Messages in this thread Patch in this message | | | Date | Sat, 18 Jun 2022 16:42:06 +0800 | Subject | Re: [PATCH -next v5 2/8] arm64: extable: make uaaccess helper use extable type EX_TYPE_UACCESS_ERR_ZERO | From | Tong Tiangen <> |
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在 2022/6/18 11:26, Tong Tiangen 写道: > > > 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@arm.com> >>> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> >>> --- >>> 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.
I tried to using data filelds as with C version, but here assembly code we can not using operator such as << and |, if we use lsl and orr instructions, the gpr will be occupied.
So how about using 0x3ff directly here? it means err register and zero register both set to x31.
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 >>> >> . > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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