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SubjectRe: [PATCH v3 04/11] modpost: add support for symbol namespaces
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@android.com>
>>Signed-off-by: Martijn Coenen <maco@android.com>
>>Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
>>Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>Signed-off-by: Matthias Maennich <maennich@google.com>
>>---
>>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
>>

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