[Crash-utility] Re: PATCH] support vmcores with 64k page size on 4kpage size kernels
Haren Myneni
haren at us.ibm.com
Fri Sep 15 20:06:42 UTC 2006
Dave Anderson wrote:
> 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 at in.ibm.com>
>> > --
>> >
>> > 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?
>
Sachin, Yes, we should be hardcoding the stack size value (16K). It does
not matter for hardware intr stack which is used only for 2.4 kernel and
supports only 4K page. Uses soft IRQ and hard IRQ stacks in 2.6 kernel
for interrupt context and their sizes are the same as THREAD_SIZE.
This patch should also support backward compatibility since the symbol
__hash_page_64K does not exist and thus the page size is always 4K.
> Dave
>
>
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>
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