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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Christophe Leroy <christophe.leroy@c-s.fr>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>, ruscur@russell.cc
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2 07/10] powerpc/8xx: Add Kernel Userspace Access Protection
In-Reply-To: <bac688f0f7f60d6862d839982c9cccbeda6fec3c.1552292207.git.christophe.leroy@c-s.fr>
References: <cover.1552292207.git.christophe.leroy@c-s.fr> <bac688f0f7f60d6862d839982c9cccbeda6fec3c.1552292207.git.christophe.leroy@c-s.fr>
Date:   Thu, 18 Apr 2019 16:53:40 +1000
Message-ID: <87k1fru7m3.fsf@concordia.ellerman.id.au>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
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Christophe Leroy <christophe.leroy@c-s.fr> writes:
> diff --git a/arch/powerpc/include/asm/nohash/32/kup-8xx.h b/arch/powerpc/include/asm/nohash/32/kup-8xx.h
> new file mode 100644
> index 000000000000..a44cc6c1b901
> --- /dev/null
> +++ b/arch/powerpc/include/asm/nohash/32/kup-8xx.h
> @@ -0,0 +1,68 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_POWERPC_KUP_8XX_H_
> +#define _ASM_POWERPC_KUP_8XX_H_
> +
> +#include <asm/bug.h>
> +
> +#ifdef CONFIG_PPC_KUAP
> +
> +#ifdef __ASSEMBLY__
> +
> +.macro kuap_save_and_lock	sp, thread, gpr1, gpr2, gpr3
> +	lis	\gpr2, MD_APG_KUAP@h	/* only APG0 and APG1 are used */
> +	mfspr	\gpr1, SPRN_MD_AP
> +	mtspr	SPRN_MD_AP, \gpr2
> +	stw	\gpr1, STACK_REGS_KUAP(\sp)
> +.endm
> +
> +.macro kuap_restore	sp, current, gpr1, gpr2, gpr3
> +	lwz	\gpr1, STACK_REGS_KUAP(\sp)
> +	mtspr	SPRN_MD_AP, \gpr1
> +.endm
> +
> +.macro kuap_check	current, gpr
> +#ifdef CONFIG_PPC_KUAP_DEBUG
> +	mfspr	\gpr, SPRN_MD_AP
> +	rlwinm	\gpr, \gpr, 16, 0xffff
> +999:	twnei	\gpr, MD_APG_KUAP@h
> +	EMIT_BUG_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE)
> +#endif
> +.endm
> +
> +#else /* !__ASSEMBLY__ */
> +
> +#include <asm/reg.h>
> +
> +static inline void allow_user_access(void __user *to, const void __user *from,
> +				     unsigned long size)
> +{
> +	mtspr(SPRN_MD_AP, MD_APG_INIT);
> +}
> +
> +static inline void prevent_user_access(void __user *to, const void __user *from,
> +				       unsigned long size)
> +{
> +	mtspr(SPRN_MD_AP, MD_APG_KUAP);
> +}
> +
> +static inline void allow_read_from_user(const void __user *from, unsigned long size)
> +{
> +	allow_user_access(NULL, from, size);
> +}
> +
> +static inline void allow_write_to_user(void __user *to, unsigned long size)
> +{
> +	allow_user_access(to, NULL, size);
> +}

I dropped the two above functions when rebasing on my v6.

cheers