Patchwork [U-Boot,RESEND,v14,04/10] arm64: Add tool to statically apply RELA relocations

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Submitter fenghua@phytium.com.cn
Date Oct. 15, 2013, 3:34 a.m.
Message ID <1381808089-8535-5-git-send-email-fenghua@phytium.com.cn>
Download mbox | patch
Permalink /patch/283454/
State Superseded
Delegated to: Albert ARIBAUD
Headers show

Comments

fenghua@phytium.com.cn - Oct. 15, 2013, 3:34 a.m.
From: Scott Wood <scottwood@freescale.com>

ARM64 uses the newer RELA-style relocations rather than the older REL.
RELA relocations have an addend in the relocation struct, rather than
expecting the loader to read a value from the location to be updated.

While this is beneficial for ordinary program loading, it's problematic
for U-Boot because the location to be updated starts out with zero,
rather than a pre-relocation value.  Since we need to be able to run C
code before relocation, we need a tool to apply the relocations at
build time.

In theory this tool is applicable to other newer architectures (mainly
64-bit), but currently the only relocations it supports are for arm64,
and it assumes a 64-bit little-endian target.  If the latter limitation
is ever to be changed, we'll need a way to tell the tool what format
the image is in.  Eventually this may be replaced by a tool that uses
libelf or similar and operates directly on the ELF file.  I've written
some code for such an approach but libelf does not make it easy to poke
addresses by memory address (rather than by section), and I was
hesitant to write code to manually parse the program headers and do the
update outside of libelf (or to iterate over sections) -- especially
since it wouldn't get test coverage on things like binaries with
multiple PT_LOAD segments.  This should be good enough for now to let
the manual relocation stuff be removed from the arm64 patches.

NOTE: Please make sure R_AARCH64_RELATIVE is defined at system include
      files or manually defined. Otherwise, the rela relocation will
      not apply.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: David Feng <fenghua@phytium.com.cn>
---
 Makefile              |   12 ++++
 tools/Makefile        |    6 ++
 tools/relocate-rela.c |  185 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 203 insertions(+)
 create mode 100644 tools/relocate-rela.c

Patch

diff --git a/Makefile b/Makefile
index b09bfcc..5dd28a9 100644
--- a/Makefile
+++ b/Makefile
@@ -392,6 +392,17 @@  else
 BOARD_SIZE_CHECK =
 endif
 
+# Statically apply RELA-style relocations (currently arm64 only)
+ifneq ($(CONFIG_STATIC_RELA),)
+# $(1) is u-boot ELF, $(2) is u-boot bin, $(3) is text base
+DO_STATIC_RELA = \
+	start=$$($(NM) $(1) | grep __rel_dyn_start | cut -f 1 -d ' '); \
+	end=$$($(NM) $(1) | grep __rel_dyn_end | cut -f 1 -d ' '); \
+	$(obj)tools/relocate-rela $(2) $(3) $$start $$end
+else
+DO_STATIC_RELA =
+endif
+
 # Always append ALL so that arch config.mk's can add custom ones
 ALL-y += $(obj)u-boot.srec $(obj)u-boot.bin $(obj)System.map
 
@@ -431,6 +442,7 @@  $(obj)u-boot.srec:	$(obj)u-boot
 
 $(obj)u-boot.bin:	$(obj)u-boot
 		$(OBJCOPY) ${OBJCFLAGS} -O binary $< $@
+		$(call DO_STATIC_RELA,$<,$@,$(CONFIG_SYS_TEXT_BASE))
 		$(BOARD_SIZE_CHECK)
 
 $(obj)u-boot.ldr:	$(obj)u-boot
diff --git a/tools/Makefile b/tools/Makefile
index c36cde2..a5eb85e 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -59,6 +59,7 @@  BIN_FILES-$(CONFIG_NETCONSOLE) += ncb$(SFX)
 BIN_FILES-$(CONFIG_SHA1_CHECK_UB_IMG) += ubsha1$(SFX)
 BIN_FILES-$(CONFIG_KIRKWOOD) += kwboot$(SFX)
 BIN_FILES-y += proftool(SFX)
+BIN_FILES-$(CONFIG_STATIC_RELA) += relocate-rela$(SFX)
 
 # Source files which exist outside the tools directory
 EXT_OBJ_FILES-$(CONFIG_BUILD_ENVCRC) += common/env_embedded.o
@@ -84,6 +85,7 @@  NOPED_OBJ_FILES-y += os_support.o
 NOPED_OBJ_FILES-y += pblimage.o
 NOPED_OBJ_FILES-y += proftool.o
 NOPED_OBJ_FILES-y += ublimage.o
+NOPED_OBJ_FILES-y += relocate-rela.o
 OBJ_FILES-$(CONFIG_BUILD_ENVCRC) += envcrc.o
 OBJ_FILES-$(CONFIG_CMD_LOADS) += img2srec.o
 OBJ_FILES-$(CONFIG_CMD_NET) += gen_eth_addr.o
@@ -250,6 +252,10 @@  $(obj)kwboot$(SFX): $(obj)kwboot.o
 	$(HOSTCC) $(HOSTCFLAGS) $(HOSTLDFLAGS) -o $@ $^
 	$(HOSTSTRIP) $@
 
+$(obj)relocate-rela$(SFX): $(obj)relocate-rela.o
+	$(HOSTCC) $(HOSTCFLAGS) $(HOSTLDFLAGS) -o $@ $^
+	$(HOSTSTRIP) $@
+
 # Some of the tool objects need to be accessed from outside the tools directory
 $(obj)%.o: $(SRCTREE)/common/%.c
 	$(HOSTCC) -g $(HOSTCFLAGS_NOPED) -c -o $@ $<
diff --git a/tools/relocate-rela.c b/tools/relocate-rela.c
new file mode 100644
index 0000000..47afe0b
--- /dev/null
+++ b/tools/relocate-rela.c
@@ -0,0 +1,185 @@ 
+/*
+ * 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>
+
+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) % 24) {
+		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;
+}