Re: [PATCH v4 01/10] s390/uaccess: Add copy_from/to_user_key functions

From: Claudio Imbrenda
Date: Mon Feb 14 2022 - 19:00:26 EST

On Fri, 11 Feb 2022 19:22:06 +0100
Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx> wrote:

> Add copy_from/to_user_key functions, which perform storage key checking.
> These functions can be used by KVM for emulating instructions that need
> to be key checked.
> These functions differ from their non _key counterparts in
> include/linux/uaccess.h only in the additional key argument and must be
> kept in sync with those.
>
> Since the existing uaccess implementation on s390 makes use of move
> instructions that support having an additional access key supplied,
> we can implement raw_copy_from/to_user_key by enhancing the
> existing implementation.
>
> Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx>
> Acked-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
> Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
> Acked-by: Janosch Frank <frankja@xxxxxxxxxxxxx>

Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>

> ---
> arch/s390/include/asm/uaccess.h | 22 +++++++++
> arch/s390/lib/uaccess.c | 81 +++++++++++++++++++++++++--------
> 2 files changed, 85 insertions(+), 18 deletions(-)
>
> diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
> index d74e26b48604..ba1bcb91af95 100644
> --- a/arch/s390/include/asm/uaccess.h
> +++ b/arch/s390/include/asm/uaccess.h
> @@ -44,6 +44,28 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n);
> #define INLINE_COPY_TO_USER
> #endif
>
> +unsigned long __must_check
> +_copy_from_user_key(void *to, const void __user *from, unsigned long n, unsigned long key);
> +
> +static __always_inline unsigned long __must_check
> +copy_from_user_key(void *to, const void __user *from, unsigned long n, unsigned long key)
> +{
> + if (likely(check_copy_size(to, n, false)))
> + n = _copy_from_user_key(to, from, n, key);
> + return n;
> +}
> +
> +unsigned long __must_check
> +_copy_to_user_key(void __user *to, const void *from, unsigned long n, unsigned long key);
> +
> +static __always_inline unsigned long __must_check
> +copy_to_user_key(void __user *to, const void *from, unsigned long n, unsigned long key)
> +{
> + if (likely(check_copy_size(from, n, true)))
> + n = _copy_to_user_key(to, from, n, key);
> + return n;
> +}
> +
> int __put_user_bad(void) __attribute__((noreturn));
> int __get_user_bad(void) __attribute__((noreturn));
>
> diff --git a/arch/s390/lib/uaccess.c b/arch/s390/lib/uaccess.c
> index 8a5d21461889..b709239feb5d 100644
> --- a/arch/s390/lib/uaccess.c
> +++ b/arch/s390/lib/uaccess.c
> @@ -59,11 +59,13 @@ static inline int copy_with_mvcos(void)
> #endif
>
> static inline unsigned long copy_from_user_mvcos(void *x, const void __user *ptr,
> - unsigned long size)
> + unsigned long size, unsigned long key)
> {
> unsigned long tmp1, tmp2;
> union oac spec = {
> + .oac2.key = key,
> .oac2.as = PSW_BITS_AS_SECONDARY,
> + .oac2.k = 1,
> .oac2.a = 1,
> };
>
> @@ -94,19 +96,19 @@ static inline unsigned long copy_from_user_mvcos(void *x, const void __user *ptr
> }
>
> static inline unsigned long copy_from_user_mvcp(void *x, const void __user *ptr,
> - unsigned long size)
> + unsigned long size, unsigned long key)
> {
> unsigned long tmp1, tmp2;
>
> tmp1 = -256UL;
> asm volatile(
> " sacf 0\n"
> - "0: mvcp 0(%0,%2),0(%1),%3\n"
> + "0: mvcp 0(%0,%2),0(%1),%[key]\n"
> "7: jz 5f\n"
> "1: algr %0,%3\n"
> " la %1,256(%1)\n"
> " la %2,256(%2)\n"
> - "2: mvcp 0(%0,%2),0(%1),%3\n"
> + "2: mvcp 0(%0,%2),0(%1),%[key]\n"
> "8: jnz 1b\n"
> " j 5f\n"
> "3: la %4,255(%1)\n" /* %4 = ptr + 255 */
> @@ -115,7 +117,7 @@ static inline unsigned long copy_from_user_mvcp(void *x, const void __user *ptr,
> " slgr %4,%1\n"
> " clgr %0,%4\n" /* copy crosses next page boundary? */
> " jnh 6f\n"
> - "4: mvcp 0(%4,%2),0(%1),%3\n"
> + "4: mvcp 0(%4,%2),0(%1),%[key]\n"
> "9: slgr %0,%4\n"
> " j 6f\n"
> "5: slgr %0,%0\n"
> @@ -123,24 +125,49 @@ static inline unsigned long copy_from_user_mvcp(void *x, const void __user *ptr,
> EX_TABLE(0b,3b) EX_TABLE(2b,3b) EX_TABLE(4b,6b)
> EX_TABLE(7b,3b) EX_TABLE(8b,3b) EX_TABLE(9b,6b)
> : "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
> - : : "cc", "memory");
> + : [key] "d" (key << 4)
> + : "cc", "memory");
> return size;
> }
>
> -unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
> +static unsigned long raw_copy_from_user_key(void *to, const void __user *from,
> + unsigned long n, unsigned long key)
> {
> if (copy_with_mvcos())
> - return copy_from_user_mvcos(to, from, n);
> - return copy_from_user_mvcp(to, from, n);
> + return copy_from_user_mvcos(to, from, n, key);
> + return copy_from_user_mvcp(to, from, n, key);
> +}
> +
> +unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
> +{
> + return raw_copy_from_user_key(to, from, n, 0);
> }
> EXPORT_SYMBOL(raw_copy_from_user);
>
> +unsigned long _copy_from_user_key(void *to, const void __user *from,
> + unsigned long n, unsigned long key)
> +{
> + unsigned long res = n;
> +
> + might_fault();
> + if (!should_fail_usercopy()) {
> + instrument_copy_from_user(to, from, n);
> + res = raw_copy_from_user_key(to, from, n, key);
> + }
> + if (unlikely(res))
> + memset(to + (n - res), 0, res);
> + return res;
> +}
> +EXPORT_SYMBOL(_copy_from_user_key);
> +
> static inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x,
> - unsigned long size)
> + unsigned long size, unsigned long key)
> {
> unsigned long tmp1, tmp2;
> union oac spec = {
> + .oac1.key = key,
> .oac1.as = PSW_BITS_AS_SECONDARY,
> + .oac1.k = 1,
> .oac1.a = 1,
> };
>
> @@ -171,19 +198,19 @@ static inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x,
> }
>
> static inline unsigned long copy_to_user_mvcs(void __user *ptr, const void *x,
> - unsigned long size)
> + unsigned long size, unsigned long key)
> {
> unsigned long tmp1, tmp2;
>
> tmp1 = -256UL;
> asm volatile(
> " sacf 0\n"
> - "0: mvcs 0(%0,%1),0(%2),%3\n"
> + "0: mvcs 0(%0,%1),0(%2),%[key]\n"
> "7: jz 5f\n"
> "1: algr %0,%3\n"
> " la %1,256(%1)\n"
> " la %2,256(%2)\n"
> - "2: mvcs 0(%0,%1),0(%2),%3\n"
> + "2: mvcs 0(%0,%1),0(%2),%[key]\n"
> "8: jnz 1b\n"
> " j 5f\n"
> "3: la %4,255(%1)\n" /* %4 = ptr + 255 */
> @@ -192,7 +219,7 @@ static inline unsigned long copy_to_user_mvcs(void __user *ptr, const void *x,
> " slgr %4,%1\n"
> " clgr %0,%4\n" /* copy crosses next page boundary? */
> " jnh 6f\n"
> - "4: mvcs 0(%4,%1),0(%2),%3\n"
> + "4: mvcs 0(%4,%1),0(%2),%[key]\n"
> "9: slgr %0,%4\n"
> " j 6f\n"
> "5: slgr %0,%0\n"
> @@ -200,18 +227,36 @@ static inline unsigned long copy_to_user_mvcs(void __user *ptr, const void *x,
> EX_TABLE(0b,3b) EX_TABLE(2b,3b) EX_TABLE(4b,6b)
> EX_TABLE(7b,3b) EX_TABLE(8b,3b) EX_TABLE(9b,6b)
> : "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
> - : : "cc", "memory");
> + : [key] "d" (key << 4)
> + : "cc", "memory");
> return size;
> }
>
> -unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
> +static unsigned long raw_copy_to_user_key(void __user *to, const void *from,
> + unsigned long n, unsigned long key)
> {
> if (copy_with_mvcos())
> - return copy_to_user_mvcos(to, from, n);
> - return copy_to_user_mvcs(to, from, n);
> + return copy_to_user_mvcos(to, from, n, key);
> + return copy_to_user_mvcs(to, from, n, key);
> +}
> +
> +unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
> +{
> + return raw_copy_to_user_key(to, from, n, 0);
> }
> EXPORT_SYMBOL(raw_copy_to_user);
>
> +unsigned long _copy_to_user_key(void __user *to, const void *from,
> + unsigned long n, unsigned long key)
> +{
> + might_fault();
> + if (should_fail_usercopy())
> + return n;
> + instrument_copy_to_user(to, from, n);
> + return raw_copy_to_user_key(to, from, n, key);
> +}
> +EXPORT_SYMBOL(_copy_to_user_key);
> +
> static inline unsigned long clear_user_mvcos(void __user *to, unsigned long size)
> {
> unsigned long tmp1, tmp2;