linux-kernel - Re: [PATCH] x86: define arch_crash_save_vmcoreinfo() if CONFIG_CRASH

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Message-ID: <20191218104113.GB24886@zn.tnic>
Date:   Wed, 18 Dec 2019 11:41:13 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Omar Sandoval <osandov@...ndov.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: define arch_crash_save_vmcoreinfo() if
 CONFIG_CRASH_CORE=y

On Mon, Dec 02, 2019 at 10:02:29AM -0800, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@...com>
> 
> kernel/crash_core.c calls arch_crash_save_vmcoreinfo() to get
> arch-specific bits for vmcoreinfo. If it is not defined, then it has a
> no-op fallback. kernel/crash_core.c is gated behind CONFIG_CRASH_CORE.
> However, x86 defines arch_crash_save_vmcoreinfo() in
> arch/x86/kernel/machine_kexec_*.c, which is gated behind
> CONFIG_KEXEC_CORE. So, a kernel with CONFIG_CRASH_CORE=y and
> CONFIG_KEXEC_CORE=n

How does that even happen?

Symbol: KEXEC_CORE [=y]
Type  : bool
  Defined at arch/Kconfig:17
  Selects: CRASH_CORE [=y]
  Selected by [y]:
  - KEXEC [=y]
  - KEXEC_FILE [=y] && X86_64 [=y] && CRYPTO [=y]=y && CRYPTO_SHA256 [=y]=y

In order to do crash dumps, you need to select KEXEC, which selects
KEXEC_CORE, which selects CRASH_CORE...

Or are you talking about the PROC_KCORE use angle where it selects
CRASH_CORE and the crash_save_vmcoreinfo_init() initcall is then
supposed to save arch-specific crash info?

Thx.

-- 
Regards/Gruss,
    Boris.

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