diff mbox series

[v3,3/6] modules: Introduce data_layout

Message ID 230bfd896f24ca7a9281783aaa8c0ebfebd0bc7e.1643475473.git.christophe.leroy@csgroup.eu (mailing list archive)
State Superseded
Headers show
Series Allocate module text and data separately | expand

Commit Message

Christophe Leroy Jan. 29, 2022, 5:02 p.m. UTC 
In order to allow separation of data from text, add another layout,
called data_layout. For architectures requesting separation of text
and data, only text will go in core_layout and data will go in
data_layout.

For architectures which keep text and data together, make data_layout
an alias of core_layout, that way data_layout can be used for all
data manipulations, regardless of whether data is in core_layout or
data_layout.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 kernel/module.c | 52 ++++++++++++++++++++++++++++---------------------
 1 file changed, 30 insertions(+), 22 deletions(-)

Comments

Luis Chamberlain Feb. 2, 2022, 11:48 p.m. UTC | #1 
On Sat, Jan 29, 2022 at 05:02:07PM +0000, Christophe Leroy wrote:
> diff --git a/kernel/module.c b/kernel/module.c
> index 163e32e39064..11f51e17fb9f 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -81,6 +81,8 @@
>  /* If this is set, the section belongs in the init part of the module */
>  #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
>  
> +#define	data_layout core_layout
> +
>  /*
>   * Mutex protects:
>   * 1) List of modules (also safely readable with preempt_disable),
> @@ -2451,7 +2454,10 @@ static void layout_sections(struct module *mod, struct load_info *info)
>  			    || s->sh_entsize != ~0UL
>  			    || module_init_layout_section(sname))
>  				continue;
> -			s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
> +			if (m)
> +				s->sh_entsize = get_offset(mod, &mod->data_layout.size, s, i);
> +			else
> +				s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
>  			pr_debug("\t%s\n", sname);

Huh why is this branching here, given you just used mod->data_layout in
all other areas?

> @@ -3468,6 +3474,8 @@ static int move_module(struct module *mod, struct load_info *info)
>  		if (shdr->sh_entsize & INIT_OFFSET_MASK)
>  			dest = mod->init_layout.base
>  				+ (shdr->sh_entsize & ~INIT_OFFSET_MASK);
> +		else if (!(shdr->sh_flags & SHF_EXECINSTR))
> +			dest = mod->data_layout.base + shdr->sh_entsize;
>  		else
>  			dest = mod->core_layout.base + shdr->sh_entsize;
>  

Likewise here.

  Luis
Christophe Leroy Feb. 3, 2022, 6:58 a.m. UTC | #2 
Le 03/02/2022 à 00:48, Luis Chamberlain a écrit :
> On Sat, Jan 29, 2022 at 05:02:07PM +0000, Christophe Leroy wrote:
>> diff --git a/kernel/module.c b/kernel/module.c
>> index 163e32e39064..11f51e17fb9f 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -81,6 +81,8 @@
>>   /* If this is set, the section belongs in the init part of the module */
>>   #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
>>   
>> +#define	data_layout core_layout
>> +
>>   /*
>>    * Mutex protects:
>>    * 1) List of modules (also safely readable with preempt_disable),
>> @@ -2451,7 +2454,10 @@ static void layout_sections(struct module *mod, struct load_info *info)
>>   			    || s->sh_entsize != ~0UL
>>   			    || module_init_layout_section(sname))
>>   				continue;
>> -			s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
>> +			if (m)
>> +				s->sh_entsize = get_offset(mod, &mod->data_layout.size, s, i);
>> +			else
>> +				s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
>>   			pr_debug("\t%s\n", sname);
> 
> Huh why is this branching here, given you just used mod->data_layout in
> all other areas?

The module text remains in core_layout, so the text section still needs 
core_layout. In the masks[][] table, it corresponds to the first line, 
which has flag  SHF_EXECINSTR. In the loop that's when 'm' is 0.

In the following switch/case, case 0 still uses core_layout.

> 
>> @@ -3468,6 +3474,8 @@ static int move_module(struct module *mod, struct load_info *info)
>>   		if (shdr->sh_entsize & INIT_OFFSET_MASK)
>>   			dest = mod->init_layout.base
>>   				+ (shdr->sh_entsize & ~INIT_OFFSET_MASK);
>> +		else if (!(shdr->sh_flags & SHF_EXECINSTR))
>> +			dest = mod->data_layout.base + shdr->sh_entsize;
>>   		else
>>   			dest = mod->core_layout.base + shdr->sh_entsize;
>>   
> 
> Likewise here.

Same here, the section with flag SHF_EXECINSTR is a text section, it 
stays in core_layout.

Christophe
diff mbox series

Patch

diff --git a/kernel/module.c b/kernel/module.c
index 163e32e39064..11f51e17fb9f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -81,6 +81,8 @@ 
 /* If this is set, the section belongs in the init part of the module */
 #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
 
+#define	data_layout core_layout
+
 /*
  * Mutex protects:
  * 1) List of modules (also safely readable with preempt_disable),
@@ -2014,19 +2016,20 @@  static void module_enable_ro(const struct module *mod, bool after_init)
 	set_vm_flush_reset_perms(mod->init_layout.base);
 	frob_text(&mod->core_layout, set_memory_ro);
 
-	frob_rodata(&mod->core_layout, set_memory_ro);
+	frob_rodata(&mod->data_layout, set_memory_ro);
+
 	frob_text(&mod->init_layout, set_memory_ro);
 	frob_rodata(&mod->init_layout, set_memory_ro);
 
 	if (after_init)
-		frob_ro_after_init(&mod->core_layout, set_memory_ro);
+		frob_ro_after_init(&mod->data_layout, set_memory_ro);
 }
 
 static void module_enable_nx(const struct module *mod)
 {
-	frob_rodata(&mod->core_layout, set_memory_nx);
-	frob_ro_after_init(&mod->core_layout, set_memory_nx);
-	frob_writable_data(&mod->core_layout, set_memory_nx);
+	frob_rodata(&mod->data_layout, set_memory_nx);
+	frob_ro_after_init(&mod->data_layout, set_memory_nx);
+	frob_writable_data(&mod->data_layout, set_memory_nx);
 	frob_rodata(&mod->init_layout, set_memory_nx);
 	frob_writable_data(&mod->init_layout, set_memory_nx);
 }
@@ -2204,7 +2207,7 @@  static void free_module(struct module *mod)
 	percpu_modfree(mod);
 
 	/* Free lock-classes; relies on the preceding sync_rcu(). */
-	lockdep_free_key_range(mod->core_layout.base, mod->core_layout.size);
+	lockdep_free_key_range(mod->data_layout.base, mod->data_layout.size);
 
 	/* Finally, free the core (containing the module structure) */
 	module_memfree(mod->core_layout.base);
@@ -2451,7 +2454,10 @@  static void layout_sections(struct module *mod, struct load_info *info)
 			    || s->sh_entsize != ~0UL
 			    || module_init_layout_section(sname))
 				continue;
-			s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
+			if (m)
+				s->sh_entsize = get_offset(mod, &mod->data_layout.size, s, i);
+			else
+				s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
 			pr_debug("\t%s\n", sname);
 		}
 		switch (m) {
@@ -2460,15 +2466,15 @@  static void layout_sections(struct module *mod, struct load_info *info)
 			mod->core_layout.text_size = mod->core_layout.size;
 			break;
 		case 1: /* RO: text and ro-data */
-			mod->core_layout.size = debug_align(mod->core_layout.size);
-			mod->core_layout.ro_size = mod->core_layout.size;
+			mod->data_layout.size = debug_align(mod->data_layout.size);
+			mod->data_layout.ro_size = mod->data_layout.size;
 			break;
 		case 2: /* RO after init */
-			mod->core_layout.size = debug_align(mod->core_layout.size);
-			mod->core_layout.ro_after_init_size = mod->core_layout.size;
+			mod->data_layout.size = debug_align(mod->data_layout.size);
+			mod->data_layout.ro_after_init_size = mod->data_layout.size;
 			break;
 		case 4: /* whole core */
-			mod->core_layout.size = debug_align(mod->core_layout.size);
+			mod->data_layout.size = debug_align(mod->data_layout.size);
 			break;
 		}
 	}
@@ -2721,12 +2727,12 @@  static void layout_symtab(struct module *mod, struct load_info *info)
 	}
 
 	/* Append room for core symbols at end of core part. */
-	info->symoffs = ALIGN(mod->core_layout.size, symsect->sh_addralign ?: 1);
-	info->stroffs = mod->core_layout.size = info->symoffs + ndst * sizeof(Elf_Sym);
-	mod->core_layout.size += strtab_size;
-	info->core_typeoffs = mod->core_layout.size;
-	mod->core_layout.size += ndst * sizeof(char);
-	mod->core_layout.size = debug_align(mod->core_layout.size);
+	info->symoffs = ALIGN(mod->data_layout.size, symsect->sh_addralign ?: 1);
+	info->stroffs = mod->data_layout.size = info->symoffs + ndst * sizeof(Elf_Sym);
+	mod->data_layout.size += strtab_size;
+	info->core_typeoffs = mod->data_layout.size;
+	mod->data_layout.size += ndst * sizeof(char);
+	mod->data_layout.size = debug_align(mod->data_layout.size);
 
 	/* Put string table section at end of init part of module. */
 	strsect->sh_flags |= SHF_ALLOC;
@@ -2770,9 +2776,9 @@  static void add_kallsyms(struct module *mod, const struct load_info *info)
 	 * Now populate the cut down core kallsyms for after init
 	 * and set types up while we still have access to sections.
 	 */
-	mod->core_kallsyms.symtab = dst = mod->core_layout.base + info->symoffs;
-	mod->core_kallsyms.strtab = s = mod->core_layout.base + info->stroffs;
-	mod->core_kallsyms.typetab = mod->core_layout.base + info->core_typeoffs;
+	mod->core_kallsyms.symtab = dst = mod->data_layout.base + info->symoffs;
+	mod->core_kallsyms.strtab = s = mod->data_layout.base + info->stroffs;
+	mod->core_kallsyms.typetab = mod->data_layout.base + info->core_typeoffs;
 	src = mod->kallsyms->symtab;
 	for (ndst = i = 0; i < mod->kallsyms->num_symtab; i++) {
 		mod->kallsyms->typetab[i] = elf_type(src + i, info);
@@ -3468,6 +3474,8 @@  static int move_module(struct module *mod, struct load_info *info)
 		if (shdr->sh_entsize & INIT_OFFSET_MASK)
 			dest = mod->init_layout.base
 				+ (shdr->sh_entsize & ~INIT_OFFSET_MASK);
+		else if (!(shdr->sh_flags & SHF_EXECINSTR))
+			dest = mod->data_layout.base + shdr->sh_entsize;
 		else
 			dest = mod->core_layout.base + shdr->sh_entsize;
 
@@ -4173,7 +4181,7 @@  static int load_module(struct load_info *info, const char __user *uargs,
 	mutex_unlock(&module_mutex);
  free_module:
 	/* Free lock-classes; relies on the preceding sync_rcu() */
-	lockdep_free_key_range(mod->core_layout.base, mod->core_layout.size);
+	lockdep_free_key_range(mod->data_layout.base, mod->data_layout.size);
 
 	module_deallocate(mod, info);
  free_copy: