[Crash-utility] Fwd: s390x fixes

[Michael Holzheu]

Hi Dave,

On Wed, 02 May 2012 09:21:57 -0400 (EDT)
Dave Anderson <anderson at redhat.com> 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;
 

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