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SubjectRe: [PATCH v3 04/11] modpost: add support for symbol namespaces
+++ Matthias Maennich [27/08/19 15:41 +0100]:
>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?

Maybe we can ease any possible breakage caused by the new format by
putting the namespace column last? Then the first 4 fields crc,
symbol, module, export type will remain in the same order, with
namespace last. In-tree, I think we would need to update
scripts/export_report.pl.

kmod is likely to be affected too - Lucas, would the addition of a new
field (in the order described above) in Module.symvers break any kmod tools?

Thanks,

Jessica

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