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()
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
