modpost: support objects with more than 64k sections

This patch makes modpost able to process object files with more than
64k sections. Needed for huge kernel builds (allyesconfig, for example)
with -ffunction-sections. 64k sections handling is covered, for example,
by this document:

"IA-64 gABI Proposal 74: Section Indexes"
http://www.codesourcery.com/public/cxx-abi/abi/prop-74-sindex.html

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

1 files changed, 43 insertions, 0 deletions

diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index be987a44f250..0388cfccac8d 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -129,8 +129,51 @@ struct elf_info {
         const char   *strtab;
         char         *modinfo;
         unsigned int modinfo_len;
+
+        /* support for 32bit section numbers */
+
+        unsigned int num_sections; /* max_secindex + 1 */
+        unsigned int secindex_strings;
+        /* if Nth symbol table entry has .st_shndx = SHN_XINDEX,
+         * take shndx from symtab_shndx_start[N] instead */
+        Elf32_Word   *symtab_shndx_start;
+        Elf32_Word   *symtab_shndx_stop;
 };
 
+static inline int is_shndx_special(unsigned int i)
+{
+        return i != SHN_XINDEX && i >= SHN_LORESERVE && i <= SHN_HIRESERVE;
+}
+
+/* shndx is in [0..SHN_LORESERVE) U (SHN_HIRESERVE, 0xfffffff], thus:
+ * shndx == 0               <=> sechdrs[0]
+ * ......
+ * shndx == SHN_LORESERVE-1 <=> sechdrs[SHN_LORESERVE-1]
+ * shndx == SHN_HIRESERVE+1 <=> sechdrs[SHN_LORESERVE]
+ * shndx == SHN_HIRESERVE+2 <=> sechdrs[SHN_LORESERVE+1]
+ * ......
+ * fyi: sym->st_shndx is uint16, SHN_LORESERVE = ff00, SHN_HIRESERVE = ffff,
+ * so basically we map  0000..feff -> 0000..feff
+ *                      ff00..ffff -> (you are a bad boy, dont do it)
+ *                     10000..xxxx -> ff00..(xxxx-0x100)
+ */
+static inline unsigned int shndx2secindex(unsigned int i)
+{
+        if (i <= SHN_HIRESERVE)
+                return i;
+        return i - (SHN_HIRESERVE + 1 - SHN_LORESERVE);
+}
+
+/* Accessor for sym->st_shndx, hides ugliness of "64k sections" */
+static inline unsigned int get_secindex(const struct elf_info *info,
+                                        const Elf_Sym *sym)
+{
+        if (sym->st_shndx != SHN_XINDEX)
+                return sym->st_shndx;
+        return shndx2secindex(info->symtab_shndx_start[sym -
+                                                       info->symtab_start]);
+}
+
 /* file2alias.c */
 extern unsigned int cross_build;
 void handle_moddevtable(struct module *mod, struct elf_info *info,