scripts/sortextable: support objects with more than 64K sections.

Building with a large config and -ffunction-sections results in a large
number of sections and sortextable needs to be able to handle that.
Implement support for > 64K sections as modpost does.

Signed-off-by: Jamie Iles <jamie.iles@oracle.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 47 insertions, 3 deletions

diff --git a/scripts/sortextable.c b/scripts/sortextable.c
index 7c2310c5b996..5f7a8b663cb9 100644
--- a/scripts/sortextable.c
+++ b/scripts/sortextable.c
@@ -152,6 +152,30 @@ static void (*w2)(uint16_t, uint16_t *);
 
 typedef void (*table_sort_t)(char *, int);
 
+/*
+ * Move reserved section indices SHN_LORESERVE..SHN_HIRESERVE out of
+ * the way to -256..-1, to avoid conflicting with real section
+ * indices.
+ */
+#define SPECIAL(i) ((i) - (SHN_HIRESERVE + 1))
+
+static inline int is_shndx_special(unsigned int i)
+{
+        return i != SHN_XINDEX && i >= SHN_LORESERVE && i <= SHN_HIRESERVE;
+}
+
+/* Accessor for sym->st_shndx, hides ugliness of "64k sections" */
+static inline unsigned int get_secindex(unsigned int shndx,
+                                        unsigned int sym_offs,
+                                        const Elf32_Word *symtab_shndx_start)
+{
+        if (is_shndx_special(shndx))
+                return SPECIAL(shndx);
+        if (shndx != SHN_XINDEX)
+                return shndx;
+        return r(&symtab_shndx_start[sym_offs]);
+}
+
 /* 32 bit and 64 bit are very similar */
 #include "sortextable.h"
 #define SORTEXTABLE_64
diff --git a/scripts/sortextable.h b/scripts/sortextable.h
index f5eb43d42926..8fac3fd697a6 100644
--- a/scripts/sortextable.h
+++ b/scripts/sortextable.h
@@ -98,6 +98,8 @@ do_func(Elf_Ehdr *ehdr, char const *const fname, table_sort_t custom_sort)
         Elf_Shdr *symtab_sec = NULL;
         Elf_Shdr *extab_sec = NULL;
         Elf_Sym *sym;
+        const Elf_Sym *symtab;
+        Elf32_Word *symtab_shndx_start = NULL;
         Elf_Sym *sort_needed_sym;
         Elf_Shdr *sort_needed_sec;
         Elf_Rel *relocs = NULL;
@@ -109,11 +111,22 @@ do_func(Elf_Ehdr *ehdr, char const *const fname, table_sort_t custom_sort)
         int extab_index = 0;
         int i;
         int idx;
+        unsigned int num_sections;
+        unsigned int secindex_strings;
 
         shdr = (Elf_Shdr *)((char *)ehdr + _r(&ehdr->e_shoff));
-        shstrtab_sec = shdr + r2(&ehdr->e_shstrndx);
+
+        num_sections = r2(&ehdr->e_shnum);
+        if (num_sections == SHN_UNDEF)
+                num_sections = _r(&shdr[0].sh_size);
+
+        secindex_strings = r2(&ehdr->e_shstrndx);
+        if (secindex_strings == SHN_XINDEX)
+                secindex_strings = r(&shdr[0].sh_link);
+
+        shstrtab_sec = shdr + secindex_strings;
         secstrtab = (const char *)ehdr + _r(&shstrtab_sec->sh_offset);
-        for (i = 0; i < r2(&ehdr->e_shnum); i++) {
+        for (i = 0; i < num_sections; i++) {
                 idx = r(&shdr[i].sh_name);
                 if (strcmp(secstrtab + idx, "__ex_table") == 0) {
                         extab_sec = shdr + i;
@@ -129,6 +142,9 @@ do_func(Elf_Ehdr *ehdr, char const *const fname, table_sort_t custom_sort)
                         symtab_sec = shdr + i;
                 if (strcmp(secstrtab + idx, ".strtab") == 0)
                         strtab_sec = shdr + i;
+                if (r(&shdr[i].sh_type) == SHT_SYMTAB_SHNDX)
+                        symtab_shndx_start = (Elf32_Word *)(
+                                (const char *)ehdr + _r(&shdr[i].sh_offset));
         }
         if (strtab_sec == NULL) {
                 fprintf(stderr, "no .strtab in  file: %s\n", fname);
@@ -138,6 +154,8 @@ do_func(Elf_Ehdr *ehdr, char const *const fname, table_sort_t custom_sort)
                 fprintf(stderr, "no .symtab in  file: %s\n", fname);
                 fail_file();
         }
+        symtab = (const Elf_Sym *)((const char *)ehdr +
+                                   _r(&symtab_sec->sh_offset));
         if (extab_sec == NULL) {
                 fprintf(stderr, "no __ex_table in  file: %s\n", fname);
                 fail_file();
@@ -176,7 +194,9 @@ do_func(Elf_Ehdr *ehdr, char const *const fname, table_sort_t custom_sort)
                         fname);
                 fail_file();
         }
-        sort_needed_sec = &shdr[r2(&sort_needed_sym->st_shndx)];
+        sort_needed_sec = &shdr[get_secindex(r2(&sym->st_shndx),
+                                             sort_needed_sym - symtab,
+                                             symtab_shndx_start)];
         sort_done_location = (void *)ehdr +
                 _r(&sort_needed_sec->sh_offset) +
                 _r(&sort_needed_sym->st_value) -