OFFSET(printk_log.len));
        if (!msglen)
-               logptr = logbuf;
+               return logbuf;
 
        return logptr;
 }
 
 static void *
-log_next(void *_logptr, void *_logbuf)
+log_next(void *logptr, void *logbuf)
 {
-       char *logptr = _logptr;
-       char *logbuf = _logbuf;
        unsigned int msglen;
 
        /*

Thanks,
Kazu

>  	/*
>  	 * A length == 0 record is the end of buffer marker. Wrap around and
>  	 * read the message at the start of the buffer as *this* one, and
> @@ -5519,10 +5515,10 @@ log_next(unsigned int idx, char *logbuf)
>  	msglen = USHORT(logptr + OFFSET(printk_log.len));
>  	if (!msglen) {
>  		msglen = USHORT(logbuf + OFFSET(printk_log.len));
> -		return msglen;
> +		return logbuf + msglen;
>  	}
> 
> -	return idx + msglen;
> +	return logptr + msglen;
>  }
> 
>  int
> @@ -5530,11 +5526,12 @@ dump_dmesg()
>  {
>  	int log_buf_len, length_log, length_oldlog, ret = FALSE;
>  	unsigned long index, log_buf, log_end;
> -	unsigned int idx, log_first_idx, log_next_idx;
> +	unsigned int log_first_idx, log_next_idx;
>  	unsigned long long first_idx_sym;
>  	unsigned long log_end_2_6_24;
>  	unsigned      log_end_2_6_25;
>  	char *log_buffer = NULL, *log_ptr = NULL;
> +	char *ptr;
> 
>  	/*
>  	 * log_end has been changed to "unsigned" since linux-2.6.25.
> @@ -5681,13 +5678,13 @@ dump_dmesg()
>  			ERRMSG("Can't open output file.\n");
>  			goto out;
>  		}
> -		idx = log_first_idx;
> -		while (idx != log_next_idx) {
> -			log_ptr = log_from_idx(idx, log_buffer);
> +		ptr = log_buffer + log_first_idx;
> +		while (ptr != log_buffer + log_next_idx) {
> +			log_ptr = log_from_ptr(ptr, log_buffer);
>  			if (!dump_log_entry(log_ptr, info->fd_dumpfile,
>  					    info->name_dumpfile))
>  				goto out;
> -			idx = log_next(idx, log_buffer);
> +			ptr = log_next(ptr, log_buffer);
>  		}
>  		if (!close_files_for_creating_dumpfile())
>  			goto out;
> --
> 2.35.1