Re: [PATCH 12/13] riscv: define syscall_get_arch()

[Palmer Dabbelt]

On Thu, 08 Nov 2018 19:17:13 PST (-0800), ldv@xxxxxxxxxxxx wrote:
> syscall_get_arch() is required to be implemented on all architectures
> that use tracehook_report_syscall_entry() in order to extend
> the generic ptrace API with PTRACE_GET_SYSCALL_INFO request.
>
> Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
> ---
>  arch/riscv/include/asm/syscall.h | 6 ++++++
>  include/uapi/linux/audit.h       | 1 +
>  2 files changed, 7 insertions(+)
>
> diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
> index 8d25f8904c00..7e1e26ca7317 100644
> --- a/arch/riscv/include/asm/syscall.h
> +++ b/arch/riscv/include/asm/syscall.h
> @@ -18,6 +18,7 @@
>  #ifndef _ASM_RISCV_SYSCALL_H
>  #define _ASM_RISCV_SYSCALL_H
>
> +#include <uapi/linux/audit.h>
>  #include <linux/sched.h>
>  #include <linux/err.h>
>
> @@ -99,4 +100,9 @@ static inline void syscall_set_arguments(struct task_struct *task,
>  	memcpy(&regs->a1 + i * sizeof(regs->a1), args, n * sizeof(regs->a0));
>  }
>
> +static inline int syscall_get_arch(void)
> +{
> +	return AUDIT_ARCH_RISCV;
> +}
> +
>  #endif	/* _ASM_RISCV_SYSCALL_H */
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index c4c8b131af48..ad4105c602a1 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -405,6 +405,7 @@ enum {
>  /* do not define AUDIT_ARCH_PPCLE since it is not supported by audit */
>  #define AUDIT_ARCH_PPC64	(EM_PPC64|__AUDIT_ARCH_64BIT)
>  #define AUDIT_ARCH_PPC64LE	(EM_PPC64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
> +#define AUDIT_ARCH_RISCV	(EM_RISCV|__AUDIT_ARCH_64BIT)
>  #define AUDIT_ARCH_S390		(EM_S390)
>  #define AUDIT_ARCH_S390X	(EM_S390|__AUDIT_ARCH_64BIT)
>  #define AUDIT_ARCH_SH		(EM_SH)

I think this is incorrect: EM_RISCV has 32-bit and 64-bit variants, and if I 
understand what's going on here this is marking all RISC-V targets as 64-bit.  
Since this is a userspace header, I think the right thing to switch on is 
__riscv_xlen, which will be defined to either 32 or 64 depending on the base 
ISA.

We're also little endian.