Commit 8ac6f5d7 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Russell King (Oracle)
Browse files

ARM: 9113/1: uaccess: remove set_fs() implementation 



There are no remaining callers of set_fs(), so just remove it
along with all associated code that operates on
thread_info->addr_limit.

There are still further optimizations that can be done:

- In get_user(), the address check could be moved entirely
  into the out of line code, rather than passing a constant
  as an argument,

- I assume the DACR handling can be simplified as we now
  only change it during user access when CONFIG_CPU_SW_DOMAIN_PAN
  is set, but not during set_fs().

Acked-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
parent 2df4c9a7

arch/arm/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -126,7 +126,6 @@ config ARM 
	select PCI_SYSCALL if PCI

	select PERF_USE_VMALLOC

	select RTC_LIB

	select SET_FS

	select SYS_SUPPORTS_APM_EMULATION

	# Above selects are sorted alphabetically; please add new ones

	# according to that.  Thanks.

arch/arm/include/asm/ptrace.h

+0 −1
Original line number Diff line number Diff line
@@ -19,7 +19,6 @@ struct pt_regs { 
struct svc_pt_regs {

	struct pt_regs regs;

	u32 dacr;

	u32 addr_limit;

};



#define to_svc_pt_regs(r) container_of(r, struct svc_pt_regs, regs)

arch/arm/include/asm/thread_info.h

+0 −4
Original line number Diff line number Diff line
@@ -31,8 +31,6 @@ struct task_struct; 


#include <asm/types.h>



typedef unsigned long mm_segment_t;



struct cpu_context_save {

	__u32	r4;

	__u32	r5;
@@ -54,7 +52,6 @@ struct cpu_context_save { 
struct thread_info {

	unsigned long		flags;		/* low level flags */

	int			preempt_count;	/* 0 => preemptable, <0 => bug */

	mm_segment_t		addr_limit;	/* address limit */

	struct task_struct	*task;		/* main task structure */

	__u32			cpu;		/* cpu */

	__u32			cpu_domain;	/* cpu domain */
@@ -80,7 +77,6 @@ struct thread_info { 
	.task		= &tsk,						\

	.flags		= 0,						\

	.preempt_count	= INIT_PREEMPT_COUNT,				\

	.addr_limit	= KERNEL_DS,					\

}



/*

arch/arm/include/asm/uaccess-asm.h

+0 −6
Original line number Diff line number Diff line
@@ -84,12 +84,8 @@ 
	 * if \disable is set.

	 */

	.macro	uaccess_entry, tsk, tmp0, tmp1, tmp2, disable

	ldr	\tmp1, [\tsk, #TI_ADDR_LIMIT]

	ldr	\tmp2, =TASK_SIZE

	str	\tmp2, [\tsk, #TI_ADDR_LIMIT]

 DACR(	mrc	p15, 0, \tmp0, c3, c0, 0)

 DACR(	str	\tmp0, [sp, #SVC_DACR])

	str	\tmp1, [sp, #SVC_ADDR_LIMIT]

	.if \disable && IS_ENABLED(CONFIG_CPU_SW_DOMAIN_PAN)

	/* kernel=client, user=no access */

	mov	\tmp2, #DACR_UACCESS_DISABLE
@@ -106,9 +102,7 @@ 


	/* Restore the user access state previously saved by uaccess_entry */

	.macro	uaccess_exit, tsk, tmp0, tmp1

	ldr	\tmp1, [sp, #SVC_ADDR_LIMIT]

 DACR(	ldr	\tmp0, [sp, #SVC_DACR])

	str	\tmp1, [\tsk, #TI_ADDR_LIMIT]

 DACR(	mcr	p15, 0, \tmp0, c3, c0, 0)

	.endm

arch/arm/include/asm/uaccess.h

+4 −42
Original line number Diff line number Diff line
@@ -52,32 +52,8 @@ static __always_inline void uaccess_restore(unsigned int flags) 
extern int __get_user_bad(void);

extern int __put_user_bad(void);



/*

 * Note that this is actually 0x1,0000,0000

 */

#define KERNEL_DS	0x00000000



#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)

{

	current_thread_info()->addr_limit = fs;



	/*

	 * Prevent a mispredicted conditional call to set_fs from forwarding

	 * the wrong address limit to access_ok under speculation.

	 */

	dsb(nsh);

	isb();



	modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER);

}



#define uaccess_kernel()	(get_fs() == KERNEL_DS)



/*

 * We use 33-bit arithmetic here.  Success returns zero, failure returns

 * addr_limit.  We take advantage that addr_limit will be zero for KERNEL_DS,
@@ -89,7 +65,7 @@ static inline void set_fs(mm_segment_t fs) 
	__asm__(".syntax unified\n" \

		"adds %1, %2, %3; sbcscc %1, %1, %0; movcc %0, #0" \

		: "=&r" (flag), "=&r" (roksum) \

		: "r" (addr), "Ir" (size), "0" (current_thread_info()->addr_limit) \

		: "r" (addr), "Ir" (size), "0" (TASK_SIZE) \

		: "cc"); \

	flag; })
@@ -120,7 +96,7 @@ static inline void __user *__uaccess_mask_range_ptr(const void __user *ptr, 
	"	subshs	%1, %1, %2\n"

	"	movlo	%0, #0\n"

	: "+r" (safe_ptr), "=&r" (tmp)

	: "r" (size), "r" (current_thread_info()->addr_limit)

	: "r" (size), "r" (TASK_SIZE)

	: "cc");



	csdb();
@@ -194,7 +170,7 @@ extern int __get_user_64t_4(void *); 


#define __get_user_check(x, p)						\

	({								\

		unsigned long __limit = current_thread_info()->addr_limit - 1; \

		unsigned long __limit = TASK_SIZE - 1; \

		register typeof(*(p)) __user *__p asm("r0") = (p);	\

		register __inttype(x) __r2 asm("r2");			\

		register unsigned long __l asm("r1") = __limit;		\
@@ -245,7 +221,7 @@ extern int __put_user_8(void *, unsigned long long); 


#define __put_user_check(__pu_val, __ptr, __err, __s)			\

	({								\

		unsigned long __limit = current_thread_info()->addr_limit - 1; \

		unsigned long __limit = TASK_SIZE - 1; \

		register typeof(__pu_val) __r2 asm("r2") = __pu_val;	\

		register const void __user *__p asm("r0") = __ptr;	\

		register unsigned long __l asm("r1") = __limit;		\
@@ -262,19 +238,8 @@ extern int __put_user_8(void *, unsigned long long); 


#else /* CONFIG_MMU */



/*

 * uClinux has only one addr space, so has simplified address limits.

 */

#define USER_DS			KERNEL_DS



#define uaccess_kernel()	(true)

#define __addr_ok(addr)		((void)(addr), 1)

#define __range_ok(addr, size)	((void)(addr), 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_check __put_user_nocheck
@@ -283,9 +248,6 @@ static inline void set_fs(mm_segment_t fs) 


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



#define user_addr_max() \

	(uaccess_kernel() ? ~0UL : get_fs())



#ifdef CONFIG_CPU_SPECTRE

/*

 * When mitigating Spectre variant 1, it is not worth fixing the non-