Messages in this thread | | | Date | Tue, 18 Jan 2022 14:18:40 +0100 | Subject | Re: [RFC PATCH v1 01/10] s390/uaccess: Add storage key checked access to user memory | From | Janosch Frank <> |
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On 1/18/22 10:52, Janis Schoetterl-Glausch wrote: > KVM needs a mechanism to do accesses to guest memory that honor > storage key protection. > Since the copy_to/from_user implementation makes use of move > instructions that support having an additional access key supplied, > we can implement __copy_from/to_user_with_key by enhancing the > existing implementation. > > Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
For this I'd like to have buy-in from the kernel maintainers. The patch looks good to me but currently I don't understand all of the background so:
Acked-by: Janosch Frank <frankja@linux.ibm.com>
> --- > arch/s390/include/asm/uaccess.h | 32 ++++++++++++++++++ > arch/s390/lib/uaccess.c | 57 +++++++++++++++++++++++---------- > 2 files changed, 72 insertions(+), 17 deletions(-) > > diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h > index 02b467461163..5138040348cc 100644 > --- a/arch/s390/include/asm/uaccess.h > +++ b/arch/s390/include/asm/uaccess.h > @@ -33,6 +33,38 @@ static inline int __range_ok(unsigned long addr, unsigned long size) > > #define access_ok(addr, size) __access_ok(addr, size) > > +unsigned long __must_check > +raw_copy_from_user_with_key(void *to, const void __user *from, unsigned long n, > + char key); > + > +unsigned long __must_check > +raw_copy_to_user_with_key(void __user *to, const void *from, unsigned long n, > + char key); > + > +static __always_inline __must_check unsigned long > +__copy_from_user_with_key(void *to, const void __user *from, unsigned long n, > + char key) > +{ > + might_fault(); > + if (should_fail_usercopy()) > + return n; > + instrument_copy_from_user(to, from, n); > + check_object_size(to, n, false); > + return raw_copy_from_user_with_key(to, from, n, key); > +} > + > +static __always_inline __must_check unsigned long > +__copy_to_user_with_key(void __user *to, const void *from, unsigned long n, > + char key) > +{ > + might_fault(); > + if (should_fail_usercopy()) > + return n; > + instrument_copy_to_user(to, from, n); > + check_object_size(from, n, true); > + return raw_copy_to_user_with_key(to, from, n, key); > +} > + > unsigned long __must_check > raw_copy_from_user(void *to, const void __user *from, unsigned long n); > > diff --git a/arch/s390/lib/uaccess.c b/arch/s390/lib/uaccess.c > index d3a700385875..ce7a150dd93a 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, char 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, char 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 +125,36 @@ 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) > { > 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, 0); > + return copy_from_user_mvcp(to, from, n, 0); > } > EXPORT_SYMBOL(raw_copy_from_user); > > -static inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x, > - unsigned long size) > +unsigned long raw_copy_from_user_with_key(void *to, const void __user *from, > + unsigned long n, char key) > +{ > + if (copy_with_mvcos()) > + return copy_from_user_mvcos(to, from, n, key); > + return copy_from_user_mvcp(to, from, n, key); > +} > +EXPORT_SYMBOL(raw_copy_from_user_with_key); > + > +inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x, > + unsigned long size, char 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 +185,19 @@ 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, char 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 +206,7 @@ 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" > @@ -200,17 +214,26 @@ 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) > { > 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, 0); > + return copy_to_user_mvcs(to, from, n, 0); > } > EXPORT_SYMBOL(raw_copy_to_user); > +unsigned long raw_copy_to_user_with_key(void __user *to, const void *from, > + unsigned long n, char key) > +{ > + if (copy_with_mvcos()) > + return copy_to_user_mvcos(to, from, n, key); > + return copy_to_user_mvcs(to, from, n, key); > +} > +EXPORT_SYMBOL(raw_copy_to_user_with_key); > > static inline unsigned long clear_user_mvcos(void __user *to, unsigned long size) > { >
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