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s390/uaccess: introduce bit field for OAC specifier
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Previously, we've used  magic values to specify the OAC
(operand-access control) for mvcos.

Instead we introduce a bit field for it.

When using a bit field, we cannot use an immediate value with K
constraint anymore, since GCC older than 10 doesn't recognize
the bit field union as a compile time constant.
To make things work with older compilers,
load the OAC value through a register.

Bloat-o-meter reports a slight increase in kernel size with this change:
Total: Before=15692135, After=15693015, chg +0.01%

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Co-developed-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Link: https://lore.kernel.org/r/20220111100003.743116-1-scgl@linux.ibm.com
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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Nico Boehr authored and Heiko Carstens committed Jan 17, 2022
1 parent 745f5d2 commit 012a224
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Showing 2 changed files with 95 additions and 49 deletions.
120 changes: 77 additions & 43 deletions arch/s390/include/asm/uaccess.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -49,51 +49,85 @@ int __get_user_bad(void) __attribute__((noreturn));

#ifdef CONFIG_HAVE_MARCH_Z10_FEATURES

#define __put_get_user_asm(to, from, size, insn) \
({ \
int __rc; \
\
asm volatile( \
insn " 0,%[spec]\n" \
"0: mvcos %[_to],%[_from],%[_size]\n" \
"1: xr %[rc],%[rc]\n" \
"2:\n" \
".pushsection .fixup, \"ax\"\n" \
"3: lhi %[rc],%[retval]\n" \
" jg 2b\n" \
".popsection\n" \
EX_TABLE(0b,3b) EX_TABLE(1b,3b) \
: [rc] "=&d" (__rc), [_to] "+Q" (*(to)) \
: [_size] "d" (size), [_from] "Q" (*(from)), \
[retval] "K" (-EFAULT), [spec] "K" (0x81UL) \
: "cc", "0"); \
__rc; \
union oac {
unsigned int val;
struct {
struct {
unsigned short key : 4;
unsigned short : 4;
unsigned short as : 2;
unsigned short : 4;
unsigned short k : 1;
unsigned short a : 1;
} oac1;
struct {
unsigned short key : 4;
unsigned short : 4;
unsigned short as : 2;
unsigned short : 4;
unsigned short k : 1;
unsigned short a : 1;
} oac2;
};
};

#define __put_get_user_asm(to, from, size, oac_spec) \
({ \
int __rc; \
\
asm volatile( \
" lr 0,%[spec]\n" \
"0: mvcos %[_to],%[_from],%[_size]\n" \
"1: xr %[rc],%[rc]\n" \
"2:\n" \
".pushsection .fixup, \"ax\"\n" \
"3: lhi %[rc],%[retval]\n" \
" jg 2b\n" \
".popsection\n" \
EX_TABLE(0b,3b) EX_TABLE(1b,3b) \
: [rc] "=&d" (__rc), [_to] "+Q" (*(to)) \
: [_size] "d" (size), [_from] "Q" (*(from)), \
[retval] "K" (-EFAULT), [spec] "d" (oac_spec.val) \
: "cc", "0"); \
__rc; \
})

#define __put_user_asm(to, from, size) \
__put_get_user_asm(to, from, size, ((union oac) { \
.oac1.as = PSW_BITS_AS_SECONDARY, \
.oac1.a = 1 \
}))

#define __get_user_asm(to, from, size) \
__put_get_user_asm(to, from, size, ((union oac) { \
.oac2.as = PSW_BITS_AS_SECONDARY, \
.oac2.a = 1 \
})) \

static __always_inline int __put_user_fn(void *x, void __user *ptr, unsigned long size)
{
int rc;

switch (size) {
case 1:
rc = __put_get_user_asm((unsigned char __user *)ptr,
(unsigned char *)x,
size, "llilh");
rc = __put_user_asm((unsigned char __user *)ptr,
(unsigned char *)x,
size);
break;
case 2:
rc = __put_get_user_asm((unsigned short __user *)ptr,
(unsigned short *)x,
size, "llilh");
rc = __put_user_asm((unsigned short __user *)ptr,
(unsigned short *)x,
size);
break;
case 4:
rc = __put_get_user_asm((unsigned int __user *)ptr,
(unsigned int *)x,
size, "llilh");
rc = __put_user_asm((unsigned int __user *)ptr,
(unsigned int *)x,
size);
break;
case 8:
rc = __put_get_user_asm((unsigned long __user *)ptr,
(unsigned long *)x,
size, "llilh");
rc = __put_user_asm((unsigned long __user *)ptr,
(unsigned long *)x,
size);
break;
default:
__put_user_bad();
Expand All @@ -108,24 +142,24 @@ static __always_inline int __get_user_fn(void *x, const void __user *ptr, unsign

switch (size) {
case 1:
rc = __put_get_user_asm((unsigned char *)x,
(unsigned char __user *)ptr,
size, "lghi");
rc = __get_user_asm((unsigned char *)x,
(unsigned char __user *)ptr,
size);
break;
case 2:
rc = __put_get_user_asm((unsigned short *)x,
(unsigned short __user *)ptr,
size, "lghi");
rc = __get_user_asm((unsigned short *)x,
(unsigned short __user *)ptr,
size);
break;
case 4:
rc = __put_get_user_asm((unsigned int *)x,
(unsigned int __user *)ptr,
size, "lghi");
rc = __get_user_asm((unsigned int *)x,
(unsigned int __user *)ptr,
size);
break;
case 8:
rc = __put_get_user_asm((unsigned long *)x,
(unsigned long __user *)ptr,
size, "lghi");
rc = __get_user_asm((unsigned long *)x,
(unsigned long __user *)ptr,
size);
break;
default:
__get_user_bad();
Expand Down
24 changes: 18 additions & 6 deletions arch/s390/lib/uaccess.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -62,10 +62,14 @@ static inline unsigned long copy_from_user_mvcos(void *x, const void __user *ptr
unsigned long size)
{
unsigned long tmp1, tmp2;
union oac spec = {
.oac2.as = PSW_BITS_AS_SECONDARY,
.oac2.a = 1,
};

tmp1 = -4096UL;
asm volatile(
" lghi 0,%[spec]\n"
" lr 0,%[spec]\n"
"0: .insn ss,0xc80000000000,0(%0,%2),0(%1),0\n"
"6: jz 4f\n"
"1: algr %0,%3\n"
Expand All @@ -84,7 +88,7 @@ static inline unsigned long copy_from_user_mvcos(void *x, const void __user *ptr
"5:\n"
EX_TABLE(0b,2b) EX_TABLE(3b,5b) EX_TABLE(6b,2b) EX_TABLE(7b,5b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: [spec] "K" (0x81UL)
: [spec] "d" (spec.val)
: "cc", "memory", "0");
return size;
}
Expand Down Expand Up @@ -135,10 +139,14 @@ static inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x,
unsigned long size)
{
unsigned long tmp1, tmp2;
union oac spec = {
.oac1.as = PSW_BITS_AS_SECONDARY,
.oac1.a = 1,
};

tmp1 = -4096UL;
asm volatile(
" llilh 0,%[spec]\n"
" lr 0,%[spec]\n"
"0: .insn ss,0xc80000000000,0(%0,%1),0(%2),0\n"
"6: jz 4f\n"
"1: algr %0,%3\n"
Expand All @@ -157,7 +165,7 @@ static inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x,
"5:\n"
EX_TABLE(0b,2b) EX_TABLE(3b,5b) EX_TABLE(6b,2b) EX_TABLE(7b,5b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: [spec] "K" (0x81UL)
: [spec] "d" (spec.val)
: "cc", "memory", "0");
return size;
}
Expand Down Expand Up @@ -207,10 +215,14 @@ EXPORT_SYMBOL(raw_copy_to_user);
static inline unsigned long clear_user_mvcos(void __user *to, unsigned long size)
{
unsigned long tmp1, tmp2;
union oac spec = {
.oac1.as = PSW_BITS_AS_SECONDARY,
.oac1.a = 1,
};

tmp1 = -4096UL;
asm volatile(
" llilh 0,%[spec]\n"
" lr 0,%[spec]\n"
"0: .insn ss,0xc80000000000,0(%0,%1),0(%4),0\n"
" jz 4f\n"
"1: algr %0,%2\n"
Expand All @@ -228,7 +240,7 @@ static inline unsigned long clear_user_mvcos(void __user *to, unsigned long size
"5:\n"
EX_TABLE(0b,2b) EX_TABLE(3b,5b)
: "+a" (size), "+a" (to), "+a" (tmp1), "=a" (tmp2)
: "a" (empty_zero_page), [spec] "K" (0x81UL)
: "a" (empty_zero_page), [spec] "d" (spec.val)
: "cc", "memory", "0");
return size;
}
Expand Down

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