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Date:   Thu, 11 Apr 2019 14:15:36 -0400
From:   Sinan Kaya <>
To:     Masahiro Yamada <>
Cc:     Linux Kernel Mailing List <>,
        Josh Triplett <>,
        Kees Cook <>,
        Andrew Morton <>,
        "Peter Zijlstra (Intel)" <>,
        Johannes Weiner <>,
        Nicholas Piggin <>,
        Mathieu Desnoyers <>,
        Vasily Gorbik <>,
        Adrian Reber <>,
        Richard Guy Briggs <>,
        Andy Shevchenko <>,
        Petr Mladek <>,
        Joe Lawrence <>,
        Matthew Wilcox <>,
        Randy Dunlap <>,
        Mikulas Patocka <>,
        Robin Murphy <>,
        Tetsuo Handa <>,
        Changbin Du <>
Subject: Re: [PATCH v3] init: Do not select DEBUG_KERNEL by default

On 4/11/2019 1:48 AM, Masahiro Yamada wrote:
>> I was going by what Kconfig tells me
>> Symbol: KALLSYMS_ALL [=n]
>>    Depends on: DEBUG_KERNEL [=n] && KALLSYMS [=y]
> Lots of features have 'depends on DEBUG_KERNEL'.
> What is special about KALLSYMS_ALL here?

I had to do some learning about KALLSYSM_ALL. Based on my limited
searching, KALLSYMS_ALL allows you to locate the symbol location
at runtime from the kernel.

Without KALLSYM_ALL, you can only locate the kernel code only. With
KALLSYMS_ALL, you can locate the symbols for any data structure
including kernel modules.

I'm not a KALLSYMS person but based on my search, I'd consider
KALLSYMS_ALL a debug feature as it is today.

kernel/kallsyms.c:              else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
kernel/livepatch/Kconfig:       depends on KALLSYMS_ALL
kernel/module.c:#ifdef CONFIG_KALLSYMS_ALL
kernel/module.c:#ifndef CONFIG_KALLSYMS_ALL

lib/Kconfig.debug:      select KALLSYMS_ALL
     config LOCKDEP
             depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
             select KALLSYMS
             select KALLSYMS_ALL

lib/Kconfig.debug:      select KALLSYMS_ALL
     config LATENCYTOP
             bool "Latency measuring infrastructure"
             select KALLSYMS
             select KALLSYMS_ALL

scripts/        if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then

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