在 2022/6/18 20:40, Mark Rutland 写道:
On Sat, Jun 18, 2022 at 04:42:06PM +0800, Tong Tiangen wrote:
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.
I had a go at implementing this, and it seems simple enough. Please see:
https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/extable/asm-uaccess
I made the following modifications, and the other parts are based on
your implementation:
arch/arm64/include/asm/asm-extable.h
[...]
.macro _asm_extable_uaccess, insn, fixup
_ASM_EXTABLE_UACCESS(\insn, \fixup)
.endm
[...]
The following errors are reported during compilation:
[...]
arch/arm64/lib/clear_user.S:45: Error: invalid operands (*ABS* and *UND*
sections) for `<<'
[...]
"<<" is invalid operands in assembly, is there something wrong with me?
Thanks,
Tong.
Mark.
.
