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    Subject[PATCH v7 07/11] modpost: use null string instead of NULL pointer for default namespace
    Date
    The default namespace is the null string, "".

    When set, the null string "" is converted to NULL:

    s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL;

    When printed, the NULL pointer is get back to the null string:

    sym->namespace ?: ""

    This saves 1 byte memory allocated for "", but loses the readability.

    In kernel-space, we strive to save memory, but modpost is a userspace
    tool used to build the kernel. On modern systems, such small piece of
    memory is not a big deal.

    Handle the namespace string as is.

    Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
    Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
    ---

    scripts/mod/modpost.c | 17 +++++++++++------
    1 file changed, 11 insertions(+), 6 deletions(-)

    diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
    index 4b0a009de0fb..7044b257424a 100644
    --- a/scripts/mod/modpost.c
    +++ b/scripts/mod/modpost.c
    @@ -300,6 +300,13 @@ static bool contains_namespace(struct list_head *head, const char *namespace)
    {
    struct namespace_list *list;

    + /*
    + * The default namespace is null string "", which is always implicitly
    + * contained.
    + */
    + if (!namespace[0])
    + return true;
    +
    list_for_each_entry(list, head, list) {
    if (!strcmp(list->namespace, namespace))
    return true;
    @@ -369,7 +376,7 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod,
    s = alloc_symbol(name);
    s->module = mod;
    s->is_gpl_only = gpl_only;
    - s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL;
    + s->namespace = NOFAIL(strdup(namespace));
    list_add_tail(&s->list, &mod->exported_symbols);
    hash_add_symbol(s);

    @@ -1823,8 +1830,7 @@ static void check_exports(struct module *mod)
    else
    basename = mod->name;

    - if (exp->namespace &&
    - !contains_namespace(&mod->imported_namespaces, exp->namespace)) {
    + if (!contains_namespace(&mod->imported_namespaces, exp->namespace)) {
    modpost_log(allow_missing_ns_imports ? LOG_WARN : LOG_ERROR,
    "module %s uses symbol %s from namespace %s, but does not import it.\n",
    basename, exp->name, exp->namespace);
    @@ -1910,8 +1916,7 @@ static void add_exported_symbols(struct buffer *buf, struct module *mod)
    list_for_each_entry(sym, &mod->exported_symbols, list)
    buf_printf(buf, "KSYMTAB_%s(%s, \"%s\", \"%s\");\n",
    sym->is_func ? "FUNC" : "DATA", sym->name,
    - sym->is_gpl_only ? "_gpl" : "",
    - sym->namespace ?: "");
    + sym->is_gpl_only ? "_gpl" : "", sym->namespace);

    if (!modversions)
    return;
    @@ -2179,7 +2184,7 @@ static void write_dump(const char *fname)
    buf_printf(&buf, "0x%08x\t%s\t%s\tEXPORT_SYMBOL%s\t%s\n",
    sym->crc, sym->name, mod->name,
    sym->is_gpl_only ? "_GPL" : "",
    - sym->namespace ?: "");
    + sym->namespace);
    }
    }
    write_buf(&buf, fname);
    --
    2.39.2
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