On Mon, 2003-11-10 at 21:21, Prasanna Meda wrote: > Albert Cahalan wrote: > > > On Mon, 2003-11-10 at 19:21, Prasanna Meda wrote: > > > > > In reply to > > > http://lists.debian.org/debian-user/2002/debian-user-200206/msg01866.html > > > > > > I also noticed the same problem. It is due to > > > ps trying to access the past end of mmaped > > > System.map file in my case. What does your > > > trace show? Is this fixed in later versions? > > > It is mapping one byte more and accessing > > > that byte and is getting SIGBUS. > > > > Back in the Linux 1.x.xx era, Linus deliberately > > made an allowance for the above. It seemed, and > > still seems, to be good kernel behavior. After all, > > an incomplete page is padded with '\0' characters. > > Why should a full page be any different? > > > > Unfortunately, some idiot got SIGBUS into the > > UNIX standard. With regret, Linus changed the > > kernel. This broke even his own mkdep code > > that was part of the kernel build process. > > > > The procps-3.x.xx releases available in recent > > versions of Debian no longer rely on this > > wonderful old Linux feature. > > Yes, I see the semantics change in kernel from > 2.2 to 2.4, but what is the reason behind your > mapping filesize+1 bytes in first than filesize > bytes? > In my case, the file size is 475136 bytes, that is > exactly 116 pages, mmap is done for 475137 > bytes.
It's to get System.map as a NUL-terminated string. Processing is easier when the kernel guarantees that there will be a '\0' on the end. I was bitten by an ABI change. :-( -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
