Re: [Crash-utility] Re: PATCH] support vmcores with 64k page size on 4kpage size kernels

Dave Anderson wrote: > "Sachin P. Sant" wrote: > > > Hi Dave > > Recently there were changes made to kexec tools to support 64K page > size. > > With those changes vmcore file obtained from a kernel which > supports 64K > > page size cannot be analyzed using crash on a machine running with > kernel > > supporting 4K page size. > > > > The following changes in crash tool resolves the problem. > > Look if the symbol __hash_page_64k exists. This symbol is defined only > > for kernels with 64K PAGE SIZE support. If yes then the dump was taken > > with a kernel supporting 64k page size. So use the vmcore page > size[64K] > > instead of getpagesize(). > > > > Thanks > > -Sachin > > > > > ------------------------------------------------------------------------------------------------------------------------ > > > * Recently there were changes made to kexec tools to support 64K > page size. > > With those changes vmcore file obtained from a kernel which > supports 64K > > page size cannot be analyzed using crash on a machine running > with kernel > > supporting 4K page size. > > The following change were made in crash tool to solve the problem. > > Look if the symbol __hash_page_64k exists. If yes then the dump > was taken > > with a kernel supporting 64k page size. So change the page size > accordingly. > > > > Signed-Off-By: Sachin Sant <sachinp(a)in.ibm.com&gt; > > -- > > > > diff -Naurp crash-4.0/defs.h crash-4.0-new/defs.h > > --- crash-4.0/defs.h 2006-09-14 21:41:50.000000000 -0400 > > +++ crash-4.0-new/defs.h 2006-09-14 21:48:37.000000000 -0400 > > @@ -2297,6 +2297,7 @@ struct efi_memory_desc_t { > > #define _64BIT_ > > #define MACHINE_TYPE "PPC64" > > > > +#define PPC64_64K_PAGE_SIZE 65536 > > #define PAGEBASE(X) (((ulong)(X)) & (ulong)machdep->pagemask) > > > > #define PTOV(X) ((unsigned long)(X)+(machdep->kvbase)) > > diff -Naurp crash-4.0/ppc64.c crash-4.0-new/ppc64.c > > --- crash-4.0/ppc64.c 2006-09-14 21:41:50.000000000 -0400 > > +++ crash-4.0-new/ppc64.c 2006-09-14 21:50:26.000000000 -0400 > > @@ -67,19 +67,6 @@ ppc64_init(int when) > > machdep->verify_symbol = ppc64_verify_symbol; > > if (pc->flags & KERNEL_DEBUG_QUERY) > > return; > > - machdep->pagesize = memory_page_size(); > > - machdep->pageshift = ffs(machdep->pagesize) - 1; > > - machdep->pageoffset = machdep->pagesize - 1; > > - machdep->pagemask = ~((ulonglong)machdep->pageoffset); > > - machdep->stacksize = 4 * machdep->pagesize; > > - if ((machdep->pgd = (char *)malloc(PAGESIZE())) == > NULL) > > - error(FATAL, "cannot malloc pgd space."); > > - if ((machdep->pmd = (char *)malloc(PAGESIZE())) == > NULL) > > - error(FATAL, "cannot malloc pmd space."); > > - if ((machdep->ptbl = (char *)malloc(PAGESIZE())) == > NULL) > > - error(FATAL, "cannot malloc ptbl space."); > > - if ((machdep->machspec->level4 = (char > *)malloc(PAGESIZE())) == NULL) > > - error(FATAL, "cannot malloc level4 space."); > > machdep->last_pgd_read = 0; > > machdep->last_pmd_read = 0; > > machdep->last_ptbl_read = 0; > > @@ -93,6 +80,40 @@ ppc64_init(int when) > > break; > > > > case PRE_GDB: > > + /* > > + * Recently there were changes made to kexec tools > > + * to support 64K page size. With those changes > > + * vmcore file obtained from a kernel which supports > > + * 64K page size cannot be analyzed using crash on a > > + * machine running with kernel supporting 4K page size > > + * > > + * The following modifications are required in crash > > + * tool to be in sync with kexec tools. > > + * > > + * Look if the following symbol exists. If yes then > > + * the dump was taken with a kernel supporting 64k > > + * page size. So change the page size accordingly. > > + * > > + * Also moved the following code block from > > + * PRE_SYMTAB case here. > > + */ > > + if (symbol_exists("__hash_page_64K")) > > + machdep->pagesize = PPC64_64K_PAGE_SIZE; > > + else > > + machdep->pagesize = memory_page_size(); > > + machdep->pageshift = ffs(machdep->pagesize) - 1; > > + machdep->pageoffset = machdep->pagesize - 1; > > + machdep->pagemask = ~((ulonglong)machdep->pageoffset); > > + machdep->stacksize = 4 * machdep->pagesize; > > + if ((machdep->pgd = (char *)malloc(PAGESIZE())) == > NULL) > > + error(FATAL, "cannot malloc pgd space."); > > + if ((machdep->pmd = (char *)malloc(PAGESIZE())) == > NULL) > > + error(FATAL, "cannot malloc pmd space."); > > + if ((machdep->ptbl = (char *)malloc(PAGESIZE())) == > NULL) > > + error(FATAL, "cannot malloc ptbl space."); > > + if ((machdep->machspec->level4 = (char > *)malloc(PAGESIZE())) == NULL) > > + error(FATAL, "cannot malloc level4 space."); > > + > > machdep->kvbase = symbol_value("_stext"); > > machdep->identity_map_base = machdep->kvbase; > > machdep->is_kvaddr = generic_is_kvaddr; > > The patch looks safe enough. > > A couple things I just noticed though... > > Is it true that the process stack size will be 256K? And the > ppc64 hardware interrupt stack would be 512K? Based upon > the machdep->pagesize value, these inititializations get done > later: > > machdep->stacksize = 4 * machdep->pagesize; > > machdep->machspec->hwstacksize = 8 * machdep->pagesize; > > If they have not increased, won't the backtrace code get confused? > > Thanks, > Dave > The kernel's asm-powerpc/thread_info.h file doesn't show any change in stack size, which I didn't expect it would anyway: #ifdef __KERNEL__ /* We have 8k stacks on ppc32 and 16k on ppc64 */ #ifdef CONFIG_PPC64 #define THREAD_SHIFT 14 #else #define THREAD_SHIFT 13 #endif #define THREAD_SIZE (1 << THREAD_SHIFT) and the hardware interrupt stack seems to only be in the paca_struct in 2.4 kernels. I think we can safely hardwire those two values anyway, right?

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