Re: [PATCH v2 08/24] linux-user/syscall: introduce prctl for indirect branch tracking

[Richard Henderson]

On 7/30/24 03:53, Deepak Gupta wrote:
> Each application enables indirect branch tracking (forward cfi) for itself
> via prctl. Adding branch tracking prctl in linux-user/syscall.
>
> Using same prctl code as proposed in cfi patches in kernel mailing list [1]
>
> [1] - https://lore.kernel.org/all/20240403234054.2020347-1-debug@rivosinc.com/
>
> Signed-off-by: Deepak Gupta <debug@rivosinc.com>
> Co-developed-by: Jim Shu <jim.shu@sifive.com>
> Co-developed-by: Andy Chiu <andy.chiu@sifive.com>
> Co-developed-by: Jesse Huang <jesse.huang@sifive.com>
> ---
>   linux-user/syscall.c | 19 +++++++++++++++++++
>   1 file changed, 19 insertions(+)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index b8c278b91d..ec157c1088 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -6295,6 +6295,17 @@ abi_long do_arch_prctl(CPUX86State *env, int code, 
> abi_ulong addr)
>   # define PR_SME_VL_INHERIT   (1 << 17)
>   #endif
>   
> +#ifndef PR_GET_INDIR_BR_LP_STATUS
> +# define PR_GET_INDIR_BR_LP_STATUS      74
> +#endif
> +#ifndef PR_SET_INDIR_BR_LP_STATUS
> +# define PR_SET_INDIR_BR_LP_STATUS      75
> +# define PR_INDIR_BR_LP_ENABLE          (1UL << 0)
> +#endif
> +#ifndef PR_LOCK_INDIR_BR_LP_STATUS
> +# define PR_LOCK_INDIR_BR_LP_STATUS     76
> +#endif

This will of course have to wait until the uapi lands upstream.

> @@ -6477,6 +6488,14 @@ static abi_long do_prctl(CPUArchState *env, abi_long 
> option, abi_long arg2,
>       case PR_SET_TSC:
>           /* Disable to prevent the target disabling stuff we need. */
>           return -TARGET_EINVAL;
> +    case PR_GET_INDIR_BR_LP_STATUS:
> +    case PR_SET_INDIR_BR_LP_STATUS:
> +    case PR_LOCK_INDIR_BR_LP_STATUS:
> +#ifndef do_prctl_cfi
> +        return do_prctl_inval1(env, arg2);
> +#else
> +        return do_prctl_cfi(env, option, arg2);
> +#endif

Do not combine 3 prctl into one.
Do not put the ifdef here; put it above with the rest, e.g.

#ifndef do_prctl_set_fp_mode
#define do_prctl_set_fp_mode do_prctl_inval1
#endif


r~