Re: [Crash-utility] [PATCH] s390x: Fix virtual address check for 5 level page tables

Hello Dave, I was talking about the users pace. The "vtop -u" or "rd -u" commands do not work for user space memory mapped above 8 PB. Memory is reported as not mapped. See the sample below:

*crash> rd -u 0x60000000000000 rd: invalid user virtual address: 60000000000000 type: "64-bit UVADDR" crash> vtop -u 0x60000000000000 VIRTUAL PHYSICAL 60000000000000 (not mapped) VMA START END FLAGS FILE 62e5bde8 60000000000000 60000000001000 8100073 * Thanks, Mikhail Zaslonko On 11.05.2017 20:26, Dave Anderson wrote: > > ----- Original Message ----- >> Hello Dave, >> >> We have recently found that Crash is not capable of processing 5 level >> page tables virtual addresses (higher than 8 Petabytes). Please find the >> enclosed patch below. >> >> Thanks, >> Mikhail Zaslonko > Hi Mikhail, > > For the changelog, can you give an example of the symptoms of the > failure? Does it fail to handle kernel modules during session > initialization, or what? > > Thanks, > Dave > > >> >> [PATCH] s390x: Fix virtual address check for 5 level page tables >> >> >> The current validity check for virtual addresses fails for >> five level page tables because in that case it uses a 64 bit >> left-shift operation which is undefined in the C standard. >> >> Quote from C99 standard: >> >> If the value of the right operand is negative or is >> greater than or equal to the width of the promoted left operand, >> the behavior is undefined. >> >> To fix this, we just skip the validity check in case of highest >> page-level (level = 3) due to redundancy >> >> Signed-off-by: Mikhail Zaslonko <zaslonko(a)linux.vnet.ibm.com&gt; >> --- >> s390x.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/s390x.c b/s390x.c >> index e13bd59..96ce3dc 100644 >> --- a/s390x.c >> +++ b/s390x.c >> @@ -688,7 +688,7 @@ int s390x_vtop(ulong table, ulong vaddr, physaddr_t >> *phys_addr, int verbose) >> /* Read the first entry to find the number of page table levels. */ >> readmem(table, KVADDR, &entry, sizeof(entry), "entry", >> FAULT_ON_ERROR); >> level = (entry & 0xcULL) >> 2; >> - if ((vaddr >> (31 + 11*level)) != 0ULL) { >> + if ((level < 3) && (vaddr >> (31 + 11*level)) != 0ULL) { >> /* Address too big for the number of page table levels. */ >> return FALSE; >> } >> -- >> 2.10.2 >> >>