On Mon, Dec 21, 2015 at 08:37:25AM -0500, Dave Anderson wrote: > > > Hi Drew, > > I am out of the office until Jan 4th, so I may not get around to checking > this out fully until then. But in the meantime, can you save this dumpfile > and send me a pointer to it offline? I want to keep it around for future > testing. OK, I've got a 90MB kdump-zlib core I can put somewhere. I don't know where though, other than just telling you where in RH's network you can grab it from. Also the vmlinux associated with it is one of my own builds, basically a RHELSA kernel, but with 4K pages (4K pages needed in order to use 32-bit user binaries). Thanks, drew > > Thanks, > Dave > > > ----- Original Message ----- > > Hi Dave, > > > > When crash gets a prstatus for an AArch32 (compat) user mode stack frame, > > but assumes it can look at prstatus->sp for the stack pointer, and > > prstatus->sp has a stale AArch64 kernel address in it, then crash > > segfaults. > > > > This is because the stack pointer isn't a user stack address, and thus > > crash expects the stack to include at least two frames, which would mean > > fp is non-zero, but in this case it's not[1], and that leads to the > > calculation of a bad stack pointer (see arm64.c:1209), which then gets > > used as an offset into the stack buffer (see arm64.c:1001), overflowing > > it. > > > > The patch[2] I just sent resolves this issue for me, but only because > > it no longer tries to use prstatus->sp. We should probably still look > > into fixing this in another way, such as making sure fp is non-zero, as > > dumps can have all sorts of corruption breaking our assumptions. > > > > Thanks, > > drew > > > > [1] The dump was captured with QEMU, which doesn't require a real crash, > > i.e. panic() being called in the guest kernel, thus cpus can actually > > be in user mode, rather than in the 64-bit cpu-stop IPI handler, or > > other crashing kernel code. > > [2] https://www.redhat.com/archives/crash-utility/2015-December/msg00024.html > > -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility