linux-kernel - Re: [PATCH 2/2] riscv: Fixup static

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Message-ID: <CAOnJCU+xwnQz9tbCDjBbstOzBFT-DU-uTcc0K_M7ppT_Z-V1Fg@mail.gmail.com>
Date:   Wed, 7 Oct 2020 12:46:17 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Guo Ren <guoren@...nel.org>
Cc:     Palmer Dabbelt <palmerdabbelt@...gle.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Andreas Schwab <schwab@...ux-m68k.org>, aurelien@...el32.net,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH 2/2] riscv: Fixup static_obj() fail v2

On Wed, Oct 7, 2020 at 8:09 AM <guoren@...nel.org> wrote:
>
> From: Guo Ren <guoren@...ux.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@...ux.alibaba.com>
> Reported-by: Aurelien Jarno <aurelien@...el32.net>
> Cc: Palmer Dabbelt <palmerdabbelt@...gle.com>
> Cc: Atish Patra <atishp@...shpatra.org>
> Cc: Andreas Schwab <schwab@...ux-m68k.org>
> Cc: Aurelien Jarno <aurelien@...el32.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

You may want to rebase it on top of for-next as UEFI series also adds this file.
.

> @@ -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;
> +}
> --
> 2.7.4
>

Looks good. Much cleaner than the first approach.
FYI: I am still looking into separating __init text & data so that
different permissions can be applied to them.
With this patch, we can just separate it on top of _stext.


Reviewed-by: Atish Patra <atish.patra@....com>

-- 
Regards,
Atish