linux-kernel - Re: [PATCH V2 5/9] objtool: Add support for intra-function calls

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Message-ID: <20200407130729.GZ20730@hirez.programming.kicks-ass.net>
Date:   Tue, 7 Apr 2020 15:07:29 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, jpoimboe@...hat.com,
        jthierry@...hat.com, tglx@...utronix.de
Subject: Re: [PATCH V2 5/9] objtool: Add support for intra-function calls

On Tue, Apr 07, 2020 at 09:31:38AM +0200, Alexandre Chartre wrote:

> index a62e032863a8..7ee1561bf7ad 100644
> --- a/tools/objtool/arch/x86/decode.c
> +++ b/tools/objtool/arch/x86/decode.c
> @@ -497,3 +497,15 @@ void arch_initial_func_cfi_state(struct cfi_state *state)
>  	state->regs[16].base = CFI_CFA;
>  	state->regs[16].offset = -8;
>  }
> +
> +
> +void arch_configure_intra_function_call(struct stack_op *op)
> +{
> +	/*
> +	 * For the impact on the stack, make an intra-function
> +	 * call behaves like a push of an immediate value (the
> +	 * return address).
> +	 */
> +	op->src.type = OP_SRC_CONST;
> +	op->dest.type = OP_DEST_PUSH;
> +}

An alternative is to always set up stack ops for CALL/RET on decode, but
conditionally run update_insn_state() for them.

Not sure that makes more logical sense, but the patch would be simpler I
think.