On Sun, Mar 9, 2025 at 9:00 AM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> The third argument of the syscall contains the size of the
> cpu mask in bytes, not bits. Nor is the size rounded up to
> a multiple of sizeof(abi_ulong).
>
> Cc: qemu-stable@nongnu.org
> Reported-by: Andreas Schwab <schwab@suse.de>
> Fixes: 9e1c7d982d7 ("linux-user/riscv: Add syscall riscv_hwprobe")
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Thanks!
Applied to riscv-to-apply.next
Alistair
> ---
> linux-user/syscall.c | 55 +++++++++++++++++++++++---------------------
> 1 file changed, 29 insertions(+), 26 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 02ea4221c9..fcc77c094d 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -9118,35 +9118,38 @@ static void risc_hwprobe_fill_pairs(CPURISCVState *env,
> }
> }
>
> -static int cpu_set_valid(abi_long arg3, abi_long arg4)
> +/*
> + * If the cpumask_t of (target_cpus, cpusetsize) cannot be read: -EFAULT.
> + * If the cpumast_t has no bits set: -EINVAL.
> + * Otherwise the cpumask_t contains some bit set: 0.
> + * Unlike the kernel, we do not mask cpumask_t by the set of online cpus,
> + * nor bound the search by cpumask_size().
> + */
> +static int nonempty_cpu_set(abi_ulong cpusetsize, abi_ptr target_cpus)
> {
> - int ret, i, tmp;
> - size_t host_mask_size, target_mask_size;
> - unsigned long *host_mask;
> + unsigned char *p = lock_user(VERIFY_READ, target_cpus, cpusetsize, 1);
> + int ret = -TARGET_EFAULT;
>
> - /*
> - * cpu_set_t represent CPU masks as bit masks of type unsigned long *.
> - * arg3 contains the cpu count.
> - */
> - tmp = (8 * sizeof(abi_ulong));
> - target_mask_size = ((arg3 + tmp - 1) / tmp) * sizeof(abi_ulong);
> - host_mask_size = (target_mask_size + (sizeof(*host_mask) - 1)) &
> - ~(sizeof(*host_mask) - 1);
> -
> - host_mask = alloca(host_mask_size);
> -
> - ret = target_to_host_cpu_mask(host_mask, host_mask_size,
> - arg4, target_mask_size);
> - if (ret != 0) {
> - return ret;
> - }
> -
> - for (i = 0 ; i < host_mask_size / sizeof(*host_mask); i++) {
> - if (host_mask[i] != 0) {
> - return 0;
> + if (p) {
> + ret = -TARGET_EINVAL;
> + /*
> + * Since we only care about the empty/non-empty state of the cpumask_t
> + * not the individual bits, we do not need to repartition the bits
> + * from target abi_ulong to host unsigned long.
> + *
> + * Note that the kernel does not round up cpusetsize to a multiple of
> + * sizeof(abi_ulong). After bounding cpusetsize by cpumask_size(),
> + * it copies exactly cpusetsize bytes into a zeroed buffer.
> + */
> + for (abi_ulong i = 0; i < cpusetsize; ++i) {
> + if (p[i]) {
> + ret = 0;
> + break;
> + }
> }
> + unlock_user(p, target_cpus, 0);
> }
> - return -TARGET_EINVAL;
> + return ret;
> }
>
> static abi_long do_riscv_hwprobe(CPUArchState *cpu_env, abi_long arg1,
> @@ -9163,7 +9166,7 @@ static abi_long do_riscv_hwprobe(CPUArchState *cpu_env, abi_long arg1,
>
> /* check cpu_set */
> if (arg3 != 0) {
> - ret = cpu_set_valid(arg3, arg4);
> + ret = nonempty_cpu_set(arg3, arg4);
> if (ret != 0) {
> return ret;
> }
> --
> 2.43.0
>
>