Re: [Crash-utility] kernel module parsing failure - mips

On Sat, Dec 3, 2016 at 1:59 AM, Rabin Vincent <rabin(a)rab.in&gt; wrote: > On Fri, Dec 02, 2016 at 04:06:20PM -0800, Sagar Borikar wrote: >> With 7.1.7, crash is working for MIPS when all drivers are embedded >> inside kernel. >> When I make the driver loadable and panic the kernel, crash doesn't >> locate some symbols correctly. >> >> please wait... (gathering module symbol data) >> crash: invalid size request: 0 type: "pgd page" >> >> debugged further and find that PGD_ORDER provides incorrect number >> due to which the PGD_SIZE macro results in 0. >> >> Just for fun, I replaced PGD_ORDER with 0(I know its incorrect) and it >> went ahead but couldn't run "mod" command successfully as it threw >> following error >> >> crash> mod >> mod: cannot access vmalloc'd module memory > > In order to access vmalloc'd memory we need interpret the page tables > correctly. This isn't needed when the modules are built in since then > the memory will be in the direct-mapped kseg0 segment. So the "mod" > failure is just a consequence of replacing PGD_ORDER with 0. Yes, mod will not work as I said earlier. Crash was exiting hence I wanted to have quick workaround. > So the first error should be fixed properly before attempting "mod". What > kernel version is this and what page size do to use? 4.4.20 kernel and page size is 16K > > Try running the "help -m" and "mach" commands (you can skip module loading > with > --no_modules to get to the crash> prompt) and check if the values for the > various page table sizes and bits match what your kernel is using. > > crash> help -m > ... > pagesize: 4096 > pageshift: 12 > pagemask: fffffffffffff000 > pageoffset: fff > pgdir_shift: 22 > ptrs_per_pgd: 1024 > ptrs_per_pte: 1024 > ... > > > crash-mips> mach > PAGE SIZE: 4096 > > _PAGE_PRESENT: 00000001 > _PAGE_READ: 00000002 > _PAGE_WRITE: 00000004 > _PAGE_ACCESSED: 00000008 > _PAGE_MODIFIED: 00000010 > _PAGE_GLOBAL: 00000020 > _PAGE_VALID: 00000040 > _PAGE_DIRTY: 00000080 This appears to be correct info for my platform. Thanks

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