relocate-rela.c

/*
 * Copyright 2013 Freescale Semiconductor, Inc.
 *
 * SPDX-License-Identifier:	GPL-2.0+ BSD-2-Clause
 *
 * 64-bit and little-endian target only until we need to support a different
 * arch that needs this.
 */

#include <elf.h>
#include <errno.h>
#include <inttypes.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifndef R_AARCH64_RELATIVE
#define R_AARCH64_RELATIVE	1027
#endif

static const bool debug_en;

static void debug(const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	if (debug_en)
		vprintf(fmt, args);
}

static bool supported_rela(Elf64_Rela *rela)
{
	uint64_t mask = 0xffffffffULL; /* would be different on 32-bit */
	uint32_t type = rela->r_info & mask;

	switch (type) {
#ifdef R_AARCH64_RELATIVE
	case R_AARCH64_RELATIVE:
		return true;
#endif
	default:
		fprintf(stderr, "warning: unsupported relocation type %"
				PRIu32 " at %" PRIx64 "\n",
			type, rela->r_offset);

		return false;
	}
}

static inline uint64_t swap64(uint64_t val)
{
	return ((val >> 56) & 0x00000000000000ffULL) |
	       ((val >> 40) & 0x000000000000ff00ULL) |
	       ((val >> 24) & 0x0000000000ff0000ULL) |
	       ((val >>  8) & 0x00000000ff000000ULL) |
	       ((val <<  8) & 0x000000ff00000000ULL) |
	       ((val << 24) & 0x0000ff0000000000ULL) |
	       ((val << 40) & 0x00ff000000000000ULL) |
	       ((val << 56) & 0xff00000000000000ULL);
}

#if __BYTE_ORDER == __LITTLE_ENDIAN
static inline uint64_t be64(uint64_t val)
{
	return swap64(val);
}

static inline uint64_t le64(uint64_t val)
{
	return val;
}
#else
static inline uint64_t le64(uint64_t val)
{
	return swap64(val);
}

static inline uint64_t be64(uint64_t val)
{
	return val;
}
#endif

static bool read_num(const char *str, uint64_t *num)
{
	char *endptr;
	*num = strtoull(str, &endptr, 16);
	return str[0] && !endptr[0];
}

int main(int argc, char **argv)
{
	FILE *f;
	int i, num;
	uint64_t rela_start, rela_end, text_base;

	if (argc != 5) {
		fprintf(stderr, "Statically apply ELF rela relocations\n");
		fprintf(stderr, "Usage: %s <bin file> <text base> " \
				"<rela start> <rela end>\n", argv[0]);
		fprintf(stderr, "All numbers in hex.\n");
		return 1;
	}

	f = fopen(argv[1], "r+b");
	if (!f) {
		fprintf(stderr, "%s: Cannot open %s: %s\n",
			argv[0], argv[1], strerror(errno));
		return 2;
	}

	if (!read_num(argv[2], &text_base) ||
	    !read_num(argv[3], &rela_start) ||
	    !read_num(argv[4], &rela_end)) {
		fprintf(stderr, "%s: bad number\n", argv[0]);
		return 3;
	}

	if (rela_start > rela_end || rela_start < text_base ||
	    (rela_end - rela_start) % sizeof(Elf64_Rela)) {
		fprintf(stderr, "%s: bad rela bounds\n", argv[0]);
		return 3;
	}

	rela_start -= text_base;
	rela_end -= text_base;

	num = (rela_end - rela_start) / sizeof(Elf64_Rela);

	for (i = 0; i < num; i++) {
		Elf64_Rela rela, swrela;
		uint64_t pos = rela_start + sizeof(Elf64_Rela) * i;
		uint64_t addr;

		if (fseek(f, pos, SEEK_SET) < 0) {
			fprintf(stderr, "%s: %s: seek to %" PRIx64
					" failed: %s\n",
				argv[0], argv[1], pos, strerror(errno));
		}

		if (fread(&rela, sizeof(rela), 1, f) != 1) {
			fprintf(stderr, "%s: %s: read rela failed at %"
					PRIx64 "\n",
				argv[0], argv[1], pos);
			return 4;
		}

		swrela.r_offset = le64(rela.r_offset);
		swrela.r_info = le64(rela.r_info);
		swrela.r_addend = le64(rela.r_addend);

		if (!supported_rela(&swrela))
			continue;

		debug("Rela %" PRIx64 " %" PRIu64 " %" PRIx64 "\n",
		      swrela.r_offset, swrela.r_info, swrela.r_addend);

		if (swrela.r_offset < text_base) {
			fprintf(stderr, "%s: %s: bad rela at %" PRIx64 "\n",
				argv[0], argv[1], pos);
			return 4;
		}

		addr = swrela.r_offset - text_base;

		if (fseek(f, addr, SEEK_SET) < 0) {
			fprintf(stderr, "%s: %s: seek to %"
					PRIx64 " failed: %s\n",
				argv[0], argv[1], addr, strerror(errno));
		}

		if (fwrite(&rela.r_addend, sizeof(rela.r_addend), 1, f) != 1) {
			fprintf(stderr, "%s: %s: write failed at %" PRIx64 "\n",
				argv[0], argv[1], addr);
			return 4;
		}
	}

	if (fclose(f) < 0) {
		fprintf(stderr, "%s: %s: close failed: %s\n",
			argv[0], argv[1], strerror(errno));
		return 4;
	}

	return 0;
}