在 2022/4/13 1:17, Robin Murphy 写道:
On 12/04/2022 6:08 pm, Robin Murphy wrote:
[...]
@@ -62,7 +63,11 @@ SYM_FUNC_START(__arch_copy_from_user)
ret
// Exception fixups
-9997: cmp dst, dstin
+9997: mrs esr, esr_el1 // Check exception first
+ and esr, esr, #ESR_ELx_FSC
+ cmp esr, #ESR_ELx_FSC_EXTABT
Should we be checking EC to make sure it's a data abort - and thus FSC
is valid - in the first place? I'm a little fuzzy on all the possible
paths into fixup_exception(), and it's not entirely obvious whether
this is actually safe or not.
In fact, thinking some more about that, I don't think there should be
any need for this sort of logic in these handlers at all. The
fixup_exception() machinery should already know enough about the
exception that's happened and the extable entry to figure this out and
not bother calling the handler at all.
Thanks,
Robin.
.
Hi Robin:
As you said, it seems that it's not good to judge esr here, how about
using the following method, i need your suggestion :)
+#define FIXUP_TYPE_NORMAL 0
+#define FIXUP_TYPE_MC 1
arch/arm64/mm/extable.c
static bool ex_handler_fixup(const struct exception_table_entry *ex,
- struct pt_regs *regs)
+ struct pt_regs *regs, int fixuptype)
{
+ regs->regs[16] = fixuptype;
[...]
}
bool fixup_exception(struct pt_regs *regs)
{
[...]
switch(ex->type) {
case EX_TYPE_UACCESS_MC:
- return ex_handler_fixup(ex, regs)
+ return ex_handler_fixup(ex, regs, FIXUP_TYPE_NORMAL)
break;
}
[...]
}
bool fixup_exception_mc(struct pt_regs *regs)
{
[...]
switch(ex->type) {
case EX_TYPE_UACCESS_MC:
- return ex_handler_fixup(ex, regs)
+ return ex_handler_fixup(ex, regs, FIXUP_TYPE_MC)
break;
}
[...]
}
arch/arm64/lib/copy_from_user.S
arch/arm64/lib/copy_to_user.S
+fixup_type .req x16
// Exception fixups
//x16: fixup type written by ex_handler_fixup
-9997: cmp dst, dstin
+9997: cmp fixup_type, #FIXUP_TYPE_MC
+ b.eq 9998f
+ cmp dst, dstin
b.ne 9998f
Thanks,
Tong.
