commit e1d2e5302b016c6f7942f46ffa27aa31326686c5

 Author: Philipp Rudo <prudo@redhat.com>

 Date:   Mon Mar 14 17:04:30 2022 +0100

     [PATCH v2 2/3] use pointer arithmetics for dump_dmesg

     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@redhat.com>

     Reviewed-and-tested-by: Dave Wysochanski <dwysocha@redhat.com>

     Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>

 diff --git a/makedumpfile-1.7.0/makedumpfile.c b/makedumpfile-1.7.0/makedumpfile.c

 index 7ed9756a8c43ae4a2b6770e86dc81763796c2187..e72dba219eec198ec865045562f39a14b5a092eb 100644

 --- a/makedumpfile-1.7.0/makedumpfile.c

 +++ b/makedumpfile-1.7.0/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

 @@ -5497,19 +5494,16 @@ log_from_idx(unsigned int idx, char *logbuf)

  	msglen = USHORT(logptr + OFFSET(printk_log.len));

  	if (!msglen)

 -		logptr = logbuf;

 +		return logbuf;

  	return logptr;

  }

 -static long

 -log_next(unsigned int idx, char *logbuf)

 +static void *

 +log_next(void *logptr, void *logbuf)

  {

 -	char *logptr;

  	unsigned int msglen;

 -	logptr = logbuf + idx;

 -

  	/*

  	 * 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 +5513,10 @@ 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 +5524,12 @@ 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 +5676,13 @@ 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;