1 files changed, 21 insertions, 44 deletions

diff --git a/kernel/module.c b/kernel/module.c
index cf9f1b6b3268..4928cffc3dcc 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -138,7 +138,6 @@ struct load_info {
         unsigned long len;
         Elf_Shdr *sechdrs;
         char *secstrings, *strtab;
-        unsigned long *strmap;
         unsigned long symoffs, stroffs;
         struct _ddebug *debug;
         unsigned int num_debug;
@@ -2178,12 +2177,19 @@ static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs,
         return true;
 }
 
+/*
+ * We only allocate and copy the strings needed by the parts of symtab
+ * we keep.  This is simple, but has the effect of making multiple
+ * copies of duplicates.  We could be more sophisticated, see
+ * linux-kernel thread starting with
+ * <73defb5e4bca04a6431392cc341112b1@localhost>.
+ */
 static void layout_symtab(struct module *mod, struct load_info *info)
 {
         Elf_Shdr *symsect = info->sechdrs + info->index.sym;
         Elf_Shdr *strsect = info->sechdrs + info->index.str;
         const Elf_Sym *src;
-        unsigned int i, nsrc, ndst;
+        unsigned int i, nsrc, ndst, strtab_size;
 
         /* Put symbol section at end of init part of module. */
         symsect->sh_flags |= SHF_ALLOC;
@@ -2194,38 +2200,23 @@ static void layout_symtab(struct module *mod, struct load_info *info)
         src = (void *)info->hdr + symsect->sh_offset;
         nsrc = symsect->sh_size / sizeof(*src);
 
-        /*
-         * info->strmap has a '1' bit for each byte of .strtab we want to
-         * keep resident in mod->core_strtab.  Everything else in .strtab
-         * is unreferenced by the symbols in mod->core_symtab, and will be
-         * discarded when add_kallsyms() compacts the string table.
-         */
-        for (ndst = i = 1; i < nsrc; ++i, ++src)
+        /* Compute total space required for the core symbols' strtab. */
+        for (ndst = i = strtab_size = 1; i < nsrc; ++i, ++src)
                 if (is_core_symbol(src, info->sechdrs, info->hdr->e_shnum)) {
-                        unsigned int j = src->st_name;
-
-                        while (!__test_and_set_bit(j, info->strmap)
-                               && info->strtab[j])
-                                ++j;
-                        ++ndst;
+                        strtab_size += strlen(&info->strtab[src->st_name]) + 1;
+                        ndst++;
                 }
 
         /* Append room for core symbols at end of core part. */
         info->symoffs = ALIGN(mod->core_size, symsect->sh_addralign ?: 1);
-        mod->core_size = info->symoffs + ndst * sizeof(Elf_Sym);
+        info->stroffs = mod->core_size = info->symoffs + ndst * sizeof(Elf_Sym);
+        mod->core_size += strtab_size;
 
         /* Put string table section at end of init part of module. */
         strsect->sh_flags |= SHF_ALLOC;
         strsect->sh_entsize = get_offset(mod, &mod->init_size, strsect,
                                          info->index.str) | INIT_OFFSET_MASK;
         DEBUGP("\t%s\n", info->secstrings + strsect->sh_name);
-
-        /* Append room for core symbols' strings at end of core part. */
-        info->stroffs = mod->core_size;
-
-        /* First strtab byte (and first symtab entry) are zeroes. */
-        __set_bit(0, info->strmap);
-        mod->core_size += bitmap_weight(info->strmap, strsect->sh_size);
 }
 
 static void add_kallsyms(struct module *mod, const struct load_info *info)
@@ -2246,22 +2237,19 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
                 mod->symtab[i].st_info = elf_type(&mod->symtab[i], info);
 
         mod->core_symtab = dst = mod->module_core + info->symoffs;
+        mod->core_strtab = s = mod->module_core + info->stroffs;
         src = mod->symtab;
         *dst = *src;
+        *s++ = 0;
         for (ndst = i = 1; i < mod->num_symtab; ++i, ++src) {
                 if (!is_core_symbol(src, info->sechdrs, info->hdr->e_shnum))
                         continue;
+
                 dst[ndst] = *src;
-                dst[ndst].st_name = bitmap_weight(info->strmap,
-                                                  dst[ndst].st_name);
-                ++ndst;
+                dst[ndst++].st_name = s - mod->core_strtab;
+                s += strlcpy(s, &mod->strtab[src->st_name], KSYM_NAME_LEN) + 1;
         }
         mod->core_num_syms = ndst;
-
-        mod->core_strtab = s = mod->module_core + info->stroffs;
-        for (*s = 0, i = 1; i < info->sechdrs[info->index.str].sh_size; ++i)
-                if (test_bit(i, info->strmap))
-                        *++s = mod->strtab[i];
 }
 #else
 static inline void layout_symtab(struct module *mod, struct load_info *info)
@@ -2751,27 +2739,18 @@ static struct module *layout_and_allocate(struct load_info *info)
            this is done generically; there doesn't appear to be any
            special cases for the architectures. */
         layout_sections(mod, info);
-
-        info->strmap = kzalloc(BITS_TO_LONGS(info->sechdrs[info->index.str].sh_size)
-                         * sizeof(long), GFP_KERNEL);
-        if (!info->strmap) {
-                err = -ENOMEM;
-                goto free_percpu;
-        }
         layout_symtab(mod, info);
 
         /* Allocate and move to the final place */
         err = move_module(mod, info);
         if (err)
-                goto free_strmap;
+                goto free_percpu;
 
         /* Module has been copied to its final place now: return it. */
         mod = (void *)info->sechdrs[info->index.mod].sh_addr;
         kmemleak_load_module(mod, info);
         return mod;
 
-free_strmap:
-        kfree(info->strmap);
 free_percpu:
         percpu_modfree(mod);
 out:
@@ -2781,7 +2760,6 @@ out:
 /* mod is no longer valid after this! */
 static void module_deallocate(struct module *mod, struct load_info *info)
 {
-        kfree(info->strmap);
         percpu_modfree(mod);
         module_free(mod, mod->module_init);
         module_free(mod, mod->module_core);
@@ -2911,8 +2889,7 @@ static struct module *load_module(void __user *umod,
         if (err < 0)
                 goto unlink;
 
-        /* Get rid of temporary copy and strmap. */
-        kfree(info.strmap);
+        /* Get rid of temporary copy. */
         free_copy(&info);
 
         /* Done! */