Re: [Crash-utility] [PATCH] ppc64: do page traversal if vmemmap_list not populated
On Thu, Sep 21, 2023 at 01:51:27PM +0800, lijiang wrote:
On Mon, Sep 18, 2023 at 7:34 PM lijiang <lijiang(a)redhat.com>
wrote:
>>
>> ---
>> ---
>> ppc64.c | 47 +++++++++++++++++++++++++++++++++--------------
>> 1 file changed, 33 insertions(+), 14 deletions(-)
>>
>> diff --git a/ppc64.c b/ppc64.c
>> index fc34006f4863..1e84c5f56773 100644
>> --- a/ppc64.c
>> +++ b/ppc64.c
>> @@ -1280,8 +1280,30 @@ void ppc64_vmemmap_init(void)
>> long backing_size, virt_addr_offset, phys_offset, list_offset;
>> ulong *vmemmap_list;
>> char *vmemmap_buf;
>> - struct machine_specific *ms;
>> -
>> + struct machine_specific *ms = machdep->machspec;
>> +
>> + ld = &list_data;
>> + BZERO(ld, sizeof(struct list_data));
>> +
>> + /*
>> + * vmemmap_list is missing or set to 0 in the kernel would imply
>> + * vmemmap region is mapped in the kernel pagetable. So, read
>> vmemmap_list
>> + * anyway and use the translation method accordingly.
>> + */
>> + readmem(symbol_value("vmemmap_list"), KVADDR,
&ld->start,
>> sizeof(void *),
>> + "vmemmap_list", RETURN_ON_ERROR);
>> + if (!ld->start) {
>> + /*
>> + * vmemmap_list is set to 0 or missing. Do kernel
>> pagetable walk
>> + * for vmemmamp address translation.
>> + */
>> + ms->vmemmap_list = NULL;
>> + ms->vmemmap_cnt = 0;
>> +
>> + machdep->flags |= VMEMMAP_AWARE;
>> + return;
>> + }
>> +
>>
>
I would suggest putting the
'readmem(symbol_value("vmemmap_list"),...)'
after the 'kernel_symbol_exists("vmemmap_list")', and also check the
returned value of readmem().
Yes, I considered that, but the if condition checking for
'kernel_symbol_exists("vmemmap_list")' returns from the function if the
symbol
is not found, same with the readmem return value check earlier, we wanted to
initialise the ms->vmemmap_list and machdep->flags before that.
The readmem used to be like this, which returns from function if readmem failed:
- if (!readmem(symbol_value("vmemmap_list"),
- KVADDR, &ld->start, sizeof(void *), "vmemmap_list",
- RETURN_ON_ERROR))
- return;
So, intentionally I put it above the if and removed the return value check,
since we don't want to depend on vmemmap_list symbol being there for newer
kernels anymore.
And to be future proof in case the address mapping moves to page table for
Hash MMU case also, and since vmemmap_list is PowerPC specific, the symbol
might also be removed.
But, if it's a coding guidelines requirement to handle the return values, I can
think of how to handle the return value of readmem, any suggestions ?
And other changes are fine to me.
Thank you for your reviews Lianbo :)
Thanks,
- Aditya Gupta