cbfstool: extract rmodules as ELFs properly

With the previous ELF stage extract support the resulting
ELF files wouldn't handle rmodules correctly in that the
rmodule header as well as the relocations were a part of
the program proper. Instead, try an initial pass at
converting the stage as if it was an rmodule first. If it
doesn't work fall back on the normal ELF extraction.

TEST=Pulled an rmodule out of Chrome OS shellball. Manually
     matched up the metadata and relocations.

Change-Id: Iaf222f92d145116ca4dfaa955fb7278e583161f2
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/12222
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

3 files changed, 190 insertions, 0 deletions

diff --git a/util/cbfstool/cbfs_image.c b/util/cbfstool/cbfs_image.c
index bd432d4..c23a6e8 100644
--- a/util/cbfstool/cbfs_image.c
+++ b/util/cbfstool/cbfs_image.c
@@ -28,6 +28,7 @@
 #include "common.h"
 #include "cbfs_image.h"
 #include "elfparsing.h"
+#include "rmodule.h"
 
 /* Even though the file-adding functions---cbfs_add_entry() and
  * cbfs_add_entry_at()---perform their sizing checks against the beginning of
@@ -770,6 +771,7 @@ static int cbfs_stage_make_elf(struct buffer *buff, uint32_t arch)
 	struct elf_writer *ew;
 	struct buffer elf_out;
 	size_t empty_sz;
+	int rmod_ret;
 
 	if (cbfs_stage_decompress(&stage, buff)) {
 		ERROR("Failed to decompress stage.\n");
@@ -781,6 +783,17 @@ static int cbfs_stage_make_elf(struct buffer *buff, uint32_t arch)
 
 	ehdr.e_entry = stage.entry;
 
+	/* Attempt rmodule translation first. */
+	rmod_ret = rmodule_stage_to_elf(&ehdr, buff);
+
+	if (rmod_ret < 0) {
+		ERROR("rmodule parsing failed\n");
+		return -1;
+	} else if (rmod_ret == 0)
+		return 0;
+
+	/* Rmodule couldn't do anything with the data. Continue on with SELF. */
+
 	ew = elf_writer_init(&ehdr);
 	if (ew == NULL) {
 		ERROR("Unable to init ELF writer.\n");
diff --git a/util/cbfstool/rmodule.c b/util/cbfstool/rmodule.c
index 986ba62..96c834f 100644
--- a/util/cbfstool/rmodule.c
+++ b/util/cbfstool/rmodule.c
@@ -677,3 +677,173 @@ out:
 	rmodule_cleanup(&ctx);
 	return ret;
 }
+
+static void rmod_deserialize(struct rmodule_header *rmod, struct buffer *buff,
+				struct xdr *xdr)
+{
+	rmod->magic = xdr->get16(buff);
+	rmod->version = xdr->get8(buff);
+	rmod->type = xdr->get8(buff);
+	rmod->payload_begin_offset = xdr->get32(buff);
+	rmod->payload_end_offset = xdr->get32(buff);
+	rmod->relocations_begin_offset = xdr->get32(buff);
+	rmod->relocations_end_offset = xdr->get32(buff);
+	rmod->module_link_start_address = xdr->get32(buff);
+	rmod->module_program_size = xdr->get32(buff);
+	rmod->module_entry_point = xdr->get32(buff);
+	rmod->parameters_begin = xdr->get32(buff);
+	rmod->parameters_end = xdr->get32(buff);
+	rmod->bss_begin = xdr->get32(buff);
+	rmod->bss_end = xdr->get32(buff);
+	rmod->padding[0] = xdr->get32(buff);
+	rmod->padding[1] = xdr->get32(buff);
+	rmod->padding[2] = xdr->get32(buff);
+	rmod->padding[3] = xdr->get32(buff);
+}
+
+int rmodule_stage_to_elf(Elf64_Ehdr *ehdr, struct buffer *buff)
+{
+	struct buffer reader;
+	struct buffer elf_out;
+	struct rmodule_header rmod;
+	struct xdr *xdr;
+	struct elf_writer *ew;
+	Elf64_Shdr shdr;
+	int bit64;
+	size_t payload_sz;
+	const char *section_name = ".program";
+	const size_t input_sz = buffer_size(buff);
+
+	buffer_clone(&reader, buff);
+
+	xdr = (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) ? &xdr_be : &xdr_le;
+	bit64 = ehdr->e_ident[EI_CLASS] == ELFCLASS64;
+
+	rmod_deserialize(&rmod, &reader, xdr);
+
+	/* Indicate that file is not an rmodule if initial checks fail. */
+	if (rmod.magic != RMODULE_MAGIC)
+		return 1;
+	if (rmod.version != RMODULE_VERSION_1)
+		return 1;
+
+	if (rmod.payload_begin_offset > input_sz ||
+	    rmod.payload_end_offset > input_sz ||
+	    rmod.relocations_begin_offset > input_sz ||
+	    rmod.relocations_end_offset > input_sz) {
+		ERROR("Rmodule fields out of bounds.\n");
+		return -1;
+	}
+
+	ehdr->e_entry = rmod.module_entry_point;
+	ew = elf_writer_init(ehdr);
+
+	if (ew == NULL)
+		return -1;
+
+	payload_sz = rmod.payload_end_offset - rmod.payload_begin_offset;
+	memset(&shdr, 0, sizeof(shdr));
+	shdr.sh_type = SHT_PROGBITS;
+	shdr.sh_flags = SHF_WRITE | SHF_ALLOC | SHF_EXECINSTR;
+	shdr.sh_addr = rmod.module_link_start_address;
+	shdr.sh_size = payload_sz;
+	buffer_splice(&reader, buff, rmod.payload_begin_offset, payload_sz);
+
+	if (elf_writer_add_section(ew, &shdr, &reader, section_name)) {
+		ERROR("Unable to add ELF section: %s\n", section_name);
+		elf_writer_destroy(ew);
+		return -1;
+	}
+
+	if (payload_sz != rmod.module_program_size) {
+		struct buffer b;
+
+		buffer_init(&b, NULL, NULL, 0);
+		memset(&shdr, 0, sizeof(shdr));
+		shdr.sh_type = SHT_NOBITS;
+		shdr.sh_flags = SHF_WRITE | SHF_ALLOC;
+		shdr.sh_addr = rmod.module_link_start_address + payload_sz;
+		shdr.sh_size = rmod.module_program_size - payload_sz;
+		if (elf_writer_add_section(ew, &shdr, &b, ".empty")) {
+			ERROR("Unable to add ELF section: .empty\n");
+			elf_writer_destroy(ew);
+			return -1;
+		}
+	}
+
+	/* Provide a section symbol so the relcoations can reference that. */
+	if (elf_writer_add_symbol(ew, section_name, section_name, shdr.sh_addr,
+					0, STB_LOCAL, STT_SECTION)) {
+		ERROR("Unable to add section symbol to ELF.\n");
+		elf_writer_destroy(ew);
+		return -1;
+	}
+
+	/* Add symbols for the parameters if they are non-zero. */
+	if (rmod.parameters_begin != rmod.parameters_end) {
+		int ret = 0;
+
+		ret |= elf_writer_add_symbol(ew, "_rmodule_params",
+						section_name,
+						rmod.parameters_begin, 0,
+						STB_GLOBAL, STT_NOTYPE);
+		ret |= elf_writer_add_symbol(ew, "_ermodule_params",
+						section_name,
+						rmod.parameters_end, 0,
+						STB_GLOBAL, STT_NOTYPE);
+
+		if (ret != 0) {
+			ERROR("Unable to add module params symbols to ELF\n");
+			elf_writer_destroy(ew);
+			return -1;
+		}
+	}
+
+	if (elf_writer_add_symbol(ew, "_bss", section_name, rmod.bss_begin, 0,
+					STB_GLOBAL, STT_NOTYPE) ||
+	    elf_writer_add_symbol(ew, "_ebss", section_name, rmod.bss_end, 0,
+					STB_GLOBAL, STT_NOTYPE)) {
+		ERROR("Unable to add bss symbols to ELF\n");
+		elf_writer_destroy(ew);
+		return -1;
+	}
+
+	ssize_t relocs_sz = rmod.relocations_end_offset;
+	relocs_sz -= rmod.relocations_begin_offset;
+	buffer_splice(&reader, buff, rmod.relocations_begin_offset, relocs_sz);
+	while (relocs_sz > 0) {
+		Elf64_Addr addr;
+
+		if (bit64) {
+			relocs_sz -= sizeof(Elf64_Addr);
+			addr = xdr->get64(&reader);
+		} else {
+			relocs_sz -= sizeof(Elf32_Addr);
+			addr = xdr->get32(&reader);
+		}
+
+		/* Skip any relocations that are below the link address. */
+		if (addr < rmod.module_link_start_address)
+			continue;
+
+		if (elf_writer_add_rel(ew, section_name, addr)) {
+			ERROR("Relocation addition failure.\n");
+			elf_writer_destroy(ew);
+			return -1;
+		}
+	}
+
+	if (elf_writer_serialize(ew, &elf_out)) {
+		ERROR("ELF writer serialize failure.\n");
+		elf_writer_destroy(ew);
+		return -1;
+	}
+
+	elf_writer_destroy(ew);
+
+	/* Flip buffer with the created ELF one. */
+	buffer_delete(buff);
+	*buff = elf_out;
+
+	return 0;
+}
diff --git a/util/cbfstool/rmodule.h b/util/cbfstool/rmodule.h
index 9a65677..fa71765 100644
--- a/util/cbfstool/rmodule.h
+++ b/util/cbfstool/rmodule.h
@@ -88,4 +88,11 @@ int rmodule_collect_relocations(struct rmod_context *c, struct reloc_filter *f);
 /* Clean up the memory consumed by the rmdoule context. */
 void rmodule_cleanup(struct rmod_context *ctx);
 
+/*
+ * Create an ELF file from the passed in rmodule in the buffer. The buffer
+ * contents will be replaced with an ELF file. Returns 1 if buff doesn't
+ * contain an rmodule and < 0 on failure, 0 on success.
+ */
+int rmodule_stage_to_elf(Elf64_Ehdr *ehdr, struct buffer *buff);
+
 #endif /* TOOL_RMODULE_H */