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>

3 files changed, 122 insertions, 29 deletions

diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 220213e603d..33f436328f9 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -839,16 +839,16 @@ void handle_moddevtable(struct module *mod, struct elf_info *info,
         char *zeros = NULL;
 
         /* We're looking for a section relative symbol */
-        if (!sym->st_shndx || sym->st_shndx >= info->hdr->e_shnum)
+        if (!sym->st_shndx || get_secindex(info, sym) >= info->num_sections)
                 return;
 
         /* Handle all-NULL symbols allocated into .bss */
-        if (info->sechdrs[sym->st_shndx].sh_type & SHT_NOBITS) {
+        if (info->sechdrs[get_secindex(info, sym)].sh_type & SHT_NOBITS) {
                 zeros = calloc(1, sym->st_size);
                 symval = zeros;
         } else {
                 symval = (void *)info->hdr
-                        + info->sechdrs[sym->st_shndx].sh_offset
+                        + info->sechdrs[get_secindex(info, sym)].sh_offset
                         + sym->st_value;
         }
 
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3318692e4e7..7249ab44f44 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -253,7 +253,7 @@ static enum export export_no(const char *s)
         return export_unknown;
 }
 
-static enum export export_from_sec(struct elf_info *elf, Elf_Section sec)
+static enum export export_from_sec(struct elf_info *elf, unsigned int sec)
 {
         if (sec == elf->export_sec)
                 return export_plain;
@@ -373,6 +373,8 @@ static int parse_elf(struct elf_info *info, const char *filename)
         Elf_Ehdr *hdr;
         Elf_Shdr *sechdrs;
         Elf_Sym  *sym;
+        const char *secstrings;
+        unsigned int symtab_idx = ~0U, symtab_shndx_idx = ~0U;
 
         hdr = grab_file(filename, &info->size);
         if (!hdr) {
@@ -417,8 +419,27 @@ static int parse_elf(struct elf_info *info, const char *filename)
                 return 0;
         }
 
+        if (hdr->e_shnum == 0) {
+                /*
+                 * There are more than 64k sections,
+                 * read count from .sh_size.
+                 * note: it doesn't need shndx2secindex()
+                 */
+                info->num_sections = TO_NATIVE(sechdrs[0].sh_size);
+        }
+        else {
+                info->num_sections = hdr->e_shnum;
+        }
+        if (hdr->e_shstrndx == SHN_XINDEX) {
+                info->secindex_strings =
+                    shndx2secindex(TO_NATIVE(sechdrs[0].sh_link));
+        }
+        else {
+                info->secindex_strings = hdr->e_shstrndx;
+        }
+
         /* Fix endianness in section headers */
-        for (i = 0; i < hdr->e_shnum; i++) {
+        for (i = 0; i < info->num_sections; i++) {
                 sechdrs[i].sh_name      = TO_NATIVE(sechdrs[i].sh_name);
                 sechdrs[i].sh_type      = TO_NATIVE(sechdrs[i].sh_type);
                 sechdrs[i].sh_flags     = TO_NATIVE(sechdrs[i].sh_flags);
@@ -431,9 +452,8 @@ static int parse_elf(struct elf_info *info, const char *filename)
                 sechdrs[i].sh_entsize   = TO_NATIVE(sechdrs[i].sh_entsize);
         }
         /* Find symbol table. */
-        for (i = 1; i < hdr->e_shnum; i++) {
-                const char *secstrings
-                        = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
+        secstrings = (void *)hdr + sechdrs[info->secindex_strings].sh_offset;
+        for (i = 1; i < info->num_sections; i++) {
                 const char *secname;
                 int nobits = sechdrs[i].sh_type == SHT_NOBITS;
 
@@ -461,14 +481,26 @@ static int parse_elf(struct elf_info *info, const char *filename)
                 else if (strcmp(secname, "__ksymtab_gpl_future") == 0)
                         info->export_gpl_future_sec = i;
 
-                if (sechdrs[i].sh_type != SHT_SYMTAB)
-                        continue;
+                if (sechdrs[i].sh_type == SHT_SYMTAB) {
+                        unsigned int sh_link_idx;
+                        symtab_idx = i;
+                        info->symtab_start = (void *)hdr +
+                            sechdrs[i].sh_offset;
+                        info->symtab_stop  = (void *)hdr +
+                            sechdrs[i].sh_offset + sechdrs[i].sh_size;
+                        sh_link_idx = shndx2secindex(sechdrs[i].sh_link);
+                        info->strtab       = (void *)hdr +
+                            sechdrs[sh_link_idx].sh_offset;
+                }
 
-                info->symtab_start = (void *)hdr + sechdrs[i].sh_offset;
-                info->symtab_stop  = (void *)hdr + sechdrs[i].sh_offset
-                                                 + sechdrs[i].sh_size;
-                info->strtab       = (void *)hdr +
-                                     sechdrs[sechdrs[i].sh_link].sh_offset;
+                /* 32bit section no. table? ("more than 64k sections") */
+                if (sechdrs[i].sh_type == SHT_SYMTAB_SHNDX) {
+                        symtab_shndx_idx = i;
+                        info->symtab_shndx_start = (void *)hdr +
+                            sechdrs[i].sh_offset;
+                        info->symtab_shndx_stop  = (void *)hdr +
+                            sechdrs[i].sh_offset + sechdrs[i].sh_size;
+                }
         }
         if (!info->symtab_start)
                 fatal("%s has no symtab?\n", filename);
@@ -480,6 +512,21 @@ static int parse_elf(struct elf_info *info, const char *filename)
                 sym->st_value = TO_NATIVE(sym->st_value);
                 sym->st_size  = TO_NATIVE(sym->st_size);
         }
+
+        if (symtab_shndx_idx != ~0U) {
+                Elf32_Word *p;
+                if (symtab_idx !=
+                    shndx2secindex(sechdrs[symtab_shndx_idx].sh_link))
+                        fatal("%s: SYMTAB_SHNDX has bad sh_link: %u!=%u\n",
+                              filename,
+                              shndx2secindex(sechdrs[symtab_shndx_idx].sh_link),
+                              symtab_idx);
+                /* Fix endianness */
+                for (p = info->symtab_shndx_start; p < info->symtab_shndx_stop;
+                     p++)
+                        *p = TO_NATIVE(*p);
+        }
+
         return 1;
 }
 
@@ -514,7 +561,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
                                Elf_Sym *sym, const char *symname)
 {
         unsigned int crc;
-        enum export export = export_from_sec(info, sym->st_shndx);
+        enum export export = export_from_sec(info, get_secindex(info, sym));
 
         switch (sym->st_shndx) {
         case SHN_COMMON:
@@ -656,19 +703,19 @@ static const char *sym_name(struct elf_info *elf, Elf_Sym *sym)
                 return "(unknown)";
 }
 
-static const char *sec_name(struct elf_info *elf, int shndx)
+static const char *sec_name(struct elf_info *elf, int secindex)
 {
         Elf_Shdr *sechdrs = elf->sechdrs;
         return (void *)elf->hdr +
-                elf->sechdrs[elf->hdr->e_shstrndx].sh_offset +
-                sechdrs[shndx].sh_name;
+                elf->sechdrs[elf->secindex_strings].sh_offset +
+                sechdrs[secindex].sh_name;
 }
 
 static const char *sech_name(struct elf_info *elf, Elf_Shdr *sechdr)
 {
         return (void *)elf->hdr +
-                elf->sechdrs[elf->hdr->e_shstrndx].sh_offset +
-                sechdr->sh_name;
+                elf->sechdrs[elf->secindex_strings].sh_offset +
+                sechdr->sh_name;
 }
 
 /* if sym is empty or point to a string
@@ -1047,11 +1094,14 @@ static Elf_Sym *find_elf_symbol(struct elf_info *elf, Elf64_Sword addr,