diff mbox series

[RFC,v4,03/13] module: Move livepatch support to a separate file

Message ID 20220130213214.1042497-4-atomlin@redhat.com (mailing list archive)
State Superseded
Headers show
Series module: core code clean up | expand

Commit Message

Aaron Tomlin Jan. 30, 2022, 9:32 p.m. UTC 
No functional change.

This patch migrates livepatch support (i.e. used during module
add/or load and remove/or deletion) from core module code into
kernel/module/livepatch.c. At the moment it contains code to
persist Elf information about a given livepatch module, only.

Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
---
 include/linux/module.h    |  16 ++++--
 kernel/module/Makefile    |   3 ++
 kernel/module/internal.h  |  11 ++++
 kernel/module/livepatch.c |  74 +++++++++++++++++++++++++++
 kernel/module/main.c      | 102 ++++----------------------------------
 5 files changed, 109 insertions(+), 97 deletions(-)
 create mode 100644 kernel/module/livepatch.c

Comments

Petr Mladek Feb. 8, 2022, 11:42 a.m. UTC | #1 
On Sun 2022-01-30 21:32:04, Aaron Tomlin wrote:
> No functional change.
> 
> This patch migrates livepatch support (i.e. used during module
> add/or load and remove/or deletion) from core module code into
> kernel/module/livepatch.c. At the moment it contains code to
> persist Elf information about a given livepatch module, only.
> 
> diff --git a/include/linux/module.h b/include/linux/module.h
> index f4338235ed2c..c7daac4d16ee 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -663,17 +663,23 @@ static inline bool module_requested_async_probing(struct module *module)
>  	return module && module->async_probe_requested;
>  }
>  
> -#ifdef CONFIG_LIVEPATCH
>  static inline bool is_livepatch_module(struct module *mod)
>  {
> -	return mod->klp;
> +	if (IS_ENABLED(CONFIG_LIVEPATCH)) {
> +		if (mod->klp)
> +			return true;
> +	}
> +	return false;

The following is easier to follow for me. But it is a matter of taste.
Feel free to use whatever you prefer.

	return IS_ENABLED(CONFIG_LIVEPATCH) && mod->klp;

>  }
> -#else /* !CONFIG_LIVEPATCH */
> -static inline bool is_livepatch_module(struct module *mod)
> +
> +static inline bool set_livepatch_module(struct module *mod)
>  {
> +	if (IS_ENABLED(CONFIG_LIVEPATCH)) {
> +		mod->klp = true;
> +		return true;
> +	}
>  	return false;

This should go to internal.h.

Alternative is to move both is_livepatch_module() and
set_livepatch_module() into include/linux/livepatch.h.

I do not have strong opinion.

>  }
> -#endif /* CONFIG_LIVEPATCH */
>  
>  bool is_module_sig_enforced(void);
>  void set_module_sig_enforced(void);

Otherwise, it looks good to me.

Best Regards,
Petr
Aaron Tomlin Feb. 8, 2022, 3:18 p.m. UTC | #2 
On Tue 2022-02-08 12:42 +0100, Petr Mladek wrote:
> This should go to internal.h.
> 
> Alternative is to move both is_livepatch_module() and
> set_livepatch_module() into include/linux/livepatch.h.
> 
> I do not have strong opinion.

Hi Petr,

Firstly, thank you for your feedback.

In my opinion, I believe is_livepatch_module() should remain as it may
continue to be used externally i.e., outside of kernel/module/; albeit,
indeed set_livepatch_module() should be moved to kernel/module/internal.h
given its use is exclusive to core code.


Kind regards,
diff mbox series

Patch

diff --git a/include/linux/module.h b/include/linux/module.h
index f4338235ed2c..c7daac4d16ee 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -663,17 +663,23 @@  static inline bool module_requested_async_probing(struct module *module)
 	return module && module->async_probe_requested;
 }
 
-#ifdef CONFIG_LIVEPATCH
 static inline bool is_livepatch_module(struct module *mod)
 {
-	return mod->klp;
+	if (IS_ENABLED(CONFIG_LIVEPATCH)) {
+		if (mod->klp)
+			return true;
+	}
+	return false;
 }
-#else /* !CONFIG_LIVEPATCH */
-static inline bool is_livepatch_module(struct module *mod)
+
+static inline bool set_livepatch_module(struct module *mod)
 {
+	if (IS_ENABLED(CONFIG_LIVEPATCH)) {
+		mod->klp = true;
+		return true;
+	}
 	return false;
 }
-#endif /* CONFIG_LIVEPATCH */
 
 bool is_module_sig_enforced(void);
 void set_module_sig_enforced(void);
diff --git a/kernel/module/Makefile b/kernel/module/Makefile
index 2902fc7d0ef1..ee20d864ad19 100644
--- a/kernel/module/Makefile
+++ b/kernel/module/Makefile
@@ -7,3 +7,6 @@  obj-$(CONFIG_MODULES) += main.o
 obj-$(CONFIG_MODULE_DECOMPRESS) += decompress.o
 obj-$(CONFIG_MODULE_SIG) += signing.o
 obj-$(CONFIG_MODULE_SIG_FORMAT) += signature.o
+ifdef CONFIG_MODULES
+obj-$(CONFIG_LIVEPATCH) += livepatch.o
+endif
diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index e3c593f8767f..6150ec5ae042 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -57,6 +57,17 @@  struct load_info {
 
 extern int mod_verify_sig(const void *mod, struct load_info *info);
 
+#ifdef CONFIG_LIVEPATCH
+extern int copy_module_elf(struct module *mod, struct load_info *info);
+extern void free_module_elf(struct module *mod);
+#else /* !CONFIG_LIVEPATCH */
+static inline int copy_module_elf(struct module *mod, struct load_info *info)
+{
+	return 0;
+}
+static inline void free_module_elf(struct module *mod) { }
+#endif /* CONFIG_LIVEPATCH */
+
 #ifdef CONFIG_MODULE_DECOMPRESS
 int module_decompress(struct load_info *info, const void *buf, size_t size);
 void module_decompress_cleanup(struct load_info *info);
diff --git a/kernel/module/livepatch.c b/kernel/module/livepatch.c
new file mode 100644
index 000000000000..961045d32332
--- /dev/null
+++ b/kernel/module/livepatch.c
@@ -0,0 +1,74 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Module livepatch support
+ *
+ * Copyright (C) 2016 Jessica Yu <jeyu@redhat.com>
+ */
+
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include "internal.h"
+
+/*
+ * Persist Elf information about a module. Copy the Elf header,
+ * section header table, section string table, and symtab section
+ * index from info to mod->klp_info.
+ */
+int copy_module_elf(struct module *mod, struct load_info *info)
+{
+	unsigned int size, symndx;
+	int ret;
+
+	size = sizeof(*mod->klp_info);
+	mod->klp_info = kmalloc(size, GFP_KERNEL);
+	if (mod->klp_info == NULL)
+		return -ENOMEM;
+
+	/* Elf header */
+	size = sizeof(mod->klp_info->hdr);
+	memcpy(&mod->klp_info->hdr, info->hdr, size);
+
+	/* Elf section header table */
+	size = sizeof(*info->sechdrs) * info->hdr->e_shnum;
+	mod->klp_info->sechdrs = kmemdup(info->sechdrs, size, GFP_KERNEL);
+	if (mod->klp_info->sechdrs == NULL) {
+		ret = -ENOMEM;
+		goto free_info;
+	}
+
+	/* Elf section name string table */
+	size = info->sechdrs[info->hdr->e_shstrndx].sh_size;
+	mod->klp_info->secstrings = kmemdup(info->secstrings, size, GFP_KERNEL);
+	if (mod->klp_info->secstrings == NULL) {
+		ret = -ENOMEM;
+		goto free_sechdrs;
+	}
+
+	/* Elf symbol section index */
+	symndx = info->index.sym;
+	mod->klp_info->symndx = symndx;
+
+	/*
+	 * For livepatch modules, core_kallsyms.symtab is a complete
+	 * copy of the original symbol table. Adjust sh_addr to point
+	 * to core_kallsyms.symtab since the copy of the symtab in module
+	 * init memory is freed at the end of do_init_module().
+	 */
+	mod->klp_info->sechdrs[symndx].sh_addr = (unsigned long) mod->core_kallsyms.symtab;
+
+	return 0;
+
+free_sechdrs:
+	kfree(mod->klp_info->sechdrs);
+free_info:
+	kfree(mod->klp_info);
+	return ret;
+}
+
+void free_module_elf(struct module *mod)
+{
+	kfree(mod->klp_info->sechdrs);
+	kfree(mod->klp_info->secstrings);
+	kfree(mod->klp_info);
+}
diff --git a/kernel/module/main.c b/kernel/module/main.c
index fee64c4957f3..c91c7e57bca7 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2042,81 +2042,6 @@  static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
 }
 #endif /*  CONFIG_STRICT_MODULE_RWX */
 
-#ifdef CONFIG_LIVEPATCH
-/*
- * Persist Elf information about a module. Copy the Elf header,
- * section header table, section string table, and symtab section
- * index from info to mod->klp_info.
- */
-static int copy_module_elf(struct module *mod, struct load_info *info)
-{
-	unsigned int size, symndx;
-	int ret;
-
-	size = sizeof(*mod->klp_info);
-	mod->klp_info = kmalloc(size, GFP_KERNEL);
-	if (mod->klp_info == NULL)
-		return -ENOMEM;
-
-	/* Elf header */
-	size = sizeof(mod->klp_info->hdr);
-	memcpy(&mod->klp_info->hdr, info->hdr, size);
-
-	/* Elf section header table */
-	size = sizeof(*info->sechdrs) * info->hdr->e_shnum;
-	mod->klp_info->sechdrs = kmemdup(info->sechdrs, size, GFP_KERNEL);
-	if (mod->klp_info->sechdrs == NULL) {
-		ret = -ENOMEM;
-		goto free_info;
-	}
-
-	/* Elf section name string table */
-	size = info->sechdrs[info->hdr->e_shstrndx].sh_size;
-	mod->klp_info->secstrings = kmemdup(info->secstrings, size, GFP_KERNEL);
-	if (mod->klp_info->secstrings == NULL) {
-		ret = -ENOMEM;
-		goto free_sechdrs;
-	}
-
-	/* Elf symbol section index */
-	symndx = info->index.sym;
-	mod->klp_info->symndx = symndx;
-
-	/*
-	 * For livepatch modules, core_kallsyms.symtab is a complete
-	 * copy of the original symbol table. Adjust sh_addr to point
-	 * to core_kallsyms.symtab since the copy of the symtab in module
-	 * init memory is freed at the end of do_init_module().
-	 */
-	mod->klp_info->sechdrs[symndx].sh_addr = \
-		(unsigned long) mod->core_kallsyms.symtab;
-
-	return 0;
-
-free_sechdrs:
-	kfree(mod->klp_info->sechdrs);
-free_info:
-	kfree(mod->klp_info);
-	return ret;
-}
-
-static void free_module_elf(struct module *mod)
-{
-	kfree(mod->klp_info->sechdrs);
-	kfree(mod->klp_info->secstrings);
-	kfree(mod->klp_info);
-}
-#else /* !CONFIG_LIVEPATCH */
-static int copy_module_elf(struct module *mod, struct load_info *info)
-{
-	return 0;
-}
-
-static void free_module_elf(struct module *mod)
-{
-}
-#endif /* CONFIG_LIVEPATCH */
-
 void __weak module_memfree(void *module_region)
 {
 	/*
@@ -3091,30 +3016,23 @@  static int copy_chunked_from_user(void *dst, const void __user *usrc, unsigned l
 	return 0;
 }
 
-#ifdef CONFIG_LIVEPATCH
 static int check_modinfo_livepatch(struct module *mod, struct load_info *info)
 {
-	if (get_modinfo(info, "livepatch")) {
-		mod->klp = true;
+	if (!get_modinfo(info, "livepatch"))
+		/* Nothing more to do */
+		return 0;
+
+	if (set_livepatch_module(mod)) {
 		add_taint_module(mod, TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
 		pr_notice_once("%s: tainting kernel with TAINT_LIVEPATCH\n",
-			       mod->name);
-	}
-
-	return 0;
-}
-#else /* !CONFIG_LIVEPATCH */
-static int check_modinfo_livepatch(struct module *mod, struct load_info *info)
-{
-	if (get_modinfo(info, "livepatch")) {
-		pr_err("%s: module is marked as livepatch module, but livepatch support is disabled",
-		       mod->name);
-		return -ENOEXEC;
+				mod->name);
+		return 0;
 	}
 
-	return 0;
+	pr_err("%s: module is marked as livepatch module, but livepatch support is disabled",
+		mod->name);
+	return -ENOEXEC;
 }
-#endif /* CONFIG_LIVEPATCH */
 
 static void check_modinfo_retpoline(struct module *mod, struct load_info *info)
 {