Messages in this thread |  | | | Date | Thu, 26 Nov 2009 10:36:58 +0100 | | From | Jörn Engel <> | | Subject | Re: [PATCH/RFC v5 4/5]: core: Add dump device to call on oopses and panics |
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Just stumbled across this patch.
On Tue, 13 October 2009 15:22:35 +0200, Simon Kagstrom wrote: > +void dump_kmsg(int panic) > +{ > + unsigned long len = ACCESS_ONCE(log_end); > + struct dump_device *dump; > + const char *s1, *s2; > + unsigned long l1, l2; > + > + s1 = ""; > + l1 = 0; > + s2 = log_buf; > + l2 = len; > + > + /* Have we rotated around the circular buffer? */ > + if (len > log_buf_len) {
I believe this bit is wrong. log_end is an unsigned int, so it can wrap relatively quickly. If log_end just wrapped to 0 and dump_kmsg is called, the amount of printk buffer stored appears to be 0 as well.
To avoid this case one could either declare log_end and len as u64, causing extra computational costs. Or one could just use the conditional code below unconditionally. That could write random or zeroed printk buffer directly after bootup, but would never miss information.
> + unsigned long pos = (len & LOG_BUF_MASK); > + > + s1 = log_buf + pos; > + l1 = log_buf_len - pos; > + > + s2 = log_buf; > + l2 = pos; > + } > + > + list_for_each_entry(dump, &dump_list, list) { > + if (panic && dump->panic) > + dump->panic(dump, s1, l1, s2, l2); > + else if (!panic && dump->oops) > + dump->oops(dump, s1, l1, s2, l2); > + } > +} > -- > 1.6.0.4
Jörn
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