sparc64: Don't bark so loudly about 32-bit tasks generating 64-bit fault addresses.

[ Upstream commit e5c460f46ae7ee94831cb55cb980f942aa9e5a85 ]

This was found using Dave Jone's trinity tool.

When a user process which is 32-bit performs a load or a store, the
cpu chops off the top 32-bits of the effective address before
translating it.

This is because we run 32-bit tasks with the PSTATE_AM (address
masking) bit set.

We can't run the kernel with that bit set, so when the kernel accesses
userspace no address masking occurs.

Since a 32-bit process will have no mappings in that region we will
properly fault, so we don't try to handle this using access_ok(),
which can safely just be a NOP on sparc64.

Real faults from 32-bit processes should never generate such addresses
so a bug check was added long ago, and it barks in the logs if this
happens.

But it also barks when a kernel user access causes this condition, and
that _can_ happen.  For example, if a pointer passed into a system call
is "0xfffffffc" and the kernel access 4 bytes offset from that pointer.

Just handle such faults normally via the exception entries.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c
index a8ff0d1..4ced3fc 100644 (file)
--- a/arch/sparc/mm/fault_64.c
+++ b/arch/sparc/mm/fault_64.c
@@ -281,18 +281,6 @@ static void noinline __kprobes bogus_32bit_fault_tpc(struct pt_regs *regs)
        show_regs(regs);
 }
 
-static void noinline __kprobes bogus_32bit_fault_address(struct pt_regs *regs,
-                                                        unsigned long addr)
-{
-       static int times;
-
-       if (times++ < 10)
-               printk(KERN_ERR "FAULT[%s:%d]: 32-bit process "
-                      "reports 64-bit fault address [%lx]\n",
-                      current->comm, current->pid, addr);
-       show_regs(regs);
-}
-
 asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
 {
        enum ctx_state prev_state = exception_enter();
@@ -322,10 +310,8 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
                                goto intr_or_no_mm;
                        }
                }
-               if (unlikely((address >> 32) != 0)) {
-                       bogus_32bit_fault_address(regs, address);
+               if (unlikely((address >> 32) != 0))
                        goto intr_or_no_mm;
-               }
        }
 
        if (regs->tstate & TSTATE_PRIV) {