xtensa: clean up access to spilled registers locations

Define macros SPILL_SLOT* that return a reference to the stack location
of the spill slot for specific register and use them instead of opencoded
address calculations.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 8 insertions, 27 deletions

diff --git a/arch/xtensa/kernel/stacktrace.c b/arch/xtensa/kernel/stacktrace.c
index e7d30ee0fd48..0df4080fa20f 100644
--- a/arch/xtensa/kernel/stacktrace.c
+++ b/arch/xtensa/kernel/stacktrace.c
@@ -23,14 +23,6 @@
  */
 extern int common_exception_return;
 
-/* A struct that maps to the part of the frame containing the a0 and
- * a1 registers.
- */
-struct frame_start {
-        unsigned long a0;
-        unsigned long a1;
-};
-
 void xtensa_backtrace_user(struct pt_regs *regs, unsigned int depth,
                            int (*ufn)(struct stackframe *frame, void *data),
                            void *data)
@@ -96,26 +88,16 @@ void xtensa_backtrace_user(struct pt_regs *regs, unsigned int depth,
         /* Start from the a1 register. */
         /* a1 = regs->areg[1]; */
         while (a0 != 0 && depth--) {
-                struct frame_start frame_start;
-                /* Get the location for a1, a0 for the
-                 * previous frame from the current a1.
-                 */
-                unsigned long *psp = (unsigned long *)a1;
-
-                psp -= 4;
+                pc = MAKE_PC_FROM_RA(a0, pc);
 
                 /* Check if the region is OK to access. */
-                if (!access_ok(VERIFY_READ, psp, sizeof(frame_start)))
+                if (!access_ok(VERIFY_READ, &SPILL_SLOT(a1, 0), 8))
                         return;
                 /* Copy a1, a0 from user space stack frame. */
-                if (__copy_from_user_inatomic(&frame_start, psp,
-                                              sizeof(frame_start)))
+                if (__get_user(a0, &SPILL_SLOT(a1, 0)) ||
+                    __get_user(a1, &SPILL_SLOT(a1, 1)))
                         return;
 
-                pc = MAKE_PC_FROM_RA(a0, pc);
-                a0 = frame_start.a0;
-                a1 = frame_start.a1;
-
                 frame.pc = pc;
                 frame.sp = a1;
 
@@ -147,7 +129,6 @@ void xtensa_backtrace_kernel(struct pt_regs *regs, unsigned int depth,
          */
         while (a1 > sp_start && a1 < sp_end && depth--) {
                 struct stackframe frame;
-                unsigned long *psp = (unsigned long *)a1;
 
                 frame.pc = pc;
                 frame.sp = a1;
@@ -171,8 +152,8 @@ void xtensa_backtrace_kernel(struct pt_regs *regs, unsigned int depth,
                 sp_start = a1;
 
                 pc = MAKE_PC_FROM_RA(a0, pc);
-                a0 = *(psp - 4);
-                a1 = *(psp - 3);
+                a0 = SPILL_SLOT(a1, 0);
+                a1 = SPILL_SLOT(a1, 1);
         }
 }
 EXPORT_SYMBOL(xtensa_backtrace_kernel);
@@ -196,8 +177,8 @@ void walk_stackframe(unsigned long *sp,
 
                 sp = (unsigned long *)a1;
 
-                a0 = *(sp - 4);
-                a1 = *(sp - 3);
+                a0 = SPILL_SLOT(a1, 0);
+                a1 = SPILL_SLOT(a1, 1);
 
                 if (a1 <= (unsigned long)sp)
                         break;