powerpc/perf: Consolidate perf_callchain_user_[64|32]()

perf_callchain_user_64() and perf_callchain_user_32() are nearly
identical. Consolidate into one function with thin wrappers.
Suggested-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
[mpe: Adapt to copy_from_user_nofault(), minor formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200406210022.32265-1-msuchanek@suse.de

arch/powerpc/perf/callchain.h

@@ -2,7 +2,7 @@
 #ifndef _POWERPC_PERF_CALLCHAIN_H
 #define _POWERPC_PERF_CALLCHAIN_H
 
-int read_user_stack_slow(void __user *ptr, void *buf, int nb);
+int read_user_stack_slow(const void __user *ptr, void *buf, int nb);
 void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 			    struct pt_regs *regs);
 void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
@@ -16,4 +16,27 @@ static inline bool invalid_user_sp(unsigned long sp)
 	return (!sp || (sp & mask) || (sp > top));
 }
 
+/*
+ * On 32-bit we just access the address and let hash_page create a
+ * HPTE if necessary, so there is no need to fall back to reading
+ * the page tables.  Since this is called at interrupt level,
+ * do_page_fault() won't treat a DSI as a page fault.
+ */
+static inline int __read_user_stack(const void __user *ptr, void *ret,
+				    size_t size)
+{
+	unsigned long addr = (unsigned long)ptr;
+	int rc;
+
+	if (addr > TASK_SIZE - size || (addr & (size - 1)))
+		return -EFAULT;
+
+	rc = copy_from_user_nofault(ret, ptr, size);
+
+	if (IS_ENABLED(CONFIG_PPC64) && rc)
+		return read_user_stack_slow(ptr, ret, size);
+
+	return rc;
+}
+
 #endif /* _POWERPC_PERF_CALLCHAIN_H */

arch/powerpc/perf/callchain_32.c

@@ -30,26 +30,9 @@
 
 #endif /* CONFIG_PPC64 */
 
-/*
- * On 32-bit we just access the address and let hash_page create a
- * HPTE if necessary, so there is no need to fall back to reading
- * the page tables.  Since this is called at interrupt level,
- * do_page_fault() won't treat a DSI as a page fault.
- */
-static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
+static int read_user_stack_32(const unsigned int __user *ptr, unsigned int *ret)
 {
-	int rc;
-
-	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
-	    ((unsigned long)ptr & 3))
-		return -EFAULT;
-
-	rc = copy_from_user_nofault(ret, ptr, sizeof(*ret));
-
-	if (IS_ENABLED(CONFIG_PPC64) && rc)
-		return read_user_stack_slow(ptr, ret, 4);
-
-	return rc;
+	return __read_user_stack(ptr, ret, sizeof(*ret));
 }
 
 /*

arch/powerpc/perf/callchain_64.c

@@ -23,7 +23,7 @@
  * interrupt context, so if the access faults, we read the page tables
  * to find which page (if any) is mapped and access it directly.
  */
-int read_user_stack_slow(void __user *ptr, void *buf, int nb)
+int read_user_stack_slow(const void __user *ptr, void *buf, int nb)
 {
 
 	unsigned long addr = (unsigned long) ptr;
@@ -44,16 +44,9 @@ int read_user_stack_slow(void __user *ptr, void *buf, int nb)
 	return -EFAULT;
 }
 
-static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
+static int read_user_stack_64(const unsigned long __user *ptr, unsigned long *ret)
 {
-	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
-	    ((unsigned long)ptr & 7))
-		return -EFAULT;
-
-	if (!copy_from_user_nofault(ret, ptr, sizeof(*ret)))
-		return 0;
-
-	return read_user_stack_slow(ptr, ret, 8);
+	return __read_user_stack(ptr, ret, sizeof(*ret));
 }
 
 /*