Re: [PATCH -next v5 2/8] arm64: extable: make uaaccess helper use extable type EX_TYPE_UACCESS_ERR_ZERO

[Tong Tiangen]

在 2022/6/17 16:24, Mark Rutland 写道:
> On Sat, May 28, 2022 at 06:50:50AM +0000, Tong Tiangen wrote:
> > Currnetly, the extable type used by __arch_copy_from/to_user() is
> > EX_TYPE_FIXUP. In fact, It is more clearly to use meaningful
> > EX_TYPE_UACCESS_*.
> >
> > Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
> > Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> > ---
> >   arch/arm64/include/asm/asm-extable.h |  8 ++++++++
> >   arch/arm64/include/asm/asm-uaccess.h | 12 ++++++------
> >   2 files changed, 14 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
> > index 56ebe183e78b..9c94ac1f082c 100644
> > --- a/arch/arm64/include/asm/asm-extable.h
> > +++ b/arch/arm64/include/asm/asm-extable.h
> > @@ -28,6 +28,14 @@
> >   	__ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
> >   	.endm
> >   
> > +/*
> > + * Create an exception table entry for uaccess `insn`, which will branch to `fixup`
> > + * when an unhandled fault is taken.
> > + * ex->data = ~0 means both reg_err and reg_zero is set to wzr(x31).
> > + */
> > +	.macro          _asm_extable_uaccess, insn, fixup
> > +	__ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_UACCESS_ERR_ZERO, ~0)
> > +	.endm
>
> I'm not too keen on using `~0` here, since that also sets other bits in the
> data field, and its somewhat opaque.
>
> How painful is it to generate the data fields as with the C version of this
> macro, so that we can pass in wzr explciitly for the two sub-fields?
>
> Other than that, this looks good to me.
>
> Thanks,
> Mark.

ok, will fix next version.

Thanks,
Tong.

> >   /*
> >    * Create an exception table entry for `insn` if `fixup` is provided. Otherwise
> >    * do nothing.
> > diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
> > index 0557af834e03..75b211c98dea 100644
> > --- a/arch/arm64/include/asm/asm-uaccess.h
> > +++ b/arch/arm64/include/asm/asm-uaccess.h
> > @@ -61,7 +61,7 @@ alternative_else_nop_endif
> >   
> >   #define USER(l, x...)				\
> >   9999:	x;					\
> > -	_asm_extable	9999b, l
> > +	_asm_extable_uaccess	9999b, l
> >   
> >   /*
> >    * Generate the assembly for LDTR/STTR with exception table entries.
> > @@ -73,8 +73,8 @@ alternative_else_nop_endif
> >   8889:		ldtr	\reg2, [\addr, #8];
> >   		add	\addr, \addr, \post_inc;
> >   
> > -		_asm_extable	8888b,\l;
> > -		_asm_extable	8889b,\l;
> > +		_asm_extable_uaccess	8888b, \l;
> > +		_asm_extable_uaccess	8889b, \l;
> >   	.endm
> >   
> >   	.macro user_stp l, reg1, reg2, addr, post_inc
> > @@ -82,14 +82,14 @@ alternative_else_nop_endif
> >   8889:		sttr	\reg2, [\addr, #8];
> >   		add	\addr, \addr, \post_inc;
> >   
> > -		_asm_extable	8888b,\l;
> > -		_asm_extable	8889b,\l;
> > +		_asm_extable_uaccess	8888b,\l;
> > +		_asm_extable_uaccess	8889b,\l;
> >   	.endm
> >   
> >   	.macro user_ldst l, inst, reg, addr, post_inc
> >   8888:		\inst		\reg, [\addr];
> >   		add		\addr, \addr, \post_inc;
> >   
> > -		_asm_extable	8888b,\l;
> > +		_asm_extable_uaccess	8888b, \l;
> >   	.endm
> >   #endif
> > --
> > 2.25.1
> .