symbol namespaces: revert to previous __ksymtab name scheme

The introduction of Symbol Namespaces changed the naming schema of the
__ksymtab entries from __kysmtab__symbol to __ksymtab_NAMESPACE.symbol.

That caused some breakages in tools that depend on the name layout in
either the binaries(vmlinux,*.ko) or in System.map. E.g. kmod's depmod
would not be able to read System.map without a patch to support symbol
namespaces. A warning reported by depmod for namespaced symbols would
look like

  depmod: WARNING: [...]/uas.ko needs unknown symbol usb_stor_adjust_quirks

In order to address this issue, revert to the original naming scheme and
rather read the __kstrtabns_<symbol> entries and their corresponding
values from __ksymtab_strings to update the namespace values for
symbols. After having read all symbols and handled them in
handle_modversions(), the symbols are created. In a second pass, read
the __kstrtabns_ entries and update the namespaces accordingly.

Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
Reported-by: Stefan Wahren <stefan.wahren@i2se.com>
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>

diff --git a/include/linux/export.h b/include/linux/export.h
index 621158ecd2e2146c697e3ab7cc7b0a3dd6bbc714..941d075f03d684d20b3c1c27c3a6304324e185f5 100644 (file)
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -18,8 +18,6 @@ extern struct module __this_module;
 #define THIS_MODULE ((struct module *)0)
 #endif
 
-#define NS_SEPARATOR "."
-
 #ifdef CONFIG_MODVERSIONS
 /* Mark the CRC weak since genksyms apparently decides not to
  * generate a checksums for some symbols */
@@ -48,11 +46,11 @@ extern struct module __this_module;
  * absolute relocations that require runtime processing on relocatable
  * kernels.
  */
-#define __KSYMTAB_ENTRY_NS(sym, sec, ns)                               \
+#define __KSYMTAB_ENTRY_NS(sym, sec)                                   \
        __ADDRESSABLE(sym)                                              \
        asm("   .section \"___ksymtab" sec "+" #sym "\", \"a\"  \n"     \
            "   .balign 4                                       \n"     \
-           "__ksymtab_" #ns NS_SEPARATOR #sym ":               \n"     \
+           "__ksymtab_" #sym ":                                \n"     \
            "   .long   " #sym "- .                             \n"     \
            "   .long   __kstrtab_" #sym "- .                   \n"     \
            "   .long   __kstrtabns_" #sym "- .                 \n"     \
@@ -74,16 +72,14 @@ struct kernel_symbol {
        int namespace_offset;
 };
 #else
-#define __KSYMTAB_ENTRY_NS(sym, sec, ns)                               \
-       static const struct kernel_symbol __ksymtab_##sym##__##ns       \
-       asm("__ksymtab_" #ns NS_SEPARATOR #sym)                         \
+#define __KSYMTAB_ENTRY_NS(sym, sec)                                   \
+       static const struct kernel_symbol __ksymtab_##sym               \
        __attribute__((section("___ksymtab" sec "+" #sym), used))       \
        __aligned(sizeof(void *))                                       \
        = { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
 
 #define __KSYMTAB_ENTRY(sym, sec)                                      \
        static const struct kernel_symbol __ksymtab_##sym               \
-       asm("__ksymtab_" #sym)                                          \
        __attribute__((section("___ksymtab" sec "+" #sym), used))       \
        __aligned(sizeof(void *))                                       \
        = { (unsigned long)&sym, __kstrtab_##sym, NULL }
@@ -115,7 +111,7 @@ struct kernel_symbol {
        static const char __kstrtabns_##sym[]                           \
        __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
        = #ns;                                                          \
-       __KSYMTAB_ENTRY_NS(sym, sec, ns)
+       __KSYMTAB_ENTRY_NS(sym, sec)
 
 #define ___EXPORT_SYMBOL(sym, sec)                                     \
        ___export_symbol_common(sym, sec);                              \

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index c43f1b1532f7f95d9c61426acf26f6c3905e9143..d2a30a7b3f07cc884889555948054acb911e1fc7 100644 (file)
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -348,18 +348,11 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec)
                return export_unknown;
 }
 
-static char *sym_extract_namespace(const char **symname)
+static const char *namespace_from_kstrtabns(struct elf_info *info,
+                                           Elf_Sym *kstrtabns)
 {
-       char *namespace = NULL;
-       char *ns_separator;
-
-       ns_separator = strchr(*symname, '.');
-       if (ns_separator) {
-               namespace = NOFAIL(strndup(*symname, ns_separator - *symname));
-               *symname = ns_separator + 1;
-       }
-
-       return namespace;
+       char *value = info->ksymtab_strings + kstrtabns->st_value;
+       return value[0] ? value : NULL;
 }
 
 static void sym_update_namespace(const char *symname, const char *namespace)
@@ -600,6 +593,10 @@ static int parse_elf(struct elf_info *info, const char *filename)
                        info->export_unused_gpl_sec = i;
                else if (strcmp(secname, "__ksymtab_gpl_future") == 0)
                        info->export_gpl_future_sec = i;
+               else if (strcmp(secname, "__ksymtab_strings") == 0)
+                       info->ksymtab_strings = (void *)hdr +
+                                               sechdrs[i].sh_offset -
+                                               sechdrs[i].sh_addr;
 
                if (sechdrs[i].sh_type == SHT_SYMTAB) {
                        unsigned int sh_link_idx;
@@ -689,7 +686,6 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
        enum export export;
        bool is_crc = false;
        const char *name;
-       char *namespace;
 
        if ((!is_vmlinux(mod->name) || mod->is_dot_o) &&
            strstarts(symname, "__ksymtab"))
@@ -762,10 +758,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
                /* All exported symbols */
                if (strstarts(symname, "__ksymtab_")) {
                        name = symname + strlen("__ksymtab_");
-                       namespace = sym_extract_namespace(&name);
                        sym_add_exported(name, mod, export);
-                       sym_update_namespace(name, namespace);
-                       free(namespace);
                }
                if (strcmp(symname, "init_module") == 0)
                        mod->has_init = 1;
@@ -2061,6 +2054,16 @@ static void read_symbols(const char *modname)
                handle_moddevtable(mod, &info, sym, symname);
        }
 
+       /* Apply symbol namespaces from __kstrtabns_<symbol> entries. */
+       for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
+               symname = remove_dot(info.strtab + sym->st_name);
+
+               if (strstarts(symname, "__kstrtabns_"))
+                       sym_update_namespace(symname + strlen("__kstrtabns_"),
+                                            namespace_from_kstrtabns(&info,
+                                                                     sym));
+       }
+
        // check for static EXPORT_SYMBOL_* functions && global vars
        for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
                unsigned char bind = ELF_ST_BIND(sym->st_info);

diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 92a926d375d287c0629facef7de45cee938aa99c..ad271bc6c3130410ab9f515b75d1efea26f89b97 100644 (file)
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -143,6 +143,7 @@ struct elf_info {
        Elf_Section  export_gpl_sec;
        Elf_Section  export_unused_gpl_sec;
        Elf_Section  export_gpl_future_sec;
+       char         *ksymtab_strings;
        char         *strtab;
        char         *modinfo;
        unsigned int modinfo_len;