在 2022/6/17 16:24, Mark Rutland 写道:

On Sat, May 28, 2022 at 06:50:50AM +0000, Tong Tiangen wrote:

quoted

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.

ok, will fix next version.

Thanks,
Tong.

quoted

  /*
   * 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

.