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Re: [PATCH v6 2/8] module: use relative references for __ksymtab entries

To: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v6 2/8] module: use relative references for __ksymtab entries
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Wed, 27 Dec 2017 20:11:19 +0000
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "H. Peter Anvin" <hpa@zytor.com>, Ralf Baechle <ralf@linux-mips.org>, Arnd Bergmann <arnd@arndb.de>, Heiko Carstens <heiko.carstens@de.ibm.com>, Kees Cook <keescook@chromium.org>, Will Deacon <will.deacon@arm.com>, Michael Ellerman <mpe@ellerman.id.au>, Thomas Garnier <thgarnie@google.com>, Thomas Gleixner <tglx@linutronix.de>, "Serge E. Hallyn" <serge@hallyn.com>, Bjorn Helgaas <bhelgaas@google.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Russell King <linux@armlinux.org.uk>, Paul Mackerras <paulus@samba.org>, Catalin Marinas <catalin.marinas@arm.com>, "David S. Miller" <davem@davemloft.net>, Petr Mladek <pmladek@suse.com>, Ingo Molnar <mingo@redhat.com>, James Morris <james.l.morris@oracle.com>, Andrew Morton <akpm@linux-foundation.org>, Nicolas Pitre <nico@linaro.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Steven Rostedt <rostedt@goodmis.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Jessica Yu <jeyu@kernel.org>, linux-arm-kernel@lists.infradead.org, linux-mips <linux-mips@linux-mips.org>, ppc-dev <linuxppc-dev@lists.ozlabs.org>, linux-s390 <linux-s390@vger.kernel.org>, sparclinux@vger.kernel.org, "the arch/x86 maintainers" <x86@kernel.org>, Ingo Molnar <mingo@kernel.org>
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References: <20171227085033.22389-1-ard.biesheuvel@linaro.org> <20171227085033.22389-3-ard.biesheuvel@linaro.org> <CA+55aFxqJqJq_7VUzBVTppgXFPc-8Ou55iLsZjp3fr6B2gRyTQ@mail.gmail.com>
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On 27 December 2017 at 20:07, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Wed, Dec 27, 2017 at 12:50 AM, Ard Biesheuvel
> <ard.biesheuvel@linaro.org> wrote:
>> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
>> index 52e611ab9a6c..fe752d365334 100644
>> --- a/include/linux/compiler.h
>> +++ b/include/linux/compiler.h
>> @@ -327,4 +327,15 @@ static __always_inline void __write_once_size(volatile 
>> void *p, void *res, int s
>>         compiletime_assert(__native_word(t),                            \
>>                 "Need native word sized stores/loads for atomicity.")
>>
>> +/*
>> + * Force the compiler to emit 'sym' as a symbol, so that we can reference
>> + * it from inline assembler. Necessary in case 'sym' could be inlined
>> + * otherwise, or eliminated entirely due to lack of references that are
>> + * visibile to the compiler.
>> + */
>> +#define __ADDRESSABLE(sym) \
>> +       static void *__attribute__((section(".discard.text"), used))    \
>> +               __PASTE(__discard_##sym, __LINE__)(void)                \
>> +                       { return (void *)&sym; }                        \
>> +
>>  #endif /* __LINUX_COMPILER_H */
>
> Isn't this logically the point where you should add the arm64
> vmlinux.lds.S change, and explain how ".discard.text" turns into
> ".init.discard.text" for some odd arm64 reason?
>

I tried to keep the generic patches generic, so perhaps I should just
put the arm64 vmlinux.lds.S change in a patch on its own?

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