linux-kernel - Re: [PATCH v2 1/3] kernel/uprobes: Warn if unable to install breakpoint

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Message-ID: <20170915155309.GA590@redhat.com>
Date:   Fri, 15 Sep 2017 17:53:09 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Anton Blanchard <anton@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] kernel/uprobes: Warn if unable to install
 breakpoint

On 09/14, Naveen N. Rao wrote:
>
> +static void uprobe_warn(struct task_struct *t, const char *msg)
> +{
> +	pr_warn("uprobe: %s:%d failed to %s\n",
> +			current->comm, current->pid, msg);
> +}
> +
>  /*
>   * valid_vma: Verify if the specified vma is an executable vma
>   * Relax restrictions while unregistering: vm_flags might have
> @@ -1087,7 +1093,14 @@ int uprobe_mmap(struct vm_area_struct *vma)
>  		if (!fatal_signal_pending(current) &&
>  		    filter_chain(uprobe, UPROBE_FILTER_MMAP, vma->vm_mm)) {
>  			unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
> -			install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
> +			int ret = install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
> +			if (ret) {
> +				char msg[64];
> +				snprintf(msg, sizeof(msg),
> +						"setup probe at 0x%llx (%d)",
> +						uprobe->offset, ret);
> +				uprobe_warn(current, (const char *)msg);

Agreed, but... this is cosmetic, but I don't really like this snprintf().

I won't insist too much, but wouldn't it better to turn uprobe_warn() into
uprobe_warn(struct task_struct *t, char *fmt, ...) ?

Oleg.