linux-kernel - Re: [PATCH v2 3/3] objtool: Support stack-swizzle

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Date:   Tue, 9 Feb 2021 11:35:28 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Miroslav Benes <mbenes@...e.cz>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Julien Thierry <jthierry@...hat.com>,
        Kees Cook <keescook@...omium.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] objtool: Support stack-swizzle

On Tue, Feb 09, 2021 at 10:16:03AM +0100, Peter Zijlstra wrote:
> @@ -2193,6 +2232,12 @@ static int update_cfi_state(struct instr
>  			/* mov reg, disp(%rsp) */
>  			save_reg(cfi, op->src.reg, CFI_CFA,
>  				 op->dest.offset - cfi->stack_size);
> +
> +		} else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
> +
> +			/* mov %rsp, (%reg); # setup a stack swizzle. */
> +			cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
> +			cfi->vals[op->dest.reg].offset = cfi->cfa.offset;

I'll change that to:

			cfi->vals[op->dest.reg].offset = cfa->offset;

To be more consistent with the rest of the code.

>  		}
>  
>  		break;
> 
>