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powerpc: Add a framework for Kernel Userspace Access Protection

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This patch implements a framework for Kernel Userspace Access
Protection.

Then subarches will have the possibility to provide their own
implementation by providing setup_kuap() and
allow/prevent_user_access().

Some platforms will need to know the area accessed and whether it is
accessed from read, write or both. Therefore source, destination and
size and handed over to the two functions.

mpe: Rename to allow/prevent rather than unlock/lock, and add
read/write wrappers. Drop the 32-bit code for now until we have an
implementation for it. Add kuap to pt_regs for 64-bit as well as
32-bit. Don't split strings, use pr_crit_ratelimited().

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy
2019-04-18 16:51:20 +10:00
committed by Michael Ellerman
parent 0fb1c25ab5
commit de78a9c42a
10 changed files with 121 additions and 15 deletions
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4
arch/powerpc/include/asm/futex.h
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@@ -35,6 +35,7 @@ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
{
int oldval = 0, ret;
allow_write_to_user(uaddr, sizeof(*uaddr));
pagefault_disable();
switch (op) {
@@ -62,6 +63,7 @@ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
if (!ret)
*oval = oldval;
prevent_write_to_user(uaddr, sizeof(*uaddr));
return ret;
}
@@ -75,6 +77,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
if (!access_ok(uaddr, sizeof(u32)))
return -EFAULT;
allow_write_to_user(uaddr, sizeof(*uaddr));
__asm__ __volatile__ (
PPC_ATOMIC_ENTRY_BARRIER
"1: lwarx %1,0,%3 # futex_atomic_cmpxchg_inatomic\n\
@@ -95,6 +98,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
: "cc", "memory");
*uval = prev;
prevent_write_to_user(uaddr, sizeof(*uaddr));
return ret;
}