module: swap the order of symbol.namespace

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>

diff --git a/include/linux/export.h b/include/linux/export.h
index 95f55b7f83a0a28a67898e441c959ae05b32e24f..0695d4e847d9feb749667fa7217dce6268ee083e 100644 (file)
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -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 }

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3961941e8e7a9c95062bde8983c88efd001dba6d..c4b536ac13276c356f2d2fd034bacdc5d4327d8f 100644 (file)
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -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;
 }
 
 /**