Date: Sat, 29 Nov 1997 12:36:19 +1100 From: David Dawes <dawes@rf900.physics.usyd.edu.au> To: hackers@FreeBSD.ORG Subject: Re: Shared Libraries and debugging Message-ID: <19971129123619.61979@rf900.physics.usyd.edu.au> In-Reply-To: <Pine.BSF.3.96.971127163806.28870A-100000@darkstar.home>; from Charles Mott on Thu, Nov 27, 1997 at 04:40:35PM -0700 References: <199711272255.OAA18209@austin.polstra.com> <Pine.BSF.3.96.971127163806.28870A-100000@darkstar.home>
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On Thu, Nov 27, 1997 at 04:40:35PM -0700, Charles Mott wrote: >On Thu, 27 Nov 1997, John Polstra wrote: >> Judging by the cause of the problem, I doubt that it ever worked. In >> order to examine shared libraries, gdb needs to look at the dynamic >> linker's table which records where they were loaded into memory. The >> dynamic linker has always recorded this information in a MAP_ANON >> region way up high in the address space. But such regions are not >> written to the core file when a core dump occurs. So gdb has not been >> able to get the information it needs. > >So memory allocated with mmap() is not dumped in a core file? Is this not >possible or just not desirable? Linux seems to (but then it uses ELF). I've seen an unfortunate side-effect of this on Linux when reading the mmapped MMIO area from a Millennium while dumping an Xserver core file. The result was a machine lockup because reads from a part of the MMIO area can initiate a graphics command. We worked around this by unmapping when receiving a trapped signal, but that doesn't help when signal trapping is turned off. David
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