module: swap the order of symbol.namespace (bf70b050) · Commits · 戴 / test

Currently, EXPORT_SYMBOL_NS(_GPL) constructs the kernel symbol as follows: __ksymtab_SYMBOL.NAMESPACE The sym_extract_namespace() in modpost allocates memory for the part SYMBOL.NAMESPACE when '.' is contained. One problem is that the pointer returned by strdup() is lost because the symbol name will be copied to malloc'ed memory by alloc_symbol(). No one will keep track of the pointer of strdup'ed memory. sym->namespace still points to the NAMESPACE part. So, you can free it with complicated code like this: free(sym->namespace - strlen(sym->name) - 1); It complicates memory free. To fix it elegantly, I swapped the order of the symbol and the namespace as follows: __ksymtab_NAMESPACE.SYMBOL then, simplified sym_extract_namespace() so that it allocates memory only for the NAMESPACE part. I prefer this order because it is intuitive and also matches to major languages. For example, NAMESPACE::NAME in C++, MODULE.NAME in Python. Reviewed-by:

Matthias Maennich <maennich@google.com> Signed-off-by:

Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by:

Jessica Yu <jeyu@kernel.org>

include/linux/export.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -52,7 +52,7 @@ extern struct module __this_module;
		__ADDRESSABLE(sym) \
		asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \
		" .balign 4 \n" \
		"__ksymtab_" #sym NS_SEPARATOR #ns ": \n" \
		"__ksymtab_" #ns NS_SEPARATOR #sym ": \n" \
		" .long " #sym "- . \n" \
		" .long __kstrtab_" #sym "- . \n" \
		" .long __kstrtab_ns_" #sym "- . \n" \
		@@ -76,7 +76,7 @@ struct kernel_symbol {
		#else
		#define __KSYMTAB_ENTRY_NS(sym, sec, ns) \
		static const struct kernel_symbol __ksymtab_##sym##__##ns \
		asm("__ksymtab_" #sym NS_SEPARATOR #ns) \
		asm("__ksymtab_" #ns NS_SEPARATOR #sym) \
		__attribute__((section("___ksymtab" sec "+" #sym), used)) \
		__aligned(sizeof(void *)) \
		= { (unsigned long)&sym, __kstrtab_##sym, __kstrtab_ns_##sym }

scripts/mod/modpost.c

+7 −9

Original line number	Diff line number	Diff line
		@@ -350,18 +350,16 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec)

		static const char sym_extract_namespace(const char *symname)
		{
		size_t n;
		char *dupsymname;
		char *namespace = NULL;
		char *ns_separator;

		n = strcspn(*symname, ".");
		if (n < strlen(*symname) - 1) {
		dupsymname = NOFAIL(strdup(*symname));
		dupsymname[n] = '\0';
		*symname = dupsymname;
		return dupsymname + n + 1;
		ns_separator = strchr(*symname, '.');
		if (ns_separator) {
		namespace = NOFAIL(strndup(symname, ns_separator - symname));
		*symname = ns_separator + 1;
		}

		return NULL;
		return namespace;
		}

		/**

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