Re: [PATCH 06/13] arc: define syscall_get_arch()

[Vineet Gupta]

On 11/8/18 7:16 PM, Dmitry V. Levin 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/arc/include/asm/syscall.h | 6 ++++++
>  include/uapi/linux/audit.h     | 1 +
>  2 files changed, 7 insertions(+)
>
> diff --git a/arch/arc/include/asm/syscall.h b/arch/arc/include/asm/syscall.h
> index 29de09804306..5662778a7411 100644
> --- a/arch/arc/include/asm/syscall.h
> +++ b/arch/arc/include/asm/syscall.h
> @@ -9,6 +9,7 @@
>  #ifndef _ASM_ARC_SYSCALL_H
>  #define _ASM_ARC_SYSCALL_H  1
>  
> +#include <uapi/linux/audit.h>
>  #include <linux/err.h>
>  #include <linux/sched.h>
>  #include <asm/unistd.h>
> @@ -68,4 +69,9 @@ syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
>  	}
>  }
>  
> +static inline int syscall_get_arch(void)
> +{
> +	return AUDIT_ARCH_ARC;
> +}
> +

Does ptrace (or user of this API) need a unique value per arch. Otherwise instead
of adding the boilerplate code to all arches, they could simply define AUDIT_ARCH
and common code could return it. Also the EM_xxx are not there in
include/uapi/linux/elf.h to begin with since libc elf.h already defines them.

>  #endif
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 818ae690ab79..a7149ceb5b98 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -375,6 +375,7 @@ enum {
>  
>  #define AUDIT_ARCH_AARCH64	(EM_AARCH64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
>  #define AUDIT_ARCH_ALPHA	(EM_ALPHA|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
> +#define AUDIT_ARCH_ARC		(EM_ARC)
>  #define AUDIT_ARCH_ARM		(EM_ARM|__AUDIT_ARCH_LE)
>  #define AUDIT_ARCH_ARMEB	(EM_ARM)
>  #define AUDIT_ARCH_CRIS		(EM_CRIS|__AUDIT_ARCH_LE)

So I don't have the context of this patch (or coverletter) but what exactly are we
trying to do with this (adding LE to audit)  - what happens when an arch is
capable of either and is say built for BE ?