linux-kernel - Re: [PATCH V2 2/2] riscv: Add modules to virtual kernel memory layout dump

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Message-ID: <3975689.5fSG56mABF@diego>
Date:   Thu, 14 Jul 2022 11:46:20 +0200
From:   Heiko Stübner <heiko@...ech.de>
To:     Arnd Bergmann <arnd@...db.de>,
        Xianting Tian <xianting.tian@...ux.alibaba.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexandre Ghiti <alexandre.ghiti@...onical.com>,
        Guo Ren <guoren@...nel.org>, Anup Patel <anup@...infault.org>,
        Nick Kossifidis <mick@....forth.gr>,
        Mike Rapoport <rppt@...nel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        huanyi.xj@...baba-inc.com
Subject: Re: [PATCH V2 2/2] riscv: Add modules to virtual kernel memory layout dump

Am Donnerstag, 14. Juli 2022, 11:17:26 CEST schrieb Xianting Tian:
> 
> 在 2022/7/14 下午4:24, Arnd Bergmann 写道:
> > On Thu, Jul 14, 2022 at 4:59 AM Xianting Tian
> > <xianting.tian@...ux.alibaba.com> wrote:
> >> As MODULES is only defined for CONFIG_64BIT, so we dump it when
> >> CONFIG_64BIT.
> > Doesn't this cause a compile-time error on 32-bit?
> I tested, rv32 compile is OK.

> >>                  (unsigned long)VMEMMAP_END);
> >>          print_ml("vmalloc", (unsigned long)VMALLOC_START,
> >>                  (unsigned long)VMALLOC_END);
> >> +       if (IS_ENABLED(CONFIG_64BIT))
> >> +               print_ml("modules", (unsigned long)MODULES_VADDR,
> >> +                       (unsigned long)MODULES_END);
> > The IS_ENABLED() check prevents the line from getting executed, but
> > unlike an #ifdef it still relies on it to be parsable.
> Thanks, I will use #ifdef instead of IS_ENABLED

Patch1 also has that issue with the

      if (IS_ENABLED(CONFIG_64BIT)) {
              vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR);
              vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END);
      ....


module_alloc falls back to a weak variant [0] which is the same as the riscv variant
only then using VMALLOC_START - VMALLOC_END as range, as the riscv-variant
conditional to CONFIG_64BIT.

I'm wondering if it wouldn't be easier in the long run to just define
MODULES_VADDR, MODULES_END for 32bit to use these values and get rid of
the CONFIG_64BIT ifdef we already have for MODULES (and new ones we are
introducing now).


Heiko


[0] https://elixir.bootlin.com/linux/latest/source/kernel/module.c#L2835