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[ARM] nommu: uaccess tweaks
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MMUless systems have only one address space for all threads, so
both the usual access_ok() checks, and the exception handling do
not make much sense.

Hence, discard the fixup and exception tables at link time, use
memcpy/memset for the user copy/clearing functions, and define
the permission check macros to be constants.

Some of this patch was derived from the equivalent patch by
Hyok S. Choi.

Signed-off-by: Hyok S. Choi <hyok.choi@samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Russell King authored and Russell King committed Jun 28, 2006
1 parent 002547b commit 9641c7c
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Showing 4 changed files with 108 additions and 59 deletions.
7 changes: 5 additions & 2 deletions arch/arm/kernel/armksyms.c
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Original file line number Diff line number Diff line change
Expand Up @@ -109,11 +109,13 @@ EXPORT_SYMBOL(memchr);
EXPORT_SYMBOL(__memzero);

/* user mem (segment) */
EXPORT_SYMBOL(__strnlen_user);
EXPORT_SYMBOL(__strncpy_from_user);

#ifdef CONFIG_MMU
EXPORT_SYMBOL(__copy_from_user);
EXPORT_SYMBOL(__copy_to_user);
EXPORT_SYMBOL(__clear_user);
EXPORT_SYMBOL(__strnlen_user);
EXPORT_SYMBOL(__strncpy_from_user);

EXPORT_SYMBOL(__get_user_1);
EXPORT_SYMBOL(__get_user_2);
Expand All @@ -123,6 +125,7 @@ EXPORT_SYMBOL(__put_user_1);
EXPORT_SYMBOL(__put_user_2);
EXPORT_SYMBOL(__put_user_4);
EXPORT_SYMBOL(__put_user_8);
#endif

/* crypto hash */
EXPORT_SYMBOL(sha_transform);
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8 changes: 8 additions & 0 deletions arch/arm/kernel/vmlinux.lds.S
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Original file line number Diff line number Diff line change
Expand Up @@ -80,14 +80,20 @@ SECTIONS
*(.exit.text)
*(.exit.data)
*(.exitcall.exit)
#ifndef CONFIG_MMU
*(.fixup)
*(__ex_table)
#endif
}

.text : { /* Real text segment */
_text = .; /* Text and read-only data */
*(.text)
SCHED_TEXT
LOCK_TEXT
#ifdef CONFIG_MMU
*(.fixup)
#endif
*(.gnu.warning)
*(.rodata)
*(.rodata.*)
Expand Down Expand Up @@ -142,7 +148,9 @@ SECTIONS
*/
. = ALIGN(32);
__start___ex_table = .;
#ifdef CONFIG_MMU
*(__ex_table)
#endif
__stop___ex_table = .;

/*
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13 changes: 8 additions & 5 deletions arch/arm/lib/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -6,28 +6,31 @@

lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \
csumpartialcopy.o csumpartialcopyuser.o clearbit.o \
copy_page.o delay.o findbit.o memchr.o memcpy.o \
delay.o findbit.o memchr.o memcpy.o \
memmove.o memset.o memzero.o setbit.o \
strncpy_from_user.o strnlen_user.o \
strchr.o strrchr.o \
testchangebit.o testclearbit.o testsetbit.o \
getuser.o putuser.o clear_user.o \
ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \
ucmpdi2.o lib1funcs.o div64.o sha1.o \
io-readsb.o io-writesb.o io-readsl.o io-writesl.o

mmu-y := clear_user.o copy_page.o getuser.o putuser.o

# the code in uaccess.S is not preemption safe and
# probably faster on ARMv3 only
ifeq ($(CONFIG_PREEMPT),y)
lib-y += copy_from_user.o copy_to_user.o
mmu-y += copy_from_user.o copy_to_user.o
else
ifneq ($(CONFIG_CPU_32v3),y)
lib-y += copy_from_user.o copy_to_user.o
mmu-y += copy_from_user.o copy_to_user.o
else
lib-y += uaccess.o
mmu-y += uaccess.o
endif
endif

lib-$(CONFIG_MMU) += $(mmu-y)

ifeq ($(CONFIG_CPU_32v3),y)
lib-y += io-readsw-armv3.o io-writesw-armv3.o
else
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139 changes: 87 additions & 52 deletions include/asm-arm/uaccess.h
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Original file line number Diff line number Diff line change
Expand Up @@ -40,16 +40,25 @@ struct exception_table_entry

extern int fixup_exception(struct pt_regs *regs);

/*
* These two are intentionally not defined anywhere - if the kernel
* code generates any references to them, that's a bug.
*/
extern int __get_user_bad(void);
extern int __put_user_bad(void);

/*
* Note that this is actually 0x1,0000,0000
*/
#define KERNEL_DS 0x00000000
#define USER_DS TASK_SIZE

#define get_ds() (KERNEL_DS)

#ifdef CONFIG_MMU

#define USER_DS TASK_SIZE
#define get_fs() (current_thread_info()->addr_limit)

static inline void set_fs (mm_segment_t fs)
static inline void set_fs(mm_segment_t fs)
{
current_thread_info()->addr_limit = fs;
modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER);
Expand All @@ -75,8 +84,6 @@ static inline void set_fs (mm_segment_t fs)
: "cc"); \
flag; })

#define access_ok(type,addr,size) (__range_ok(addr,size) == 0)

/*
* Single-value transfer routines. They automatically use the right
* size if we just have the right pointer type. Note that the functions
Expand All @@ -87,20 +94,10 @@ static inline void set_fs (mm_segment_t fs)
* fixup code, but there are a few places where it intrudes on the
* main code path. When we only write to user space, there is no
* problem.
*
* The "__xxx" versions of the user access functions do not verify the
* address space - it must have been done previously with a separate
* "access_ok()" call.
*
* The "xxx_error" versions set the third argument to EFAULT if an
* error occurs, and leave it unchanged on success. Note that these
* versions are void (ie, don't return a value as such).
*/

extern int __get_user_1(void *);
extern int __get_user_2(void *);
extern int __get_user_4(void *);
extern int __get_user_bad(void);

#define __get_user_x(__r2,__p,__e,__s,__i...) \
__asm__ __volatile__ ( \
Expand Down Expand Up @@ -131,6 +128,74 @@ extern int __get_user_bad(void);
__e; \
})

extern int __put_user_1(void *, unsigned int);
extern int __put_user_2(void *, unsigned int);
extern int __put_user_4(void *, unsigned int);
extern int __put_user_8(void *, unsigned long long);

#define __put_user_x(__r2,__p,__e,__s) \
__asm__ __volatile__ ( \
__asmeq("%0", "r0") __asmeq("%2", "r2") \
"bl __put_user_" #__s \
: "=&r" (__e) \
: "0" (__p), "r" (__r2) \
: "ip", "lr", "cc")

#define put_user(x,p) \
({ \
const register typeof(*(p)) __r2 asm("r2") = (x); \
const register typeof(*(p)) __user *__p asm("r0") = (p);\
register int __e asm("r0"); \
switch (sizeof(*(__p))) { \
case 1: \
__put_user_x(__r2, __p, __e, 1); \
break; \
case 2: \
__put_user_x(__r2, __p, __e, 2); \
break; \
case 4: \
__put_user_x(__r2, __p, __e, 4); \
break; \
case 8: \
__put_user_x(__r2, __p, __e, 8); \
break; \
default: __e = __put_user_bad(); break; \
} \
__e; \
})

#else /* CONFIG_MMU */

/*
* uClinux has only one addr space, so has simplified address limits.
*/
#define USER_DS KERNEL_DS

#define segment_eq(a,b) (1)
#define __addr_ok(addr) (1)
#define __range_ok(addr,size) (0)
#define get_fs() (KERNEL_DS)

static inline void set_fs(mm_segment_t fs)
{
}

#define get_user(x,p) __get_user(x,p)
#define put_user(x,p) __put_user(x,p)

#endif /* CONFIG_MMU */

#define access_ok(type,addr,size) (__range_ok(addr,size) == 0)

/*
* The "__xxx" versions of the user access functions do not verify the
* address space - it must have been done previously with a separate
* "access_ok()" call.
*
* The "xxx_error" versions set the third argument to EFAULT if an
* error occurs, and leave it unchanged on success. Note that these
* versions are void (ie, don't return a value as such).
*/
#define __get_user(x,ptr) \
({ \
long __gu_err = 0; \
Expand Down Expand Up @@ -212,43 +277,6 @@ do { \
: "r" (addr), "i" (-EFAULT) \
: "cc")

extern int __put_user_1(void *, unsigned int);
extern int __put_user_2(void *, unsigned int);
extern int __put_user_4(void *, unsigned int);
extern int __put_user_8(void *, unsigned long long);
extern int __put_user_bad(void);

#define __put_user_x(__r2,__p,__e,__s) \
__asm__ __volatile__ ( \
__asmeq("%0", "r0") __asmeq("%2", "r2") \
"bl __put_user_" #__s \
: "=&r" (__e) \
: "0" (__p), "r" (__r2) \
: "ip", "lr", "cc")

#define put_user(x,p) \
({ \
const register typeof(*(p)) __r2 asm("r2") = (x); \
const register typeof(*(p)) __user *__p asm("r0") = (p);\
register int __e asm("r0"); \
switch (sizeof(*(__p))) { \
case 1: \
__put_user_x(__r2, __p, __e, 1); \
break; \
case 2: \
__put_user_x(__r2, __p, __e, 2); \
break; \
case 4: \
__put_user_x(__r2, __p, __e, 4); \
break; \
case 8: \
__put_user_x(__r2, __p, __e, 8); \
break; \
default: __e = __put_user_bad(); break; \
} \
__e; \
})

#define __put_user(x,ptr) \
({ \
long __pu_err = 0; \
Expand Down Expand Up @@ -354,9 +382,16 @@ do { \
: "cc")


#ifdef CONFIG_MMU
extern unsigned long __copy_from_user(void *to, const void __user *from, unsigned long n);
extern unsigned long __copy_to_user(void __user *to, const void *from, unsigned long n);
extern unsigned long __clear_user(void __user *addr, unsigned long n);
#else
#define __copy_from_user(to,from,n) (memcpy(to, (void __force *)from, n), 0)
#define __copy_to_user(to,from,n) (memcpy((void __force *)to, from, n), 0)
#define __clear_user(addr,n) (memset((void __force *)addr, 0, n), 0)
#endif

extern unsigned long __strncpy_from_user(char *to, const char __user *from, unsigned long count);
extern unsigned long __strnlen_user(const char __user *s, long n);

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