linux-kernel - Re: [PATCH V2 6/6] arm64: Add uprobe support

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Message-ID: <20161030140901.h6mdxbb4pgqpqs7j@localhost>
Date:   Sun, 30 Oct 2016 14:09:01 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Pratyush Anand <panand@...hat.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
        srikar@...ux.vnet.ibm.com, vijaya.kumar@...iumnetworks.com,
        will.deacon@....com, linux-kernel@...r.kernel.org, oleg@...hat.com,
        dave.long@...aro.org, steve.capper@...aro.org, wcohen@...hat.com
Subject: Re: [PATCH V2 6/6] arm64: Add uprobe support

On Tue, Sep 27, 2016 at 01:18:00PM +0530, Pratyush Anand wrote:
> --- /dev/null
> +++ b/arch/arm64/kernel/probes/uprobes.c
> @@ -0,0 +1,221 @@
> +/*
> + * Copyright (C) 2014-2016 Pratyush Anand <panand@...hat.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +#include <linux/highmem.h>
> +#include <linux/ptrace.h>
> +#include <linux/uprobes.h>
> +#include <asm/cacheflush.h>
> +
> +#include "decode-insn.h"
> +
> +#define UPROBE_INV_FAULT_CODE	UINT_MAX
> +
> +bool is_trap_insn(uprobe_opcode_t *insn)
> +{
> +	return false;
> +}

On the previous series, I had a comment left unanswered with regards to
always returning false in is_trap_insn():

Looking at handle_swbp(), if we hit a breakpoint for which we don't have
a valid uprobe, this function currently sends a SIGTRAP. But if
is_trap_insn() returns false always, is_trap_at_addr() would return 0 in
this case so the SIGTRAP is never issued.

-- 
Catalin