Re: [Crash-utility] crash-4.0-2.10 ppc64 4-level pagetable fixes

Badari Pulavarty wrote: > Hi Dave, > > Here are the fixes to make crash understand PPC64 4-level pagetable > layout. > > I am not a PPC64 expert, I coded up looking at the ppc64 kernel > pagetable handling code. It seems to work fine for most part. > > But I do get occasional, "user virtual" translation failures. > I think I screwed up PMD calculations. I am not able to spot > the problem. Can some one help ? > > Thanks, > Badari > It's possible that the virtual address that you're examining is not backed by physical memory (yet). If you do a "vtop" on the address that gives you the error, you may see it's simply not mapped. For example, I created a little program call "bogus" that does a malloc of 1000000, prints the beginning address of the region, and then pauses: main() { char *buf; buf = malloc(1000000); printf("buf: %lx\n", buf); pause(); } When I run it, it prints "buf: 2a95586010". If I look at it with crash, the first page of data is instantiated, i.e. it was already in place before the malloc() call, but if I go to any page beyond that, it does this: crash> set 13474 PID: 13474 COMMAND: "bogus" TASK: 100310f57f0 [THREAD_INFO: 10005394000] CPU: 1 STATE: TASK_INTERRUPTIBLE crash> rd 2a95586010 2a95586010: 0000000000000000 ........ crash> rd 2a95587010 rd: invalid user virtual address: 2a95587010 type: "64-bit UVADDR" crash> vtop 2a95587010 VIRTUAL PHYSICAL 2a95587010 (not mapped) PGD: 279cb550 => 365fa067 PMD: 365fa550 => 27ce6067 PTE: 27ce6c38 => 0 VMA START END FLAGS FILE 1003c5898d8 2a95584000 2a9567c000 100073 crash>