Subject: Re: linux-next: manual merge of the modules tree with the mm tree

From: Stephen Rothwell <[email-masked]>
Date: Fri, 17 May 2024 09:35:34 +1000

Hi all,

On Fri, 17 May 2024 09:23:47 +1000 Stephen Rothwell <[email-masked]> wrote:
>
> On Fri, 12 Apr 2024 12:04:21 +1000 Stephen Rothwell <[email-masked]> wrote:
> >
> > Today's linux-next merge of the modules tree got a conflict in:
> > 
> >   kernel/module/main.c
> > 
> > between commit:
> > 
> >   58782d7a7ccd ("lib: prevent module unloading if memory is not freed")
> > 
> > from the mm-unstable branch of the mm tree and commit:
> > 
> >   a4ee8c9b86bd ("module: make module_memory_{alloc,free} more self-contained")
> > 
> > from the modules tree.
> > 
> 
> This is now a conflict between the mm-stable tree and Linus' tree.

The actual final resolution (due to more patches) is below.

-- 
Cheers,
Stephen Rothwell

diff --cc kernel/module/main.c
index 91e185607d4b,2d25eebc549d..d18a94b973e1
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@@ -56,8 -56,8 +56,9 @@@
  #include <linux/dynamic_debug.h>
  #include <linux/audit.h>
  #include <linux/cfi.h>
+ #include <linux/codetag.h>
  #include <linux/debugfs.h>
 +#include <linux/execmem.h>
  #include <uapi/linux/module.h>
  #include "internal.h"
  
@@@ -1188,50 -1198,32 +1189,54 @@@ void __weak module_arch_freeing_init(st
  {
  }
  
 -static bool mod_mem_use_vmalloc(enum mod_mem_type type)
 +static int module_memory_alloc(struct module *mod, enum mod_mem_type type)
  {
 -	return IS_ENABLED(CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC) &&
 -		mod_mem_type_is_core_data(type);
 -}
 +	unsigned int size = PAGE_ALIGN(mod->mem[type].size);
 +	enum execmem_type execmem_type;
 +	void *ptr;
  
 -static void *module_memory_alloc(unsigned int size, enum mod_mem_type type)
 -{
 -	if (mod_mem_use_vmalloc(type))
 -		return vzalloc(size);
 -	return module_alloc(size);
 +	mod->mem[type].size = size;
 +
 +	if (mod_mem_type_is_data(type))
 +		execmem_type = EXECMEM_MODULE_DATA;
 +	else
 +		execmem_type = EXECMEM_MODULE_TEXT;
 +
 +	ptr = execmem_alloc(execmem_type, size);
 +	if (!ptr)
 +		return -ENOMEM;
 +
 +	/*
 +	 * The pointer to these blocks of memory are stored on the module
 +	 * structure and we keep that around so long as the module is
 +	 * around. We only free that memory when we unload the module.
 +	 * Just mark them as not being a leak then. The .init* ELF
 +	 * sections *do* get freed after boot so we *could* treat them
 +	 * slightly differently with kmemleak_ignore() and only grey
 +	 * them out as they work as typical memory allocations which
 +	 * *do* eventually get freed, but let's just keep things simple
 +	 * and avoid *any* false positives.
 +	 */
 +	kmemleak_not_leak(ptr);
 +
 +	memset(ptr, 0, size);
 +	mod->mem[type].base = ptr;
 +
 +	return 0;
  }
  
- static void module_memory_free(struct module *mod, enum mod_mem_type type)
 -static void module_memory_free(void *ptr, enum mod_mem_type type,
++static void module_memory_free(struct module *mod, enum mod_mem_type type,
+ 			       bool unload_codetags)
  {
 +	void *ptr = mod->mem[type].base;
 +
+ 	if (!unload_codetags && mod_mem_type_is_core_data(type))
+ 		return;
+ 
 -	if (mod_mem_use_vmalloc(type))
 -		vfree(ptr);
 -	else
 -		module_memfree(ptr);
 +	execmem_free(ptr);
  }
  
- static void free_mod_mem(struct module *mod)
+ static void free_mod_mem(struct module *mod, bool unload_codetags)
  {
  	for_each_mod_mem_type(type) {
  		struct module_memory *mod_mem = &mod->mem[type];
@@@ -1242,12 -1234,13 +1247,12 @@@
  		/* Free lock-classes; relies on the preceding sync_rcu(). */
  		lockdep_free_key_range(mod_mem->base, mod_mem->size);
  		if (mod_mem->size)
- 			module_memory_free(mod, type);
 -			module_memory_free(mod_mem->base, type,
 -					   unload_codetags);
++			module_memory_free(mod, type, unload_codetags);
  	}
  
  	/* MOD_DATA hosts mod, so free it at last */
  	lockdep_free_key_range(mod->mem[MOD_DATA].base, mod->mem[MOD_DATA].size);
- 	module_memory_free(mod, MOD_DATA);
 -	module_memory_free(mod->mem[MOD_DATA].base, MOD_DATA, unload_codetags);
++	module_memory_free(mod, MOD_DATA, unload_codetags);
  }
  
  /* Free a module, remove from lists, etc. */
@@@ -2287,7 -2309,7 +2299,7 @@@ static int move_module(struct module *m
  	return 0;
  out_enomem:
  	for (t--; t >= 0; t--)
- 		module_memory_free(mod, t);
 -		module_memory_free(mod->mem[t].base, t, true);
++		module_memory_free(mod, t, true);
  	return ret;
  }