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

From: "Heiko Stübner" <heiko@sntech.de>
To: Arnd Bergmann <arnd@arndb.de>,
	Xianting Tian <xianting.tian@linux.alibaba.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alexandre.ghiti@canonical.com>,
	Guo Ren <guoren@kernel.org>, Anup Patel <anup@brainfault.org>,
	Nick Kossifidis <mick@ics.forth.gr>,
	Mike Rapoport <rppt@kernel.org>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	huanyi.xj@alibaba-inc.com
Subject: Re: [PATCH V2 2/2] riscv: Add modules to virtual kernel memory layout dump
Date: Thu, 14 Jul 2022 11:46:20 +0200	[thread overview]
Message-ID: <3975689.5fSG56mABF@diego> (raw)
In-Reply-To: <f706ddff-8444-bba1-a98a-23a1333cc70a@linux.alibaba.com>

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@linux.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

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