Subject: Re: [PATCH 06/18] powerpc sstep: Add support for prefixed integer load/stores

From: Balamuruhan S <[email-masked]>
Date: Fri, 10 Jan 2020 20:43:36 +0530

On Tue, Nov 26, 2019 at 04:21:29PM +1100, Jordan Niethe wrote:
> This adds emulation support for the following prefixed integer
> load/stores:
>   * Prefixed Load Byte and Zero (plbz)
>   * Prefixed Load Halfword and Zero (plhz)
>   * Prefixed Load Halfword Algebraic (plha)
>   * Prefixed Load Word and Zero (plwz)
>   * Prefixed Load Word Algebraic (plwa)
>   * Prefixed Load Doubleword (pld)
>   * Prefixed Store Byte (pstb)
>   * Prefixed Store Halfword (psth)
>   * Prefixed Store Word (pstw)
>   * Prefixed Store Doubleword (pstd)
>   * Prefixed Load Quadword (plq)
>   * Prefixed Store Quadword (pstq)
> 
> Signed-off-by: Jordan Niethe <[email-masked]>
> ---
>  arch/powerpc/lib/sstep.c | 110 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 110 insertions(+)
> 
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index ade3f5eba2e5..4f5ad1f602d8 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -187,6 +187,43 @@ static nokprobe_inline unsigned long xform_ea(unsigned int instr,
>  	return ea;
>  }
>  
> +/*
> + * Calculate effective address for a MLS:D-form / 8LS:D-form prefixed instruction
> + */
> +static nokprobe_inline unsigned long mlsd_8lsd_ea(unsigned int instr,
> +						  unsigned int sufx,
> +						  const struct pt_regs *regs)
> +{
> +	int ra, prefix_r;
> +	unsigned int  dd;
> +	unsigned long ea, d0, d1, d;
> +
> +	prefix_r = instr & (1ul << 20);
> +	ra = (sufx >> 16) & 0x1f;
> +
> +	d0 = instr & 0x3ffff;
> +	d1 = sufx & 0xffff;
> +	d = (d0 << 16) | d1;
> +
> +	/*
> +	 * sign extend a 34 bit number
> +	 */
> +	dd = (unsigned int) (d >> 2);
> +	ea = (signed int) dd;
> +	ea = (ea << 2) | (d & 0x3);
> +
> +	if (!prefix_r && ra)
> +		ea += regs->gpr[ra];
> +	else if (!prefix_r && !ra)
> +		; /* Leave ea as is */
> +	else if (prefix_r && !ra)
> +		ea += regs->nip;
> +	else if (prefix_r && ra)
> +		; /* Invalid form. Should already be checked for by caller! */
> +
> +	return ea;
> +}
> +
>  /*
>   * Return the largest power of 2, not greater than sizeof(unsigned long),
>   * such that x is a multiple of it.
> @@ -1166,6 +1203,7 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
>  		  unsigned int instr, unsigned int sufx)
>  {
>  	unsigned int opcode, ra, rb, rc, rd, spr, u;
> +	unsigned int sufxopcode, prefixtype, prefix_r;
>  	unsigned long int imm;
>  	unsigned long int val, val2;
>  	unsigned int mb, me, sh;
> @@ -2652,6 +2690,78 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
>  
>  	}
>  
> +/*
> + * Prefixed instructions
> + */
> +	switch (opcode) {
> +	case 1:
> +		prefix_r = instr & (1ul << 20);
> +		ra = (sufx >> 16) & 0x1f;
> +		op->update_reg = ra;
> +		rd = (sufx >> 21) & 0x1f;
> +		op->reg = rd;
> +		op->val = regs->gpr[rd];
> +
> +		sufxopcode = sufx >> 26;
> +		prefixtype = (instr >> 24) & 0x3;
> +		switch (prefixtype) {
> +		case 0: /* Type 00  Eight-Byte Load/Store */
> +			if (prefix_r && ra)
> +				break;
> +			op->ea = mlsd_8lsd_ea(instr, sufx, regs);
> +			switch (sufxopcode) {
> +			case 41:	/* plwa */
> +				op->type = MKOP(LOAD, PREFIXED | SIGNEXT, 4);
> +				break;
> +			case 56:        /* plq */
> +				op->type = MKOP(LOAD, PREFIXED, 16);
> +				break;
> +			case 57:	/* pld */
> +				op->type = MKOP(LOAD, PREFIXED | SIGNEXT, 8);
> +				break;
> +			case 60:        /* stq */
> +				op->type = MKOP(STORE, PREFIXED, 16);
> +				break;
> +			case 61:	/* pstd */
> +				op->type = MKOP(STORE, PREFIXED | SIGNEXT, 8);

sorry, we don't do SIGNEXT for 1 byte below in Type 10, so does 8 byte is used
conscious without definition in `do_signext()` as we don't really need to do
anything ?

-- Bala

> +				break;
> +			}
> +			break;
> +		case 1: /* Type 01 Modified Register-to-Register */
> +			break;
> +		case 2: /* Type 10 Modified Load/Store */
> +			if (prefix_r && ra)
> +				break;
> +			op->ea = mlsd_8lsd_ea(instr, sufx, regs);
> +			switch (sufxopcode) {
> +			case 32:	/* plwz */
> +				op->type = MKOP(LOAD, PREFIXED, 4);
> +				break;
> +			case 34:	/* plbz */
> +				op->type = MKOP(LOAD, PREFIXED, 1);
> +				break;
> +			case 36:	/* pstw */
> +				op->type = MKOP(STORE, PREFIXED, 4);
> +				break;
> +			case 38:	/* pstb */
> +				op->type = MKOP(STORE, PREFIXED, 1);
> +				break;
> +			case 40:	/* plhz */
> +				op->type = MKOP(LOAD, PREFIXED, 2);
> +				break;
> +			case 42:	/* plha */
> +				op->type = MKOP(LOAD, PREFIXED | SIGNEXT, 2);
> +				break;
> +			case 44:	/* psth */
> +				op->type = MKOP(STORE, PREFIXED, 2);
> +				break;
> +			}
> +			break;
> +		case 3: /* Type 11 Modified Register-to-Register */
> +			break;
> +		}
> +	}
> +
>  #ifdef CONFIG_VSX
>  	if ((GETTYPE(op->type) == LOAD_VSX ||
>  	     GETTYPE(op->type) == STORE_VSX) &&
> -- 
> 2.20.1
>