Commit 5d442e63 authored by Kees Cook's avatar Kees Cook Committed by H. Peter Anvin
Browse files

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: default avatarKees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/1365797627-20874-3-git-send-email-keescook@chromium.org


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent bf11655c

arch/x86/tools/relocs.c

+170 −134
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#include <stdarg.h>

#include <stdlib.h>

#include <stdint.h>

#include <inttypes.h>

#include <string.h>

#include <errno.h>

#include <unistd.h>
@@ -38,10 +39,15 @@ static void die(char *fmt, ...); 


#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))

static Elf_Ehdr ehdr;

static unsigned long reloc_count, reloc_idx;

static unsigned long *relocs;

static unsigned long reloc16_count, reloc16_idx;

static unsigned long *relocs16;



struct relocs {

	uint32_t	*offset;

	unsigned long	count;

	unsigned long	size;

};



static struct relocs relocs16;

static struct relocs relocs32;



struct section {

	Elf_Shdr       shdr;
@@ -583,8 +589,23 @@ static void print_absolute_relocs(void) 
		printf("\n");

}



static void walk_relocs(void (*visit)(Elf_Rel *rel, Elf_Sym *sym),

			int use_real_mode)

static void add_reloc(struct relocs *r, uint32_t offset)

{

	if (r->count == r->size) {

		unsigned long newsize = r->size + 50000;

		void *mem = realloc(r->offset, newsize * sizeof(r->offset[0]));



		if (!mem)

			die("realloc of %ld entries for relocs failed\n",

                                newsize);

		r->offset = mem;

		r->size = newsize;

	}

	r->offset[r->count++] = offset;

}



static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel,

			Elf_Sym *sym, const char *symname))

{

	int i;

	/* Walk through the relocations */
@@ -606,17 +627,20 @@ static void walk_relocs(void (*visit)(Elf_Rel *rel, Elf_Sym *sym), 
		sh_symtab = sec_symtab->symtab;

		sym_strtab = sec_symtab->link->strtab;

		for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Rel); j++) {

			Elf_Rel *rel;

			Elf_Sym *sym;

			unsigned r_type;

			const char *symname;

			int shn_abs;

			Elf_Rel *rel = &sec->reltab[j];

			Elf_Sym *sym = &sh_symtab[ELF_R_SYM(rel->r_info)];

			const char *symname = sym_name(sym_strtab, sym);



			rel = &sec->reltab[j];

			sym = &sh_symtab[ELF_R_SYM(rel->r_info)];

			r_type = ELF_R_TYPE(rel->r_info);

			process(sec, rel, sym, symname);

		}

	}

}



			shn_abs = sym->st_shndx == SHN_ABS;

static int do_reloc(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);



	switch (r_type) {

	case R_386_NONE:
@@ -624,82 +648,121 @@ static void walk_relocs(void (*visit)(Elf_Rel *rel, Elf_Sym *sym), 
	case R_386_PC16:

	case R_386_PC8:

		/*

				 * NONE can be ignored and and PC relative

				 * relocations don't need to be adjusted.

		 * NONE can be ignored and PC relative relocations don't

		 * need to be adjusted.

		 */

		break;



	case R_386_32:

		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;

		}



		add_reloc(&relocs32, rel->r_offset);

		break;



	default:

		die("Unsupported relocation type: %s (%d)\n",

		    rel_type(r_type), r_type);

		break;

	}



	return 0;

}



static int do_reloc_real(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);



	switch (r_type) {

	case R_386_NONE:

	case R_386_PC32:

	case R_386_PC16:

	case R_386_PC8:

		/*

		 * NONE can be ignored and PC relative relocations don't

		 * need to be adjusted.

		 */

		break;



	case R_386_16:

				symname = sym_name(sym_strtab, sym);

				if (!use_real_mode)

					goto bad;

		if (shn_abs) {

			/*

			 * Whitelisted absolute symbols do not require

			 * relocation.

			 */

			if (is_reloc(S_ABS, symname))

				break;

					else if (!is_reloc(S_SEG, symname))

						goto bad;



			if (is_reloc(S_SEG, symname)) {

				add_reloc(&relocs16, rel->r_offset);

				break;

			}

		} else {

					if (is_reloc(S_LIN, symname))

						goto bad;

					else

			if (!is_reloc(S_LIN, symname))

				break;

		}

				visit(rel, sym);

		die("Invalid %s %s relocation: %s\n",

		    shn_abs ? "absolute" : "relative",

		    rel_type(r_type), symname);

		break;



	case R_386_32:

				symname = sym_name(sym_strtab, sym);

		if (shn_abs) {

			/*

			 * Whitelisted absolute symbols do not require

			 * relocation.

			 */

			if (is_reloc(S_ABS, symname))

				break;

					else if (!is_reloc(S_REL, symname))

						goto bad;



			if (is_reloc(S_REL, symname)) {

				add_reloc(&relocs32, rel->r_offset);

				break;

			}

		} else {

					if (use_real_mode &&

					    !is_reloc(S_LIN, symname))

			if (is_reloc(S_LIN, symname))

				add_reloc(&relocs32, rel->r_offset);

			break;

		}

				visit(rel, sym);

		die("Invalid %s %s relocation: %s\n",

		    shn_abs ? "absolute" : "relative",

		    rel_type(r_type), symname);

		break;



	default:

		die("Unsupported relocation type: %s (%d)\n",

		    rel_type(r_type), r_type);

		break;

			bad:

				symname = sym_name(sym_strtab, sym);

				die("Invalid %s %s relocation: %s\n",

				    shn_abs ? "absolute" : "relative",

				    rel_type(r_type), symname);

			}

		}

	}

	}



static void count_reloc(Elf_Rel *rel, Elf_Sym *sym)

{

	if (ELF_R_TYPE(rel->r_info) == R_386_16)

		reloc16_count++;

	else

		reloc_count++;

}



static void collect_reloc(Elf_Rel *rel, Elf_Sym *sym)

{

	/* Remember the address that needs to be adjusted. */

	if (ELF_R_TYPE(rel->r_info) == R_386_16)

		relocs16[reloc16_idx++] = rel->r_offset;

	else

		relocs[reloc_idx++] = rel->r_offset;

	return 0;

}



static int cmp_relocs(const void *va, const void *vb)

{

	const unsigned long *a, *b;

	const uint32_t *a, *b;

	a = va; b = vb;

	return (*a == *b)? 0 : (*a > *b)? 1 : -1;

}



static int write32(unsigned int v, FILE *f)

static void sort_relocs(struct relocs *r)

{

	qsort(r->offset, r->count, sizeof(r->offset[0]), cmp_relocs);

}



static int write32(uint32_t v, FILE *f)

{

	unsigned char buf[4];
@@ -707,33 +770,25 @@ static int write32(unsigned int v, FILE *f) 
	return fwrite(buf, 1, 4, f) == 4 ? 0 : -1;

}



static int write32_as_text(uint32_t v, FILE *f)

{

	return fprintf(f, "\t.long 0x%08"PRIx32"\n", v) > 0 ? 0 : -1;

}



static void emit_relocs(int as_text, int use_real_mode)

{

	int i;

	/* Count how many relocations I have and allocate space for them. */

	reloc_count = 0;

	walk_relocs(count_reloc, use_real_mode);

	relocs = malloc(reloc_count * sizeof(relocs[0]));

	if (!relocs) {

		die("malloc of %d entries for relocs failed\n",

			reloc_count);

	}

	int (*write_reloc)(uint32_t, FILE *) = write32;



	relocs16 = malloc(reloc16_count * sizeof(relocs[0]));

	if (!relocs16) {

		die("malloc of %d entries for relocs16 failed\n",

			reloc16_count);

	}

	/* Collect up the relocations */

	reloc_idx = 0;

	walk_relocs(collect_reloc, use_real_mode);

	walk_relocs(use_real_mode ? do_reloc_real : do_reloc);



	if (reloc16_count && !use_real_mode)

	if (relocs16.count && !use_real_mode)

		die("Segment relocations found but --realmode not specified\n");



	/* Order the relocations for more efficient processing */

	qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs);

	qsort(relocs16, reloc16_count, sizeof(relocs16[0]), cmp_relocs);

	sort_relocs(&relocs16);

	sort_relocs(&relocs32);



	/* Print the relocations */

	if (as_text) {
@@ -742,43 +797,24 @@ static void emit_relocs(int as_text, int use_real_mode) 
		 */

		printf(".section \".data.reloc\",\"a\"\n");

		printf(".balign 4\n");

		if (use_real_mode) {

			printf("\t.long %lu\n", reloc16_count);

			for (i = 0; i < reloc16_count; i++)

				printf("\t.long 0x%08lx\n", relocs16[i]);

			printf("\t.long %lu\n", reloc_count);

			for (i = 0; i < reloc_count; i++) {

				printf("\t.long 0x%08lx\n", relocs[i]);

			}

		} else {

			/* Print a stop */

			printf("\t.long 0x%08lx\n", (unsigned long)0);

			for (i = 0; i < reloc_count; i++) {

				printf("\t.long 0x%08lx\n", relocs[i]);

			}

		write_reloc = write32_as_text;

	}



		printf("\n");

	}

	else {

	if (use_real_mode) {

			write32(reloc16_count, stdout);

			for (i = 0; i < reloc16_count; i++)

				write32(relocs16[i], stdout);

			write32(reloc_count, stdout);

		write_reloc(relocs16.count, stdout);

		for (i = 0; i < relocs16.count; i++)

			write_reloc(relocs16.offset[i], stdout);



			/* Now print each relocation */

			for (i = 0; i < reloc_count; i++)

				write32(relocs[i], stdout);

		write_reloc(relocs32.count, stdout);

		for (i = 0; i < relocs32.count; i++)

			write_reloc(relocs32.offset[i], stdout);

	} else {

		/* Print a stop */

			write32(0, stdout);

		write_reloc(0, stdout);



		/* Now print each relocation */

			for (i = 0; i < reloc_count; i++) {

				write32(relocs[i], stdout);

			}

		}

		for (i = 0; i < relocs32.count; i++)

			write_reloc(relocs32.offset[i], stdout);

	}

}

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