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x86, relocs: Consolidate processing logic
Instead of counting and then processing relocations, do it in a single pass. This splits the processing logic into separate functions for realmode and 32-bit (and paves the way for 64-bit). Also extracts helper functions when emitting relocations. Based on work by Neill Clift and Michael Davidson. Signed-off-by: Kees Cook <keescook@chromium.org> Link: http://lkml.kernel.org/r/1365797627-20874-3-git-send-email-keescook@chromium.org Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Kees Cook
H. Peter Anvin
parent
bf11655cf2
commit
5d442e63d6
@ -2,6 +2,7 @@
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#include <stdarg.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <inttypes.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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@ -38,10 +39,15 @@ static void die(char *fmt, ...);
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#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
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static Elf_Ehdr ehdr;
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static unsigned long reloc_count, reloc_idx;
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static unsigned long *relocs;
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static unsigned long reloc16_count, reloc16_idx;
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static unsigned long *relocs16;
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struct relocs {
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uint32_t *offset;
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unsigned long count;
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unsigned long size;
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};
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static struct relocs relocs16;
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static struct relocs relocs32;
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struct section {
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Elf_Shdr shdr;
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@ -583,8 +589,23 @@ static void print_absolute_relocs(void)
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printf("\n");
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}
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static void walk_relocs(void (*visit)(Elf_Rel *rel, Elf_Sym *sym),
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int use_real_mode)
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static void add_reloc(struct relocs *r, uint32_t offset)
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{
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if (r->count == r->size) {
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unsigned long newsize = r->size + 50000;
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void *mem = realloc(r->offset, newsize * sizeof(r->offset[0]));
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if (!mem)
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die("realloc of %ld entries for relocs failed\n",
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newsize);
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r->offset = mem;
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r->size = newsize;
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}
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r->offset[r->count++] = offset;
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}
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static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel,
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Elf_Sym *sym, const char *symname))
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{
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int i;
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/* Walk through the relocations */
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@ -606,100 +627,142 @@ static void walk_relocs(void (*visit)(Elf_Rel *rel, Elf_Sym *sym),
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sh_symtab = sec_symtab->symtab;
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sym_strtab = sec_symtab->link->strtab;
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for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Rel); j++) {
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Elf_Rel *rel;
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Elf_Sym *sym;
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unsigned r_type;
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const char *symname;
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int shn_abs;
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Elf_Rel *rel = &sec->reltab[j];
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Elf_Sym *sym = &sh_symtab[ELF_R_SYM(rel->r_info)];
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const char *symname = sym_name(sym_strtab, sym);
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rel = &sec->reltab[j];
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sym = &sh_symtab[ELF_R_SYM(rel->r_info)];
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r_type = ELF_R_TYPE(rel->r_info);
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shn_abs = sym->st_shndx == SHN_ABS;
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switch (r_type) {
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case R_386_NONE:
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case R_386_PC32:
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case R_386_PC16:
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case R_386_PC8:
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/*
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* NONE can be ignored and and PC relative
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* relocations don't need to be adjusted.
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*/
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break;
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case R_386_16:
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symname = sym_name(sym_strtab, sym);
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if (!use_real_mode)
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goto bad;
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if (shn_abs) {
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if (is_reloc(S_ABS, symname))
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break;
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else if (!is_reloc(S_SEG, symname))
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goto bad;
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} else {
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if (is_reloc(S_LIN, symname))
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goto bad;
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else
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break;
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}
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visit(rel, sym);
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break;
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case R_386_32:
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symname = sym_name(sym_strtab, sym);
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if (shn_abs) {
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if (is_reloc(S_ABS, symname))
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break;
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else if (!is_reloc(S_REL, symname))
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goto bad;
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} else {
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if (use_real_mode &&
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!is_reloc(S_LIN, symname))
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break;
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}
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visit(rel, sym);
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break;
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default:
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die("Unsupported relocation type: %s (%d)\n",
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rel_type(r_type), r_type);
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break;
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bad:
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symname = sym_name(sym_strtab, sym);
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die("Invalid %s %s relocation: %s\n",
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shn_abs ? "absolute" : "relative",
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rel_type(r_type), symname);
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}
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process(sec, rel, sym, symname);
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}
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}
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}
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static void count_reloc(Elf_Rel *rel, Elf_Sym *sym)
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static int do_reloc(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
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const char *symname)
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{
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if (ELF_R_TYPE(rel->r_info) == R_386_16)
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reloc16_count++;
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else
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reloc_count++;
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unsigned r_type = ELF32_R_TYPE(rel->r_info);
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int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
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switch (r_type) {
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case R_386_NONE:
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case R_386_PC32:
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case R_386_PC16:
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case R_386_PC8:
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/*
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* NONE can be ignored and PC relative relocations don't
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* need to be adjusted.
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*/
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break;
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case R_386_32:
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if (shn_abs) {
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/*
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* Whitelisted absolute symbols do not require
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* relocation.
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*/
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if (is_reloc(S_ABS, symname))
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break;
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die("Invalid absolute %s relocation: %s\n",
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rel_type(r_type), symname);
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break;
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}
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add_reloc(&relocs32, rel->r_offset);
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break;
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default:
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die("Unsupported relocation type: %s (%d)\n",
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rel_type(r_type), r_type);
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break;
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}
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return 0;
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}
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static void collect_reloc(Elf_Rel *rel, Elf_Sym *sym)
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static int do_reloc_real(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
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const char *symname)
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{
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/* Remember the address that needs to be adjusted. */
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if (ELF_R_TYPE(rel->r_info) == R_386_16)
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relocs16[reloc16_idx++] = rel->r_offset;
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else
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relocs[reloc_idx++] = rel->r_offset;
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unsigned r_type = ELF32_R_TYPE(rel->r_info);
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int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
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switch (r_type) {
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case R_386_NONE:
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case R_386_PC32:
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case R_386_PC16:
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case R_386_PC8:
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/*
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* NONE can be ignored and PC relative relocations don't
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* need to be adjusted.
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*/
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break;
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case R_386_16:
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if (shn_abs) {
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/*
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* Whitelisted absolute symbols do not require
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* relocation.
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*/
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if (is_reloc(S_ABS, symname))
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break;
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if (is_reloc(S_SEG, symname)) {
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add_reloc(&relocs16, rel->r_offset);
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break;
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}
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} else {
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if (!is_reloc(S_LIN, symname))
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break;
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}
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die("Invalid %s %s relocation: %s\n",
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shn_abs ? "absolute" : "relative",
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rel_type(r_type), symname);
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break;
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case R_386_32:
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if (shn_abs) {
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/*
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* Whitelisted absolute symbols do not require
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* relocation.
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*/
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if (is_reloc(S_ABS, symname))
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break;
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if (is_reloc(S_REL, symname)) {
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add_reloc(&relocs32, rel->r_offset);
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break;
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}
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} else {
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if (is_reloc(S_LIN, symname))
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add_reloc(&relocs32, rel->r_offset);
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break;
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}
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die("Invalid %s %s relocation: %s\n",
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shn_abs ? "absolute" : "relative",
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rel_type(r_type), symname);
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break;
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default:
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die("Unsupported relocation type: %s (%d)\n",
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rel_type(r_type), r_type);
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break;
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}
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return 0;
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}
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static int cmp_relocs(const void *va, const void *vb)
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{
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const unsigned long *a, *b;
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const uint32_t *a, *b;
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a = va; b = vb;
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return (*a == *b)? 0 : (*a > *b)? 1 : -1;
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}
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static int write32(unsigned int v, FILE *f)
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static void sort_relocs(struct relocs *r)
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{
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qsort(r->offset, r->count, sizeof(r->offset[0]), cmp_relocs);
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}
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static int write32(uint32_t v, FILE *f)
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{
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unsigned char buf[4];
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@ -707,33 +770,25 @@ static int write32(unsigned int v, FILE *f)
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return fwrite(buf, 1, 4, f) == 4 ? 0 : -1;
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}
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static int write32_as_text(uint32_t v, FILE *f)
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{
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return fprintf(f, "\t.long 0x%08"PRIx32"\n", v) > 0 ? 0 : -1;
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}
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static void emit_relocs(int as_text, int use_real_mode)
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{
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int i;
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/* Count how many relocations I have and allocate space for them. */
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reloc_count = 0;
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walk_relocs(count_reloc, use_real_mode);
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relocs = malloc(reloc_count * sizeof(relocs[0]));
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if (!relocs) {
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die("malloc of %d entries for relocs failed\n",
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reloc_count);
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}
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int (*write_reloc)(uint32_t, FILE *) = write32;
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relocs16 = malloc(reloc16_count * sizeof(relocs[0]));
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if (!relocs16) {
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die("malloc of %d entries for relocs16 failed\n",
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reloc16_count);
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}
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/* Collect up the relocations */
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reloc_idx = 0;
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walk_relocs(collect_reloc, use_real_mode);
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walk_relocs(use_real_mode ? do_reloc_real : do_reloc);
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if (reloc16_count && !use_real_mode)
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if (relocs16.count && !use_real_mode)
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die("Segment relocations found but --realmode not specified\n");
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/* Order the relocations for more efficient processing */
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qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs);
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qsort(relocs16, reloc16_count, sizeof(relocs16[0]), cmp_relocs);
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sort_relocs(&relocs16);
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sort_relocs(&relocs32);
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/* Print the relocations */
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if (as_text) {
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@ -742,43 +797,24 @@ static void emit_relocs(int as_text, int use_real_mode)
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*/
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printf(".section \".data.reloc\",\"a\"\n");
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printf(".balign 4\n");
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if (use_real_mode) {
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printf("\t.long %lu\n", reloc16_count);
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for (i = 0; i < reloc16_count; i++)
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printf("\t.long 0x%08lx\n", relocs16[i]);
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printf("\t.long %lu\n", reloc_count);
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for (i = 0; i < reloc_count; i++) {
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printf("\t.long 0x%08lx\n", relocs[i]);
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}
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} else {
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/* Print a stop */
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printf("\t.long 0x%08lx\n", (unsigned long)0);
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for (i = 0; i < reloc_count; i++) {
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printf("\t.long 0x%08lx\n", relocs[i]);
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}
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}
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printf("\n");
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write_reloc = write32_as_text;
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}
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else {
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if (use_real_mode) {
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write32(reloc16_count, stdout);
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for (i = 0; i < reloc16_count; i++)
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write32(relocs16[i], stdout);
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write32(reloc_count, stdout);
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/* Now print each relocation */
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for (i = 0; i < reloc_count; i++)
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write32(relocs[i], stdout);
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} else {
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/* Print a stop */
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write32(0, stdout);
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if (use_real_mode) {
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write_reloc(relocs16.count, stdout);
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for (i = 0; i < relocs16.count; i++)
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write_reloc(relocs16.offset[i], stdout);
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/* Now print each relocation */
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for (i = 0; i < reloc_count; i++) {
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write32(relocs[i], stdout);
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}
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}
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write_reloc(relocs32.count, stdout);
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for (i = 0; i < relocs32.count; i++)
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write_reloc(relocs32.offset[i], stdout);
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} else {
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/* Print a stop */
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write_reloc(0, stdout);
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/* Now print each relocation */
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for (i = 0; i < relocs32.count; i++)
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write_reloc(relocs32.offset[i], stdout);
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}
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}
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