Re: [PATCH v3 04/11] modpost: add support for symbol namespaces
From: Matthias Maennich
Date: Tue Aug 27 2019 - 10:41:26 EST
On Mon, Aug 26, 2019 at 06:21:38PM +0200, Jessica Yu wrote:
+++ Matthias Maennich [21/08/19 12:49 +0100]:
Add support for symbols that are exported into namespaces. For that,
extract any namespace suffix from the symbol name. In addition, emit a
warning whenever a module refers to an exported symbol without
explicitly importing the namespace that it is defined in. This patch
consistently adds the namespace suffix to symbol names exported into
Module.symvers.
Example warning emitted by modpost in case of the above violation:
WARNING: module ums-usbat uses symbol usb_stor_resume from namespace
USB_STORAGE, but does not import it.
Co-developed-by: Martijn Coenen <maco@xxxxxxxxxxx>
Signed-off-by: Martijn Coenen <maco@xxxxxxxxxxx>
Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Matthias Maennich <maennich@xxxxxxxxxx>
---
scripts/mod/modpost.c | 91 +++++++++++++++++++++++++++++++++++++------
scripts/mod/modpost.h | 7 ++++
2 files changed, 87 insertions(+), 11 deletions(-)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f277e116e0eb..538bb24ffee3 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -164,6 +164,7 @@ struct symbol {
struct module *module;
unsigned int crc;
int crc_valid;
+ const 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
@@ -233,6 +234,37 @@ static struct symbol *find_symbol(const char *name)
return NULL;
}
+static bool contains_namespace(struct namespace_list *list,
+ const char *namespace)
+{
+ struct namespace_list *ns_entry;
+
+ for (ns_entry = list; ns_entry != NULL; ns_entry = ns_entry->next)
+ if (strcmp(ns_entry->namespace, namespace) == 0)
+ return true;
+
+ return false;
+}
+
+static void add_namespace(struct namespace_list **list, const char *namespace)
+{
+ struct namespace_list *ns_entry;
+
+ if (!contains_namespace(*list, namespace)) {
+ ns_entry = NOFAIL(malloc(sizeof(struct namespace_list) +
+ strlen(namespace) + 1));
+ strcpy(ns_entry->namespace, namespace);
+ ns_entry->next = *list;
+ *list = ns_entry;
+ }
+}
+
+static bool module_imports_namespace(struct module *module,
+ const char *namespace)
+{
+ return contains_namespace(module->imported_namespaces, namespace);
+}
+
static const struct {
const char *str;
enum export export;
@@ -312,6 +344,22 @@ 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)
+{
+ size_t n;
+ char *dupsymname;
+
+ n = strcspn(*symname, ".");
+ if (n < strlen(*symname) - 1) {
+ dupsymname = NOFAIL(strdup(*symname));
+ dupsymname[n] = '\0';
+ *symname = dupsymname;
+ return dupsymname + n + 1;
+ }
+
+ return NULL;
+}
+
/**
* Add an exported symbol - it may have already been added without a
* CRC, in this case just update the CRC
@@ -319,16 +367,18 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec)
static struct symbol *sym_add_exported(const char *name, struct module *mod,
enum export export)
{
- struct symbol *s = find_symbol(name);
+ const char *symbol_name = name;
+ const char *namespace = sym_extract_namespace(&symbol_name);
+ struct symbol *s = find_symbol(symbol_name);
if (!s) {
- s = new_symbol(name, mod, export);
+ s = new_symbol(symbol_name, mod, export);
+ s->namespace = namespace;
} else {
if (!s->preloaded) {
- warn("%s: '%s' exported twice. Previous export "
- "was in %s%s\n", mod->name, name,
- s->module->name,
- is_vmlinux(s->module->name) ?"":".ko");
+ warn("%s: '%s' exported twice. Previous export was in %s%s\n",
+ mod->name, symbol_name, s->module->name,
+ is_vmlinux(s->module->name) ? "" : ".ko");
} else {
/* In case Module.symvers was out of date */
s->module = mod;
@@ -1943,6 +1993,7 @@ static void read_symbols(const char *modname)
const char *symname;
char *version;
char *license;
+ char *namespace;
struct module *mod;
struct elf_info info = { };
Elf_Sym *sym;
@@ -1974,6 +2025,12 @@ static void read_symbols(const char *modname)
license = get_next_modinfo(&info, "license", license);
}
+ namespace = get_modinfo(&info, "import_ns");
+ while (namespace) {
+ add_namespace(&mod->imported_namespaces, namespace);
+ namespace = get_next_modinfo(&info, "import_ns", namespace);
+ }
+
for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
symname = remove_dot(info.strtab + sym->st_name);
@@ -2118,6 +2175,13 @@ static int check_exports(struct module *mod)
basename++;
else
basename = mod->name;
+
+ if (exp->namespace &&
+ !module_imports_namespace(mod, exp->namespace)) {
+ warn("module %s uses symbol %s from namespace %s, but does not import it.\n",
+ basename, exp->name, exp->namespace);
+ }
+
if (!mod->gpl_compatible)
check_for_gpl_usage(exp->export, basename, exp->name);
check_for_unused(exp->export, basename, exp->name);
@@ -2395,16 +2459,21 @@ static void write_dump(const char *fname)
{
struct buffer buf = { };
struct symbol *symbol;
+ const char *namespace;
int n;
for (n = 0; n < SYMBOL_HASH_SIZE ; n++) {
symbol = symbolhash[n];
while (symbol) {
- if (dump_sym(symbol))
- buf_printf(&buf, "0x%08x\t%s\t%s\t%s\n",
- symbol->crc, symbol->name,
- symbol->module->name,
- export_str(symbol->export));
+ if (dump_sym(symbol)) {
+ namespace = symbol->namespace;
+ buf_printf(&buf, "0x%08x\t%s%s%s\t%s\t%s\n",
+ symbol->crc, symbol->name,
+ namespace ? "." : "",
+ namespace ? namespace : "",
I think it might be cleaner to just have namespace be a separate
field in Module.symvers, rather than appending a dot and the
namespace at the end of a symbol name. Maybe something like
<crc> <symbol_name> <namespace> <module>
For symbols without a namespace, we could just have "", with all
fields delimited by tabs. This is just a stylistic suggestion, what do
you think?
I thought of something like that initially, but did not do it to not
break users of this file. But as I am anyway breaking users by changing
the symbol name into symbol.NS, I might as well do it as you suggested.
Since read_dump() also knew already how to extract the namespaces from
symbol.NS, it had already worked without a change to the reading code
of modpost. Are there any other consumers of Module.symvers that we
should be aware of?
Regardless of the chosen format, I think we need to document how
namespaces are represented in Documentation/kbuild/modules.rst, where
it describes the Module.symvers format.
Agreed. I will update the documentation. It anyway needs an update.
Cheers,
Matthias
+ symbol->module->name,
+ export_str(symbol->export));
+ }
symbol = symbol->next;
}
}
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 8453d6ac2f77..9626bf3e7424 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -109,6 +109,11 @@ buf_printf(struct buffer *buf, const char *fmt, ...);
void
buf_write(struct buffer *buf, const char *s, int len);
+struct namespace_list {
+ struct namespace_list *next;
+ char namespace[0];
+};
+
struct module {
struct module *next;
const char *name;
@@ -121,6 +126,8 @@ struct module {
struct buffer dev_table_buf;
char srcversion[25];
int is_dot_o;
+ // Actual imported namespaces
+ struct namespace_list *imported_namespaces;
};
struct elf_info {
--
2.23.0.rc1.153.gdeed80330f-goog