Re: [PATCH 2/2] riscv: Fixup static_obj() fail v2

[Atish Patra <atishp@atishpatra.org>]

On Thu, Oct 8, 2020 at 6:53 PM Guo Ren <guoren@kernel.org> wrote:
>
> On Thu, Oct 8, 2020 at 11:54 AM Palmer Dabbelt <palmerdabbelt@google.com> wrote:
> >
> > On Wed, 07 Oct 2020 08:08:33 PDT (-0700), guoren@kernel.org wrote:
> > > From: Guo Ren <guoren@linux.alibaba.com>
> > >
> > > v1 is commit: 6184358da0004c8fd940afda6c0a0fa4027dc911 which has
> > > been reverted.
> > >
> > > When enable LOCKDEP, static_obj() will cause error:
> > >
> > > [    0.067192] INFO: trying to register non-static key.
> > > [    0.067325] the code is fine but needs lockdep annotation.
> > > [    0.067449] turning off the locking correctness validator.
> > > [    0.067718] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.7.0-rc7-dirty #44
> > > [    0.067945] Call Trace:
> > > [    0.068369] [<ffffffe00020323c>] walk_stackframe+0x0/0xa4
> > > [    0.068506] [<ffffffe000203422>] show_stack+0x2a/0x34
> > > [    0.068631] [<ffffffe000521e4e>] dump_stack+0x94/0xca
> > > [    0.068757] [<ffffffe000255a4e>] register_lock_class+0x5b8/0x5bc
> > > [    0.068969] [<ffffffe000255abe>] __lock_acquire+0x6c/0x1d5c
> > > [    0.069101] [<ffffffe0002550fe>] lock_acquire+0xae/0x312
> > > [    0.069228] [<ffffffe000989a8e>] _raw_spin_lock_irqsave+0x40/0x5a
> > > [    0.069357] [<ffffffe000247c64>] complete+0x1e/0x50
> > > [    0.069479] [<ffffffe000984c38>] rest_init+0x1b0/0x28a
> > > [    0.069660] [<ffffffe0000016a2>] 0xffffffe0000016a2
> > > [    0.069779] [<ffffffe000001b84>] 0xffffffe000001b84
> > > [    0.069953] [<ffffffe000001092>] 0xffffffe000001092
> > >
> > > Because some __initdata static variables is before _stext:
> > >
> > > static int static_obj(const void *obj)
> > > {
> > >         unsigned long start = (unsigned long) &_stext,
> > >                       end   = (unsigned long) &_end,
> > >                       addr  = (unsigned long) obj;
> > >
> > >         /*
> > >          * static variable?
> > >          */
> > >         if ((addr >= start) && (addr < end))
> > >                 return 1;
> > >
> > >       if (arch_is_kernel_data(addr))
> > >               return 1;
> > >
> > > We could implement arch_is_kernel_data to fixup it.
> > >
> > > Link: https://lore.kernel.org/linux-riscv/1593266228-61125-1-git-send-email-guoren@kernel.org/T/#t
> > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > > Reported-by: Aurelien Jarno <aurelien@aurel32.net>
> > > Cc: Palmer Dabbelt <palmerdabbelt@google.com>
> > > Cc: Atish Patra <atishp@atishpatra.org>
> > > Cc: Andreas Schwab <schwab@linux-m68k.org>
> > > Cc: Aurelien Jarno <aurelien@aurel32.net>
> > > ---
> > >  arch/riscv/include/asm/sections.h | 20 ++++++++++++++++++++
> > >  arch/riscv/kernel/setup.c         |  9 +++++++++
> > >  2 files changed, 29 insertions(+)
> > >  create mode 100644 arch/riscv/include/asm/sections.h
> > >
> > > diff --git a/arch/riscv/include/asm/sections.h b/arch/riscv/include/asm/sections.h
> > > new file mode 100644
> > > index 00000000..2317b9e
> > > --- /dev/null
> > > +++ b/arch/riscv/include/asm/sections.h
> > > @@ -0,0 +1,20 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-only */
> > > +
> > > +#ifndef _ASM_RISCV_SECTIONS_H
> > > +#define _ASM_RISCV_SECTIONS_H
> > > +
> > > +#define arch_is_kernel_data arch_is_kernel_data
> > > +
> > > +#include <asm-generic/sections.h>
> > > +
> > > +extern bool init_mem_is_free;
> > > +
> > > +static inline int arch_is_kernel_data(unsigned long addr)
> > > +{
> > > +     if (init_mem_is_free)
> > > +             return 0;
> > > +
> > > +     return addr >= (unsigned long)__init_begin &&
> > > +             addr < (unsigned long)__init_end;
> > > +}
> > > +#endif /* _ASM_RISCV_SECTIONS_H */
> > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> > > index 2c6dd32..9ebd5eb4 100644
> > > --- a/arch/riscv/kernel/setup.c
> > > +++ b/arch/riscv/kernel/setup.c
> > > @@ -17,6 +17,7 @@
> > >  #include <linux/sched/task.h>
> > >  #include <linux/swiotlb.h>
> > >  #include <linux/smp.h>
> > > +#include <linux/poison.h>
> > >
> > >  #include <asm/cpu_ops.h>
> > >  #include <asm/setup.h>
> > > @@ -112,3 +113,11 @@ static int __init topology_init(void)
> > >       return 0;
> > >  }
> > >  subsys_initcall(topology_init);
> > > +
> > > +bool init_mem_is_free = false;
> > > +
> > > +void free_initmem(void)
> > > +{
> > > +     free_initmem_default(POISON_FREE_INITMEM);
> > > +     init_mem_is_free = true;
> > > +}
> >
> > I'm a bit confused as to what you're trying to do here.  Yesterday I got
> > another version of this patch set that moves init data around, today a
> > different one.  Yesterday's is tested and simpler, and given it's so late in
> > the process I'm inclined to take that as I don't want to break anything.
> >
> > Right now I have
> >
> > 84814460eef9 ("riscv: Fixup bootup failure with HARDENED_USERCOPY")
> > a78c6f5956a9 ("RISC-V: Make sure memblock reserves the memory containing DT")
> > 549738f15da0 ("Linux 5.9-rc8")
> >
> > Unless there's some functional bug, that's what I'm going to send out for 5.9
> > -- I'm not all that worried about lacking the ability to free init data.  The
> > above seems like fine 5.10 material.
> >
> > Let me know if I'm missing something here.
> 84814460eef9 could resolve the problem and Atish ask for any other
> idea? So It's another choice, I forgot RFC in prefix.
>

I prefer this fix as it is cleaner and doesn't waste memory. I have
sent another series
on top of this fix, that addresses the init section protections we
talked about. All of these are definitely
next merge window material.

> 6184358da0004c8fd940afda6c0a0fa4027dc911("riscv: Fixup static_obj()
> fail") is a sloppy patch that introduces another problem. Sorry about
> that.
>
> --
> Best Regards
>  Guo Ren
>
> ML: https://lore.kernel.org/linux-csky/



-- 
Regards,
Atish