From: Peter Zijlstra <peterz@infradead.org>
To: 王贇 <yun.wang@linux.alibaba.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
"open list:PERFORMANCE EVENTS SUBSYSTEM"
<linux-perf-users@vger.kernel.org>,
"open list:PERFORMANCE EVENTS SUBSYSTEM"
<linux-kernel@vger.kernel.org>,
"open list:BPF (Safe dynamic programs and tools)"
<netdev@vger.kernel.org>,
"open list:BPF (Safe dynamic programs and tools)"
<bpf@vger.kernel.org>,
jroedel@suse.de, x86@kernel.org
Subject: Re: [PATCH] x86/dumpstack/64: Add guard pages to stack_info
Date: Thu, 16 Sep 2021 10:00:15 +0200 [thread overview]
Message-ID: <YUL5j/lY0mtx4NMq@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <76de02b7-4d87-4a3a-e4d4-048829749887@linux.alibaba.com>
On Thu, Sep 16, 2021 at 11:47:49AM +0800, 王贇 wrote:
> I did some debug and found the issue, we are missing:
>
> @@ -122,7 +137,10 @@ static __always_inline bool in_exception_stack(unsigned long *stack, struct stac
> info->type = ep->type;
> info->begin = (unsigned long *)begin;
> info->end = (unsigned long *)end;
> - info->next_sp = (unsigned long *)regs->sp;
> +
> + if (!(ep->type & STACK_TYPE_GUARD))
> + info->next_sp = (unsigned long *)regs->sp;
> +
> return true;
> }
>
> as the guard page are not working as real stack I guess?
Correct, but I thought I put if (type & GUARD) terminators in all paths
that ended up caring about ->next_sp. Clearly I seem to have missed one
:/
Let me try and figure out where that happens.
> With that one things going on correctly, and some trivials below.
> > enum stack_type {
> > - STACK_TYPE_UNKNOWN,
> > + STACK_TYPE_UNKNOWN = 0,
>
> Is this necessary?
No, but it makes it more explicit we care about the value.
> > STACK_TYPE_TASK,
> > STACK_TYPE_IRQ,
> > STACK_TYPE_SOFTIRQ,
> > STACK_TYPE_ENTRY,
> > STACK_TYPE_EXCEPTION,
> > STACK_TYPE_EXCEPTION_LAST = STACK_TYPE_EXCEPTION + N_EXCEPTION_STACKS-1,
> > + STACK_TYPE_GUARD = 0x80,
Note that this is a flag.
> > };
> >
> > struct stack_info {
> > --- a/arch/x86/kernel/dumpstack_64.c
> > +++ b/arch/x86/kernel/dumpstack_64.c
> > @@ -32,9 +32,15 @@ const char *stack_type_name(enum stack_t
> > {
> > BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
> >
> > + if (type == STACK_TYPE_TASK)
> > + return "TASK";
> > +
> > if (type == STACK_TYPE_IRQ)
> > return "IRQ";
> >
> > + if (type == STACK_TYPE_SOFTIRQ)
> > + return "SOFTIRQ";
> > +
>
> Do we need one for GUARD too?
No, GUARD is not a single type but a flag. The caller can trivially do
something like:
"%s %s", stack_type_name(type & ~GUARD),
(type & GUARD) ? "GUARD" : ""
> > if (type == STACK_TYPE_ENTRY) {
> > /*
> > * On 64-bit, we have a generic entry stack that we
> > @@ -111,10 +122,11 @@ static __always_inline bool in_exception
> > k = (stk - begin) >> PAGE_SHIFT;
> > /* Lookup the page descriptor */
> > ep = &estack_pages[k];
> > - /* Guard page? */
> > + /* unknown entry */
> > if (!ep->size)
> > return false;
> >
> > +
>
> Extra line?
Gone now, thanks!
next prev parent reply other threads:[~2021-09-16 8:00 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-09 3:13 [RFC PATCH] perf: fix panic by mark recursion inside perf_log_throttle 王贇
2021-09-09 6:10 ` 王贇
2021-09-10 15:38 ` Peter Zijlstra
2021-09-13 3:00 ` 王贇
2021-09-13 3:21 ` 王贇
2021-09-13 10:24 ` Peter Zijlstra
2021-09-13 10:36 ` Peter Zijlstra
2021-09-14 2:02 ` 王贇
2021-09-14 1:58 ` 王贇
2021-09-14 10:28 ` Peter Zijlstra
2021-09-15 1:51 ` 王贇
2021-09-15 15:17 ` [PATCH] x86/dumpstack/64: Add guard pages to stack_info Peter Zijlstra
2021-09-16 3:34 ` 王贇
2021-09-16 3:47 ` 王贇
2021-09-16 8:00 ` Peter Zijlstra [this message]
2021-09-16 8:03 ` Peter Zijlstra
2021-09-16 10:02 ` Peter Zijlstra
2021-09-17 2:15 ` 王贇
2021-09-17 3:02 ` 王贇
2021-09-17 10:21 ` Peter Zijlstra
2021-09-17 16:40 ` Peter Zijlstra
2021-09-18 2:30 ` 王贇
2021-09-18 6:56 ` Peter Zijlstra
2021-09-18 2:38 ` 王贇
2021-09-13 3:30 ` [PATCH] perf: fix panic by disable ftrace on fault.c 王贇
2021-09-13 14:49 ` Dave Hansen
2021-09-14 1:52 ` 王贇
2021-09-14 3:02 ` 王贇
2021-09-14 7:23 ` 王贇
2021-09-14 16:16 ` Dave Hansen
2021-09-15 1:56 ` 王贇
2021-09-15 3:27 ` Dave Hansen
2021-09-15 7:22 ` 王贇
2021-09-15 7:34 ` 王贇
2021-09-15 15:19 ` [PATCH] x86: Increase exception stack sizes Peter Zijlstra
2021-09-16 3:42 ` 王贇
2021-09-21 7:28 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-09-21 12:41 ` tip-bot2 for Peter Zijlstra
2021-09-14 2:08 ` [PATCH] perf: fix panic by disable ftrace on fault.c 王贇
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