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

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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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Arnd Bergmann
2021-08-11 08:30:26 +01:00
committed by Russell King (Oracle)
parent 2df4c9a741
commit 8ac6f5d7f8
11 changed files with 7 additions and 86 deletions
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46
arch/arm/include/asm/uaccess.h
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@@ -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-