Thread (22 messages) 22 messages, 4 authors, 2022-02-11

Re: [PATCH v5 04/13] module: Move livepatch support to a separate file

From: Christophe Leroy <hidden>
Date: 2022-02-09 18:55:18
Also in: live-patching, lkml


Le 09/02/2022 à 18:03, Aaron Tomlin a écrit :
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.
   LD      .tmp_vmlinux.kallsyms1
powerpc64-linux-ld: kernel/livepatch/core.o: in function `klp_enable_patch':
(.text+0x1a0c): undefined reference to `is_livepatch_module'
powerpc64-linux-ld: kernel/module/main.o: in function `free_module':
main.c:(.text+0x50f4): undefined reference to `is_livepatch_module'
powerpc64-linux-ld: kernel/module/main.o: in function `load_module':
main.c:(.text+0x6f20): undefined reference to `is_livepatch_module'
powerpc64-linux-ld: main.c:(.text+0x8390): undefined reference to 
`is_livepatch_module'
powerpc64-linux-ld: main.c:(.text+0x8d6c): undefined reference to 
`is_livepatch_module'
make: *** [Makefile:1155 : vmlinux] Erreur 1


I don't understand why you are uninlining that so simple function.
Such a function is likely a single instruction in assembly, it is 
definitely not worth inlining.

Christophe
quoted hunk ↗ jump to hunk
Signed-off-by: Aaron Tomlin <redacted>
---
  include/linux/module.h    |   5 +-
  kernel/module/Makefile    |   3 ++
  kernel/module/internal.h  |  18 +++++++
  kernel/module/livepatch.c |  80 ++++++++++++++++++++++++++++++
  kernel/module/main.c      | 102 ++++----------------------------------
  5 files changed, 112 insertions(+), 96 deletions(-)
  create mode 100644 kernel/module/livepatch.c
diff --git a/include/linux/module.h b/include/linux/module.h
index 1e135fd5c076..680b31ff57fa 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -664,10 +664,7 @@ static inline bool module_requested_async_probing(struct module *module)
  }
  
  #ifdef CONFIG_LIVEPATCH
-static inline bool is_livepatch_module(struct module *mod)
-{
-	return mod->klp;
-}
+bool is_livepatch_module(struct module *mod);
  #else /* !CONFIG_LIVEPATCH */
  static inline bool is_livepatch_module(struct module *mod)
  {
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 1cf5d6dabc97..d252e0af1c54 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -58,6 +58,24 @@ struct load_info {
  
  int mod_verify_sig(const void *mod, struct load_info *info);
  
+#ifdef CONFIG_LIVEPATCH
+int copy_module_elf(struct module *mod, struct load_info *info);
+void free_module_elf(struct module *mod);
+bool set_livepatch_module(struct module *mod);
+#else /* !CONFIG_LIVEPATCH */
+static inline int copy_module_elf(struct module *mod, struct load_info *info)
+{
+	return 0;
+}
+
+static inline bool set_livepatch_module(struct module *mod)
+{
+	return false;
+}
+
+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..7e9cf530c3f0
--- /dev/null
+++ b/kernel/module/livepatch.c
@@ -0,0 +1,80 @@
+// 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);
+}
+
+inline bool set_livepatch_module(struct module *mod)
+{
+	mod->klp = true;
+	return true;
+}
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 750e3ad28679..5f5bd7152b55 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)
  {
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