From: Guo Ren <guoren@kernel.org>
To: Jisheng Zhang <jszhang@kernel.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
llvm@lists.linux.dev
Subject: Re: [PATCH 3/4] riscv: fix race when vmap stack overflow and remove shadow_stack
Date: Tue, 27 Sep 2022 10:00:19 +0800 [thread overview]
Message-ID: <CAJF2gTRkPc7AQsUNZopevey61PD8o6BQBZKjgeLHmOgX+pj6dA@mail.gmail.com> (raw)
In-Reply-To: <YzJBXsiWrbmxM6Q2@xhacker>
On Tue, Sep 27, 2022 at 8:28 AM Jisheng Zhang <jszhang@kernel.org> wrote:
>
>
> > > #ifdef CONFIG_VMAP_STACK
> > > -static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
> > > - overflow_stack)__aligned(16);
> > > -/*
> > > - * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used
> > > - * to get per-cpu overflow stack(get_overflow_stack).
> > > - */
> > > -long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)];
> > > -asmlinkage unsigned long get_overflow_stack(void)
> > > -{
> > > - return (unsigned long)this_cpu_ptr(overflow_stack) +
> > > - OVERFLOW_STACK_SIZE;
> > > -}
> > > +unsigned long overflow_stack[NR_CPUS][OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16);
>
> If NR_CPUS is large, there's a non-trival memory waste, I have a
> solution for this case, will send a new version today.
Er...
Yes, we can't bypass the percpu mechanism. I also forgot the percpu
basic concept. In the end, I prefer the previous solution, maybe just
simply giving an atomic flag would be okay. (But we only have one
register (sp) which could be used, it seems not simple.)
>
> Thanks
--
Best Regards
Guo Ren
next prev parent reply other threads:[~2022-09-27 2:00 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-25 17:53 [PATCH 0/4] riscv: entry: further clean up and VMAP_STACK fix Jisheng Zhang
2022-09-25 17:53 ` [PATCH 1/4] riscv: remove extra level wrappers of trace_hardirqs_{on,off} Jisheng Zhang
2022-09-25 23:18 ` Guo Ren
2022-09-25 17:53 ` [PATCH 2/4] riscv: consolidate ret_from_kernel_thread into ret_from_fork Jisheng Zhang
2022-09-25 23:25 ` Guo Ren
2022-09-26 16:05 ` Jisheng Zhang
2022-09-26 23:55 ` Guo Ren
2022-09-28 16:40 ` Jisheng Zhang
2022-09-30 11:42 ` Guo Ren
2022-09-25 17:53 ` [PATCH 3/4] riscv: fix race when vmap stack overflow and remove shadow_stack Jisheng Zhang
2022-09-25 23:46 ` Guo Ren
2022-09-27 0:18 ` Jisheng Zhang
2022-09-27 2:00 ` Guo Ren [this message]
2022-11-23 17:02 ` Deepak Gupta
2022-09-25 17:53 ` [PATCH 4/4] riscv: entry: consolidate general regs saving into save_gp Jisheng Zhang
2022-09-25 23:29 ` Guo Ren
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