2022-04-08 12:08:58

by Peter Zijlstra

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

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 <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
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;

2022-04-08 21:18:33

by Josh Poimboeuf

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

On Fri, Apr 08, 2022 at 11:45:53AM +0200, Peter Zijlstra wrote:
> 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 <[email protected]>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>

Presumably because of

ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += -fno-inline-functions-called-once
endif

which I've been wanting to remove since its only true purpose seems to
be creating countless __always_inline patches...

--
Josh

2022-04-22 19:09:42

by tip-bot2 for Jacob Pan

Subject: [tip: x86/urgent] lib/strn*,objtool: Enforce user_access_begin() rules

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: 226d44acf6dfe71c9df5804b82364e93cf908b53
Gitweb: https://git.kernel.org/tip/226d44acf6dfe71c9df5804b82364e93cf908b53
Author: Peter Zijlstra <[email protected]>
AuthorDate: Fri, 08 Apr 2022 11:45:53 +02:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Tue, 19 Apr 2022 21:58:47 +02:00

lib/strn*,objtool: Enforce user_access_begin() rules

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 <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
lib/strncpy_from_user.c | 2 +-
lib/strnlen_user.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 08fc72d..6432b8c 100644
--- 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;
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
index bffa0eb..feeb935 100644
--- 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;