[PATCH v7 1/3] powerpc/mm: Move get_user() out of store_updates_sp()

[Christophe Leroy]

In preparation of the following patch which will focus on calling
that get_user() only when necessary, this patch takes out of
store_updates_sp() the call to get_user() used to read the faulting
instruction.

Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
 v7: New

 arch/powerpc/mm/fault.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index c01d627e687a..fcbb34431da2 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -66,15 +66,11 @@ static inline bool notify_page_fault(struct pt_regs *regs)
 }
 
 /*
- * Check whether the instruction at regs->nip is a store using
+ * Check whether the instruction inst is a store using
  * an update addressing form which will update r1.
  */
-static bool store_updates_sp(struct pt_regs *regs)
+static bool store_updates_sp(unsigned int inst)
 {
-       unsigned int inst;
-
-       if (get_user(inst, (unsigned int __user *)regs->nip))
-               return false;
        /* check for 1 in the rA field */
        if (((inst >> 16) & 0x1f) != 1)
                return false;
@@ -235,7 +231,7 @@ static bool bad_kernel_fault(bool is_exec, unsigned long 
error_code,
 
 static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address,
                                struct vm_area_struct *vma,
-                               bool store_update_sp)
+                               unsigned int inst)
 {
        /*
         * N.B. The POWER/Open ABI allows programs to access up to
@@ -264,7 +260,7 @@ static bool bad_stack_expansion(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))
                        return true;
        }
        return false;
@@ -403,7 +399,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned 
long address,
        int is_user = user_mode(regs);
        int is_write = page_fault_is_write(error_code);
        int fault, major = 0;
-       bool store_update_sp = false;
+       unsigned int inst = 0;
 
        if (notify_page_fault(regs))
                return 0;
@@ -455,7 +451,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned 
long address,
         * mmap_sem held
         */
        if (is_write && is_user)
-               store_update_sp = store_updates_sp(regs);
+               get_user(inst, (unsigned int __user *)regs->nip);
 
        if (is_user)
                flags |= FAULT_FLAG_USER;
@@ -503,7 +499,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned 
long address,
                return bad_area(regs, address);
 
        /* The stack is being expanded, check if it's valid */
-       if (unlikely(bad_stack_expansion(regs, address, vma, store_update_sp)))
+       if (unlikely(bad_stack_expansion(regs, address, vma, inst)))
                return bad_area(regs, address);
 
        /* Try to expand it */
-- 
2.13.3