在 2022/6/18 11:26, Tong Tiangen 写道:

在 2022/6/17 16:24, Mark Rutland 写道:

quoted

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.

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.

quoted

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

.

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