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linux/arch/powerpc/include/asm/uaccess.h
Michael Ellerman 50934945d5 powerpc/uaccess: Use YZ asm constraint for ld 
The 'ld' instruction requires a 4-byte aligned displacement because it
is a DS-form instruction. But the "m" asm constraint doesn't enforce
that.

Add a special case of __get_user_asm2_goto() so that the "YZ" constraint
can be used for "ld".

The "Z" constraint is documented in the GCC manual PowerPC machine
constraints, and specifies a "memory operand accessed with indexed or
indirect addressing". "Y" is not documented in the manual but specifies
a "memory operand for a DS-form instruction". Using both allows the
compiler to generate a DS-form "ld" or X-form "ldx" as appropriate.

The change has to be conditional on CONFIG_PPC_KERNEL_PREFIXED because
the "Y" constraint does not guarantee 4-byte alignment when prefixed
instructions are enabled.

No build errors have been reported due to this, but the possibility is
there depending on compiler code generation decisions.

Fixes: c20beffeec ("powerpc/uaccess: Use flexible addressing with __put_user()/__get_user()")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240529123029.146953-2-mpe@ellerman.id.au
2024-05-30 22:57:27 +10:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ARCH_POWERPC_UACCESS_H
#define _ARCH_POWERPC_UACCESS_H
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/extable.h>
#include <asm/kup.h>
#ifdef __powerpc64__
/* We use TASK_SIZE_USER64 as TASK_SIZE is not constant */
#define TASK_SIZE_MAX TASK_SIZE_USER64
#endif
#include <asm-generic/access_ok.h>
/*
* These are the main single-value transfer routines. They automatically
* use the right size if we just have the right pointer type.
*
* This gets kind of ugly. We want to return _two_ values in "get_user()"
* and yet we don't want to do any pointers, because that is too much
* of a performance impact. Thus we have a few rather ugly macros here,
* and hide all the ugliness from the user.
*
* The "__xxx" versions of the user access functions are versions that
* do not verify the address space, that must have been done previously
* with a separate "access_ok()" call (this is used when we do multiple
* accesses to the same area of user memory).
*
* As we use the same address space for kernel and user data on the
* PowerPC, we can just do these as direct assignments. (Of course, the
* exception handling means that it's no longer "just"...)
*
*/
#define __put_user(x, ptr) \
({ \
long __pu_err; \
__typeof__(*(ptr)) __user *__pu_addr = (ptr); \
__typeof__(*(ptr)) __pu_val = (__typeof__(*(ptr)))(x); \
__typeof__(sizeof(*(ptr))) __pu_size = sizeof(*(ptr)); \
\
might_fault(); \
do { \
__label__ __pu_failed; \
\
allow_write_to_user(__pu_addr, __pu_size); \
__put_user_size_goto(__pu_val, __pu_addr, __pu_size, __pu_failed); \
prevent_write_to_user(__pu_addr, __pu_size); \
__pu_err = 0; \
break; \
\
__pu_failed: \
prevent_write_to_user(__pu_addr, __pu_size); \
__pu_err = -EFAULT; \
} while (0); \
\
__pu_err; \
})
#define put_user(x, ptr) \
({ \
__typeof__(*(ptr)) __user *_pu_addr = (ptr); \
\
access_ok(_pu_addr, sizeof(*(ptr))) ? \
__put_user(x, _pu_addr) : -EFAULT; \
})
/*
* We don't tell gcc that we are accessing memory, but this is OK
* because we do not write to any memory gcc knows about, so there
* are no aliasing issues.
*/
/* -mprefixed can generate offsets beyond range, fall back hack */
#ifdef CONFIG_PPC_KERNEL_PREFIXED
#define __put_user_asm_goto(x, addr, label, op) \
asm goto( \
"1: " op " %0,0(%1) # put_user\n" \
EX_TABLE(1b, %l2) \
: \
: "r" (x), "b" (addr) \
: \
: label)
#else
#define __put_user_asm_goto(x, addr, label, op) \
asm goto( \
"1: " op "%U1%X1 %0,%1 # put_user\n" \
EX_TABLE(1b, %l2) \
: \
: "r" (x), "m<>" (*addr) \
: \
: label)
#endif
#ifdef CONFIG_CC_IS_CLANG
#define DS_FORM_CONSTRAINT "Z<>"
#else
#define DS_FORM_CONSTRAINT "YZ<>"
#endif
#ifdef __powerpc64__
#ifdef CONFIG_PPC_KERNEL_PREFIXED
#define __put_user_asm2_goto(x, ptr, label) \
__put_user_asm_goto(x, ptr, label, "std")
#else
#define __put_user_asm2_goto(x, addr, label) \
asm goto ("1: std%U1%X1 %0,%1 # put_user\n" \
EX_TABLE(1b, %l2) \
: \
: "r" (x), DS_FORM_CONSTRAINT (*addr) \
: \
: label)
#endif // CONFIG_PPC_KERNEL_PREFIXED
#else /* __powerpc64__ */
#define __put_user_asm2_goto(x, addr, label) \
asm goto( \
"1: stw%X1 %0, %1\n" \
"2: stw%X1 %L0, %L1\n" \
EX_TABLE(1b, %l2) \
EX_TABLE(2b, %l2) \
: \
: "r" (x), "m" (*addr) \
: \
: label)
#endif /* __powerpc64__ */
#define __put_user_size_goto(x, ptr, size, label) \
do { \
__typeof__(*(ptr)) __user *__pus_addr = (ptr); \
\
switch (size) { \
case 1: __put_user_asm_goto(x, __pus_addr, label, "stb"); break; \
case 2: __put_user_asm_goto(x, __pus_addr, label, "sth"); break; \
case 4: __put_user_asm_goto(x, __pus_addr, label, "stw"); break; \
case 8: __put_user_asm2_goto(x, __pus_addr, label); break; \
default: BUILD_BUG(); \
} \
} while (0)
/*
* This does an atomic 128 byte aligned load from userspace.
* Upto caller to do enable_kernel_vmx() before calling!
*/
#define __get_user_atomic_128_aligned(kaddr, uaddr, err) \
__asm__ __volatile__( \
".machine push\n" \
".machine altivec\n" \
"1: lvx 0,0,%1 # get user\n" \
" stvx 0,0,%2 # put kernel\n" \
".machine pop\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: li %0,%3\n" \
" b 2b\n" \
".previous\n" \
EX_TABLE(1b, 3b) \
: "=r" (err) \
: "b" (uaddr), "b" (kaddr), "i" (-EFAULT), "0" (err))
#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
/* -mprefixed can generate offsets beyond range, fall back hack */
#ifdef CONFIG_PPC_KERNEL_PREFIXED
#define __get_user_asm_goto(x, addr, label, op) \
asm_goto_output( \
"1: "op" %0,0(%1) # get_user\n" \
EX_TABLE(1b, %l2) \
: "=r" (x) \
: "b" (addr) \
: \
: label)
#else
#define __get_user_asm_goto(x, addr, label, op) \
asm_goto_output( \
"1: "op"%U1%X1 %0, %1 # get_user\n" \
EX_TABLE(1b, %l2) \
: "=r" (x) \
: "m<>" (*addr) \
: \
: label)
#endif
#ifdef __powerpc64__
#ifdef CONFIG_PPC_KERNEL_PREFIXED
#define __get_user_asm2_goto(x, addr, label) \
__get_user_asm_goto(x, addr, label, "ld")
#else
#define __get_user_asm2_goto(x, addr, label) \
asm_goto_output( \
"1: ld%U1%X1 %0, %1 # get_user\n" \
EX_TABLE(1b, %l2) \
: "=r" (x) \
: DS_FORM_CONSTRAINT (*addr) \
: \
: label)
#endif // CONFIG_PPC_KERNEL_PREFIXED
#else /* __powerpc64__ */
#define __get_user_asm2_goto(x, addr, label) \
asm_goto_output( \
"1: lwz%X1 %0, %1\n" \
"2: lwz%X1 %L0, %L1\n" \
EX_TABLE(1b, %l2) \
EX_TABLE(2b, %l2) \
: "=&r" (x) \
: "m" (*addr) \
: \
: label)
#endif /* __powerpc64__ */
#define __get_user_size_goto(x, ptr, size, label) \
do { \
BUILD_BUG_ON(size > sizeof(x)); \
switch (size) { \
case 1: __get_user_asm_goto(x, (u8 __user *)ptr, label, "lbz"); break; \
case 2: __get_user_asm_goto(x, (u16 __user *)ptr, label, "lhz"); break; \
case 4: __get_user_asm_goto(x, (u32 __user *)ptr, label, "lwz"); break; \
case 8: __get_user_asm2_goto(x, (u64 __user *)ptr, label); break; \
default: x = 0; BUILD_BUG(); \
} \
} while (0)
#define __get_user_size_allowed(x, ptr, size, retval) \
do { \
__label__ __gus_failed; \
\
__get_user_size_goto(x, ptr, size, __gus_failed); \
retval = 0; \
break; \
__gus_failed: \
x = 0; \
retval = -EFAULT; \
} while (0)
#else /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
#define __get_user_asm(x, addr, err, op) \
__asm__ __volatile__( \
"1: "op"%U2%X2 %1, %2 # get_user\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: li %0,%3\n" \
" li %1,0\n" \
" b 2b\n" \
".previous\n" \
EX_TABLE(1b, 3b) \
: "=r" (err), "=r" (x) \
: "m<>" (*addr), "i" (-EFAULT), "0" (err))
#ifdef __powerpc64__
#define __get_user_asm2(x, addr, err) \
__get_user_asm(x, addr, err, "ld")
#else /* __powerpc64__ */
#define __get_user_asm2(x, addr, err) \
__asm__ __volatile__( \
"1: lwz%X2 %1, %2\n" \
"2: lwz%X2 %L1, %L2\n" \
"3:\n" \
".section .fixup,\"ax\"\n" \
"4: li %0,%3\n" \
" li %1,0\n" \
" li %1+1,0\n" \
" b 3b\n" \
".previous\n" \
EX_TABLE(1b, 4b) \
EX_TABLE(2b, 4b) \
: "=r" (err), "=&r" (x) \
: "m" (*addr), "i" (-EFAULT), "0" (err))
#endif /* __powerpc64__ */
#define __get_user_size_allowed(x, ptr, size, retval) \
do { \
retval = 0; \
BUILD_BUG_ON(size > sizeof(x)); \
switch (size) { \
case 1: __get_user_asm(x, (u8 __user *)ptr, retval, "lbz"); break; \
case 2: __get_user_asm(x, (u16 __user *)ptr, retval, "lhz"); break; \
case 4: __get_user_asm(x, (u32 __user *)ptr, retval, "lwz"); break; \
case 8: __get_user_asm2(x, (u64 __user *)ptr, retval); break; \
default: x = 0; BUILD_BUG(); \
} \
} while (0)
#define __get_user_size_goto(x, ptr, size, label) \
do { \
long __gus_retval; \
\
__get_user_size_allowed(x, ptr, size, __gus_retval); \
if (__gus_retval) \
goto label; \
} while (0)
#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
/*
* This is a type: either unsigned long, if the argument fits into
* that type, or otherwise unsigned long long.
*/
#define __long_type(x) \
__typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
#define __get_user(x, ptr) \
({ \
long __gu_err; \
__long_type(*(ptr)) __gu_val; \
__typeof__(*(ptr)) __user *__gu_addr = (ptr); \
__typeof__(sizeof(*(ptr))) __gu_size = sizeof(*(ptr)); \
\
might_fault(); \
allow_read_from_user(__gu_addr, __gu_size); \
__get_user_size_allowed(__gu_val, __gu_addr, __gu_size, __gu_err); \
prevent_read_from_user(__gu_addr, __gu_size); \
(x) = (__typeof__(*(ptr)))__gu_val; \
\
__gu_err; \
})
#define get_user(x, ptr) \
({ \
__typeof__(*(ptr)) __user *_gu_addr = (ptr); \
\
access_ok(_gu_addr, sizeof(*(ptr))) ? \
__get_user(x, _gu_addr) : \
((x) = (__force __typeof__(*(ptr)))0, -EFAULT); \
})
/* more complex routines */
extern unsigned long __copy_tofrom_user(void __user *to,
const void __user *from, unsigned long size);
#ifdef __powerpc64__
static inline unsigned long
raw_copy_in_user(void __user *to, const void __user *from, unsigned long n)
{
unsigned long ret;
allow_read_write_user(to, from, n);
ret = __copy_tofrom_user(to, from, n);
prevent_read_write_user(to, from, n);
return ret;
}
#endif /* __powerpc64__ */
static inline unsigned long raw_copy_from_user(void *to,
const void __user *from, unsigned long n)
{
unsigned long ret;
allow_read_from_user(from, n);
ret = __copy_tofrom_user((__force void __user *)to, from, n);
prevent_read_from_user(from, n);
return ret;
}
static inline unsigned long
raw_copy_to_user(void __user *to, const void *from, unsigned long n)
{
unsigned long ret;
allow_write_to_user(to, n);
ret = __copy_tofrom_user(to, (__force const void __user *)from, n);
prevent_write_to_user(to, n);
return ret;
}
unsigned long __arch_clear_user(void __user *addr, unsigned long size);
static inline unsigned long __clear_user(void __user *addr, unsigned long size)
{
unsigned long ret;
might_fault();
allow_write_to_user(addr, size);
ret = __arch_clear_user(addr, size);
prevent_write_to_user(addr, size);
return ret;
}
static inline unsigned long clear_user(void __user *addr, unsigned long size)
{
return likely(access_ok(addr, size)) ? __clear_user(addr, size) : size;
}
extern long strncpy_from_user(char *dst, const char __user *src, long count);
extern __must_check long strnlen_user(const char __user *str, long n);
#ifdef CONFIG_ARCH_HAS_COPY_MC
unsigned long __must_check
copy_mc_generic(void *to, const void *from, unsigned long size);
static inline unsigned long __must_check
copy_mc_to_kernel(void *to, const void *from, unsigned long size)
{
return copy_mc_generic(to, from, size);
}
#define copy_mc_to_kernel copy_mc_to_kernel
static inline unsigned long __must_check
copy_mc_to_user(void __user *to, const void *from, unsigned long n)
{
if (check_copy_size(from, n, true)) {
if (access_ok(to, n)) {
allow_write_to_user(to, n);
n = copy_mc_generic((void __force *)to, from, n);
prevent_write_to_user(to, n);
}
}
return n;
}
#endif
extern long __copy_from_user_flushcache(void *dst, const void __user *src,
unsigned size);
static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len)
{
if (unlikely(!access_ok(ptr, len)))
return false;
might_fault();
allow_read_write_user((void __user *)ptr, ptr, len);
return true;
}
#define user_access_begin user_access_begin
#define user_access_end prevent_current_access_user
#define user_access_save prevent_user_access_return
#define user_access_restore restore_user_access
static __must_check __always_inline bool
user_read_access_begin(const void __user *ptr, size_t len)
{
if (unlikely(!access_ok(ptr, len)))
return false;
might_fault();
allow_read_from_user(ptr, len);
return true;
}
#define user_read_access_begin user_read_access_begin
#define user_read_access_end prevent_current_read_from_user
static __must_check __always_inline bool
user_write_access_begin(const void __user *ptr, size_t len)
{
if (unlikely(!access_ok(ptr, len)))
return false;
might_fault();
allow_write_to_user((void __user *)ptr, len);
return true;
}
#define user_write_access_begin user_write_access_begin
#define user_write_access_end prevent_current_write_to_user
#define unsafe_get_user(x, p, e) do { \
__long_type(*(p)) __gu_val; \
__typeof__(*(p)) __user *__gu_addr = (p); \
\
__get_user_size_goto(__gu_val, __gu_addr, sizeof(*(p)), e); \
(x) = (__typeof__(*(p)))__gu_val; \
} while (0)
#define unsafe_put_user(x, p, e) \
__put_user_size_goto((__typeof__(*(p)))(x), (p), sizeof(*(p)), e)
#define unsafe_copy_from_user(d, s, l, e) \
do { \
u8 *_dst = (u8 *)(d); \
const u8 __user *_src = (const u8 __user *)(s); \
size_t _len = (l); \
int _i; \
\
for (_i = 0; _i < (_len & ~(sizeof(u64) - 1)); _i += sizeof(u64)) \
unsafe_get_user(*(u64 *)(_dst + _i), (u64 __user *)(_src + _i), e); \
if (_len & 4) { \
unsafe_get_user(*(u32 *)(_dst + _i), (u32 __user *)(_src + _i), e); \
_i += 4; \
} \
if (_len & 2) { \
unsafe_get_user(*(u16 *)(_dst + _i), (u16 __user *)(_src + _i), e); \
_i += 2; \
} \
if (_len & 1) \
unsafe_get_user(*(u8 *)(_dst + _i), (u8 __user *)(_src + _i), e); \
} while (0)
#define unsafe_copy_to_user(d, s, l, e) \
do { \
u8 __user *_dst = (u8 __user *)(d); \
const u8 *_src = (const u8 *)(s); \
size_t _len = (l); \
int _i; \
\
for (_i = 0; _i < (_len & ~(sizeof(u64) - 1)); _i += sizeof(u64)) \
unsafe_put_user(*(u64 *)(_src + _i), (u64 __user *)(_dst + _i), e); \
if (_len & 4) { \
unsafe_put_user(*(u32*)(_src + _i), (u32 __user *)(_dst + _i), e); \
_i += 4; \
} \
if (_len & 2) { \
unsafe_put_user(*(u16*)(_src + _i), (u16 __user *)(_dst + _i), e); \
_i += 2; \
} \
if (_len & 1) \
unsafe_put_user(*(u8*)(_src + _i), (u8 __user *)(_dst + _i), e); \
} while (0)
#define __get_kernel_nofault(dst, src, type, err_label) \
__get_user_size_goto(*((type *)(dst)), \
(__force type __user *)(src), sizeof(type), err_label)
#define __put_kernel_nofault(dst, src, type, err_label) \
__put_user_size_goto(*((type *)(src)), \
(__force type __user *)(dst), sizeof(type), err_label)
#endif /* _ARCH_POWERPC_UACCESS_H */
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