linux-kernel - Re: [PATCH v3 06/29] riscv: zicfiss / zicfilp extension csr and bit definitions

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Date: Fri, 10 May 2024 15:37:32 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Deepak Gupta <debug@...osinc.com>
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Subject: Re: [PATCH v3 06/29] riscv: zicfiss / zicfilp extension csr and bit
 definitions

On Wed, Apr 03, 2024 at 04:34:54PM -0700, Deepak Gupta wrote:
> zicfiss and zicfilp extension gets enabled via b3 and b2 in *envcfg CSR.
> menvcfg controls enabling for S/HS mode. henvcfg control enabling for VS
> while senvcfg controls enabling for U/VU mode.
> 
> zicfilp extension extends *status CSR to hold `expected landing pad` bit.
> A trap or interrupt can occur between an indirect jmp/call and target
> instr. `expected landing pad` bit from CPU is recorded into xstatus CSR so
> that when supervisor performs xret, `expected landing pad` state of CPU can
> be restored.
> 
> zicfiss adds one new CSR
> - CSR_SSP: CSR_SSP contains current shadow stack pointer.
> 
> Signed-off-by: Deepak Gupta <debug@...osinc.com>
> ---
>  arch/riscv/include/asm/csr.h | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index bbd2207adb39..3bb126d1c5ff 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -18,6 +18,15 @@
>  #define SR_MPP		_AC(0x00001800, UL) /* Previously Machine */
>  #define SR_SUM		_AC(0x00040000, UL) /* Supervisor User Memory Access */
>  
> +/* zicfilp landing pad status bit */
> +#define SR_SPELP	_AC(0x00800000, UL)
> +#define SR_MPELP	_AC(0x020000000000, UL)
> +#ifdef CONFIG_RISCV_M_MODE
> +#define SR_ELP		SR_MPELP
> +#else
> +#define SR_ELP		SR_SPELP
> +#endif
> +
>  #define SR_FS		_AC(0x00006000, UL) /* Floating-point Status */
>  #define SR_FS_OFF	_AC(0x00000000, UL)
>  #define SR_FS_INITIAL	_AC(0x00002000, UL)
> @@ -196,6 +205,8 @@
>  #define ENVCFG_PBMTE			(_AC(1, ULL) << 62)
>  #define ENVCFG_CBZE			(_AC(1, UL) << 7)
>  #define ENVCFG_CBCFE			(_AC(1, UL) << 6)
> +#define ENVCFG_LPE			(_AC(1, UL) << 2)
> +#define ENVCFG_SSE			(_AC(1, UL) << 3)
>  #define ENVCFG_CBIE_SHIFT		4
>  #define ENVCFG_CBIE			(_AC(0x3, UL) << ENVCFG_CBIE_SHIFT)
>  #define ENVCFG_CBIE_ILL			_AC(0x0, UL)
> @@ -216,6 +227,11 @@
>  #define SMSTATEEN0_HSENVCFG		(_ULL(1) << SMSTATEEN0_HSENVCFG_SHIFT)
>  #define SMSTATEEN0_SSTATEEN0_SHIFT	63
>  #define SMSTATEEN0_SSTATEEN0		(_ULL(1) << SMSTATEEN0_SSTATEEN0_SHIFT)
> +/*
> + * zicfiss user mode csr
> + * CSR_SSP holds current shadow stack pointer.
> + */
> +#define CSR_SSP                 0x011
>  
>  /* symbolic CSR names: */
>  #define CSR_CYCLE		0xc00
> -- 
> 2.43.2
> 

Reviewed-by: Charlie Jenkins <charlie@...osinc.com>