linux-kernel - Re: [PATCH v2 1/3] objtool: check: Fully validate the stack frame

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Date:   Tue, 29 Sep 2020 14:18:34 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Julien Thierry <jthierry@...hat.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, mbenes@...e.cz,
        raphael.gault@....com, benh@...nel.crashing.org
Subject: Re: [PATCH v2 1/3] objtool: check: Fully validate the stack frame

On Mon, Sep 28, 2020 at 10:36:29AM +0100, Julien Thierry wrote:
> +++ b/tools/objtool/arch/x86/include/cfi_regs.h
> @@ -22,4 +22,7 @@
>  #define CFI_RA			16
>  #define CFI_NUM_REGS		17

A few more naming nitpicks:

> +#define STACKFRAME_BP_OFFSET	-16
> +#define STACKFRAME_RA_OFFSET	-8

"Stack frame" has more than one meaning now, I suppose.  i.e. it could
also include the callee-saved registers and any other stack space
allocated by the function.

Would "call frame" be clearer?

  CALL_FRAME_BP_OFFSET
  CALL_FRAME_RA_OFFSET

?

> +++ b/tools/objtool/cfi.h
> @@ -35,4 +35,6 @@ struct cfi_state {
>  	bool end;
>  };
>  
> +#define STACKFRAME_SIZE	16

CALL_FRAME_SIZE ?

I'm sort of contradicting my previous comment here, but even though this
value may be generic, it's also very much intertwined with the
CALL_FRAME_{BP|RA}_OFFSET values.  So I get the feeling it really
belongs in the arch-specific cfi_regs.h next to the other defines after
all.

-- 
Josh