Re: [PATCH -next v5 2/8] arm64: extable: make uaaccess helper use extable type EX_TYPE_UACCESS_ERR_ZERO
From: Mark Rutland <mark.rutland@arm.com>
Date: 2022-06-17 08:24:54
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On Sat, May 28, 2022 at 06:50:50AM +0000, Tong Tiangen wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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.
quoted hunk ↗ jump to hunk
/* * 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
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