[PATCH 1/4] lib/strn*,objtool: Enforce user_access_begin() rules

From: Peter Zijlstra
Date: Fri Apr 08 2022 - 05:48:17 EST


Apparently GCC can fail to inline a 'static inline' single caller
function:

lib/strnlen_user.o: warning: objtool: strnlen_user()+0x33: call to do_strnlen_user() with UACCESS enabled
lib/strncpy_from_user.o: warning: objtool: strncpy_from_user()+0x33: call to do_strncpy_from_user() with UACCESS enabled

Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
lib/strncpy_from_user.c | 2 +-
lib/strnlen_user.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -25,7 +25,7 @@
* hit it), 'max' is the address space maximum (and we return
* -EFAULT if we hit it).
*/
-static inline long do_strncpy_from_user(char *dst, const char __user *src,
+static __always_inline long do_strncpy_from_user(char *dst, const char __user *src,
unsigned long count, unsigned long max)
{
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
--- a/lib/strnlen_user.c
+++ b/lib/strnlen_user.c
@@ -20,7 +20,7 @@
* if it fits in a aligned 'long'. The caller needs to check
* the return value against "> max".
*/
-static inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
+static __always_inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
{
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
unsigned long align, res = 0;