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Subject: Re: [PATCH v8 13/30] powerpc: Add a probe_user_read_inst() function
To: Jordan Niethe <jniethe5@gmail.com>, linuxppc-dev@lists.ozlabs.org
References: <20200506034050.24806-1-jniethe5@gmail.com>
 <20200506034050.24806-14-jniethe5@gmail.com>
From: Christophe Leroy <christophe.leroy@csgroup.eu>
Message-ID: <e4bd592e-2e35-9c73-854e-1380222f34ef@csgroup.eu>
Date: Thu, 14 May 2020 07:46:25 +0200
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Le 06/05/2020 à 05:40, Jordan Niethe a écrit :
> Introduce a probe_user_read_inst() function to use in cases where
> probe_user_read() is used for getting an instruction. This will be more
> useful for prefixed instructions.
> 
> Reviewed-by: Alistair Popple <alistair@popple.id.au>
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> ---
> v6: - New to series
> ---
>   arch/powerpc/include/asm/inst.h |  3 +++
>   arch/powerpc/lib/Makefile       |  2 +-
>   arch/powerpc/lib/inst.c         | 18 ++++++++++++++++++
>   arch/powerpc/mm/fault.c         |  2 +-
>   4 files changed, 23 insertions(+), 2 deletions(-)
>   create mode 100644 arch/powerpc/lib/inst.c
> 
> diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
> index 552e953bf04f..3e9a58420151 100644
> --- a/arch/powerpc/include/asm/inst.h
> +++ b/arch/powerpc/include/asm/inst.h
> @@ -37,4 +37,7 @@ static inline bool ppc_inst_equal(struct ppc_inst x, struct ppc_inst y)
>   	return ppc_inst_val(x) == ppc_inst_val(y);
>   }
>   
> +int probe_user_read_inst(struct ppc_inst *inst,
> +			 struct ppc_inst *nip);
> +
>   #endif /* _ASM_INST_H */
> diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
> index b8de3be10eb4..546591848219 100644
> --- a/arch/powerpc/lib/Makefile
> +++ b/arch/powerpc/lib/Makefile
> @@ -16,7 +16,7 @@ CFLAGS_code-patching.o += -DDISABLE_BRANCH_PROFILING
>   CFLAGS_feature-fixups.o += -DDISABLE_BRANCH_PROFILING
>   endif
>   
> -obj-y += alloc.o code-patching.o feature-fixups.o pmem.o
> +obj-y += alloc.o code-patching.o feature-fixups.o pmem.o inst.o
>   
>   ifndef CONFIG_KASAN
>   obj-y	+=	string.o memcmp_$(BITS).o
> diff --git a/arch/powerpc/lib/inst.c b/arch/powerpc/lib/inst.c
> new file mode 100644
> index 000000000000..eaf786afad2b
> --- /dev/null
> +++ b/arch/powerpc/lib/inst.c
> @@ -0,0 +1,18 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + *  Copyright 2020, IBM Corporation.
> + */
> +
> +#include <linux/uaccess.h>
> +#include <asm/inst.h>
> +
> +int probe_user_read_inst(struct ppc_inst *inst,
> +			 struct ppc_inst *nip)
> +{
> +	unsigned int val;
> +	int err;
> +
> +	err = probe_user_read(&val, nip, sizeof(val));
> +	*inst = ppc_inst(val);
> +	return err;
> +}
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 4a50f125ec18..f3a943eae305 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -281,7 +281,7 @@ static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address,
>   		    access_ok(nip, sizeof(*nip))) {
>   			struct ppc_inst inst;
>   
> -			if (!probe_user_read(&inst, nip, sizeof(inst)))
> +			if (!probe_user_read_inst(&inst, (struct ppc_inst __user *)nip))

Shouldn't 'nip' become de 'struct ppc_inst __user *' instead of casting ?

>   				return !store_updates_sp(inst);
>   			*must_retry = true;
>   		}
> 

Christophe