Re: [PATCH Part2 RFC v4 08/40] x86/traps: Define RMP violation #PF error code

[Sean Christopherson]

On Wed, Jul 07, 2021, Brijesh Singh wrote:
> Bit 31 in the page fault-error bit will be set when processor encounters
> an RMP violation.
> 
> While at it, use the BIT() macro.
> 
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> ---
>  arch/x86/include/asm/trap_pf.h | 18 +++++++++++-------
>  arch/x86/mm/fault.c            |  1 +
>  2 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/include/asm/trap_pf.h b/arch/x86/include/asm/trap_pf.h
> index 10b1de500ab1..29f678701753 100644
> --- a/arch/x86/include/asm/trap_pf.h
> +++ b/arch/x86/include/asm/trap_pf.h
> @@ -2,6 +2,8 @@
>  #ifndef _ASM_X86_TRAP_PF_H
>  #define _ASM_X86_TRAP_PF_H
>  
> +#include <vdso/bits.h>  /* BIT() macro */

What are people's thoughts on using linux/bits.h instead of vdso.bits.h, even
though the vDSO version is technically sufficient?  Seeing the "vdso" reference
definitely made me blink slowly a few times.

> +
>  /*
>   * Page fault error code bits:
>   *
> @@ -12,15 +14,17 @@
>   *   bit 4 ==				1: fault was an instruction fetch
>   *   bit 5 ==				1: protection keys block access
>   *   bit 15 ==				1: SGX MMU page-fault
> + *   bit 31 ==				1: fault was an RMP violation
>   */
>  enum x86_pf_error_code {
> -	X86_PF_PROT	=		1 << 0,
> -	X86_PF_WRITE	=		1 << 1,
> -	X86_PF_USER	=		1 << 2,
> -	X86_PF_RSVD	=		1 << 3,
> -	X86_PF_INSTR	=		1 << 4,
> -	X86_PF_PK	=		1 << 5,
> -	X86_PF_SGX	=		1 << 15,
> +	X86_PF_PROT	=		BIT(0),
> +	X86_PF_WRITE	=		BIT(1),
> +	X86_PF_USER	=		BIT(2),
> +	X86_PF_RSVD	=		BIT(3),
> +	X86_PF_INSTR	=		BIT(4),
> +	X86_PF_PK	=		BIT(5),
> +	X86_PF_SGX	=		BIT(15),
> +	X86_PF_RMP	=		BIT(31),
>  };
>  
>  #endif /* _ASM_X86_TRAP_PF_H */
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 1c548ad00752..2715240c757e 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -545,6 +545,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
>  		 !(error_code & X86_PF_PROT) ? "not-present page" :
>  		 (error_code & X86_PF_RSVD)  ? "reserved bit violation" :
>  		 (error_code & X86_PF_PK)    ? "protection keys violation" :
> +		 (error_code & X86_PF_RMP)   ? "rmp violation" :
>  					       "permissions violation");
>  
>  	if (!(error_code & X86_PF_USER) && user_mode(regs)) {
> -- 
> 2.17.1
>