module: Introduce data_layout

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 <[email protected]>
Signed-off-by: Luis Chamberlain <[email protected]>

Author: chleroy

kernel/module/internal.h

@@ -20,6 +20,8 @@
 /* Maximum number of characters written by module_flags() */
 #define MODULE_FLAGS_BUF_SIZE (TAINT_FLAGS_COUNT + 4)
 
+#define	data_layout core_layout
+
 /*
  * Modules' sections will be aligned on page boundaries
  * to ensure complete separation of code and data, but

kernel/module/kallsyms.c

@@ -134,12 +134,12 @@ 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 = strict_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 = strict_align(mod->data_layout.size);
 
 	/* Put string table section at end of init part of module. */
 	strsect->sh_flags |= SHF_ALLOC;
@@ -187,9 +187,9 @@ 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 = rcu_dereference_sched(mod->kallsyms)->symtab;
 	for (ndst = i = 0; i < rcu_dereference_sched(mod->kallsyms)->num_symtab; i++) {
 		rcu_dereference_sched(mod->kallsyms)->typetab[i] = elf_type(src + i, info);

kernel/module/main.c

@@ -1190,7 +1190,7 @@ 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);
@@ -1431,13 +1431,15 @@ static void layout_sections(struct module *mod, struct load_info *info)
 		for (i = 0; i < info->hdr->e_shnum; ++i) {
 			Elf_Shdr *s = &info->sechdrs[i];
 			const char *sname = info->secstrings + s->sh_name;
+			unsigned int *sizep;
 
 			if ((s->sh_flags & masks[m][0]) != masks[m][0]
 			    || (s->sh_flags & masks[m][1])
 			    || s->sh_entsize != ~0UL
 			    || module_init_layout_section(sname))
 				continue;
-			s->sh_entsize = module_get_offset(mod, &mod->core_layout.size, s, i);
+			sizep = m ? &mod->data_layout.size : &mod->core_layout.size;
+			s->sh_entsize = module_get_offset(mod, sizep, s, i);
 			pr_debug("\t%s\n", sname);
 		}
 		switch (m) {
@@ -1446,15 +1448,15 @@ 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 = strict_align(mod->core_layout.size);
-			mod->core_layout.ro_size = mod->core_layout.size;
+			mod->data_layout.size = strict_align(mod->data_layout.size);
+			mod->data_layout.ro_size = mod->data_layout.size;
 			break;
 		case 2: /* RO after init */
-			mod->core_layout.size = strict_align(mod->core_layout.size);
-			mod->core_layout.ro_after_init_size = mod->core_layout.size;
+			mod->data_layout.size = strict_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 = strict_align(mod->core_layout.size);
+			mod->data_layout.size = strict_align(mod->data_layout.size);
 			break;
 		}
 	}
@@ -2134,6 +2136,8 @@ 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;
 
@@ -2829,7 +2833,7 @@ 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:

kernel/module/strict_rwx.c

@@ -101,22 +101,22 @@ 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);
 }
 
 void module_enable_nx(const struct module *mod)
 {
 	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
 		return;
 
-	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);
 }