linux-kernel - Re: [PATCH v10 16/38] x86/ptrace: Add FRED additional information to the pt

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Message-ID: <336f77d6-1d94-d2b7-f429-855bfbc3f271@suse.com>
Date:   Wed, 20 Sep 2023 15:57:20 +0300
From:   Nikolay Borisov <nik.borisov@...e.com>
To:     Xin Li <xin3.li@...el.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
        linux-hyperv@...r.kernel.org, kvm@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        luto@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        peterz@...radead.org, jgross@...e.com, ravi.v.shankar@...el.com,
        mhiramat@...nel.org, andrew.cooper3@...rix.com,
        jiangshanlai@...il.com
Subject: Re: [PATCH v10 16/38] x86/ptrace: Add FRED additional information to
 the pt_regs structure



On 14.09.23 г. 7:47 ч., Xin Li wrote:
> FRED defines additional information in the upper 48 bits of cs/ss
> fields. Therefore add the information definitions into the pt_regs
> structure.
> 
> Specially introduce a new structure fred_ss to denote the FRED flags
> above SS selector, which avoids FRED_SSX_ macros and makes the code
> simpler and easier to read.
> 
> Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
> Tested-by: Shan Kang <shan.kang@...el.com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Xin Li <xin3.li@...el.com>
> ---
> 
> Changes since v9:
> * Introduce a new structure fred_ss to denote the FRED flags above SS
>    selector, which avoids FRED_SSX_ macros and makes the code simpler
>    and easier to read (Thomas Gleixner).
> * Use type u64 to define FRED bit fields instead of type unsigned int
>    (Thomas Gleixner).
> 
> Changes since v8:
> * Reflect stack frame definition changes from FRED spec 3.0 to 5.0.
> * Use __packed instead of __attribute__((__packed__)) (Borislav Petkov).
> * Put all comments above the members, like the rest of the file does
>    (Borislav Petkov).
> 
> Changes since v3:
> * Rename csl/ssl of the pt_regs structure to csx/ssx (x for extended)
>    (Andrew Cooper).
> ---
>   arch/x86/include/asm/ptrace.h | 51 +++++++++++++++++++++++++++++++----
>   1 file changed, 46 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
> index f08ea073edd6..5786c8ca5f4c 100644
> --- a/arch/x86/include/asm/ptrace.h
> +++ b/arch/x86/include/asm/ptrace.h
> @@ -56,6 +56,25 @@ struct pt_regs {
>   
>   #else /* __i386__ */
>   
> +struct fred_ss {
> +	u64	ss	: 16,	// SS selector

Is this structure conformant to the return state as described in FRED 5.0?

— The stack segment of the interrupted context, 64 bits formatted as follows:

• Bits 15:0 contain the SS selector. < - WE HAVE THIS

• Bits 31:16 are not currently defined and will be zero until they are. < - MISSING hole?


> +		sti	:  1,	// STI state < -
> +		swevent	:  1,	// Set if syscall, sysenter or INT n
> +		nmi	:  1,	// Event is NMI type
> +			: 13,
> +		vector	:  8,	// Event vector
> +			:  8,
> +		type	:  4,	// Event type
> +			:  4,
> +		enclave	:  1,	// Event was incident to enclave execution
> +		lm	:  1,	// CPU was in long mode
> +		nested	:  1,	// Nested exception during FRED delivery
> +				// not set for #DF
> +			:  1,
> +		insnlen	:  4;	// The length of the instruction causing the event
> +				// Only set for INT0, INT1, INT3, INT n, SYSCALL
> +};				// and SYSENTER. 0 otherwise.
> +

<Snip>