x86, relocs: Add 64-bit ELF support to relocs tool

This adds the ability to process relocations from the 64-bit kernel ELF,
if built with ELF_BITS=64 defined. The special case for the percpu area is
handled, along with some other symbols specific to the 64-bit kernel.

Based on work by Neill Clift and Michael Davidson.

Signed-off-by: Kees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/1365797627-20874-4-git-send-email-keescook@chromium.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 261 insertions, 6 deletions

diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index bdc5930b3a1b..1f7ff3d11a05 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -17,19 +17,39 @@
 #define _ElfW(bits, type)       __ElfW(bits, type)
 #define __ElfW(bits, type)      Elf##bits##_##type
 
+#ifndef ELF_BITS
 #define ELF_BITS                32
+#endif
+
+#if (ELF_BITS == 64)
+#define ELF_MACHINE             EM_X86_64
+#define ELF_MACHINE_NAME        "x86_64"
+#define SHT_REL_TYPE            SHT_RELA
+#define Elf_Rel                 Elf64_Rela
+#else
 #define ELF_MACHINE             EM_386
 #define ELF_MACHINE_NAME        "i386"
 #define SHT_REL_TYPE            SHT_REL
+#define Elf_Rel                 ElfW(Rel)
+#endif
 
+#if (ELF_BITS == 64)
+#define ELF_CLASS               ELFCLASS64
+#define ELF_R_SYM(val)          ELF64_R_SYM(val)
+#define ELF_R_TYPE(val)         ELF64_R_TYPE(val)
+#define ELF_ST_TYPE(o)          ELF64_ST_TYPE(o)
+#define ELF_ST_BIND(o)          ELF64_ST_BIND(o)
+#define ELF_ST_VISIBILITY(o)    ELF64_ST_VISIBILITY(o)
+#else
 #define ELF_CLASS               ELFCLASS32
 #define ELF_R_SYM(val)          ELF32_R_SYM(val)
 #define ELF_R_TYPE(val)         ELF32_R_TYPE(val)
 #define ELF_ST_TYPE(o)          ELF32_ST_TYPE(o)
 #define ELF_ST_BIND(o)          ELF32_ST_BIND(o)
 #define ELF_ST_VISIBILITY(o)    ELF32_ST_VISIBILITY(o)
+#endif
 
-#define Elf_Rel                 ElfW(Rel)
+#define Elf_Addr                ElfW(Addr)
 #define Elf_Ehdr                ElfW(Ehdr)
 #define Elf_Phdr                ElfW(Phdr)
 #define Elf_Shdr                ElfW(Shdr)
@@ -48,6 +68,7 @@ struct relocs {
 
 static struct relocs relocs16;
 static struct relocs relocs32;
+static struct relocs relocs64;
 
 struct section {
         Elf_Shdr       shdr;
@@ -77,6 +98,9 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
         "^(xen_irq_disable_direct_reloc$|"
         "xen_save_fl_direct_reloc$|"
         "VDSO|"
+#if (ELF_BITS == 64)
+        "__vvar_page|"
+#endif
         "__crc_)",
 
 /*
@@ -100,6 +124,11 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
         "__end_rodata|"
         "__initramfs_start|"
         "(jiffies|jiffies_64)|"
+#if (ELF_BITS == 64)
+        "__per_cpu_load|"
+        "init_per_cpu__.*|"
+        "__end_rodata_hpage_align|"
+#endif
         "_end)$"
 };
 
@@ -226,6 +255,24 @@ static const char *rel_type(unsigned type)
 {
         static const char *type_name[] = {
 #define REL_TYPE(X) [X] = #X
+#if (ELF_BITS == 64)
+                REL_TYPE(R_X86_64_NONE),
+                REL_TYPE(R_X86_64_64),
+                REL_TYPE(R_X86_64_PC32),
+                REL_TYPE(R_X86_64_GOT32),
+                REL_TYPE(R_X86_64_PLT32),
+                REL_TYPE(R_X86_64_COPY),
+                REL_TYPE(R_X86_64_GLOB_DAT),
+                REL_TYPE(R_X86_64_JUMP_SLOT),
+                REL_TYPE(R_X86_64_RELATIVE),
+                REL_TYPE(R_X86_64_GOTPCREL),
+                REL_TYPE(R_X86_64_32),
+                REL_TYPE(R_X86_64_32S),
+                REL_TYPE(R_X86_64_16),
+                REL_TYPE(R_X86_64_PC16),
+                REL_TYPE(R_X86_64_8),
+                REL_TYPE(R_X86_64_PC8),
+#else
                 REL_TYPE(R_386_NONE),
                 REL_TYPE(R_386_32),
                 REL_TYPE(R_386_PC32),
@@ -241,6 +288,7 @@ static const char *rel_type(unsigned type)
                 REL_TYPE(R_386_PC8),
                 REL_TYPE(R_386_16),
                 REL_TYPE(R_386_PC16),
+#endif
 #undef REL_TYPE
         };
         const char *name = "unknown type rel type name";
@@ -281,15 +329,42 @@ static const char *sym_name(const char *sym_strtab, Elf_Sym *sym)
         return name;
 }
 
+static Elf_Sym *sym_lookup(const char *symname)
+{
+        int i;
+        for (i = 0; i < ehdr.e_shnum; i++) {
+                struct section *sec = &secs[i];
+                long nsyms;
+                char *strtab;
+                Elf_Sym *symtab;
+                Elf_Sym *sym;
 
+                if (sec->shdr.sh_type != SHT_SYMTAB)
+                        continue;
+
+                nsyms = sec->shdr.sh_size/sizeof(Elf_Sym);
+                symtab = sec->symtab;
+                strtab = sec->link->strtab;
+
+                for (sym = symtab; --nsyms >= 0; sym++) {
+                        if (!sym->st_name)
+                                continue;
+                        if (strcmp(symname, strtab + sym->st_name) == 0)
+                                return sym;
+                }
+        }
+        return 0;
+}
 
 #if BYTE_ORDER == LITTLE_ENDIAN
 #define le16_to_cpu(val) (val)
 #define le32_to_cpu(val) (val)
+#define le64_to_cpu(val) (val)
 #endif
 #if BYTE_ORDER == BIG_ENDIAN
 #define le16_to_cpu(val) bswap_16(val)
 #define le32_to_cpu(val) bswap_32(val)
+#define le64_to_cpu(val) bswap_64(val)
 #endif
 
 static uint16_t elf16_to_cpu(uint16_t val)
@@ -304,9 +379,20 @@ static uint32_t elf32_to_cpu(uint32_t val)
 
 #define elf_half_to_cpu(x)      elf16_to_cpu(x)
 #define elf_word_to_cpu(x)      elf32_to_cpu(x)
+
+#if (ELF_BITS == 64)
+static uint64_t elf64_to_cpu(uint64_t val)
+{
+        return le64_to_cpu(val);
+}
+#define elf_addr_to_cpu(x)      elf64_to_cpu(x)
+#define elf_off_to_cpu(x)       elf64_to_cpu(x)
+#define elf_xword_to_cpu(x)     elf64_to_cpu(x)
+#else
 #define elf_addr_to_cpu(x)      elf32_to_cpu(x)
 #define elf_off_to_cpu(x)       elf32_to_cpu(x)
 #define elf_xword_to_cpu(x)     elf32_to_cpu(x)
+#endif
 
 static void read_ehdr(FILE *fp)
 {
@@ -483,6 +569,9 @@ static void read_relocs(FILE *fp)
                         Elf_Rel *rel = &sec->reltab[j];
                         rel->r_offset = elf_addr_to_cpu(rel->r_offset);
                         rel->r_info   = elf_xword_to_cpu(rel->r_info);
+#if (SHT_REL_TYPE == SHT_RELA)
+                        rel->r_addend = elf_xword_to_cpu(rel->r_addend);
+#endif
                 }
         }
 }
@@ -491,6 +580,13 @@ static void read_relocs(FILE *fp)
 static void print_absolute_symbols(void)
 {
         int i;
+        const char *format;
+
+        if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
+                format = "%5d %016"PRIx64" %5"PRId64" %10s %10s %12s %s\n";
+        else
+                format = "%5d %08"PRIx32"  %5"PRId32" %10s %10s %12s %s\n";
+
         printf("Absolute symbols\n");
         printf(" Num:    Value Size  Type       Bind        Visibility  Name\n");
         for (i = 0; i < ehdr.e_shnum; i++) {
@@ -510,7 +606,7 @@ static void print_absolute_symbols(void)
                         if (sym->st_shndx != SHN_ABS) {
                                 continue;
                         }
-                        printf("%5d %08x %5d %10s %10s %12s %s\n",
+                        printf(format,
                                 j, sym->st_value, sym->st_size,
                                 sym_type(ELF_ST_TYPE(sym->st_info)),
                                 sym_bind(ELF_ST_BIND(sym->st_info)),
@@ -524,6 +620,12 @@ static void print_absolute_symbols(void)
 static void print_absolute_relocs(void)
 {
         int i, printed = 0;
+        const char *format;
+
+        if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
+                format = "%016"PRIx64" %016"PRIx64" %10s %016"PRIx64"  %s\n";
+        else
+                format = "%08"PRIx32" %08"PRIx32" %10s %08"PRIx32"  %s\n";
 
         for (i = 0; i < ehdr.e_shnum; i++) {
                 struct section *sec = &secs[i];
@@ -576,7 +678,7 @@ static void print_absolute_relocs(void)
                                 printed = 1;
                         }
 
-                        printf("%08x %08x %10s %08x  %s\n",
+                        printf(format,
                                 rel->r_offset,
                                 rel->r_info,
                                 rel_type(ELF_R_TYPE(rel->r_info)),
@@ -636,8 +738,140 @@ static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel,
         }
 }
 
-static int do_reloc(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
-                    const char *symname)
+/*
+ * The .data..percpu section is a special case for x86_64 SMP kernels.
+ * It is used to initialize the actual per_cpu areas and to provide
+ * definitions for the per_cpu variables that correspond to their offsets
+ * within the percpu area. Since the values of all of the symbols need
+ * to be offsets from the start of the per_cpu area the virtual address
+ * (sh_addr) of .data..percpu is 0 in SMP kernels.
+ *
+ * This means that:
+ *
+ *      Relocations that reference symbols in the per_cpu area do not
+ *      need further relocation (since the value is an offset relative
+ *      to the start of the per_cpu area that does not change).
+ *
+ *      Relocations that apply to the per_cpu area need to have their
+ *      offset adjusted by by the value of __per_cpu_load to make them
+ *      point to the correct place in the loaded image (because the
+ *      virtual address of .data..percpu is 0).
+ *
+ * For non SMP kernels .data..percpu is linked as part of the normal
+ * kernel data and does not require special treatment.
+ *
+ */
+static int per_cpu_shndx        = -1;
+Elf_Addr per_cpu_load_addr;
+
+static void percpu_init(void)
+{
+        int i;
+        for (i = 0; i < ehdr.e_shnum; i++) {
+                ElfW(Sym) *sym;
+                if (strcmp(sec_name(i), ".data..percpu"))
+                        continue;
+
+                if (secs[i].shdr.sh_addr != 0)  /* non SMP kernel */
+                        return;
+
+                sym = sym_lookup("__per_cpu_load");
+                if (!sym)
+                        die("can't find __per_cpu_load\n");
+
+                per_cpu_shndx = i;
+                per_cpu_load_addr = sym->st_value;
+                return;
+        }
+}
+
+/*
+ * Check to see if a symbol lies in the .data..percpu section.
+ * For some as yet not understood reason the "__init_begin"
+ * symbol which immediately preceeds the .data..percpu section
+ * also shows up as it it were part of it so we do an explict
+ * check for that symbol name and ignore it.
+ */
+static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
+{
+        return (sym->st_shndx == per_cpu_shndx) &&
+                strcmp(symname, "__init_begin");
+}
+
+static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
+                      const char *symname)
+{
+        unsigned r_type = ELF64_R_TYPE(rel->r_info);
+        ElfW(Addr) offset = rel->r_offset;
+        int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
+
+        if (sym->st_shndx == SHN_UNDEF)
+                return 0;
+
+        /*
+         * Adjust the offset if this reloc applies to the percpu section.
+         */
+        if (sec->shdr.sh_info == per_cpu_shndx)
+                offset += per_cpu_load_addr;
+
+        switch (r_type) {
+        case R_X86_64_NONE:
+        case R_X86_64_PC32:
+                /*
+                 * NONE can be ignored and PC relative relocations don't
+                 * need to be adjusted.
+                 */
+                break;
+
+        case R_X86_64_32:
+        case R_X86_64_32S:
+        case R_X86_64_64:
+                /*
+                 * References to the percpu area don't need to be adjusted.
+                 */
+                if (is_percpu_sym(sym, symname))
+                        break;
+
+                if (shn_abs) {
+                        /*
+                         * Whitelisted absolute symbols do not require
+                         * relocation.
+                         */
+                        if (is_reloc(S_ABS, symname))
+                                break;
+
+                        die("Invalid absolute %s relocation: %s\n",
+                            rel_type(r_type), symname);
+                        break;
+                }
+
+                /*
+                 * Relocation offsets for 64 bit kernels are output
+                 * as 32 bits and sign extended back to 64 bits when
+                 * the relocations are processed.
+                 * Make sure that the offset will fit.
+                 */
+                if ((int32_t)offset != (int64_t)offset)
+                        die("Relocation offset doesn't fit in 32 bits\n");
+
+                if (r_type == R_X86_64_64)
+                        add_reloc(&relocs64, offset);
+                else
+                        add_reloc(&relocs32, offset);
+                break;
+
+        default:
+                die("Unsupported relocation type: %s (%d)\n",
+                    rel_type(r_type), r_type);
+                break;
+        }
+
+        return 0;
+}
+
+
+static int do_reloc32(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
+                      const char *symname)
 {
         unsigned r_type = ELF32_R_TYPE(rel->r_info);
         int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
@@ -779,9 +1013,18 @@ static void emit_relocs(int as_text, int use_real_mode)
 {
         int i;
         int (*write_reloc)(uint32_t, FILE *) = write32;
+        int (*do_reloc)(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
+                        const char *symname);
+
+        if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
+                do_reloc = do_reloc64;
+        else if (!use_real_mode)
+                do_reloc = do_reloc32;
+        else
+                do_reloc = do_reloc_real;
 
         /* Collect up the relocations */
-        walk_relocs(use_real_mode ? do_reloc_real : do_reloc);
+        walk_relocs(do_reloc);
 
         if (relocs16.count && !use_real_mode)
                 die("Segment relocations found but --realmode not specified\n");
@@ -789,6 +1032,7 @@ static void emit_relocs(int as_text, int use_real_mode)
         /* Order the relocations for more efficient processing */
         sort_relocs(&relocs16);
         sort_relocs(&relocs32);
+        sort_relocs(&relocs64);
 
         /* Print the relocations */
         if (as_text) {
@@ -809,6 +1053,15 @@ static void emit_relocs(int as_text, int use_real_mode)
                 for (i = 0; i < relocs32.count; i++)
                         write_reloc(relocs32.offset[i], stdout);
         } else {
+                if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
+                        /* Print a stop */
+                        write_reloc(0, stdout);
+
+                        /* Now print each relocation */
+                        for (i = 0; i < relocs64.count; i++)
+                                write_reloc(relocs64.offset[i], stdout);
+                }
+
                 /* Print a stop */
                 write_reloc(0, stdout);
 
@@ -876,6 +1129,8 @@ int main(int argc, char **argv)
         read_strtabs(fp);
         read_symtabs(fp);
         read_relocs(fp);
+        if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
+                percpu_init();
         if (show_absolute_syms) {
                 print_absolute_symbols();
                 goto out;