linux-kernel - Re: [PATCH v5] module: Add CONFIG_MODULE_DISABLE_INIT

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Date:   Fri, 27 Oct 2023 15:27:23 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     oe-kbuild@...ts.linux.dev, Joey Jiao <quic_jiangenj@...cinc.com>,
        linux-modules@...r.kernel.org
Cc:     lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
        quic_likaid@...cinc.com, Luis Chamberlain <mcgrof@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] module: Add CONFIG_MODULE_DISABLE_INIT_FREE option

On Fri, Oct 27, 2023 at 03:00:00PM +0300, Dan Carpenter wrote:
> 607c543f939d8c kernel/module.c      Andrii Nakryiko  2020-11-20  2579  #ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> 607c543f939d8c kernel/module.c      Andrii Nakryiko  2020-11-20  2580  	/* .BTF is not SHF_ALLOC and will get removed, so sanitize pointer */
> 607c543f939d8c kernel/module.c      Andrii Nakryiko  2020-11-20  2581  	mod->btf_data = NULL;
> 607c543f939d8c kernel/module.c      Andrii Nakryiko  2020-11-20  2582  #endif
> c749637909eea5 kernel/module.c      Rusty Russell    2015-01-20  2583  	/*
> c749637909eea5 kernel/module.c      Rusty Russell    2015-01-20  2584  	 * We want to free module_init, but be aware that kallsyms may be
> 0be964be0d4508 kernel/module.c      Peter Zijlstra   2015-05-27  2585  	 * walking this with preempt disabled.  In all the failure paths, we
> cb2f55369d3a9e kernel/module.c      Paul E. McKenney 2018-11-06  2586  	 * call synchronize_rcu(), but we don't want to slow down the success
> 1a7b7d9220819a kernel/module.c      Rick Edgecombe   2019-04-25  2587  	 * path. module_memfree() cannot be called in an interrupt, so do the
> 1a7b7d9220819a kernel/module.c      Rick Edgecombe   2019-04-25  2588  	 * work and call synchronize_rcu() in a work queue.
> 1a7b7d9220819a kernel/module.c      Rick Edgecombe   2019-04-25  2589  	 *
> ae646f0b9ca135 kernel/module.c      Jeffrey Hugo     2018-05-11  2590  	 * Note that module_alloc() on most architectures creates W+X page
> ae646f0b9ca135 kernel/module.c      Jeffrey Hugo     2018-05-11  2591  	 * mappings which won't be cleaned up until do_free_init() runs.  Any
> ae646f0b9ca135 kernel/module.c      Jeffrey Hugo     2018-05-11  2592  	 * code such as mark_rodata_ro() which depends on those mappings to
> ae646f0b9ca135 kernel/module.c      Jeffrey Hugo     2018-05-11  2593  	 * be cleaned up needs to sync with the queued work - ie
> cb2f55369d3a9e kernel/module.c      Paul E. McKenney 2018-11-06  2594  	 * rcu_barrier()
> c749637909eea5 kernel/module.c      Rusty Russell    2015-01-20  2595  	 */
> 36022a47582048 kernel/module/main.c Joey Jiao        2023-10-13  2596  	if (!IS_ENABLED(CONFIG_MODULE_DISABLE_INIT_FREE) &&
> 36022a47582048 kernel/module/main.c Joey Jiao        2023-10-13  2597  	    llist_add(&freeinit->node, &init_free_list))
> 
> Let's not allocate freeinit if CONFIG_MODULE_DISABLE_INIT_FREE is not
> enabled.

Wait.  It's the other way around actually.  freeinit isn't used if
CONFIG_MODULE_DISABLE_INIT_FREE is enabled.

regards,
dan carpenter