Re: [PATCH v3 1/2] linux-user: add sched_getattr support

[Laurent Vivier <laurent@vivier.eu>]

Le 23/12/2021 à 07:47, Tonis Tiigi a écrit :

Please copy here what you explain in PATCH 0 regarding this patch.
(do the same for PATCH 1)

> Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
> ---
>   linux-user/syscall.c      | 94 +++++++++++++++++++++++++++++++++++++++
>   linux-user/syscall_defs.h | 14 ++++++
>   2 files changed, 108 insertions(+)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index f1cfcc8104..2f5a0fac5a 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -339,6 +339,12 @@ _syscall3(int, sys_sched_getaffinity, pid_t, pid, unsigned int, len,
>   #define __NR_sys_sched_setaffinity __NR_sched_setaffinity
>   _syscall3(int, sys_sched_setaffinity, pid_t, pid, unsigned int, len,
>             unsigned long *, user_mask_ptr);
> +#define __NR_sys_sched_getattr __NR_sched_getattr
> +_syscall4(int, sys_sched_getattr, pid_t, pid, struct target_sched_attr *, attr,
> +          unsigned int, size, unsigned int, flags);
> +#define __NR_sys_sched_setattr __NR_sched_setattr
> +_syscall3(int, sys_sched_setattr, pid_t, pid, struct target_sched_attr *, attr,
> +          unsigned int, flags);
>   #define __NR_sys_getcpu __NR_getcpu
>   _syscall3(int, sys_getcpu, unsigned *, cpu, unsigned *, node, void *, tcache);
>   _syscall4(int, reboot, int, magic1, int, magic2, unsigned int, cmd,
> @@ -10593,6 +10599,94 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
>           }
>       case TARGET_NR_sched_getscheduler:
>           return get_errno(sched_getscheduler(arg1));
> +    case TARGET_NR_sched_getattr:
> +        {
> +            struct target_sched_attr *target_scha;
> +            struct target_sched_attr scha;

In fact, this scha is used with the host syscall, so it must be  sched_attr.

> +            if (arg2 == 0) {
> +                return -TARGET_EINVAL;
> +            }
> +            if (arg3 > sizeof(scha)) {
> +                arg3 = sizeof(scha);
> +            }
> +            ret = get_errno(sys_sched_getattr(arg1, &scha, arg3, arg4));
> +            if (!is_error(ret)) {
> +                target_scha = lock_user(VERIFY_WRITE, arg2, arg3, 0);
> +                if (!target_scha) {
> +                    return -TARGET_EFAULT;
> +                }
> +                target_scha->size = tswap32(scha.size);
> +                target_scha->sched_policy = tswap32(scha.sched_policy);
> +                target_scha->sched_flags = tswap64(scha.sched_flags);
> +                target_scha->sched_nice = tswap32(scha.sched_nice);
> +                target_scha->sched_priority = tswap32(scha.sched_priority);
> +                target_scha->sched_runtime = tswap64(scha.sched_runtime);
> +                target_scha->sched_deadline = tswap64(scha.sched_deadline);
> +                target_scha->sched_period = tswap64(scha.sched_period);
> +                if (scha.size > offsetof(struct target_sched_attr, sched_util_min)) {
> +                    target_scha->sched_util_min = tswap32(scha.sched_util_min);
> +                    target_scha->sched_util_max = tswap32(scha.sched_util_max);
> +                }
> +                unlock_user(target_scha, arg2, arg3);
> +            }
> +            return ret;
> +        }
> +    case TARGET_NR_sched_setattr:
> +        {
> +            struct target_sched_attr *target_scha;
> +            struct target_sched_attr scha;

scha is sched_attr as it is used with the host syscall.


> +            if (arg2 == 0) {
> +                return -TARGET_EINVAL;
> +            }
> +            uint32_t size;

QEMU coding style doesn't allow to mix declarations and statements.

> +            if (get_user_u32(size, arg2)) {
> +                return -TARGET_EFAULT;
> +            }
> +            if (!size) {
> +                size = offsetof(struct target_sched_attr, sched_util_min);
> +            }
> +            if (size < offsetof(struct target_sched_attr, sched_util_min)) {
> +                if (put_user_u32(sizeof(struct target_sched_attr), arg2)) {
> +                    return -TARGET_EFAULT;
> +                }
> +                return -TARGET_E2BIG;
> +            }
> +
> +            if (size > sizeof(scha)) {
> +                for (int i = sizeof(scha); i < size; i++) {
> +                    uint8_t b;
> +                    if (get_user_u8(b, arg2 + i)) {
> +                        return -TARGET_EFAULT;
> +                    }
> +                    if (b != 0) {
> +                        if (put_user_u32(sizeof(struct target_sched_attr), arg2)) {
> +                            return -TARGET_EFAULT;
> +                        }
> +                        return -TARGET_E2BIG;
> +                    }
> +                }
> +                size = sizeof(scha);
> +            }

I guess this is the code to mimic kernel copy_struct_from_user(), the part when usize > ksize.

It's a little bit ugly, but I can't disagree because the kernel does the same.

except that the kernel check for unsigned rather than for 8bit. Could you change that?

The best would be to define check_zeroed_user() in Qemu and use it here.

> +
> +            target_scha = lock_user(VERIFY_READ, arg2, size, 1);
> +            if (!target_scha) {
> +                return -TARGET_EFAULT;
> +            }
> +            scha.size = size;
> +            scha.sched_policy = tswap32(target_scha->sched_policy);
> +            scha.sched_flags = tswap64(target_scha->sched_flags);
> +            scha.sched_nice = tswap32(target_scha->sched_nice);
> +            scha.sched_priority = tswap32(target_scha->sched_priority);
> +            scha.sched_runtime = tswap64(target_scha->sched_runtime);
> +            scha.sched_deadline = tswap64(target_scha->sched_deadline);
> +            scha.sched_period = tswap64(target_scha->sched_period);
> +            if (size > offsetof(struct target_sched_attr, sched_util_min)) {
> +                scha.sched_util_min = tswap32(target_scha->sched_util_min);
> +                scha.sched_util_max = tswap32(target_scha->sched_util_max);
> +            }
> +            unlock_user(target_scha, arg2, 0);
> +            return get_errno(sys_sched_setattr(arg1, &scha, arg3));
> +        }
>       case TARGET_NR_sched_yield:
>           return get_errno(sched_yield());
>       case TARGET_NR_sched_get_priority_max:
> diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
> index 0b13975937..310d6ce8ad 100644
> --- a/linux-user/syscall_defs.h
> +++ b/linux-user/syscall_defs.h
> @@ -2914,4 +2914,18 @@ struct target_statx {
>      /* 0x100 */
>   };
>   
> +/* from kernel's include/linux/sched/types.h */
> +struct target_sched_attr {
> +    abi_uint size;
> +    abi_uint sched_policy;
> +    abi_ullong sched_flags;
> +    abi_int sched_nice;
> +    abi_uint sched_priority;
> +    abi_ullong sched_runtime;
> +    abi_ullong sched_deadline;
> +    abi_ullong sched_period;
> +    abi_uint sched_util_min;
> +    abi_uint sched_util_max;
> +};
> +
>   #endif

Thanks,
Laurent