----- Original Message ----- > On Sat, Dec 3, 2016 at 1:59 AM, Rabin Vincent <rabin@xxxxxx> 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 If your kernel has a 16k page size and "help -m" shows 4096 as above, then there's one major problem. The calculation of page size in mips.c is based upon the difference between the the "swapper_pg_dir" symbol and the next symbol above it: crash> sym -n swapper_pg_dir 806d0000 (B) swapper_pg_dir 806d1000 (B) invalid_pte_table crash> What does the command above on your kernel show? Dave > Sagar > > > > > -- > > Crash-utility mailing list > > Crash-utility@xxxxxxxxxx > > https://www.redhat.com/mailman/listinfo/crash-utility > > -- > Crash-utility mailing list > Crash-utility@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/crash-utility > -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility
