Dave Anderson <anderson at redhat.com> writes: >> Hi Eric and others, >> >> I think we might be running into the issues because i386, FC7 relocatable >> kernel has been compiled for 16MB physical address but effectively it >> runs at 4MB physical address. So kernel does not run at compiled address >> and any kind of debugging tools reading symbol address from System.map >> or rom vmlinux will fail as run time symbol addresses are different. >> >> /proc/kallsyms should help though. This is one problem with shift in run >> time virtual address while relocating the kernel. We should be running kernel >> at compiled address to be able to debug it. Or enable any tools to parse >> /proc/kallsyms to read the shift in symbol addresses and adjust accordingly. >> >> Thanks >> Vivek > > Right, crash was updated in version 4.0-4.5 to allow the use > of /proc/kallsyms as an alternative to the System.map file, > as well as adding a new --reloc command line argument. After > bringing up the vmlinux file in gdb (with the "wrong" addresses), > all of the minimal_symbol data structures in the gdb module are > back-patched with the /proc/kallsyms values: > > http://people.redhat.com/anderson/crash.changelog.html#4_0_4_5 > > It seems the benefit of configuring the kernel that way is debatable, > and I will do all I can to convince the RHEL-6 and beyond kernel > maintainers from doing it that way in the future. But Fedora goes > its own way. Seems totally lame to issue a bogus System.map file > though... Well, this is kgdb, so "/proc/kallsyms" is on the target machine, not the host machine. So, 'gdb' cannot read /proc/kallsyms, because, well, it's not local. However, I AM building my own kernel -- so I can certainly reconfigure it as necessary. What do I need to do to reconfigure my kernel to run at the same place it was built for? I.e., what's changing the runtime from 16M to 4M and how do I make it consistent? Thanks! > Dave -derek -- Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory Member, MIT Student Information Processing Board (SIPB) URL: http://web.mit.edu/warlord/ PP-ASEL-IA N1NWH warlord at MIT.EDU PGP key available
