[PATCH 5/6] [v2] asm-generic: uaccess: remove inline strncpy_from_user/strnlen_user

Arnd Bergmann
2021-05-15T10:20:05Z

Consolidate the asm-generic implementation with the library version
that is used everywhere else.

These are the three versions for NOMMU kernels, which can in principle
fall back to strncpy()/strnlen() as the version in asm-generic does,
but this version is particularly inefficient when it scans the string
one byte at a time twice. The generic version also lacks a check
for user_addr_max(), but this is probably ok on NOMMU targets.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/h8300/Kconfig | 2 ++
arch/m68k/Kconfig | 4 +--
arch/riscv/Kconfig | 4 +--
include/asm-generic/uaccess.h | 46 ++++++-----------------------------
4 files changed, 14 insertions(+), 42 deletions(-)

diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
index 3e3e0f16f7e0..53dfd2d47e0e 100644
--- a/arch/h8300/Kconfig
+++ b/arch/h8300/Kconfig
@@ -11,6 +11,8 @@ config H8300
select GENERIC_IRQ_SHOW
select FRAME_POINTER
select GENERIC_CPU_DEVICES
+ select GENERIC_STRNCPY_FROM_USER
+ select GENERIC_STRNLEN_USER
select MODULES_USE_ELF_RELA
select COMMON_CLK
select ARCH_WANT_FRAME_POINTERS
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index ed6b8050e3ed..5f1aafa7b2e2 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -17,8 +17,8 @@ config M68K
select GENERIC_CPU_DEVICES
select GENERIC_IOMAP
select GENERIC_IRQ_SHOW
- select GENERIC_STRNCPY_FROM_USER if MMU
- select GENERIC_STRNLEN_USER if MMU
+ select GENERIC_STRNCPY_FROM_USER
+ select GENERIC_STRNLEN_USER
select HAVE_AOUT if MMU
select HAVE_ASM_MODVERSIONS
select HAVE_DEBUG_BUGVERBOSE
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a8ad8eb76120..ada7a2918c05 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -55,8 +55,8 @@ config RISCV
select GENERIC_PTDUMP if MMU
select GENERIC_SCHED_CLOCK
select GENERIC_SMP_IDLE_THREAD
- select GENERIC_STRNCPY_FROM_USER if MMU
- select GENERIC_STRNLEN_USER if MMU
+ select GENERIC_STRNCPY_FROM_USER
+ select GENERIC_STRNLEN_USER
select GENERIC_TIME_VSYSCALL if MMU && 64BIT
select HANDLE_DOMAIN_IRQ
select HAVE_ARCH_AUDITSYSCALL
diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index c03889cc904c..83a48f430951 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -119,6 +119,11 @@ static inline void set_fs(mm_segment_t fs)
#ifndef uaccess_kernel
#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
#endif
+
+#ifndef user_addr_max
+#define user_addr_max() (uaccess_kernel() ? ~0UL : TASK_SIZE)
+#endif
+
#endif /* CONFIG_SET_FS */

#define access_ok(addr, size) __access_ok((unsigned long)(addr),(size))
@@ -243,44 +248,6 @@ static inline int __get_user_fn(size_t size, const void __user *ptr, void *x)

extern int __get_user_bad(void) __attribute__((noreturn));

-/*
- * Copy a null terminated string from userspace.
- */
-#ifndef strncpy_from_user
-static inline long
-strncpy_from_user(char *dst, const char __user *src, long count)
-{
- char *tmp;
-
- if (!access_ok(src, 1))
- return -EFAULT;
-
- strncpy(dst, (const char __force *)src, count);
- for (tmp = dst; *tmp && count > 0; tmp++, count--)
- ;
- return (tmp - dst);
-}
-#endif
-
-#ifndef strnlen_user
-/*
- * Return the size of a string (including the ending 0)
- *
- * Return 0 on exception, a value greater than N if too long
- *
- * Unlike strnlen, strnlen_user includes the nul terminator in
- * its returned count. Callers should check for a returned value
- * greater than N as an indication the string is too long.
- */
-static inline long strnlen_user(const char __user *src, long n)
-{
- if (!access_ok(src, 1))
- return 0;
-
- return strnlen(src, n) + 1;
-}
-#endif
-
/*
* Zero Userspace
*/
@@ -305,4 +272,7 @@ clear_user(void __user *to, unsigned long n)

#include <asm/extable.h>

+extern long strncpy_from_user(char *dst, const char __user *src, long count);
+extern long strnlen_user(const char __user *src, long n);
+
#endif /* __ASM_GENERIC_UACCESS_H */
--
2.29.2