Re: [Crash-utility] log command and incorrect wrapping of the buffer

Hi, I've noticed on some systems that the crash log command shows output from the kernel log buffer which is not wrapped at the correct location. All of the data from the buffer is present, but the display is not from oldest to newest. Crash uses the pointer log_start to determine the "current" location in the log buffer. This isn't correct. log_start is the next location to be read by the syslog interface. log_end is the pointer to the last byte written by printk (well, last byte written +1) and this is what should be used. The quick fix is just to replace "log_start" with "log_end" in line 3141. The following tries to optimise the code a little and save a gdb call some of the time. Thanks, Alan Tyson, HP.

--- crash-4.0-4.7/kernel.c 2007-09-25 16:01:56.000000000 +0100 +++ crash-4.0-4.7-at/kernel.c 2007-09-26 16:06:20.000000000 +0100 @@ -3111,7 +3111,7 @@ void dump_log(int msg_level) { int i; - ulong log_buf, log_start, logged_chars; + ulong log_buf, logged_chars; char *buf; char last; ulong index; @@ -3138,13 +3138,16 @@ dump_log(int msg_level) buf = GETBUF(log_buf_len); log_wrap = FALSE; - get_symbol_data("log_start", sizeof(ulong), &log_start); get_symbol_data("logged_chars", sizeof(ulong), &logged_chars); readmem(log_buf, KVADDR, buf, log_buf_len, "log_buf contents", FAULT_ON_ERROR); - log_start &= log_buf_len-1; - index = (logged_chars < log_buf_len) ? 0 : log_start; + if (logged_chars < log_buf_len) { + index = 0; + } else { + get_symbol_data("log_end", sizeof(ulong), &index); + index &= log_buf_len-1; + } if ((logged_chars < log_buf_len) && (index == 0) && (buf[index] == '<')) loglevel = TRUE; -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility