Christophe Leroy <christophe.le...@c-s.fr> writes:
> Only the get_user() in store_updates_sp() has to be done outside
> the mm semaphore. All the comparison can be done within the semaphore,
> so only when really needed.
>
> As we got a DSI exception, the address pointed by regs->nip is
> obviously valid, otherwise we would have had a instruction exception.
> So __get_user() can be used instead of get_user()
>
Reviewed-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
> Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
> ---
> arch/powerpc/mm/fault.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 67fefb59d40e..9d21e5fd383d 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -73,12 +73,8 @@ static inline int notify_page_fault(struct pt_regs *regs)
> * Check whether the instruction at regs->nip is a store using
> * an update addressing form which will update r1.
> */
> -static int store_updates_sp(struct pt_regs *regs)
> +static int store_updates_sp(unsigned int inst)
> {
> - unsigned int inst;
> -
> - if (get_user(inst, (unsigned int __user *)regs->nip))
> - return 0;
> /* check for 1 in the rA field */
> if (((inst >> 16) & 0x1f) != 1)
> return 0;
> @@ -207,7 +203,8 @@ int do_page_fault(struct pt_regs *regs, unsigned long
> address,
> int trap = TRAP(regs);
> int is_exec = trap == 0x400;
> int fault;
> - int rc = 0, store_update_sp = 0;
> + int rc = 0;
> + unsigned int inst = 0;
>
> #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
> /*
> @@ -288,7 +285,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long
> address,
> * mmap_sem held
> */
> if (is_write && user_mode(regs))
> - store_update_sp = store_updates_sp(regs);
> + __get_user(inst, (unsigned int __user *)regs->nip);
>
> if (user_mode(regs))
> flags |= FAULT_FLAG_USER;
> @@ -358,7 +355,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long
> address,
> * between the last mapped region and the stack will
> * expand the stack rather than segfaulting.
> */
> - if (address + 2048 < uregs->gpr[1] && !store_update_sp)
> + if (address + 2048 < uregs->gpr[1] && !store_updates_sp(inst))
> goto bad_area;
> }
> if (expand_stack(vma, address))
> --
> 2.12.0
