Currently, external module builds produce tons of false-positives:
WARNING: module <mod> uses symbol <sym> from namespace <ns>, but does not import it.
Here, the <ns> part shows a random string.
When you build external modules, the symbol info of vmlinux and
in-kernel modules are read from $(objtree)/Module.symvers, but
read_dump() is buggy in multiple ways:
[1] When the modpost is run for vmlinux and in-kernel modules,
sym_extract_namespace() allocates memory for the namespace. On the
other hand, read_dump() does not, then sym->namespace will point to
somewhere in the line buffer of get_next_line(). The data in the
buffer will be replaced soon, and sym->namespace will end up with
pointing to unrelated data. As a result, check_exports() will show
random strings in the warning messages.
[2] When there is no namespace, sym_extract_namespace() returns NULL.
On the other hand, read_dump() sets namespace to an empty string "".
(but, it will be later replaced with unrelated data due to bug [1].)
The check_exports() shows a warning unless exp->namespace is NULL,
so every symbol read from read_dump() emits the warning, which is
mostly false positive.
To address [1], sym_add_exported() calls strdup() for s->namespace.
The namespace from sym_extract_namespace() must be freed to avoid
memory leak.
For [2], I changed the if-conditional in check_exports().
This commit also fixes sym_add_exported() to set s->namespace correctly
when the symbol is preloaded.
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Reviewed-by: Matthias Maennich <maennich@xxxxxxxxxx>
---
Changes in v2:
- Change the approach to deal with ->preloaded
scripts/mod/modpost.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 2c644086c412..936d3ad23c83 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -166,7 +166,7 @@ struct symbol {
struct module *module;
unsigned int crc;
int crc_valid;
- const char *namespace;
+ char *namespace;
unsigned int weak:1;
unsigned int vmlinux:1; /* 1 if symbol is defined in vmlinux */
unsigned int kernel:1; /* 1 if symbol is from kernel
@@ -348,7 +348,7 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec)
return export_unknown;
}
-static const char *sym_extract_namespace(const char **symname)
+static char *sym_extract_namespace(const char **symname)
{
char *namespace = NULL;
char *ns_separator;
@@ -373,7 +373,6 @@ static struct symbol *sym_add_exported(const char *name, const char *namespace,
if (!s) {
s = new_symbol(name, mod, export);
- s->namespace = namespace;
} else {
if (!s->preloaded) {
warn("%s: '%s' exported twice. Previous export was in %s%s\n",
@@ -384,6 +383,8 @@ static struct symbol *sym_add_exported(const char *name, const char *namespace,
s->module = mod;
}
}
+ free(s->namespace);
+ s->namespace = namespace ? strdup(namespace) : NULL;
s->preloaded = 0;
s->vmlinux = is_vmlinux(mod->name);
s->kernel = 0;
@@ -670,7 +671,8 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
unsigned int crc;
enum export export;
bool is_crc = false;
- const char *name, *namespace;
+ const char *name;
+ char *namespace;
if ((!is_vmlinux(mod->name) || mod->is_dot_o) &&
strstarts(symname, "__ksymtab"))
@@ -745,6 +747,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
name = symname + strlen("__ksymtab_");
namespace = sym_extract_namespace(&name);
sym_add_exported(name, namespace, mod, export);
+ free(namespace);
}
if (strcmp(symname, "init_module") == 0)
mod->has_init = 1;
@@ -2193,7 +2196,7 @@ static int check_exports(struct module *mod)
else
basename = mod->name;
- if (exp->namespace) {
+ if (exp->namespace && exp->namespace[0]) {
add_namespace(&mod->required_namespaces,
exp->namespace);
--
2.17.1
