Re: [PATCH -next v19 20/24] riscv: Add prctl controls for userspace vector management

Palmer Dabbelt
2023-05-09T17:59:04Z

On Tue, 09 May 2023 04:14:26 PDT (-0700), heiko@sntech.de wrote:
> Hi,
>
> need to poke this more, but one issue popped up at first compile.
>
> Am Dienstag, 9. Mai 2023, 12:30:29 CEST schrieb Andy Chiu:
>> This patch add two riscv-specific prctls, to allow usespace control the
>> use of vector unit:
>>
>> * PR_RISCV_V_SET_CONTROL: control the permission to use Vector at next,
>> or all following execve for a thread. Turning off a thread's Vector
>> live is not possible since libraries may have registered ifunc that
>> may execute Vector instructions.
>> * PR_RISCV_V_GET_CONTROL: get the same permission setting for the
>> current thread, and the setting for following execve(s).
>>
>> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
>> Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
>> Reviewed-by: Vincent Chen <vincent.chen@sifive.com>
>
>
>> diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
>> index 960a343799c6..16ccb35625a9 100644
>> --- a/arch/riscv/kernel/vector.c
>> +++ b/arch/riscv/kernel/vector.c
>> @@ -9,6 +9,7 @@
>> #include <linux/slab.h>
>> #include <linux/sched.h>
>> #include <linux/uaccess.h>
>> +#include <linux/prctl.h>
>>
>> #include <asm/thread_info.h>
>> #include <asm/processor.h>
>> @@ -19,6 +20,8 @@
>> #include <asm/ptrace.h>
>> #include <asm/bug.h>
>>
>> +static bool riscv_v_implicit_uacc = !IS_ENABLED(CONFIG_RISCV_V_DISABLE);
>> +
>> unsigned long riscv_v_vsize __read_mostly;
>> EXPORT_SYMBOL_GPL(riscv_v_vsize);
>>
>> @@ -91,11 +94,51 @@ static int riscv_v_thread_zalloc(void)
>> return 0;
>> }
>>
>> +#define VSTATE_CTRL_GET_CUR(x) ((x) & PR_RISCV_V_VSTATE_CTRL_CUR_MASK)
>> +#define VSTATE_CTRL_GET_NEXT(x) (((x) & PR_RISCV_V_VSTATE_CTRL_NEXT_MASK) >> 2)
>> +#define VSTATE_CTRL_MAKE_NEXT(x) (((x) << 2) & PR_RISCV_V_VSTATE_CTRL_NEXT_MASK)
>> +#define VSTATE_CTRL_GET_INHERIT(x) (!!((x) & PR_RISCV_V_VSTATE_CTRL_INHERIT))
>> +static inline int riscv_v_get_cur_ctrl(struct task_struct *tsk)
>> +{
>> + return VSTATE_CTRL_GET_CUR(tsk->thread.vstate_ctrl);
>> +}
>> +
>> +static inline int riscv_v_get_next_ctrl(struct task_struct *tsk)
>> +{
>> + return VSTATE_CTRL_GET_NEXT(tsk->thread.vstate_ctrl);
>> +}
>> +
>> +static inline bool riscv_v_test_ctrl_inherit(struct task_struct *tsk)
>> +{
>> + return VSTATE_CTRL_GET_INHERIT(tsk->thread.vstate_ctrl);
>> +}
>> +
>> +static inline void riscv_v_set_ctrl(struct task_struct *tsk, int cur, int nxt,
>> + bool inherit)
>> +{
>> + unsigned long ctrl;
>> +
>> + ctrl = cur & PR_RISCV_V_VSTATE_CTRL_CUR_MASK;
>> + ctrl |= VSTATE_CTRL_MAKE_NEXT(nxt);
>> + if (inherit)
>> + ctrl |= PR_RISCV_V_VSTATE_CTRL_INHERIT;
>> + tsk->thread.vstate_ctrl = ctrl;
>> +}
>> +
>> +bool riscv_v_user_allowed(void)
>> +{
>> + return riscv_v_get_cur_ctrl(current) == PR_RISCV_V_VSTATE_CTRL_ON;
>> +}
>
> EXPORT_SYMBOL(riscv_v_user_allowed);
>
> kvm is allowed to be built as module, so you could end up with:
>
> ERROR: modpost: "riscv_v_user_allowed" [arch/riscv/kvm/kvm.ko] undefined!
> make[2]: *** [../scripts/Makefile.modpost:136: Module.symvers] Fehler 1
> make[1]: *** [/home/devel/hstuebner/00_git-repos/linux-riscv/Makefile:1978: modpost] Fehler 2
> make[1]: Verzeichnis „/home/devel/hstuebner/00_git-repos/linux-riscv/_build-riscv64“ wird verlassen
> make: *** [Makefile:226: __sub-make] Fehler 2

and presumably that means that "make allmodconfig" hasn't been run,
which might shake out some more issues.

>
>
> Heiko