[v5,64/67] linux-user: Add code for PR_GET/SET_UNALIGN

This requires extra work for each target, but adds the
common syscall code, and the necessary flag in CPUState.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/hw/core/cpu.h                     |  3 +++
 linux-user/generic/target_prctl_unalign.h | 27 +++++++++++++++++++++++
 cpu.c                                     | 20 ++++++++++++-----
 linux-user/syscall.c                      | 13 +++++++++--
 4 files changed, 56 insertions(+), 7 deletions(-)
 create mode 100644 linux-user/generic/target_prctl_unalign.h

On Thu, Oct 14, 2021 at 10:14 PM Richard Henderson <
richard.henderson@linaro.org> wrote:

> This requires extra work for each target, but adds the
> common syscall code, and the necessary flag in CPUState.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/hw/core/cpu.h                     |  3 +++
>  linux-user/generic/target_prctl_unalign.h | 27 +++++++++++++++++++++++
>  cpu.c                                     | 20 ++++++++++++-----
>  linux-user/syscall.c                      | 13 +++++++++--
>  4 files changed, 56 insertions(+), 7 deletions(-)
>  create mode 100644 linux-user/generic/target_prctl_unalign.h
>

Reviewed-by: Warner Losh <imp@bsdimp.com>



> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> index 1a10497af3..6202bbf9c3 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -412,6 +412,9 @@ struct CPUState {
>
>      bool ignore_memory_transaction_failures;
>
> +    /* Used for user-only emulation of prctl(PR_SET_UNALIGN). */
> +    bool prctl_unalign_sigbus;
> +
>      struct hax_vcpu_state *hax_vcpu;
>
>      struct hvf_vcpu_state *hvf;
> diff --git a/linux-user/generic/target_prctl_unalign.h
> b/linux-user/generic/target_prctl_unalign.h
> new file mode 100644
> index 0000000000..bc3b83af2a
> --- /dev/null
> +++ b/linux-user/generic/target_prctl_unalign.h
> @@ -0,0 +1,27 @@
> +/*
> + * Generic prctl unalign functions for linux-user
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +#ifndef GENERIC_TARGET_PRCTL_UNALIGN_H
> +#define GENERIC_TARGET_PRCTL_UNALIGN_H
> +
> +static abi_long do_prctl_get_unalign(CPUArchState *env, target_long arg2)
> +{
> +    CPUState *cs = env_cpu(env);
> +    uint32_t res = PR_UNALIGN_NOPRINT;
> +    if (cs->prctl_unalign_sigbus) {
> +        res |= PR_UNALIGN_SIGBUS;
> +    }
> +    return put_user_u32(res, arg2);
> +}
> +#define do_prctl_get_unalign do_prctl_get_unalign
> +
> +static abi_long do_prctl_set_unalign(CPUArchState *env, target_long arg2)
> +{
> +    env_cpu(env)->prctl_unalign_sigbus = arg2 & PR_UNALIGN_SIGBUS;
> +    return 0;
> +}
> +#define do_prctl_set_unalign do_prctl_set_unalign
> +
> +#endif /* GENERIC_TARGET_PRCTL_UNALIGN_H */
> diff --git a/cpu.c b/cpu.c
> index 9bce67ef55..9e388d9cd3 100644
> --- a/cpu.c
> +++ b/cpu.c
> @@ -179,13 +179,23 @@ void cpu_exec_unrealizefn(CPUState *cpu)
>      cpu_list_remove(cpu);
>  }
>
> +/*
> + * This can't go in hw/core/cpu.c because that file is compiled only
> + * once for both user-mode and system builds.
> + */
>  static Property cpu_common_props[] = {
> -#ifndef CONFIG_USER_ONLY
> +#ifdef CONFIG_USER_ONLY
>      /*
> -     * Create a memory property for softmmu CPU object,
> -     * so users can wire up its memory. (This can't go in hw/core/cpu.c
> -     * because that file is compiled only once for both user-mode
> -     * and system builds.) The default if no link is set up is to use
> +     * Create a property for the user-only object, so users can
> +     * adjust prctl(PR_SET_UNALIGN) from the command-line.
> +     * Has no effect if the target does not support the feature.
> +     */
> +    DEFINE_PROP_BOOL("prctl-unalign-sigbus", CPUState,
> +                     prctl_unalign_sigbus, false),
> +#else
> +    /*
> +     * Create a memory property for softmmu CPU object, so users can
> +     * wire up its memory.  The default if no link is set up is to use
>       * the system address space.
>       */
>      DEFINE_PROP_LINK("memory", CPUState, memory, TYPE_MEMORY_REGION,
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 7635c2397a..ac3bc8a330 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -6375,6 +6375,12 @@ static abi_long do_prctl_inval1(CPUArchState *env,
> abi_long arg2)
>  #ifndef do_prctl_get_tagged_addr_ctrl
>  #define do_prctl_get_tagged_addr_ctrl do_prctl_inval0
>  #endif
> +#ifndef do_prctl_get_unalign
> +#define do_prctl_get_unalign do_prctl_inval1
> +#endif
> +#ifndef do_prctl_set_unalign
> +#define do_prctl_set_unalign do_prctl_inval1
> +#endif
>
>  static abi_long do_prctl(CPUArchState *env, abi_long option, abi_long
> arg2,
>                           abi_long arg3, abi_long arg4, abi_long arg5)
> @@ -6438,6 +6444,11 @@ static abi_long do_prctl(CPUArchState *env,
> abi_long option, abi_long arg2,
>          }
>          return do_prctl_get_tagged_addr_ctrl(env);
>
> +    case PR_GET_UNALIGN:
> +        return do_prctl_get_unalign(env, arg2);
> +    case PR_SET_UNALIGN:
> +        return do_prctl_set_unalign(env, arg2);
> +
>      case PR_GET_DUMPABLE:
>      case PR_SET_DUMPABLE:
>      case PR_GET_KEEPCAPS:
> @@ -6480,8 +6491,6 @@ static abi_long do_prctl(CPUArchState *env, abi_long
> option, abi_long arg2,
>      case PR_SET_THP_DISABLE:
>      case PR_GET_TSC:
>      case PR_SET_TSC:
> -    case PR_GET_UNALIGN:
> -    case PR_SET_UNALIGN:
>      default:
>          /* Disable to prevent the target disabling stuff we need. */
>          return -TARGET_EINVAL;
> --
> 2.25.1
>
>