netdev - Re: [PATCH] x86/dumpstack/64: Add guard pages to stack

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Date:   Fri, 17 Sep 2021 11:02:07 +0800
From:   王贇 <yun.wang@...ux.alibaba.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "open list:PERFORMANCE EVENTS SUBSYSTEM" 
        <linux-perf-users@...r.kernel.org>,
        "open list:PERFORMANCE EVENTS SUBSYSTEM" 
        <linux-kernel@...r.kernel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <netdev@...r.kernel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <bpf@...r.kernel.org>, jroedel@...e.de, x86@...nel.org,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH] x86/dumpstack/64: Add guard pages to stack_info



On 2021/9/16 下午6:02, Peter Zijlstra wrote:
[snip]
>  
> +static __always_inline bool in_stack_guard(void *addr, void *begin, void *end)
> +{
> +#ifdef CONFIG_VMAP_STACK
> +	if (addr > (begin - PAGE_SIZE))
> +		return true;

After fix this logical as:

  addr >= (begin - PAGE_SIZE) && addr < begin

it's working.

Regards,
Michael Wang

> +#endif
> +	return false;
> +}
[snip]
>  
>  #ifdef CONFIG_X86_ESPFIX64
> @@ -455,9 +456,11 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
>  	 * stack even if the actual trigger for the double fault was
>  	 * something else.
>  	 */
> -	if ((unsigned long)task_stack_page(tsk) - 1 - address < PAGE_SIZE) {
> -		handle_stack_overflow("kernel stack overflow (double-fault)",
> -				      regs, address);
> +	if (get_stack_info_noinstr((void *)address, current, &info) &&
> +	    info.type & STACK_TYPE_GUARD) {
> +		const char *name = stack_type_name(info.type & ~STACK_TYPE_GUARD);
> +		pr_emerg("BUG: %s stack guard hit at %p (stack is %p..%p)\n",
> +			 name, (void *)address, info.begin, info.end);
>  	}
>  #endif
>  
> @@ -708,7 +711,9 @@ asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *r
>  	sp    = regs->sp;
>  	stack = (unsigned long *)sp;
>  
> -	if (!get_stack_info_noinstr(stack, current, &info) || info.type == STACK_TYPE_ENTRY ||
> +	if (!get_stack_info_noinstr(stack, current, &info) ||
> +	    info.type & STACK_TYPE_GUARD ||
> +	    info.type == STACK_TYPE_ENTRY ||
>  	    info.type >= STACK_TYPE_EXCEPTION_LAST)
>  		sp = __this_cpu_ist_top_va(VC2);
>  
>