[PATCH v3 14/18] smccc: Cast arguments to unsigned long
Andrew Scull
ascull at google.com
Tue Sep 8 06:58:28 EDT 2020
On Mon, Sep 07, 2020 at 02:33:17PM +0100, Marc Zyngier wrote:
> On Thu, 03 Sep 2020 14:53:03 +0100,
> Andrew Scull <ascull at google.com> wrote:
> >
> > To avoid warning about implicit casting, make the casting explicit. This
> > allows, for example, pointers to be used as arguments as are used in the
> > KVM hyp interface.
> >
> > Cc: Sudeep Holla <sudeep.holla at arm.com>
> > Signed-off-by: Andrew Scull <ascull at google.com>
> > ---
> > include/linux/arm-smccc.h | 20 ++++++++++----------
> > 1 file changed, 10 insertions(+), 10 deletions(-)
> >
> > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> > index 15c706fb0a37..3bb109a35554 100644
> > --- a/include/linux/arm-smccc.h
> > +++ b/include/linux/arm-smccc.h
> > @@ -260,7 +260,7 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
> > typeof(a1) __a1 = a1; \
> > struct arm_smccc_res *___res = res; \
> > register unsigned long r0 asm("r0") = (u32)a0; \
> > - register unsigned long r1 asm("r1") = __a1; \
> > + register unsigned long r1 asm("r1") = (unsigned long)__a1; \
>
> Given the pain we go through to extract the type of each argument, it
> seems odd to end-up with casts everywhere. I'd rather keep the type
> system alive by having:
>
> register typeof(a1) r1 asm("r1") = __a1;
>
> Is there any reason why this doesn't work?
There is. r1 is used both for the argument and the result so if
typeof(a1) cannot be implicitly assigned to unsigned long you'll get a
warning when populating arm_smccc_res.
The approach in this patch made the removal of types explicit with a
case rather then implicit in the assignment.
I had a go at breaking the link between the inputs and outputs. I've
replaced this patch with the following for the time being.
commit 16fd4f7d3c12e94f96f77c43491fbfe80417f27b
Author: Andrew Scull <ascull at google.com>
Date: Wed Jun 3 10:28:23 2020 +0100
smccc: Use separate variables for args and results
Using the same register-bound variable for both arguments and results
means these values share a type. That type must allow the arguments to
be assigned to it and must also be assignable to the unsigned long
fields of struct arm_smccc_res.
This restriction on types causes compiler warnings when the argument
cannot be implicitly assigned to an unsigned long, for example the
pointers that are used in the KVM hyp interface.
By separating the arguments and results into their own variables, the
type constraint is lifted allowing the arguments to avoid the need for
any type conversion.
Cc: Sudeep Holla <sudeep.holla at arm.com>
Signed-off-by: Andrew Scull <ascull at google.com>
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index 15c706fb0a37..4fe089ff2704 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -227,87 +227,67 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
#define __count_args(...) \
___count_args(__VA_ARGS__, 7, 6, 5, 4, 3, 2, 1, 0)
-#define __constraint_write_0 \
- "+r" (r0), "=&r" (r1), "=&r" (r2), "=&r" (r3)
-#define __constraint_write_1 \
- "+r" (r0), "+r" (r1), "=&r" (r2), "=&r" (r3)
-#define __constraint_write_2 \
- "+r" (r0), "+r" (r1), "+r" (r2), "=&r" (r3)
-#define __constraint_write_3 \
- "+r" (r0), "+r" (r1), "+r" (r2), "+r" (r3)
-#define __constraint_write_4 __constraint_write_3
-#define __constraint_write_5 __constraint_write_4
-#define __constraint_write_6 __constraint_write_5
-#define __constraint_write_7 __constraint_write_6
-
-#define __constraint_read_0
-#define __constraint_read_1
-#define __constraint_read_2
-#define __constraint_read_3
-#define __constraint_read_4 "r" (r4)
-#define __constraint_read_5 __constraint_read_4, "r" (r5)
-#define __constraint_read_6 __constraint_read_5, "r" (r6)
-#define __constraint_read_7 __constraint_read_6, "r" (r7)
+#define __constraint_read_0 "r" (arg0)
+#define __constraint_read_1 __constraint_read_0, "r" (arg1)
+#define __constraint_read_2 __constraint_read_1, "r" (arg2)
+#define __constraint_read_3 __constraint_read_2, "r" (arg3)
+#define __constraint_read_4 __constraint_read_3, "r" (arg4)
+#define __constraint_read_5 __constraint_read_4, "r" (arg5)
+#define __constraint_read_6 __constraint_read_5, "r" (arg6)
+#define __constraint_read_7 __constraint_read_6, "r" (arg7)
#define __declare_arg_0(a0, res) \
struct arm_smccc_res *___res = res; \
- register unsigned long r0 asm("r0") = (u32)a0; \
- register unsigned long r1 asm("r1"); \
- register unsigned long r2 asm("r2"); \
- register unsigned long r3 asm("r3")
+ register unsigned long arg0 asm("r0") = (u32)a0
#define __declare_arg_1(a0, a1, res) \
typeof(a1) __a1 = a1; \
struct arm_smccc_res *___res = res; \
- register unsigned long r0 asm("r0") = (u32)a0; \
- register unsigned long r1 asm("r1") = __a1; \
- register unsigned long r2 asm("r2"); \
- register unsigned long r3 asm("r3")
+ register unsigned long arg0 asm("r0") = (u32)a0; \
+ register typeof(a1) arg1 asm("r1") = __a1
#define __declare_arg_2(a0, a1, a2, res) \
typeof(a1) __a1 = a1; \
typeof(a2) __a2 = a2; \
struct arm_smccc_res *___res = res; \
- register unsigned long r0 asm("r0") = (u32)a0; \
- register unsigned long r1 asm("r1") = __a1; \
- register unsigned long r2 asm("r2") = __a2; \
- register unsigned long r3 asm("r3")
+ register unsigned long arg0 asm("r0") = (u32)a0; \
+ register typeof(a1) arg1 asm("r1") = __a1; \
+ register typeof(a2) arg2 asm("r2") = __a2
#define __declare_arg_3(a0, a1, a2, a3, res) \
typeof(a1) __a1 = a1; \
typeof(a2) __a2 = a2; \
typeof(a3) __a3 = a3; \
struct arm_smccc_res *___res = res; \
- register unsigned long r0 asm("r0") = (u32)a0; \
- register unsigned long r1 asm("r1") = __a1; \
- register unsigned long r2 asm("r2") = __a2; \
- register unsigned long r3 asm("r3") = __a3
+ register unsigned long arg0 asm("r0") = (u32)a0; \
+ register typeof(a1) arg1 asm("r1") = __a1; \
+ register typeof(a2) arg2 asm("r2") = __a2; \
+ register typeof(a3) arg3 asm("r3") = __a3
#define __declare_arg_4(a0, a1, a2, a3, a4, res) \
typeof(a4) __a4 = a4; \
__declare_arg_3(a0, a1, a2, a3, res); \
- register unsigned long r4 asm("r4") = __a4
+ register typeof(a4) arg4 asm("r4") = __a4
#define __declare_arg_5(a0, a1, a2, a3, a4, a5, res) \
typeof(a5) __a5 = a5; \
__declare_arg_4(a0, a1, a2, a3, a4, res); \
- register unsigned long r5 asm("r5") = __a5
+ register typeof(a5) arg5 asm("r5") = __a5
#define __declare_arg_6(a0, a1, a2, a3, a4, a5, a6, res) \
typeof(a6) __a6 = a6; \
__declare_arg_5(a0, a1, a2, a3, a4, a5, res); \
- register unsigned long r6 asm("r6") = __a6
+ register typeof(a6) arg6 asm("r6") = __a6
#define __declare_arg_7(a0, a1, a2, a3, a4, a5, a6, a7, res) \
typeof(a7) __a7 = a7; \
__declare_arg_6(a0, a1, a2, a3, a4, a5, a6, res); \
- register unsigned long r7 asm("r7") = __a7
+ register typeof(a7) arg7 asm("r7") = __a7
#define ___declare_args(count, ...) __declare_arg_ ## count(__VA_ARGS__)
#define __declare_args(count, ...) ___declare_args(count, __VA_ARGS__)
#define ___constraints(count) \
- : __constraint_write_ ## count \
: __constraint_read_ ## count \
: "memory"
#define __constraints(count) ___constraints(count)
@@ -319,8 +299,13 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
*/
#define __arm_smccc_1_1(inst, ...) \
do { \
+ register unsigned long r0 asm("r0"); \
+ register unsigned long r1 asm("r1"); \
+ register unsigned long r2 asm("r2"); \
+ register unsigned long r3 asm("r3"); \
__declare_args(__count_args(__VA_ARGS__), __VA_ARGS__); \
- asm volatile(inst "\n" \
+ asm volatile(inst "\n" : \
+ "=r" (r0), "=r" (r1), "=r" (r2), "=r" (r3) \
__constraints(__count_args(__VA_ARGS__))); \
if (___res) \
*___res = (typeof(*___res)){r0, r1, r2, r3}; \
@@ -366,7 +351,7 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
#define __fail_smccc_1_1(...) \
do { \
__declare_args(__count_args(__VA_ARGS__), __VA_ARGS__); \
- asm ("" __constraints(__count_args(__VA_ARGS__))); \
+ asm ("" : __constraints(__count_args(__VA_ARGS__))); \
if (___res) \
___res->a0 = SMCCC_RET_NOT_SUPPORTED; \
} while (0)
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