[v3,03/11] module: add support for symbol namespaces.
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Message ID 20190821114955.12788-4-maennich@google.com
State New
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  • [v3,01/11] module: support reading multiple values per modinfo tag
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Commit Message

Matthias Maennich Aug. 21, 2019, 11:49 a.m. UTC
The EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL() macros can be used to
export a symbol to a specific namespace.  There are no _GPL_FUTURE and
_UNUSED variants because these are currently unused, and I'm not sure
they are necessary.

I didn't add EXPORT_SYMBOL_NS() for ASM exports; this patch sets the
namespace of ASM exports to NULL by default. In case of relative
references, it will be relocatable to NULL. If there's a need, this
should be pretty easy to add.

A module that wants to use a symbol exported to a namespace must add a
MODULE_IMPORT_NS() statement to their module code; otherwise, modpost
will complain when building the module, and the kernel module loader
will emit an error and fail when loading the module.

MODULE_IMPORT_NS() adds a modinfo tag 'import_ns' to the module. That
tag can be observed by the modinfo command, modpost and kernel/module.c
at the time of loading the module.

The ELF symbols are renamed to include the namespace with an asm label;
for example, symbol 'usb_stor_suspend' in namespace USB_STORAGE becomes
'usb_stor_suspend.USB_STORAGE'.  This allows modpost to do namespace
checking, without having to go through all the effort of parsing ELF and
relocation records just to get to the struct kernel_symbols.

On x86_64 I saw no difference in binary size (compression), but at
runtime this will require a word of memory per export to hold the
namespace. An alternative could be to store namespaced symbols in their
own section and use a separate 'struct namespaced_kernel_symbol' for
that section, at the cost of making the module loader more complex.

Co-developed-by: Martijn Coenen <maco@android.com>
Signed-off-by: Martijn Coenen <maco@android.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Matthias Maennich <maennich@google.com>
---
 include/asm-generic/export.h |  6 +--
 include/linux/export.h       | 85 ++++++++++++++++++++++++++++++------
 include/linux/module.h       |  2 +
 kernel/module.c              | 43 ++++++++++++++++++
 4 files changed, 120 insertions(+), 16 deletions(-)

Comments

Jessica Yu Aug. 27, 2019, 3:37 p.m. UTC | #1
+++ Matthias Maennich [21/08/19 12:49 +0100]:
>The EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL() macros can be used to
>export a symbol to a specific namespace.  There are no _GPL_FUTURE and
>_UNUSED variants because these are currently unused, and I'm not sure
>they are necessary.
>
>I didn't add EXPORT_SYMBOL_NS() for ASM exports; this patch sets the
>namespace of ASM exports to NULL by default. In case of relative
>references, it will be relocatable to NULL. If there's a need, this
>should be pretty easy to add.
>
>A module that wants to use a symbol exported to a namespace must add a
>MODULE_IMPORT_NS() statement to their module code; otherwise, modpost
>will complain when building the module, and the kernel module loader
>will emit an error and fail when loading the module.
>
>MODULE_IMPORT_NS() adds a modinfo tag 'import_ns' to the module. That
>tag can be observed by the modinfo command, modpost and kernel/module.c
>at the time of loading the module.
>
>The ELF symbols are renamed to include the namespace with an asm label;
>for example, symbol 'usb_stor_suspend' in namespace USB_STORAGE becomes
>'usb_stor_suspend.USB_STORAGE'.  This allows modpost to do namespace
>checking, without having to go through all the effort of parsing ELF and
>relocation records just to get to the struct kernel_symbols.
>
>On x86_64 I saw no difference in binary size (compression), but at
>runtime this will require a word of memory per export to hold the
>namespace. An alternative could be to store namespaced symbols in their
>own section and use a separate 'struct namespaced_kernel_symbol' for
>that section, at the cost of making the module loader more complex.
>
>Co-developed-by: Martijn Coenen <maco@android.com>
>Signed-off-by: Martijn Coenen <maco@android.com>
>Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>Signed-off-by: Matthias Maennich <maennich@google.com>
>---
> include/asm-generic/export.h |  6 +--
> include/linux/export.h       | 85 ++++++++++++++++++++++++++++++------
> include/linux/module.h       |  2 +
> kernel/module.c              | 43 ++++++++++++++++++
> 4 files changed, 120 insertions(+), 16 deletions(-)
>
>diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
>index 63f54907317b..e2b5d0f569d3 100644
>--- a/include/asm-generic/export.h
>+++ b/include/asm-generic/export.h
>@@ -17,11 +17,11 @@
>
> .macro __put, val, name
> #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>-	.long	\val - ., \name - .
>+	.long	\val - ., \name - ., 0 - .
> #elif defined(CONFIG_64BIT)
>-	.quad	\val, \name
>+	.quad	\val, \name, 0
> #else
>-	.long	\val, \name
>+	.long	\val, \name, 0
> #endif
> .endm
>
>diff --git a/include/linux/export.h b/include/linux/export.h
>index 28a4d2150689..8e12e05444d1 100644
>--- a/include/linux/export.h
>+++ b/include/linux/export.h
>@@ -20,6 +20,8 @@ extern struct module __this_module;
>
> #ifdef CONFIG_MODULES
>
>+#define NS_SEPARATOR "."
>+
> #if defined(__KERNEL__) && !defined(__GENKSYMS__)
> #ifdef CONFIG_MODVERSIONS
> /* Mark the CRC weak since genksyms apparently decides not to
>@@ -49,6 +51,16 @@ extern struct module __this_module;
>  * absolute relocations that require runtime processing on relocatable
>  * kernels.
>  */
>+#define __KSYMTAB_ENTRY_NS(sym, sec, ns)				\
>+	__ADDRESSABLE(sym)						\
>+	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
>+	    "	.balign	4					\n"	\
>+	    "__ksymtab_" #sym NS_SEPARATOR #ns ":		\n"	\
>+	    "	.long	" #sym "- .				\n"	\
>+	    "	.long	__kstrtab_" #sym "- .			\n"	\
>+	    "	.long	__kstrtab_ns_" #sym "- .		\n"	\
>+	    "	.previous					\n")
>+
> #define __KSYMTAB_ENTRY(sym, sec)					\
> 	__ADDRESSABLE(sym)						\
> 	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
>@@ -56,32 +68,53 @@ extern struct module __this_module;
> 	    "__ksymtab_" #sym ":				\n"	\
> 	    "	.long	" #sym "- .				\n"	\
> 	    "	.long	__kstrtab_" #sym "- .			\n"	\
>+	    "	.long	0 - .					\n"	\
> 	    "	.previous					\n")
>
> struct kernel_symbol {
> 	int value_offset;
> 	int name_offset;
>+	int namespace_offset;
> };
> #else
>+#define __KSYMTAB_ENTRY_NS(sym, sec, ns)				\
>+	static const struct kernel_symbol __ksymtab_##sym##__##ns	\
>+	asm("__ksymtab_" #sym NS_SEPARATOR #ns)				\
>+	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
>+	__aligned(sizeof(void *))					\
>+	= { (unsigned long)&sym, __kstrtab_##sym, __kstrtab_ns_##sym}

Style nit: missing space after __kstrtab_ns_##sym.

>+
> #define __KSYMTAB_ENTRY(sym, sec)					\
> 	static const struct kernel_symbol __ksymtab_##sym		\
>+	asm("__ksymtab_" #sym)						\
> 	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
> 	__aligned(sizeof(void *))					\
>-	= { (unsigned long)&sym, __kstrtab_##sym }
>+	= { (unsigned long)&sym, __kstrtab_##sym, NULL }
>
> struct kernel_symbol {
> 	unsigned long value;
> 	const char *name;
>+	const char *namespace;
> };
> #endif
>
>-/* For every exported symbol, place a struct in the __ksymtab section */
>-#define ___EXPORT_SYMBOL(sym, sec)					\
>+#define ___export_symbol_common(sym, sec)				\
> 	extern typeof(sym) sym;						\
> 	__CRC_SYMBOL(sym, sec)						\
> 	static const char __kstrtab_##sym[]				\
> 	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
>-	= #sym;								\
>+	= #sym								\

Any particular reason for this change? Not that it's important, just
noticing the inconsistent inclusion of the semicolon in some of the
macros (e.g. __CRC_SYMBOL includes it but __export_symbol_common doesn't).

>+
>+/* For every exported symbol, place a struct in the __ksymtab section */
>+#define ___EXPORT_SYMBOL_NS(sym, sec, ns)				\
>+	___export_symbol_common(sym, sec);			\
>+	static const char __kstrtab_ns_##sym[]				\
>+	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
>+	= #ns;								\
>+	__KSYMTAB_ENTRY_NS(sym, sec, ns)
>+
>+#define ___EXPORT_SYMBOL(sym, sec)					\
>+	___export_symbol_common(sym, sec);				\
> 	__KSYMTAB_ENTRY(sym, sec)
>
> #if defined(__DISABLE_EXPORTS)
>@@ -91,6 +124,7 @@ struct kernel_symbol {
>  * be reused in other execution contexts such as the UEFI stub or the
>  * decompressor.
>  */
>+#define __EXPORT_SYMBOL_NS(sym, sec, ns)
> #define __EXPORT_SYMBOL(sym, sec)
>
> #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
>@@ -117,18 +151,26 @@ struct kernel_symbol {
> #define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
> #define __cond_export_sym_0(sym, sec) /* nothing */
>
>+#define __EXPORT_SYMBOL_NS(sym, sec, ns)				\
>+	__ksym_marker(sym);						\
>+	__cond_export_ns_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
>+#define __cond_export_ns_sym(sym, sec, ns, conf)			\
>+	___cond_export_ns_sym(sym, sec, ns, conf)
>+#define ___cond_export_ns_sym(sym, sec, ns, enabled)			\
>+	__cond_export_ns_sym_##enabled(sym, sec, ns)
>+#define __cond_export_ns_sym_1(sym, sec, ns) ___EXPORT_SYMBOL_NS(sym, sec, ns)
>+#define __cond_export_ns_sym_0(sym, sec, ns) /* nothing */
>+
> #else
>+#define __EXPORT_SYMBOL_NS ___EXPORT_SYMBOL_NS
> #define __EXPORT_SYMBOL ___EXPORT_SYMBOL
> #endif
>
>-#define EXPORT_SYMBOL(sym)					\
>-	__EXPORT_SYMBOL(sym, "")
>-
>-#define EXPORT_SYMBOL_GPL(sym)					\
>-	__EXPORT_SYMBOL(sym, "_gpl")
>-
>-#define EXPORT_SYMBOL_GPL_FUTURE(sym)				\
>-	__EXPORT_SYMBOL(sym, "_gpl_future")
>+#define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "")
>+#define EXPORT_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_gpl")
>+#define EXPORT_SYMBOL_GPL_FUTURE(sym) __EXPORT_SYMBOL(sym, "_gpl_future")
>+#define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL_NS(sym, "", ns)
>+#define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL_NS(sym, "_gpl", ns)
>
> #ifdef CONFIG_UNUSED_SYMBOLS
> #define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
>@@ -138,11 +180,28 @@ struct kernel_symbol {
> #define EXPORT_UNUSED_SYMBOL_GPL(sym)
> #endif
>
>-#endif	/* __GENKSYMS__ */
>+#endif	/* __KERNEL__ && !__GENKSYMS__ */
>+
>+#if defined(__GENKSYMS__)
>+/*
>+ * When we're running genksyms, ignore the namespace and make the _NS
>+ * variants look like the normal ones. There are two reasons for this:
>+ * 1) In the normal definition of EXPORT_SYMBOL_NS, the 'ns' macro
>+ *    argument is itself not expanded because it's always tokenized or
>+ *    concatenated; but when running genksyms, a blank definition of the
>+ *    macro does allow the argument to be expanded; if a namespace
>+ *    happens to collide with a #define, this can cause issues.
>+ * 2) There's no need to modify genksyms to deal with the _NS variants
>+ */
>+#define EXPORT_SYMBOL_NS(sym, ns) EXPORT_SYMBOL(sym)
>+#define EXPORT_SYMBOL_NS_GPL(sym, ns) EXPORT_SYMBOL_GPL(sym)
>+#endif
>
> #else /* !CONFIG_MODULES... */
>
> #define EXPORT_SYMBOL(sym)
>+#define EXPORT_SYMBOL_NS(sym, ns)
>+#define EXPORT_SYMBOL_NS_GPL(sym, ns)
> #define EXPORT_SYMBOL_GPL(sym)
> #define EXPORT_SYMBOL_GPL_FUTURE(sym)
> #define EXPORT_UNUSED_SYMBOL(sym)
>diff --git a/include/linux/module.h b/include/linux/module.h
>index 1455812dd325..b3611e749f72 100644
>--- a/include/linux/module.h
>+++ b/include/linux/module.h
>@@ -280,6 +280,8 @@ struct notifier_block;
>
> #ifdef CONFIG_MODULES
>
>+#define MODULE_IMPORT_NS(ns) MODULE_INFO(import_ns, #ns)
>+
> extern int modules_disabled; /* for sysctl */
> /* Get/put a kernel symbol (calls must be symmetric) */
> void *__symbol_get(const char *symbol);
>diff --git a/kernel/module.c b/kernel/module.c
>index a23067907169..57e8253f2251 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -544,6 +544,15 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
> #endif
> }
>
>+static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
>+{
>+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>+	return offset_to_ptr(&sym->namespace_offset);
>+#else
>+	return sym->namespace;
>+#endif
>+}
>+
> static int cmp_name(const void *va, const void *vb)
> {
> 	const char *a;
>@@ -1379,6 +1388,34 @@ static inline int same_magic(const char *amagic, const char *bmagic,
> }
> #endif /* CONFIG_MODVERSIONS */
>
>+static char *get_modinfo(const struct load_info *info, const char *tag);
>+static char *get_next_modinfo(const struct load_info *info, const char *tag,
>+			      char *prev);
>+
>+static int verify_namespace_is_imported(const struct load_info *info,
>+					const struct kernel_symbol *sym,
>+					struct module *mod)
>+{
>+	const char *namespace;
>+	char *imported_namespace;
>+
>+	namespace = kernel_symbol_namespace(sym);
>+	if (namespace) {
>+		imported_namespace = get_modinfo(info, "import_ns");
>+		while (imported_namespace) {
>+			if (strcmp(namespace, imported_namespace) == 0)
>+				return 0;
>+			imported_namespace = get_next_modinfo(
>+				info, "import_ns", imported_namespace);
>+		}
>+		pr_err("%s: module uses symbol (%s) from namespace %s, but does not import it.\n",
>+		       mod->name, kernel_symbol_name(sym), namespace);
>+		return -EINVAL;
>+	}
>+	return 0;
>+}
>+
>+
> /* Resolve a symbol for this module.  I.e. if we find one, record usage. */
> static const struct kernel_symbol *resolve_symbol(struct module *mod,
> 						  const struct load_info *info,
>@@ -1413,6 +1450,12 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
> 		goto getname;
> 	}
>
>+	err = verify_namespace_is_imported(info, sym, mod);
>+	if (err) {
>+		sym = ERR_PTR(err);
>+		goto getname;
>+	}

I think we should verify the namespace before taking a reference to
the owner module (just swap the verify_namespace_is_imported() and
ref_module() calls here).

Other than that, this patch looks good. Thanks!

>+
> getname:
> 	/* We must make copy under the lock if we failed to get ref. */
> 	strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
>-- 
>2.23.0.rc1.153.gdeed80330f-goog
>
Matthias Maennich Aug. 27, 2019, 4:04 p.m. UTC | #2
On Tue, Aug 27, 2019 at 05:37:18PM +0200, Jessica Yu wrote:
>+++ Matthias Maennich [21/08/19 12:49 +0100]:
>>The EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL() macros can be used to
>>export a symbol to a specific namespace.  There are no _GPL_FUTURE and
>>_UNUSED variants because these are currently unused, and I'm not sure
>>they are necessary.
>>
>>I didn't add EXPORT_SYMBOL_NS() for ASM exports; this patch sets the
>>namespace of ASM exports to NULL by default. In case of relative
>>references, it will be relocatable to NULL. If there's a need, this
>>should be pretty easy to add.
>>
>>A module that wants to use a symbol exported to a namespace must add a
>>MODULE_IMPORT_NS() statement to their module code; otherwise, modpost
>>will complain when building the module, and the kernel module loader
>>will emit an error and fail when loading the module.
>>
>>MODULE_IMPORT_NS() adds a modinfo tag 'import_ns' to the module. That
>>tag can be observed by the modinfo command, modpost and kernel/module.c
>>at the time of loading the module.
>>
>>The ELF symbols are renamed to include the namespace with an asm label;
>>for example, symbol 'usb_stor_suspend' in namespace USB_STORAGE becomes
>>'usb_stor_suspend.USB_STORAGE'.  This allows modpost to do namespace
>>checking, without having to go through all the effort of parsing ELF and
>>relocation records just to get to the struct kernel_symbols.
>>
>>On x86_64 I saw no difference in binary size (compression), but at
>>runtime this will require a word of memory per export to hold the
>>namespace. An alternative could be to store namespaced symbols in their
>>own section and use a separate 'struct namespaced_kernel_symbol' for
>>that section, at the cost of making the module loader more complex.
>>
>>Co-developed-by: Martijn Coenen <maco@android.com>
>>Signed-off-by: Martijn Coenen <maco@android.com>
>>Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>Signed-off-by: Matthias Maennich <maennich@google.com>
>>---
>>include/asm-generic/export.h |  6 +--
>>include/linux/export.h       | 85 ++++++++++++++++++++++++++++++------
>>include/linux/module.h       |  2 +
>>kernel/module.c              | 43 ++++++++++++++++++
>>4 files changed, 120 insertions(+), 16 deletions(-)
>>
>>diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
>>index 63f54907317b..e2b5d0f569d3 100644
>>--- a/include/asm-generic/export.h
>>+++ b/include/asm-generic/export.h
>>@@ -17,11 +17,11 @@
>>
>>.macro __put, val, name
>>#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>>-	.long	\val - ., \name - .
>>+	.long	\val - ., \name - ., 0 - .
>>#elif defined(CONFIG_64BIT)
>>-	.quad	\val, \name
>>+	.quad	\val, \name, 0
>>#else
>>-	.long	\val, \name
>>+	.long	\val, \name, 0
>>#endif
>>.endm
>>
>>diff --git a/include/linux/export.h b/include/linux/export.h
>>index 28a4d2150689..8e12e05444d1 100644
>>--- a/include/linux/export.h
>>+++ b/include/linux/export.h
>>@@ -20,6 +20,8 @@ extern struct module __this_module;
>>
>>#ifdef CONFIG_MODULES
>>
>>+#define NS_SEPARATOR "."
>>+
>>#if defined(__KERNEL__) && !defined(__GENKSYMS__)
>>#ifdef CONFIG_MODVERSIONS
>>/* Mark the CRC weak since genksyms apparently decides not to
>>@@ -49,6 +51,16 @@ extern struct module __this_module;
>> * absolute relocations that require runtime processing on relocatable
>> * kernels.
>> */
>>+#define __KSYMTAB_ENTRY_NS(sym, sec, ns)				\
>>+	__ADDRESSABLE(sym)						\
>>+	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
>>+	    "	.balign	4					\n"	\
>>+	    "__ksymtab_" #sym NS_SEPARATOR #ns ":		\n"	\
>>+	    "	.long	" #sym "- .				\n"	\
>>+	    "	.long	__kstrtab_" #sym "- .			\n"	\
>>+	    "	.long	__kstrtab_ns_" #sym "- .		\n"	\
>>+	    "	.previous					\n")
>>+
>>#define __KSYMTAB_ENTRY(sym, sec)					\
>>	__ADDRESSABLE(sym)						\
>>	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
>>@@ -56,32 +68,53 @@ extern struct module __this_module;
>>	    "__ksymtab_" #sym ":				\n"	\
>>	    "	.long	" #sym "- .				\n"	\
>>	    "	.long	__kstrtab_" #sym "- .			\n"	\
>>+	    "	.long	0 - .					\n"	\
>>	    "	.previous					\n")
>>
>>struct kernel_symbol {
>>	int value_offset;
>>	int name_offset;
>>+	int namespace_offset;
>>};
>>#else
>>+#define __KSYMTAB_ENTRY_NS(sym, sec, ns)				\
>>+	static const struct kernel_symbol __ksymtab_##sym##__##ns	\
>>+	asm("__ksymtab_" #sym NS_SEPARATOR #ns)				\
>>+	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
>>+	__aligned(sizeof(void *))					\
>>+	= { (unsigned long)&sym, __kstrtab_##sym, __kstrtab_ns_##sym}
>
>Style nit: missing space after __kstrtab_ns_##sym.
>
>>+
>>#define __KSYMTAB_ENTRY(sym, sec)					\
>>	static const struct kernel_symbol __ksymtab_##sym		\
>>+	asm("__ksymtab_" #sym)						\
>>	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
>>	__aligned(sizeof(void *))					\
>>-	= { (unsigned long)&sym, __kstrtab_##sym }
>>+	= { (unsigned long)&sym, __kstrtab_##sym, NULL }
>>
>>struct kernel_symbol {
>>	unsigned long value;
>>	const char *name;
>>+	const char *namespace;
>>};
>>#endif
>>
>>-/* For every exported symbol, place a struct in the __ksymtab section */
>>-#define ___EXPORT_SYMBOL(sym, sec)					\
>>+#define ___export_symbol_common(sym, sec)				\
>>	extern typeof(sym) sym;						\
>>	__CRC_SYMBOL(sym, sec)						\
>>	static const char __kstrtab_##sym[]				\
>>	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
>>-	= #sym;								\
>>+	= #sym								\
>
>Any particular reason for this change? Not that it's important, just
>noticing the inconsistent inclusion of the semicolon in some of the
>macros (e.g. __CRC_SYMBOL includes it but __export_symbol_common doesn't).
>

I tried to be consistent to let the macro "call site" provide the final
semicolon. And you are right, I could have adjusted __CRC_SYMBOL as
well. I will adjust this for the next version.

>>+
>>+/* For every exported symbol, place a struct in the __ksymtab section */
>>+#define ___EXPORT_SYMBOL_NS(sym, sec, ns)				\
>>+	___export_symbol_common(sym, sec);			\
>>+	static const char __kstrtab_ns_##sym[]				\
>>+	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
>>+	= #ns;								\
>>+	__KSYMTAB_ENTRY_NS(sym, sec, ns)
>>+
>>+#define ___EXPORT_SYMBOL(sym, sec)					\
>>+	___export_symbol_common(sym, sec);				\
>>	__KSYMTAB_ENTRY(sym, sec)
>>
>>#if defined(__DISABLE_EXPORTS)
>>@@ -91,6 +124,7 @@ struct kernel_symbol {
>> * be reused in other execution contexts such as the UEFI stub or the
>> * decompressor.
>> */
>>+#define __EXPORT_SYMBOL_NS(sym, sec, ns)
>>#define __EXPORT_SYMBOL(sym, sec)
>>
>>#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
>>@@ -117,18 +151,26 @@ struct kernel_symbol {
>>#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
>>#define __cond_export_sym_0(sym, sec) /* nothing */
>>
>>+#define __EXPORT_SYMBOL_NS(sym, sec, ns)				\
>>+	__ksym_marker(sym);						\
>>+	__cond_export_ns_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
>>+#define __cond_export_ns_sym(sym, sec, ns, conf)			\
>>+	___cond_export_ns_sym(sym, sec, ns, conf)
>>+#define ___cond_export_ns_sym(sym, sec, ns, enabled)			\
>>+	__cond_export_ns_sym_##enabled(sym, sec, ns)
>>+#define __cond_export_ns_sym_1(sym, sec, ns) ___EXPORT_SYMBOL_NS(sym, sec, ns)
>>+#define __cond_export_ns_sym_0(sym, sec, ns) /* nothing */
>>+
>>#else
>>+#define __EXPORT_SYMBOL_NS ___EXPORT_SYMBOL_NS
>>#define __EXPORT_SYMBOL ___EXPORT_SYMBOL
>>#endif
>>
>>-#define EXPORT_SYMBOL(sym)					\
>>-	__EXPORT_SYMBOL(sym, "")
>>-
>>-#define EXPORT_SYMBOL_GPL(sym)					\
>>-	__EXPORT_SYMBOL(sym, "_gpl")
>>-
>>-#define EXPORT_SYMBOL_GPL_FUTURE(sym)				\
>>-	__EXPORT_SYMBOL(sym, "_gpl_future")
>>+#define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "")
>>+#define EXPORT_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_gpl")
>>+#define EXPORT_SYMBOL_GPL_FUTURE(sym) __EXPORT_SYMBOL(sym, "_gpl_future")
>>+#define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL_NS(sym, "", ns)
>>+#define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL_NS(sym, "_gpl", ns)
>>
>>#ifdef CONFIG_UNUSED_SYMBOLS
>>#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
>>@@ -138,11 +180,28 @@ struct kernel_symbol {
>>#define EXPORT_UNUSED_SYMBOL_GPL(sym)
>>#endif
>>
>>-#endif	/* __GENKSYMS__ */
>>+#endif	/* __KERNEL__ && !__GENKSYMS__ */
>>+
>>+#if defined(__GENKSYMS__)
>>+/*
>>+ * When we're running genksyms, ignore the namespace and make the _NS
>>+ * variants look like the normal ones. There are two reasons for this:
>>+ * 1) In the normal definition of EXPORT_SYMBOL_NS, the 'ns' macro
>>+ *    argument is itself not expanded because it's always tokenized or
>>+ *    concatenated; but when running genksyms, a blank definition of the
>>+ *    macro does allow the argument to be expanded; if a namespace
>>+ *    happens to collide with a #define, this can cause issues.
>>+ * 2) There's no need to modify genksyms to deal with the _NS variants
>>+ */
>>+#define EXPORT_SYMBOL_NS(sym, ns) EXPORT_SYMBOL(sym)
>>+#define EXPORT_SYMBOL_NS_GPL(sym, ns) EXPORT_SYMBOL_GPL(sym)
>>+#endif
>>
>>#else /* !CONFIG_MODULES... */
>>
>>#define EXPORT_SYMBOL(sym)
>>+#define EXPORT_SYMBOL_NS(sym, ns)
>>+#define EXPORT_SYMBOL_NS_GPL(sym, ns)
>>#define EXPORT_SYMBOL_GPL(sym)
>>#define EXPORT_SYMBOL_GPL_FUTURE(sym)
>>#define EXPORT_UNUSED_SYMBOL(sym)
>>diff --git a/include/linux/module.h b/include/linux/module.h
>>index 1455812dd325..b3611e749f72 100644
>>--- a/include/linux/module.h
>>+++ b/include/linux/module.h
>>@@ -280,6 +280,8 @@ struct notifier_block;
>>
>>#ifdef CONFIG_MODULES
>>
>>+#define MODULE_IMPORT_NS(ns) MODULE_INFO(import_ns, #ns)
>>+
>>extern int modules_disabled; /* for sysctl */
>>/* Get/put a kernel symbol (calls must be symmetric) */
>>void *__symbol_get(const char *symbol);
>>diff --git a/kernel/module.c b/kernel/module.c
>>index a23067907169..57e8253f2251 100644
>>--- a/kernel/module.c
>>+++ b/kernel/module.c
>>@@ -544,6 +544,15 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
>>#endif
>>}
>>
>>+static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
>>+{
>>+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>>+	return offset_to_ptr(&sym->namespace_offset);
>>+#else
>>+	return sym->namespace;
>>+#endif
>>+}
>>+
>>static int cmp_name(const void *va, const void *vb)
>>{
>>	const char *a;
>>@@ -1379,6 +1388,34 @@ static inline int same_magic(const char *amagic, const char *bmagic,
>>}
>>#endif /* CONFIG_MODVERSIONS */
>>
>>+static char *get_modinfo(const struct load_info *info, const char *tag);
>>+static char *get_next_modinfo(const struct load_info *info, const char *tag,
>>+			      char *prev);
>>+
>>+static int verify_namespace_is_imported(const struct load_info *info,
>>+					const struct kernel_symbol *sym,
>>+					struct module *mod)
>>+{
>>+	const char *namespace;
>>+	char *imported_namespace;
>>+
>>+	namespace = kernel_symbol_namespace(sym);
>>+	if (namespace) {
>>+		imported_namespace = get_modinfo(info, "import_ns");
>>+		while (imported_namespace) {
>>+			if (strcmp(namespace, imported_namespace) == 0)
>>+				return 0;
>>+			imported_namespace = get_next_modinfo(
>>+				info, "import_ns", imported_namespace);
>>+		}
>>+		pr_err("%s: module uses symbol (%s) from namespace %s, but does not import it.\n",
>>+		       mod->name, kernel_symbol_name(sym), namespace);
>>+		return -EINVAL;
>>+	}
>>+	return 0;
>>+}
>>+
>>+
>>/* Resolve a symbol for this module.  I.e. if we find one, record usage. */
>>static const struct kernel_symbol *resolve_symbol(struct module *mod,
>>						  const struct load_info *info,
>>@@ -1413,6 +1450,12 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
>>		goto getname;
>>	}
>>
>>+	err = verify_namespace_is_imported(info, sym, mod);
>>+	if (err) {
>>+		sym = ERR_PTR(err);
>>+		goto getname;
>>+	}
>
>I think we should verify the namespace before taking a reference to
>the owner module (just swap the verify_namespace_is_imported() and
>ref_module() calls here).
>
>Other than that, this patch looks good. Thanks!
>

Thanks! I will address the points above.

Cheers,
Matthias

>>+
>>getname:
>>	/* We must make copy under the lock if we failed to get ref. */
>>	strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
>>-- 
>>2.23.0.rc1.153.gdeed80330f-goog
>>

Patch
diff mbox series

diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
index 63f54907317b..e2b5d0f569d3 100644
--- a/include/asm-generic/export.h
+++ b/include/asm-generic/export.h
@@ -17,11 +17,11 @@ 
 
 .macro __put, val, name
 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-	.long	\val - ., \name - .
+	.long	\val - ., \name - ., 0 - .
 #elif defined(CONFIG_64BIT)
-	.quad	\val, \name
+	.quad	\val, \name, 0
 #else
-	.long	\val, \name
+	.long	\val, \name, 0
 #endif
 .endm
 
diff --git a/include/linux/export.h b/include/linux/export.h
index 28a4d2150689..8e12e05444d1 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -20,6 +20,8 @@  extern struct module __this_module;
 
 #ifdef CONFIG_MODULES
 
+#define NS_SEPARATOR "."
+
 #if defined(__KERNEL__) && !defined(__GENKSYMS__)
 #ifdef CONFIG_MODVERSIONS
 /* Mark the CRC weak since genksyms apparently decides not to
@@ -49,6 +51,16 @@  extern struct module __this_module;
  * absolute relocations that require runtime processing on relocatable
  * kernels.
  */
+#define __KSYMTAB_ENTRY_NS(sym, sec, ns)				\
+	__ADDRESSABLE(sym)						\
+	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
+	    "	.balign	4					\n"	\
+	    "__ksymtab_" #sym NS_SEPARATOR #ns ":		\n"	\
+	    "	.long	" #sym "- .				\n"	\
+	    "	.long	__kstrtab_" #sym "- .			\n"	\
+	    "	.long	__kstrtab_ns_" #sym "- .		\n"	\
+	    "	.previous					\n")
+
 #define __KSYMTAB_ENTRY(sym, sec)					\
 	__ADDRESSABLE(sym)						\
 	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
@@ -56,32 +68,53 @@  extern struct module __this_module;
 	    "__ksymtab_" #sym ":				\n"	\
 	    "	.long	" #sym "- .				\n"	\
 	    "	.long	__kstrtab_" #sym "- .			\n"	\
+	    "	.long	0 - .					\n"	\
 	    "	.previous					\n")
 
 struct kernel_symbol {
 	int value_offset;
 	int name_offset;
+	int namespace_offset;
 };
 #else
+#define __KSYMTAB_ENTRY_NS(sym, sec, ns)				\
+	static const struct kernel_symbol __ksymtab_##sym##__##ns	\
+	asm("__ksymtab_" #sym NS_SEPARATOR #ns)				\
+	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
+	__aligned(sizeof(void *))					\
+	= { (unsigned long)&sym, __kstrtab_##sym, __kstrtab_ns_##sym}
+
 #define __KSYMTAB_ENTRY(sym, sec)					\
 	static const struct kernel_symbol __ksymtab_##sym		\
+	asm("__ksymtab_" #sym)						\
 	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
 	__aligned(sizeof(void *))					\
-	= { (unsigned long)&sym, __kstrtab_##sym }
+	= { (unsigned long)&sym, __kstrtab_##sym, NULL }
 
 struct kernel_symbol {
 	unsigned long value;
 	const char *name;
+	const char *namespace;
 };
 #endif
 
-/* For every exported symbol, place a struct in the __ksymtab section */
-#define ___EXPORT_SYMBOL(sym, sec)					\
+#define ___export_symbol_common(sym, sec)				\
 	extern typeof(sym) sym;						\
 	__CRC_SYMBOL(sym, sec)						\
 	static const char __kstrtab_##sym[]				\
 	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
-	= #sym;								\
+	= #sym								\
+
+/* For every exported symbol, place a struct in the __ksymtab section */
+#define ___EXPORT_SYMBOL_NS(sym, sec, ns)				\
+	___export_symbol_common(sym, sec);			\
+	static const char __kstrtab_ns_##sym[]				\
+	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
+	= #ns;								\
+	__KSYMTAB_ENTRY_NS(sym, sec, ns)
+
+#define ___EXPORT_SYMBOL(sym, sec)					\
+	___export_symbol_common(sym, sec);				\
 	__KSYMTAB_ENTRY(sym, sec)
 
 #if defined(__DISABLE_EXPORTS)
@@ -91,6 +124,7 @@  struct kernel_symbol {
  * be reused in other execution contexts such as the UEFI stub or the
  * decompressor.
  */
+#define __EXPORT_SYMBOL_NS(sym, sec, ns)
 #define __EXPORT_SYMBOL(sym, sec)
 
 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
@@ -117,18 +151,26 @@  struct kernel_symbol {
 #define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
 #define __cond_export_sym_0(sym, sec) /* nothing */
 
+#define __EXPORT_SYMBOL_NS(sym, sec, ns)				\
+	__ksym_marker(sym);						\
+	__cond_export_ns_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
+#define __cond_export_ns_sym(sym, sec, ns, conf)			\
+	___cond_export_ns_sym(sym, sec, ns, conf)
+#define ___cond_export_ns_sym(sym, sec, ns, enabled)			\
+	__cond_export_ns_sym_##enabled(sym, sec, ns)
+#define __cond_export_ns_sym_1(sym, sec, ns) ___EXPORT_SYMBOL_NS(sym, sec, ns)
+#define __cond_export_ns_sym_0(sym, sec, ns) /* nothing */
+
 #else
+#define __EXPORT_SYMBOL_NS ___EXPORT_SYMBOL_NS
 #define __EXPORT_SYMBOL ___EXPORT_SYMBOL
 #endif
 
-#define EXPORT_SYMBOL(sym)					\
-	__EXPORT_SYMBOL(sym, "")
-
-#define EXPORT_SYMBOL_GPL(sym)					\
-	__EXPORT_SYMBOL(sym, "_gpl")
-
-#define EXPORT_SYMBOL_GPL_FUTURE(sym)				\
-	__EXPORT_SYMBOL(sym, "_gpl_future")
+#define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "")
+#define EXPORT_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_gpl")
+#define EXPORT_SYMBOL_GPL_FUTURE(sym) __EXPORT_SYMBOL(sym, "_gpl_future")
+#define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL_NS(sym, "", ns)
+#define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL_NS(sym, "_gpl", ns)
 
 #ifdef CONFIG_UNUSED_SYMBOLS
 #define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
@@ -138,11 +180,28 @@  struct kernel_symbol {
 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
 #endif
 
-#endif	/* __GENKSYMS__ */
+#endif	/* __KERNEL__ && !__GENKSYMS__ */
+
+#if defined(__GENKSYMS__)
+/*
+ * When we're running genksyms, ignore the namespace and make the _NS
+ * variants look like the normal ones. There are two reasons for this:
+ * 1) In the normal definition of EXPORT_SYMBOL_NS, the 'ns' macro
+ *    argument is itself not expanded because it's always tokenized or
+ *    concatenated; but when running genksyms, a blank definition of the
+ *    macro does allow the argument to be expanded; if a namespace
+ *    happens to collide with a #define, this can cause issues.
+ * 2) There's no need to modify genksyms to deal with the _NS variants
+ */
+#define EXPORT_SYMBOL_NS(sym, ns) EXPORT_SYMBOL(sym)
+#define EXPORT_SYMBOL_NS_GPL(sym, ns) EXPORT_SYMBOL_GPL(sym)
+#endif
 
 #else /* !CONFIG_MODULES... */
 
 #define EXPORT_SYMBOL(sym)
+#define EXPORT_SYMBOL_NS(sym, ns)
+#define EXPORT_SYMBOL_NS_GPL(sym, ns)
 #define EXPORT_SYMBOL_GPL(sym)
 #define EXPORT_SYMBOL_GPL_FUTURE(sym)
 #define EXPORT_UNUSED_SYMBOL(sym)
diff --git a/include/linux/module.h b/include/linux/module.h
index 1455812dd325..b3611e749f72 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -280,6 +280,8 @@  struct notifier_block;
 
 #ifdef CONFIG_MODULES
 
+#define MODULE_IMPORT_NS(ns) MODULE_INFO(import_ns, #ns)
+
 extern int modules_disabled; /* for sysctl */
 /* Get/put a kernel symbol (calls must be symmetric) */
 void *__symbol_get(const char *symbol);
diff --git a/kernel/module.c b/kernel/module.c
index a23067907169..57e8253f2251 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -544,6 +544,15 @@  static const char *kernel_symbol_name(const struct kernel_symbol *sym)
 #endif
 }
 
+static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
+{
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+	return offset_to_ptr(&sym->namespace_offset);
+#else
+	return sym->namespace;
+#endif
+}
+
 static int cmp_name(const void *va, const void *vb)
 {
 	const char *a;
@@ -1379,6 +1388,34 @@  static inline int same_magic(const char *amagic, const char *bmagic,
 }
 #endif /* CONFIG_MODVERSIONS */
 
+static char *get_modinfo(const struct load_info *info, const char *tag);
+static char *get_next_modinfo(const struct load_info *info, const char *tag,
+			      char *prev);
+
+static int verify_namespace_is_imported(const struct load_info *info,
+					const struct kernel_symbol *sym,
+					struct module *mod)
+{
+	const char *namespace;
+	char *imported_namespace;
+
+	namespace = kernel_symbol_namespace(sym);
+	if (namespace) {
+		imported_namespace = get_modinfo(info, "import_ns");
+		while (imported_namespace) {
+			if (strcmp(namespace, imported_namespace) == 0)
+				return 0;
+			imported_namespace = get_next_modinfo(
+				info, "import_ns", imported_namespace);
+		}
+		pr_err("%s: module uses symbol (%s) from namespace %s, but does not import it.\n",
+		       mod->name, kernel_symbol_name(sym), namespace);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+
 /* Resolve a symbol for this module.  I.e. if we find one, record usage. */
 static const struct kernel_symbol *resolve_symbol(struct module *mod,
 						  const struct load_info *info,
@@ -1413,6 +1450,12 @@  static const struct kernel_symbol *resolve_symbol(struct module *mod,
 		goto getname;
 	}
 
+	err = verify_namespace_is_imported(info, sym, mod);
+	if (err) {
+		sym = ERR_PTR(err);
+		goto getname;
+	}
+
 getname:
 	/* We must make copy under the lock if we failed to get ref. */
 	strncpy(ownername, module_name(owner), MODULE_NAME_LEN);