| From foo@baz Fri Aug 8 08:50:32 PDT 2014 |
| From: "David S. Miller" <davem@davemloft.net> |
| Date: Tue, 6 May 2014 21:27:37 -0700 |
| Subject: sparc64: Don't bark so loudly about 32-bit tasks generating 64-bit fault addresses. |
| |
| From: "David S. Miller" <davem@davemloft.net> |
| |
| [ 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> |
| --- |
| arch/sparc/mm/fault_64.c | 16 +--------------- |
| 1 file changed, 1 insertion(+), 15 deletions(-) |
| |
| --- a/arch/sparc/mm/fault_64.c |
| +++ b/arch/sparc/mm/fault_64.c |
| @@ -280,18 +280,6 @@ static void noinline __kprobes bogus_32b |
| 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) |
| { |
| struct mm_struct *mm = current->mm; |
| @@ -320,10 +308,8 @@ asmlinkage void __kprobes do_sparc64_fau |
| 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) { |
