diff options
Diffstat (limited to 'arch/i386/boot/compressed/relocs.c')
| -rw-r--r-- | arch/i386/boot/compressed/relocs.c | 625 |
1 files changed, 625 insertions, 0 deletions
diff --git a/arch/i386/boot/compressed/relocs.c b/arch/i386/boot/compressed/relocs.c new file mode 100644 index 0000000..468da89 --- /dev/null +++ b/arch/i386/boot/compressed/relocs.c @@ -0,0 +1,625 @@ +#include <stdio.h> +#include <stdarg.h> +#include <stdlib.h> +#include <stdint.h> +#include <string.h> +#include <errno.h> +#include <unistd.h> +#include <elf.h> +#include <byteswap.h> +#define USE_BSD +#include <endian.h> + +#define MAX_SHDRS 100 +static Elf32_Ehdr ehdr; +static Elf32_Shdr shdr[MAX_SHDRS]; +static Elf32_Sym *symtab[MAX_SHDRS]; +static Elf32_Rel *reltab[MAX_SHDRS]; +static char *strtab[MAX_SHDRS]; +static unsigned long reloc_count, reloc_idx; +static unsigned long *relocs; + +/* + * Following symbols have been audited. There values are constant and do + * not change if bzImage is loaded at a different physical address than + * the address for which it has been compiled. Don't warn user about + * absolute relocations present w.r.t these symbols. + */ +static const char* safe_abs_relocs[] = { + "__kernel_vsyscall", + "__kernel_rt_sigreturn", + "__kernel_sigreturn", + "SYSENTER_RETURN", +}; + +static int is_safe_abs_reloc(const char* sym_name) +{ + int i, array_size; + + array_size = sizeof(safe_abs_relocs)/sizeof(char*); + + for(i = 0; i < array_size; i++) { + if (!strcmp(sym_name, safe_abs_relocs[i])) + /* Match found */ + return 1; + } + return 0; +} + +static void die(char *fmt, ...) +{ + va_list ap; + va_start(ap, fmt); + vfprintf(stderr, fmt, ap); + va_end(ap); + exit(1); +} + +static const char *sym_type(unsigned type) +{ + static const char *type_name[] = { +#define SYM_TYPE(X) [X] = #X + SYM_TYPE(STT_NOTYPE), + SYM_TYPE(STT_OBJECT), + SYM_TYPE(STT_FUNC), + SYM_TYPE(STT_SECTION), + SYM_TYPE(STT_FILE), + SYM_TYPE(STT_COMMON), + SYM_TYPE(STT_TLS), +#undef SYM_TYPE + }; + const char *name = "unknown sym type name"; + if (type < sizeof(type_name)/sizeof(type_name[0])) { + name = type_name[type]; + } + return name; +} + +static const char *sym_bind(unsigned bind) +{ + static const char *bind_name[] = { +#define SYM_BIND(X) [X] = #X + SYM_BIND(STB_LOCAL), + SYM_BIND(STB_GLOBAL), + SYM_BIND(STB_WEAK), +#undef SYM_BIND + }; + const char *name = "unknown sym bind name"; + if (bind < sizeof(bind_name)/sizeof(bind_name[0])) { + name = bind_name[bind]; + } + return name; +} + +static const char *sym_visibility(unsigned visibility) +{ + static const char *visibility_name[] = { +#define SYM_VISIBILITY(X) [X] = #X + SYM_VISIBILITY(STV_DEFAULT), + SYM_VISIBILITY(STV_INTERNAL), + SYM_VISIBILITY(STV_HIDDEN), + SYM_VISIBILITY(STV_PROTECTED), +#undef SYM_VISIBILITY + }; + const char *name = "unknown sym visibility name"; + if (visibility < sizeof(visibility_name)/sizeof(visibility_name[0])) { + name = visibility_name[visibility]; + } + return name; +} + +static const char *rel_type(unsigned type) +{ + static const char *type_name[] = { +#define REL_TYPE(X) [X] = #X + REL_TYPE(R_386_NONE), + REL_TYPE(R_386_32), + REL_TYPE(R_386_PC32), + REL_TYPE(R_386_GOT32), + REL_TYPE(R_386_PLT32), + REL_TYPE(R_386_COPY), + REL_TYPE(R_386_GLOB_DAT), + REL_TYPE(R_386_JMP_SLOT), + REL_TYPE(R_386_RELATIVE), + REL_TYPE(R_386_GOTOFF), + REL_TYPE(R_386_GOTPC), +#undef REL_TYPE + }; + const char *name = "unknown type rel type name"; + if (type < sizeof(type_name)/sizeof(type_name[0])) { + name = type_name[type]; + } + return name; +} + +static const char *sec_name(unsigned shndx) +{ + const char *sec_strtab; + const char *name; + sec_strtab = strtab[ehdr.e_shstrndx]; + name = "<noname>"; + if (shndx < ehdr.e_shnum) { + name = sec_strtab + shdr[shndx].sh_name; + } + else if (shndx == SHN_ABS) { + name = "ABSOLUTE"; + } + else if (shndx == SHN_COMMON) { + name = "COMMON"; + } + return name; +} + +static const char *sym_name(const char *sym_strtab, Elf32_Sym *sym) +{ + const char *name; + name = "<noname>"; + if (sym->st_name) { + name = sym_strtab + sym->st_name; + } + else { + name = sec_name(shdr[sym->st_shndx].sh_name); + } + return name; +} + + + +#if BYTE_ORDER == LITTLE_ENDIAN +#define le16_to_cpu(val) (val) +#define le32_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) +#endif + +static uint16_t elf16_to_cpu(uint16_t val) +{ + return le16_to_cpu(val); +} + +static uint32_t elf32_to_cpu(uint32_t val) +{ + return le32_to_cpu(val); +} + +static void read_ehdr(FILE *fp) +{ + if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1) { + die("Cannot read ELF header: %s\n", + strerror(errno)); + } + if (memcmp(ehdr.e_ident, ELFMAG, 4) != 0) { + die("No ELF magic\n"); + } + if (ehdr.e_ident[EI_CLASS] != ELFCLASS32) { + die("Not a 32 bit executable\n"); + } + if (ehdr.e_ident[EI_DATA] != ELFDATA2LSB) { + die("Not a LSB ELF executable\n"); + } + if (ehdr.e_ident[EI_VERSION] != EV_CURRENT) { + die("Unknown ELF version\n"); + } + /* Convert the fields to native endian */ + ehdr.e_type = elf16_to_cpu(ehdr.e_type); + ehdr.e_machine = elf16_to_cpu(ehdr.e_machine); + ehdr.e_version = elf32_to_cpu(ehdr.e_version); + ehdr.e_entry = elf32_to_cpu(ehdr.e_entry); + ehdr.e_phoff = elf32_to_cpu(ehdr.e_phoff); + ehdr.e_shoff = elf32_to_cpu(ehdr.e_shoff); + ehdr.e_flags = elf32_to_cpu(ehdr.e_flags); + ehdr.e_ehsize = elf16_to_cpu(ehdr.e_ehsize); + ehdr.e_phentsize = elf16_to_cpu(ehdr.e_phentsize); + ehdr.e_phnum = elf16_to_cpu(ehdr.e_phnum); + ehdr.e_shentsize = elf16_to_cpu(ehdr.e_shentsize); + ehdr.e_shnum = elf16_to_cpu(ehdr.e_shnum); + ehdr.e_shstrndx = elf16_to_cpu(ehdr.e_shstrndx); + + if ((ehdr.e_type != ET_EXEC) && (ehdr.e_type != ET_DYN)) { + die("Unsupported ELF header type\n"); + } + if (ehdr.e_machine != EM_386) { + die("Not for x86\n"); + } + if (ehdr.e_version != EV_CURRENT) { + die("Unknown ELF version\n"); + } + if (ehdr.e_ehsize != sizeof(Elf32_Ehdr)) { + die("Bad Elf header size\n"); + } + if (ehdr.e_phentsize != sizeof(Elf32_Phdr)) { + die("Bad program header entry\n"); + } + if (ehdr.e_shentsize != sizeof(Elf32_Shdr)) { + die("Bad section header entry\n"); + } + if (ehdr.e_shstrndx >= ehdr.e_shnum) { + die("String table index out of bounds\n"); + } +} + +static void read_shdrs(FILE *fp) +{ + int i; + if (ehdr.e_shnum > MAX_SHDRS) { + die("%d section headers supported: %d\n", + ehdr.e_shnum, MAX_SHDRS); + } + if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) { + die("Seek to %d failed: %s\n", + ehdr.e_shoff, strerror(errno)); + } + if (fread(&shdr, sizeof(shdr[0]), ehdr.e_shnum, fp) != ehdr.e_shnum) { + die("Cannot read ELF section headers: %s\n", + strerror(errno)); + } + for(i = 0; i < ehdr.e_shnum; i++) { + shdr[i].sh_name = elf32_to_cpu(shdr[i].sh_name); + shdr[i].sh_type = elf32_to_cpu(shdr[i].sh_type); + shdr[i].sh_flags = elf32_to_cpu(shdr[i].sh_flags); + shdr[i].sh_addr = elf32_to_cpu(shdr[i].sh_addr); + shdr[i].sh_offset = elf32_to_cpu(shdr[i].sh_offset); + shdr[i].sh_size = elf32_to_cpu(shdr[i].sh_size); + shdr[i].sh_link = elf32_to_cpu(shdr[i].sh_link); + shdr[i].sh_info = elf32_to_cpu(shdr[i].sh_info); + shdr[i].sh_addralign = elf32_to_cpu(shdr[i].sh_addralign); + shdr[i].sh_entsize = elf32_to_cpu(shdr[i].sh_entsize); + } + +} + +static void read_strtabs(FILE *fp) +{ + int i; + for(i = 0; i < ehdr.e_shnum; i++) { + if (shdr[i].sh_type != SHT_STRTAB) { + continue; + } + strtab[i] = malloc(shdr[i].sh_size); + if (!strtab[i]) { + die("malloc of %d bytes for strtab failed\n", + shdr[i].sh_size); + } + if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) { + die("Seek to %d failed: %s\n", + shdr[i].sh_offset, strerror(errno)); + } + if (fread(strtab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) { + die("Cannot read symbol table: %s\n", + strerror(errno)); + } + } +} + +static void read_symtabs(FILE *fp) +{ + int i,j; + for(i = 0; i < ehdr.e_shnum; i++) { + if (shdr[i].sh_type != SHT_SYMTAB) { + continue; + } + symtab[i] = malloc(shdr[i].sh_size); + if (!symtab[i]) { + die("malloc of %d bytes for symtab failed\n", + shdr[i].sh_size); + } + if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) { + die("Seek to %d failed: %s\n", + shdr[i].sh_offset, strerror(errno)); + } + if (fread(symtab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) { + die("Cannot read symbol table: %s\n", + strerror(errno)); + } + for(j = 0; j < shdr[i].sh_size/sizeof(symtab[i][0]); j++) { + symtab[i][j].st_name = elf32_to_cpu(symtab[i][j].st_name); + symtab[i][j].st_value = elf32_to_cpu(symtab[i][j].st_value); + symtab[i][j].st_size = elf32_to_cpu(symtab[i][j].st_size); + symtab[i][j].st_shndx = elf16_to_cpu(symtab[i][j].st_shndx); + } + } +} + + +static void read_relocs(FILE *fp) +{ + int i,j; + for(i = 0; i < ehdr.e_shnum; i++) { + if (shdr[i].sh_type != SHT_REL) { + continue; + } + reltab[i] = malloc(shdr[i].sh_size); + if (!reltab[i]) { + die("malloc of %d bytes for relocs failed\n", + shdr[i].sh_size); + } + if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) { + die("Seek to %d failed: %s\n", + shdr[i].sh_offset, strerror(errno)); + } + if (fread(reltab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) { + die("Cannot read symbol table: %s\n", + strerror(errno)); + } + for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) { + reltab[i][j].r_offset = elf32_to_cpu(reltab[i][j].r_offset); + reltab[i][j].r_info = elf32_to_cpu(reltab[i][j].r_info); + } + } +} + + +static void print_absolute_symbols(void) +{ + int i; + printf("Absolute symbols\n"); + printf(" Num: Value Size Type Bind Visibility Name\n"); + for(i = 0; i < ehdr.e_shnum; i++) { + char *sym_strtab; + Elf32_Sym *sh_symtab; + int j; + if (shdr[i].sh_type != SHT_SYMTAB) { + continue; + } + sh_symtab = symtab[i]; + sym_strtab = strtab[shdr[i].sh_link]; + for(j = 0; j < shdr[i].sh_size/sizeof(symtab[0][0]); j++) { + Elf32_Sym *sym; + const char *name; + sym = &symtab[i][j]; + name = sym_name(sym_strtab, sym); + if (sym->st_shndx != SHN_ABS) { + continue; + } + printf("%5d %08x %5d %10s %10s %12s %s\n", + j, sym->st_value, sym->st_size, + sym_type(ELF32_ST_TYPE(sym->st_info)), + sym_bind(ELF32_ST_BIND(sym->st_info)), + sym_visibility(ELF32_ST_VISIBILITY(sym->st_other)), + name); + } + } + printf("\n"); +} + +static void print_absolute_relocs(void) +{ + int i, printed = 0; + + for(i = 0; i < ehdr.e_shnum; i++) { + char *sym_strtab; + Elf32_Sym *sh_symtab; + unsigned sec_applies, sec_symtab; + int j; + if (shdr[i].sh_type != SHT_REL) { + continue; + } + sec_symtab = shdr[i].sh_link; + sec_applies = shdr[i].sh_info; + if (!(shdr[sec_applies].sh_flags & SHF_ALLOC)) { + continue; + } + sh_symtab = symtab[sec_symtab]; + sym_strtab = strtab[shdr[sec_symtab].sh_link]; + for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) { + Elf32_Rel *rel; + Elf32_Sym *sym; + const char *name; + rel = &reltab[i][j]; + sym = &sh_symtab[ELF32_R_SYM(rel->r_info)]; + name = sym_name(sym_strtab, sym); + if (sym->st_shndx != SHN_ABS) { + continue; + } + + /* Absolute symbols are not relocated if bzImage is + * loaded at a non-compiled address. Display a warning + * to user at compile time about the absolute + * relocations present. + * + * User need to audit the code to make sure + * some symbols which should have been section + * relative have not become absolute because of some + * linker optimization or wrong programming usage. + * + * Before warning check if this absolute symbol + * relocation is harmless. + */ + if (is_safe_abs_reloc(name)) + continue; + + if (!printed) { + printf("WARNING: Absolute relocations" + " present\n"); + printf("Offset Info Type Sym.Value " + "Sym.Name\n"); + printed = 1; + } + + printf("%08x %08x %10s %08x %s\n", + rel->r_offset, + rel->r_info, + rel_type(ELF32_R_TYPE(rel->r_info)), + sym->st_value, + name); + } + } + + if (printed) + printf("\n"); +} + +static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym)) +{ + int i; + /* Walk through the relocations */ + for(i = 0; i < ehdr.e_shnum; i++) { + char *sym_strtab; + Elf32_Sym *sh_symtab; + unsigned sec_applies, sec_symtab; + int j; + if (shdr[i].sh_type != SHT_REL) { + continue; + } + sec_symtab = shdr[i].sh_link; + sec_applies = shdr[i].sh_info; + if (!(shdr[sec_applies].sh_flags & SHF_ALLOC)) { + continue; + } + sh_symtab = symtab[sec_symtab]; + sym_strtab = strtab[shdr[sec_symtab].sh_link]; + for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) { + Elf32_Rel *rel; + Elf32_Sym *sym; + unsigned r_type; + rel = &reltab[i][j]; + sym = &sh_symtab[ELF32_R_SYM(rel->r_info)]; + r_type = ELF32_R_TYPE(rel->r_info); + /* Don't visit relocations to absolute symbols */ + if (sym->st_shndx == SHN_ABS) { + continue; + } + if (r_type == R_386_PC32) { + /* PC relative relocations don't need to be adjusted */ + } + else if (r_type == R_386_32) { + /* Visit relocations that need to be adjusted */ + visit(rel, sym); + } + else { + die("Unsupported relocation type: %d\n", r_type); + } + } + } +} + +static void count_reloc(Elf32_Rel *rel, Elf32_Sym *sym) +{ + reloc_count += 1; +} + +static void collect_reloc(Elf32_Rel *rel, Elf32_Sym *sym) +{ + /* Remember the address that needs to be adjusted. */ + relocs[reloc_idx++] = rel->r_offset; +} + +static int cmp_relocs(const void *va, const void *vb) +{ + const unsigned long *a, *b; + a = va; b = vb; + return (*a == *b)? 0 : (*a > *b)? 1 : -1; +} + +static void emit_relocs(int as_text) +{ + int i; + /* Count how many relocations I have and allocate space for them. */ + reloc_count = 0; + walk_relocs(count_reloc); + relocs = malloc(reloc_count * sizeof(relocs[0])); + if (!relocs) { + die("malloc of %d entries for relocs failed\n", + reloc_count); + } + /* Collect up the relocations */ + reloc_idx = 0; + walk_relocs(collect_reloc); + + /* Order the relocations for more efficient processing */ + qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs); + + /* Print the relocations */ + if (as_text) { + /* Print the relocations in a form suitable that + * gas will like. + */ + printf(".section \".data.reloc\",\"a\"\n"); + printf(".balign 4\n"); + for(i = 0; i < reloc_count; i++) { + printf("\t .long 0x%08lx\n", relocs[i]); + } + printf("\n"); + } + else { + unsigned char buf[4]; + buf[0] = buf[1] = buf[2] = buf[3] = 0; + /* Print a stop */ + printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]); + /* Now print each relocation */ + for(i = 0; i < reloc_count; i++) { + buf[0] = (relocs[i] >> 0) & 0xff; + buf[1] = (relocs[i] >> 8) & 0xff; + buf[2] = (relocs[i] >> 16) & 0xff; + buf[3] = (relocs[i] >> 24) & 0xff; + printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]); + } + } +} + +static void usage(void) +{ + die("relocs [--abs-syms |--abs-relocs | --text] vmlinux\n"); +} + +int main(int argc, char **argv) +{ + int show_absolute_syms, show_absolute_relocs; + int as_text; + const char *fname; + FILE *fp; + int i; + + show_absolute_syms = 0; + show_absolute_relocs = 0; + as_text = 0; + fname = NULL; + for(i = 1; i < argc; i++) { + char *arg = argv[i]; + if (*arg == '-') { + if (strcmp(argv[1], "--abs-syms") == 0) { + show_absolute_syms = 1; + continue; + } + + if (strcmp(argv[1], "--abs-relocs") == 0) { + show_absolute_relocs = 1; + continue; + } + else if (strcmp(argv[1], "--text") == 0) { + as_text = 1; + continue; + } + } + else if (!fname) { + fname = arg; + continue; + } + usage(); + } + if (!fname) { + usage(); + } + fp = fopen(fname, "r"); + if (!fp) { + die("Cannot open %s: %s\n", + fname, strerror(errno)); + } + read_ehdr(fp); + read_shdrs(fp); + read_strtabs(fp); + read_symtabs(fp); + read_relocs(fp); + if (show_absolute_syms) { + print_absolute_symbols(); + return 0; + } + if (show_absolute_relocs) { + print_absolute_relocs(); + return 0; + } + emit_relocs(as_text); + return 0; +} |
