mm/memory: Use exception ip to search exception tables

On architectures with delay slot, instruction_pointer() may differ
from where exception was triggered.

Use exception_ip we just introduced to search exception tables to
get rid of the problem.

Fixes: 4bce37a ("mips/mm: Convert to using lock_mm_and_find_vma()")
Reported-by: Xi Ruoyao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]/
Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Jiaxun Yang <[email protected]>
Signed-off-by: Thomas Bogendoerfer <[email protected]>

Author: FlyGoat

mm/memory.c

@@ -5478,7 +5478,7 @@ static inline bool get_mmap_lock_carefully(struct mm_struct *mm, struct pt_regs
 		return true;
 
 	if (regs && !user_mode(regs)) {
-		unsigned long ip = instruction_pointer(regs);
+		unsigned long ip = exception_ip(regs);
 		if (!search_exception_tables(ip))
 			return false;
 	}
@@ -5503,7 +5503,7 @@ static inline bool upgrade_mmap_lock_carefully(struct mm_struct *mm, struct pt_r
 {
 	mmap_read_unlock(mm);
 	if (regs && !user_mode(regs)) {
-		unsigned long ip = instruction_pointer(regs);
+		unsigned long ip = exception_ip(regs);
 		if (!search_exception_tables(ip))
 			return false;
 	}