linux-kernel - Re: [PATCH v2 04/15] powerpc/uaccess: Remove __get/put_user

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Message-ID: <87zgzabpo9.fsf@dja-thinkpad.axtens.net>
Date:   Thu, 11 Mar 2021 09:37:58 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 04/15] powerpc/uaccess: Remove __get/put_user_inatomic()

Hi Christophe,

> Powerpc is the only architecture having _inatomic variants of
> __get_user() and __put_user() accessors. They were introduced
> by commit e68c825bb016 ("[POWERPC] Add inatomic versions of __get_user
> and __put_user").
>
> Those variants expand to the _nosleep macros instead of expanding
> to the _nocheck macros. The only difference between the _nocheck
> and the _nosleep macros is the call to might_fault().
>
> Since commit 662bbcb2747c ("mm, sched: Allow uaccess in atomic with
> pagefault_disable()"), __get/put_user() can be used in atomic parts
> of the code, therefore __get/put_user_inatomic() have become useless.
>
> Remove __get_user_inatomic() and __put_user_inatomic().
>

This makes much more sense, thank you!

Simplifying uaccess.h is always good to me :)

Reviewed-by: Daniel Axtens <dja@...ens.net>

Kind regards,
Daniel

> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/include/asm/uaccess.h            | 37 -------------------
>  .../kernel/hw_breakpoint_constraints.c        |  2 +-
>  arch/powerpc/kernel/traps.c                   |  2 +-
>  3 files changed, 2 insertions(+), 39 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index a08c482b1315..01aea0df4dd0 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -53,11 +53,6 @@ static inline bool __access_ok(unsigned long addr, unsigned long size)
>  #define __put_user(x, ptr) \
>  	__put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
>  
> -#define __get_user_inatomic(x, ptr) \
> -	__get_user_nosleep((x), (ptr), sizeof(*(ptr)))
> -#define __put_user_inatomic(x, ptr) \
> -	__put_user_nosleep((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
> -
>  #ifdef CONFIG_PPC64
>  
>  #define ___get_user_instr(gu_op, dest, ptr)				\
> @@ -92,9 +87,6 @@ static inline bool __access_ok(unsigned long addr, unsigned long size)
>  #define __get_user_instr(x, ptr) \
>  	___get_user_instr(__get_user, x, ptr)
>  
> -#define __get_user_instr_inatomic(x, ptr) \
> -	___get_user_instr(__get_user_inatomic, x, ptr)
> -
>  extern long __put_user_bad(void);
>  
>  #define __put_user_size(x, ptr, size, retval)			\
> @@ -141,20 +133,6 @@ __pu_failed:							\
>  	__pu_err;							\
>  })
>  
> -#define __put_user_nosleep(x, ptr, size)			\
> -({								\
> -	long __pu_err;						\
> -	__typeof__(*(ptr)) __user *__pu_addr = (ptr);		\
> -	__typeof__(*(ptr)) __pu_val = (x);			\
> -	__typeof__(size) __pu_size = (size);			\
> -								\
> -	__chk_user_ptr(__pu_addr);				\
> -	__put_user_size(__pu_val, __pu_addr, __pu_size, __pu_err); \
> -								\
> -	__pu_err;						\
> -})
> -
> -
>  /*
>   * We don't tell gcc that we are accessing memory, but this is OK
>   * because we do not write to any memory gcc knows about, so there
> @@ -320,21 +298,6 @@ do {								\
>  	__gu_err;							\
>  })
>  
> -#define __get_user_nosleep(x, ptr, size)			\
> -({								\
> -	long __gu_err;						\
> -	__long_type(*(ptr)) __gu_val;				\
> -	__typeof__(*(ptr)) __user *__gu_addr = (ptr);	\
> -	__typeof__(size) __gu_size = (size);			\
> -								\
> -	__chk_user_ptr(__gu_addr);				\
> -	__get_user_size(__gu_val, __gu_addr, __gu_size, __gu_err); \
> -	(x) = (__force __typeof__(*(ptr)))__gu_val;			\
> -								\
> -	__gu_err;						\
> -})
> -
> -
>  /* more complex routines */
>  
>  extern unsigned long __copy_tofrom_user(void __user *to,
> diff --git a/arch/powerpc/kernel/hw_breakpoint_constraints.c b/arch/powerpc/kernel/hw_breakpoint_constraints.c
> index 867ee4aa026a..675d1f66ab72 100644
> --- a/arch/powerpc/kernel/hw_breakpoint_constraints.c
> +++ b/arch/powerpc/kernel/hw_breakpoint_constraints.c
> @@ -141,7 +141,7 @@ void wp_get_instr_detail(struct pt_regs *regs, struct ppc_inst *instr,
>  {
>  	struct instruction_op op;
>  
> -	if (__get_user_instr_inatomic(*instr, (void __user *)regs->nip))
> +	if (__get_user_instr(*instr, (void __user *)regs->nip))
>  		return;
>  
>  	analyse_instr(&op, regs, *instr);
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index 1583fd1c6010..1fa36bd08efe 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -864,7 +864,7 @@ static void p9_hmi_special_emu(struct pt_regs *regs)
>  	unsigned long ea, msr, msr_mask;
>  	bool swap;
>  
> -	if (__get_user_inatomic(instr, (unsigned int __user *)regs->nip))
> +	if (__get_user(instr, (unsigned int __user *)regs->nip))
>  		return;
>  
>  	/*
> -- 
> 2.25.0