linux-kernel - Re: [PATCH v2 7/9] x86/module: Use text

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Message-ID: <20200417142944.GF20730@hirez.programming.kicks-ass.net>
Date:   Fri, 17 Apr 2020 16:29:44 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jessica Yu <jeyu@...nel.org>, x86@...nel.org
Subject: Re: [PATCH v2 7/9] x86/module: Use text_poke() for late relocations

On Fri, Apr 17, 2020 at 09:04:32AM -0500, Josh Poimboeuf wrote:
> +int apply_relocate_add(Elf64_Shdr *sechdrs,
> +		   const char *strtab,
> +		   unsigned int symindex,
> +		   unsigned int relsec,
> +		   struct module *me)
> +{
> +	int ret;
> +	bool early = me->state == MODULE_STATE_UNFORMED;
> +	void *(*write)(void *, const void *, size_t) = memcpy;
> +
> +	if (!early) {
> +		write = text_poke;
> +		mutex_lock(&text_mutex);
> +	}
> +
> +	ret = __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
> +				   write);
> +
> +	if (!early) {
> +		mutex_unlock(&text_mutex);
> +		text_poke_sync();

I'm thinking text_poke_sync() wants to be inside text_mutex. Although
given that nothing should be running that text, it really doesn't
matter.

> +	}
> +
> +	return ret;
> +}
> +
>  #endif
>  
>  int module_finalize(const Elf_Ehdr *hdr,
> -- 
> 2.21.1
>