Re: [Crash-utility] Fwd: s390x fixes

Hi Dave, On Wed, 02 May 2012 09:21:57 -0400 (EDT) Dave Anderson <anderson(a)redhat.com&gt; wrote: > > ----- Original Message ----- > > > > > > > And that's because when a "machdep->uvtop()" operation is done on > > > a user page that is not resident, the machine-dependent function > > > should return FALSE -- but it should return the PTE value in the > > > paddr pointer field so that it can be translated by > > > vm_area_page_dump(). The s390x_uvtop() does not return the PTE, > > > so the failed output can vary, because it's using an > > > uninitialized "paddr" stack variable. But this is another easy > > > fix, in this case to s390x_vtop(): > > > > > > /* lookup virtual address in page tables */ > > > int s390x_vtop(ulong table, ulong vaddr, physaddr_t *phys_addr, > > > int verbose) { > > > ulong entry, paddr; > > > int level, len; > > > > > > + *phys_addr = 0; > > > > > > Looks also good. But probably I should implement a better fix that > > returns the pte for s390x swap entries. > > That's true -- so since you've got the __swp_type() and __swp_offset() > macros #define'd for s390x, presumably it should work if you just pass > it back as is? Even though you've got the common s390x_vtop() > function used by both s390x_kvtop() and s390x_uvtop(), I think it > would be safe to pass the PTE entry back in either case, because > kvtop() operations don't care about the paddr contents if you return > FALSE. The following patch implements swap entry support for s390x and fixes your issues (2) and (3). Michael --- s390x.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) --- a/s390x.c +++ b/s390x.c @@ -574,6 +574,19 @@ static ulong _kl_rsg_table_deref_s390x(u return entry; } +/* Check for swap entry */ +static int swap_entry(ulong entry) +{ + if (THIS_KERNEL_VERSION < LINUX(2,6,19)) { + if ((entry & 0x601ULL) == 0x600ULL) + return 1; + } else { + if ((entry & 0x403ULL) == 0x403ULL) + return 1; + } + return 0; +} + /* Page table traversal function */ static ulong _kl_pg_table_deref_s390x(ulong vaddr, ulong table) { @@ -583,13 +596,11 @@ static ulong _kl_pg_table_deref_s390x(ul readmem(table + offset, KVADDR, &entry, sizeof(entry), "entry", FAULT_ON_ERROR); /* - * Check if the page table entry could be read and doesn't have - * any of the reserved bits set. + * Return zero if the page table entry has any of the reserved bits + * set (0x900) or the invalid bit (0x400) is set and it is not a + * swap entry. */ - if (entry & 0x900ULL) - return 0; - /* Check if the page table entry has the invalid bit set. */ - if (entry & 0x400ULL) + if ((entry & 0xd00ULL) && !swap_entry(entry)) return 0; /* Page table entry is valid and well formed. */ return entry; @@ -601,6 +612,7 @@ int s390x_vtop(ulong table, ulong vaddr, ulong entry, paddr; int level, len; + *phys_addr = 0; /* * Walk the region and segment tables. * We assume that the table length field in the asce is set to the @@ -619,7 +631,7 @@ int s390x_vtop(ulong table, ulong vaddr, while (level >= 0) { entry = _kl_rsg_table_deref_s390x(vaddr, table, len, level); if (!entry) - return 0; + return FALSE; table = entry & ~0xfffULL; len = entry & 0x3ULL; level--; @@ -637,6 +649,12 @@ int s390x_vtop(ulong table, ulong vaddr, if (!entry) return FALSE; + /* For swap entries we have to return FALSE and phys_addr = PTE */ + if (swap_entry(entry)) { + *phys_addr = entry; + return FALSE; + } + /* Isolate the page origin from the page table entry. */ paddr = entry & ~0xfffULL;