Add section header parsing and use it in the mk-payload step
This completes the improvements to the ELF file parsing code. We can
now parse section headers too, across all 4 combinations of word size
and endianness. I had hoped to completely remove the use of htonl
until I found it in cbfs_image.c. That's a battle for another day.
There's now a handy macro to create magic numbers in host byte order.
I'm using it for all the PAYLOAD_SEGMENT_* constants and maybe
we can use it for the others too, but this is sensitive code and
I'd rather change one thing at a time.
To maximize the ease of use for users, elf parsing is accomplished with
just one function:
int
elf_headers(const struct buffer *pinput,
Elf64_Ehdr *ehdr,
Elf64_Phdr **pphdr,
Elf64_Shdr **pshdr)
which requires the ehdr and pphdr pointers to be non-NULL, but allows
the pshdr to be NULL. If pshdr is NULL, the code will not try to read
in section headers.
To satisfy our powerful scripts, I had to remove the ^M from an unrelated
microcode file.
BUG=None
TEST=Build a peppy image (known to boot) with old and new versions and verify they are bit-for-bit the same. This was also fully tested across all chromebooks for building and booting and running chromeos.
BRANCH=None
Change-Id: I54dad887d922428b6175fdb6a9cdfadd8a6bb889
Signed-off-by: Ronald G. Minnich <rminnich@google.com>
Reviewed-on: https://chromium-review.googlesource.com/181272
Reviewed-by: Ronald Minnich <rminnich@chromium.org>
Commit-Queue: Ronald Minnich <rminnich@chromium.org>
Tested-by: Ronald Minnich <rminnich@chromium.org>
Signed-off-by: Ronald G. Minnich <rminnich@google.com>
Reviewed-on: http://review.coreboot.org/5098
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
diff --git a/util/cbfstool/elfheaders.c b/util/cbfstool/elfheaders.c
new file mode 100644
index 0000000..fd7a1a1
--- /dev/null
+++ b/util/cbfstool/elfheaders.c
@@ -0,0 +1,343 @@
+/*
+ * elf header parsing.
+ *
+ * Copyright (C) 2013 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA, 02110-1301 USA
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "elf.h"
+#include "common.h"
+#include "cbfs.h"
+
+/*
+ * Short form: this is complicated, but we've tried making it simple
+ * and we keep hitting problems with our ELF parsing.
+ *
+ * The ELF parsing situation has always been a bit tricky. In fact,
+ * we (and most others) have been getting it wrong in small ways for
+ * years. Recently this has caused real trouble for the ARM V8 build.
+ * In this file we attempt to finally get it right for all variations
+ * of endian-ness and word size and target architectures and
+ * architectures we might get run on. Phew!. To do this we borrow a
+ * page from the FreeBSD NFS xdr model (see elf_ehdr and elf_phdr),
+ * the Plan 9 endianness functions (see xdr.c), and Go interfaces (see
+ * how we use buffer structs in this file). This ends up being a bit
+ * wordy at the lowest level, but greatly simplifies the elf parsing
+ * code and removes a common source of bugs, namely, forgetting to
+ * flip type endianness when referencing a struct member.
+ *
+ * ELF files can have four combinations of data layout: 32/64, and
+ * big/little endian. Further, to add to the fun, depending on the
+ * word size, the size of the ELF structs varies. The coreboot SELF
+ * format is simpler in theory: it's supposed to be always BE, and the
+ * various struct members allow room for growth: the entry point is
+ * always 64 bits, for example, so the size of a SELF struct is
+ * constant, regardless of target architecture word size. Hence, we
+ * need to do some transformation of the ELF files.
+ *
+ * A given architecture, realistically, only supports one of the four
+ * combinations at a time as the 'native' format. Hence, our code has
+ * been sprinkled with every variation of [nh]to[hn][sll] over the
+ * years. We've never quite gotten it all right, however, and a quick
+ * pass over this code revealed another bug. It's all worked because,
+ * until now, all the working platforms that had CBFS were 32 LE. Even then,
+ * however, bugs crept in: we recently realized that we're not
+ * transforming the entry point to big format when we store into the
+ * SELF image.
+ *
+ * The problem is essentially an XDR operation:
+ * we have something in a foreign format and need to transform it.
+ * It's most like XDR because:
+ * 1) the byte order can be wrong
+ * 2) the word size can be wrong
+ * 3) the size of elements in the stream depends on the value
+ * of other elements in the stream
+ * it's not like XDR because:
+ * 1) the byte order can be right
+ * 2) the word size can be right
+ * 3) the struct members are all on a natural alignment
+ *
+ * Hence, this new approach. To cover word size issues, we *always*
+ * transform the two structs we care about, the file header and
+ * program header, into a native struct in the 64 bit format:
+ *
+ * [32,little] -> [Elf64_Ehdr, Elf64_Phdr]
+ * [64,little] -> [Elf64_Ehdr, Elf64_Phdr]
+ * [32,big] -> [Elf64_Ehdr, Elf64_Phdr]
+ * [64,big] -> [Elf64_Ehdr, Elf64_Phdr]
+ * Then we just use those structs, and all the need for inline ntoh* goes away,
+ * as well as all the chances for error.
+ * This works because all the SELF structs have fields large enough for
+ * the largest ELF 64 struct members, and all the Elf64 struct members
+ * are at least large enough for all ELF 32 struct members.
+ * We end up with one function to do all our ELF parsing, and two functions
+ * to transform the headers. For the put case, we also have
+ * XDR functions, and hopefully we'll never again spend 5 years with the
+ * wrong endian-ness on an output value :-)
+ * This should work for all word sizes and endianness we hope to target.
+ * I *really* don't want to be here for 128 bit addresses.
+ *
+ * The parse functions are called with a pointer to an input buffer
+ * struct. One might ask: are there enough bytes in the input buffer?
+ * We know there need to be at *least* sizeof(Elf32_Ehdr) +
+ * sizeof(Elf32_Phdr) bytes. Realistically, there has to be some data
+ * too. If we start to worry, though we have not in the past, we
+ * might apply the simple test: the input buffer needs to be at least
+ * sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr) bytes because, even if it's
+ * ELF 32, there's got to be *some* data! This is not theoretically
+ * accurate but it is actually good enough in practice. It allows the
+ * header transformation code to ignore the possibility of underrun.
+ *
+ * We also must accomodate different ELF files, and hence formats,
+ * in the same cbfs invocation. We might load a 64-bit payload
+ * on a 32-bit machine; we might even have a mixed armv7/armv8
+ * SOC or even a system with an x86/ARM!
+ *
+ * A possibly problematic (though unlikely to be so) assumption
+ * is that we expect the BIOS to remain in the lowest 32 bits
+ * of the physical address space. Since ARMV8 has standardized
+ * on that, and x86_64 also has, this seems a safe assumption.
+ *
+ * To repeat, ELF structs are different sizes because ELF struct
+ * members are different sizes, depending on values in the ELF file
+ * header. For this we use the functions defined in xdr.c, which
+ * consume bytes, convert the endianness, and advance the data pointer
+ * in the buffer struct.
+ */
+
+/* Get the ident array, so we can figure out
+ * endian-ness, word size, and in future other useful
+ * parameters
+ */
+static void
+elf_eident(struct buffer *input, Elf64_Ehdr *ehdr)
+{
+ memmove(ehdr->e_ident, input->data, sizeof(ehdr->e_ident));
+ input->data += sizeof(ehdr->e_ident);
+ input->size -= sizeof(ehdr->e_ident);
+}
+
+
+static void
+elf_ehdr(struct buffer *input, Elf64_Ehdr *ehdr, struct xdr *xdr, int bit64)
+{
+ ehdr->e_type = xdr->get16(input);
+ ehdr->e_machine = xdr->get16(input);
+ ehdr->e_version = xdr->get32(input);
+ if (bit64){
+ ehdr->e_entry = xdr->get64(input);
+ ehdr->e_phoff = xdr->get64(input);
+ ehdr->e_shoff = xdr->get64(input);
+ } else {
+ ehdr->e_entry = xdr->get32(input);
+ ehdr->e_phoff = xdr->get32(input);
+ ehdr->e_shoff = xdr->get32(input);
+ }
+ ehdr->e_flags = xdr->get32(input);
+ ehdr->e_ehsize = xdr->get16(input);
+ ehdr->e_phentsize = xdr->get16(input);
+ ehdr->e_phnum = xdr->get16(input);
+ ehdr->e_shentsize = xdr->get16(input);
+ ehdr->e_shnum = xdr->get16(input);
+ ehdr->e_shstrndx = xdr->get16(input);
+}
+
+static void
+elf_phdr(struct buffer *pinput, Elf64_Phdr *phdr,
+ int entsize, struct xdr *xdr, int bit64)
+{
+ /*
+ * The entsize need not be sizeof(*phdr).
+ * Hence, it is easier to keep a copy of the input,
+ * as the xdr functions may not advance the input
+ * pointer the full entsize; rather than get tricky
+ * we just advance it below.
+ */
+ struct buffer input = *pinput;
+ if (bit64){
+ phdr->p_type = xdr->get32(&input);
+ phdr->p_flags = xdr->get32(&input);
+ phdr->p_offset = xdr->get64(&input);
+ phdr->p_vaddr = xdr->get64(&input);
+ phdr->p_paddr = xdr->get64(&input);
+ phdr->p_filesz = xdr->get64(&input);
+ phdr->p_memsz = xdr->get64(&input);
+ phdr->p_align = xdr->get64(&input);
+ } else {
+ phdr->p_type = xdr->get32(&input);
+ phdr->p_offset = xdr->get32(&input);
+ phdr->p_vaddr = xdr->get32(&input);
+ phdr->p_paddr = xdr->get32(&input);
+ phdr->p_filesz = xdr->get32(&input);
+ phdr->p_memsz = xdr->get32(&input);
+ phdr->p_flags = xdr->get32(&input);
+ phdr->p_align = xdr->get32(&input);
+ }
+ pinput->size -= entsize;
+ pinput->data += entsize;
+}
+
+static void
+elf_shdr(struct buffer *pinput, Elf64_Shdr *shdr,
+ int entsize, struct xdr *xdr, int bit64)
+{
+ /*
+ * The entsize need not be sizeof(*shdr).
+ * Hence, it is easier to keep a copy of the input,
+ * as the xdr functions may not advance the input
+ * pointer the full entsize; rather than get tricky
+ * we just advance it below.
+ */
+ struct buffer input = *pinput;
+ if (bit64){
+ shdr->sh_name = xdr->get32(&input);
+ shdr->sh_type = xdr->get32(&input);
+ shdr->sh_flags = xdr->get64(&input);
+ shdr->sh_addr = xdr->get64(&input);
+ shdr->sh_offset = xdr->get64(&input);
+ shdr->sh_size= xdr->get64(&input);
+ shdr->sh_link = xdr->get32(&input);
+ shdr->sh_info = xdr->get32(&input);
+ shdr->sh_addralign = xdr->get64(&input);
+ shdr->sh_entsize = xdr->get64(&input);
+ } else {
+ shdr->sh_name = xdr->get32(&input);
+ shdr->sh_type = xdr->get32(&input);
+ shdr->sh_flags = xdr->get32(&input);
+ shdr->sh_addr = xdr->get32(&input);
+ shdr->sh_offset = xdr->get32(&input);
+ shdr->sh_size = xdr->get32(&input);
+ shdr->sh_link = xdr->get32(&input);
+ shdr->sh_info = xdr->get32(&input);
+ shdr->sh_addralign = xdr->get32(&input);
+ shdr->sh_entsize = xdr->get32(&input);
+ }
+ pinput->size -= entsize;
+ pinput->data += entsize;
+}
+
+/* Get the headers from the buffer.
+ * Return -1 in the event of an error.
+ * The section headers are optional; if NULL
+ * is passed in for pshdr they won't be parsed.
+ * We don't (yet) make payload parsing optional
+ * because we've never seen a use case.
+ */
+int
+elf_headers(const struct buffer *pinput,
+ Elf64_Ehdr *ehdr,
+ Elf64_Phdr **pphdr,
+ Elf64_Shdr **pshdr)
+{
+ int i;
+ struct xdr *xdr = &xdr_le;
+ int bit64 = 0;
+ struct buffer input = *(struct buffer *)pinput;
+ struct buffer phdr_buf;
+ struct buffer shdr_buf;
+ Elf64_Phdr *phdr;
+ Elf64_Shdr *shdr;
+
+ if (!iself((unsigned char *)pinput->data)) {
+ ERROR("The stage file is not in ELF format!\n");
+ return -1;
+ }
+
+ elf_eident(&input, ehdr);
+ bit64 = ehdr->e_ident[EI_CLASS] == ELFCLASS64;
+ /* Assume LE unless we are sure otherwise.
+ * We're not going to take on the task of
+ * fully validating the ELF file. That way
+ * lies madness.
+ */
+ if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
+ xdr = &xdr_be;
+
+ elf_ehdr(&input, ehdr, xdr, bit64);
+
+ // The tool may work in architecture-independent way.
+ if (arch != CBFS_ARCHITECTURE_UNKNOWN &&
+ !((ehdr->e_machine == EM_ARM) && (arch == CBFS_ARCHITECTURE_ARMV7)) &&
+ !((ehdr->e_machine == EM_386) && (arch == CBFS_ARCHITECTURE_X86))) {
+ ERROR("The stage file has the wrong architecture\n");
+ return -1;
+ }
+
+ if (pinput->size < ehdr->e_phoff){
+ ERROR("The program header offset is greater than "
+ "the remaining file size."
+ "%ld bytes left, program header offset is %ld \n",
+ pinput->size, ehdr->e_phoff);
+ return -1;
+ }
+ /* cons up an input buffer for the headers.
+ * Note that the program headers can be anywhere,
+ * per the ELF spec, You'd be surprised how many ELF
+ * readers miss this little detail.
+ */
+ phdr_buf.data = &pinput->data[ehdr->e_phoff];
+ phdr_buf.size = ehdr->e_phentsize * ehdr->e_phnum;
+ if (phdr_buf.size > (pinput->size - ehdr->e_phoff)){
+ ERROR("The file is not large enough for the program headers."
+ "%ld bytes left, %ld bytes of headers\n",
+ pinput->size - ehdr->e_phoff, phdr_buf.size);
+ return -1;
+ }
+ /* gather up all the phdrs.
+ * We do them all at once because there is more
+ * than one loop over all the phdrs.
+ */
+ phdr = calloc(sizeof(*phdr), ehdr->e_phnum);
+ for (i = 0; i < ehdr->e_phnum; i++)
+ elf_phdr(&phdr_buf, &phdr[i], ehdr->e_phentsize, xdr, bit64);
+ *pphdr = phdr;
+
+ if (!pshdr)
+ return 0;
+
+ if (pinput->size < ehdr->e_shoff){
+ ERROR("The section header offset is greater than "
+ "the remaining file size."
+ "%ld bytes left, program header offset is %ld \n",
+ pinput->size, ehdr->e_shoff);
+ return -1;
+ }
+ /* cons up an input buffer for the section headers.
+ * Note that the section headers can be anywhere,
+ * per the ELF spec, You'd be surprised how many ELF
+ * readers miss this little detail.
+ */
+ shdr_buf.data = &pinput->data[ehdr->e_shoff];
+ shdr_buf.size = ehdr->e_shentsize * ehdr->e_shnum;
+ if (shdr_buf.size > (pinput->size - ehdr->e_shoff)){
+ ERROR("The file is not large enough for the section headers."
+ "%ld bytes left, %ld bytes of headers\n",
+ pinput->size - ehdr->e_shoff, shdr_buf.size);
+ return -1;
+ }
+ /* gather up all the shdrs. */
+
+ shdr = calloc(sizeof(*shdr), ehdr->e_shnum);
+ for (i = 0; i < ehdr->e_shnum; i++)
+ elf_shdr(&shdr_buf, &shdr[i], ehdr->e_shentsize, xdr, bit64);
+ *pshdr = shdr;
+
+ return 0;
+}
+