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SubjectRe: [PATCH v3 04/11] modpost: add support for symbol namespaces
+++ Matthias Maennich [28/08/19 10:55 +0100]:
>On Wed, Aug 28, 2019 at 11:43:26AM +0200, Jessica Yu wrote:
>>+++ 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?
>>
>
>According to the comment right above read_dump() and having a look a the
>implementation of it, the format is
>
> 0x12345678<tab>symbol<tab>module[[<tab>export]<tab>something]
>
>So, independently of what 'something' is, also export seems to be
>optional. OTOH, write_dump() seems to consistently write
>
> 0x12345678<tab>symbol<tab>module<tab>export
>
>Not sure if there is something modifying Module.symvers afterwards or
>whether this is something that historically needs to be supported, but
>if we could rule that out, I would prefer
>
> 0x12345678<tab>symbol<tab>namespace<tab>module<tab>export
>
>as you initially suggested.

I don't mind either format :-) As long as the kmod folks are OK with it.

Thanks,

Jessica


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