[PATCH] Support for booting ELF images.
Owen Kirby
osk at exegin.com
Thu Jun 26 14:11:32 PDT 2014
>From 1edc77c7b960d5b42ac3c03000ac5063018195f9 Mon Sep 17 00:00:00 2001
From: Owen Kirby <osk at exegin.com>
Date: Thu, 26 Jun 2014 13:40:06 -0700
Subject: [PATCH] Support for booting ELF images.
This patch adds a bootelf command to load and execute OS kernels from the ELF format.
Signed-off-by: Owen Kirby <osk at exegin.com>
---
commands/Kconfig | 7 ++
commands/Makefile | 1 +
commands/bootelf.c | 112 ++++++++++++++++++++++++++
common/Kconfig | 3 +
common/Makefile | 1 +
common/elf.c | 222 ++++++++++++++++++++++++++++++++++++++++++++++++++++
common/filetype.c | 3 +
include/elf.h | 4 +
include/filetype.h | 1 +
9 files changed, 354 insertions(+)
create mode 100644 commands/bootelf.c
create mode 100644 common/elf.c
diff --git a/commands/Kconfig b/commands/Kconfig
index cc014f3..c4e4649 100644
--- a/commands/Kconfig
+++ b/commands/Kconfig
@@ -507,6 +507,13 @@ config CMD_BOOTU
compile in the 'bootu' command to start raw (uncompressed)
Linux images
+config CMD_BOOTELF
+ select ELF
+ tristate
+ prompt "elf"
+ help
+ compile the 'bootelf' command to start ELF images
+
config FLEXIBLE_BOOTARGS
bool
prompt "flexible Linux bootargs generation"
diff --git a/commands/Makefile b/commands/Makefile
index e463031..fd57811 100644
--- a/commands/Makefile
+++ b/commands/Makefile
@@ -1,5 +1,6 @@
obj-$(CONFIG_STDDEV) += stddev.o
obj-$(CONFIG_CMD_BOOTM) += bootm.o
+obj-$(CONFIG_CMD_BOOTELF) += bootelf.o
obj-$(CONFIG_CMD_UIMAGE) += uimage.o
obj-$(CONFIG_CMD_LINUX16) += linux16.o
obj-$(CONFIG_CMD_LOADB) += loadb.o
diff --git a/commands/bootelf.c b/commands/bootelf.c
new file mode 100644
index 0000000..dc38b9e
--- /dev/null
+++ b/commands/bootelf.c
@@ -0,0 +1,112 @@
+/*
+ * bootelf.c - ELF booting code
+ *
+ * Copyright (c) 2014 Owen Kirby <osk at exegin.com>, Exegin Technologies Limited
+ *
+ * partly based on U-Boot ELF code.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * 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.
+ */
+#include <common.h>
+#include <command.h>
+#include <malloc.h>
+#include <fcntl.h>
+#include <fs.h>
+#include <elf.h>
+
+static int do_readelf(int argc, char *argv[])
+{
+ void *hdr;
+ int fd;
+
+ if (argc < 2)
+ return COMMAND_ERROR_USAGE;
+
+ fd = open(argv[1], O_RDONLY);
+ if (fd < 0) {
+ printf("could not open: %s\n", errno_str());
+ return 1;
+ }
+ hdr = elf_load_header(fd);
+ if (!hdr) {
+ close(fd);
+ return 1;
+ }
+ elf_print_header(hdr);
+ free(hdr);
+ close(fd);
+ return 0;
+}
+
+BAREBOX_CMD_START(readelf)
+ .cmd = do_readelf,
+ .usage = "Read an ELF image header",
+BAREBOX_CMD_END
+
+static int do_bootelf(int argc, char *argv[])
+{
+ void *hdr;
+ void *addr;
+ int (*func)(int argc, char *argv[]);
+ int fd;
+
+ if (argc < 2)
+ return COMMAND_ERROR_USAGE;
+
+ fd = open(argv[1], O_RDONLY);
+ if (fd < 0) {
+ printf("could not open: %s\n", errno_str());
+ return 1;
+ }
+
+ /* Print the ELF header for the user. */
+ hdr = elf_load_header(fd);
+ if (!hdr) {
+ close(fd);
+ return 1;
+ }
+ elf_print_header(hdr);
+ free(hdr);
+
+ /* Load the ELF sections. */
+ addr = elf_load_sections(fd);
+ if (!addr) {
+ close(fd);
+ return 1;
+ }
+
+ /* Launch the application */
+ printf("## Starting application at 0x%p ...\n", addr);
+ console_flush();
+ func = addr;
+ shutdown_barebox();
+
+ if (do_execute)
+ do_execute(func, argc - 1, &argv[1]);
+ else
+ func(argc - 1, &argv[1]);
+
+ /*
+ * The application returned. Since we have shutdown barebox and
+ * we know nothing about the state of the cpu/memory we can't
+ * do anything here.
+ */
+ while (1);
+ return 0;
+}
+
+BAREBOX_CMD_START(bootelf)
+ .cmd = do_bootelf,
+ .usage = "Boot an ELF image",
+BAREBOX_CMD_END
+
diff --git a/common/Kconfig b/common/Kconfig
index 0031cc8..0d22a58 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -53,6 +53,9 @@ config UIMAGE
select CRC32
bool
+config ELF
+ bool
+
config GLOBALVAR
bool
diff --git a/common/Makefile b/common/Makefile
index 204241c..9decc96 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_CONSOLE_FULL) += console.o
obj-$(CONFIG_CONSOLE_SIMPLE) += console_simple.o
obj-$(CONFIG_DIGEST) += digest.o
obj-$(CONFIG_DDR_SPD) += ddr_spd.o
+obj-$(CONFIG_ELF) += elf.o
obj-$(CONFIG_ENV_HANDLING) += environment.o
obj-$(CONFIG_ENVIRONMENT_VARIABLES) += env.o
obj-$(CONFIG_FILETYPE) += filetype.o
diff --git a/common/elf.c b/common/elf.c
new file mode 100644
index 0000000..1383ccc
--- /dev/null
+++ b/common/elf.c
@@ -0,0 +1,222 @@
+/*
+ * elf.c - ELF handling code
+ *
+ * Copyright (c) 2014 Owen Kirby <osk at exegin.com>, Exegin Technologies Limited
+ *
+ * partly based on U-Boot ELF code.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * 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.
+ */
+#include <common.h>
+#include <malloc.h>
+#include <fcntl.h>
+#include <fs.h>
+#include <elf.h>
+
+const char *elf_types[] = {
+ [ET_NONE] = "None",
+ [ET_REL] = "Relocatable",
+ [ET_EXEC] = "Executable",
+ [ET_DYN] = "Dynamic",
+ [ET_CORE] = "Core Dump",
+};
+
+void *elf_load_header(int fd)
+{
+ unsigned char ident[EI_NIDENT];
+
+ if ((lseek(fd, 0, SEEK_SET) < 0) || (read(fd, ident, sizeof(ident)) < 0)) {
+ printf("could not read ident header: %s\n", errno_str());
+ return NULL;
+ }
+ /* Ensure we find the ELF magic number. */
+ if (strncmp(ident, ELFMAG, SELFMAG)) {
+ printf("Bad Magic Number\n");
+ return NULL;
+ }
+
+ /* Read the ELF32 header. */
+ if (ident[EI_CLASS] == ELFCLASS32) {
+ Elf32_Ehdr *hdr = xzalloc(sizeof(Elf32_Ehdr));
+ memcpy(hdr->e_ident, ident, EI_NIDENT);
+ if (read(fd, &hdr->e_type, sizeof(*hdr) - EI_NIDENT) >= 0) return hdr;
+ printf("could not read ELF header: %s\n", errno_str());
+ free(hdr);
+ return NULL;
+ }
+ if (ident[EI_CLASS] == ELFCLASS64) {
+ Elf64_Ehdr *hdr = xzalloc(sizeof(Elf64_Ehdr));
+ memcpy(hdr->e_ident, ident, EI_NIDENT);
+ if (read(fd, &hdr->e_type, sizeof(*hdr) - EI_NIDENT) >= 0) return hdr;
+ printf("could not read ELF header: %s\n", errno_str());
+ free(hdr);
+ return NULL;
+ }
+ printf("Unknown ELF image class\n");
+ return NULL;
+} /* elf_load_header */
+EXPORT_SYMBOL(elf_load_header);
+
+#define ELF_FMT " %-16s"
+
+/* A rough clone of readelf for debugging and stuff. */
+void elf_print_header(const void *hdr)
+{
+ const unsigned char *ident = hdr;
+ int i;
+
+ /* Ensure we find the ELF magic number. */
+ if (strncmp(ident, ELFMAG, SELFMAG)) {
+ printf("Bad Magic Number\n");
+ return;
+ }
+ printf(" Magic:");
+ for (i=0; i<EI_NIDENT; i++) printf(" %02x", ident[i]);
+ printf("\n");
+
+ /* Print the rest of the ident string. */
+ switch (ident[EI_CLASS]) {
+ case ELFCLASSNONE: printf(ELF_FMT "%s\n", "Class:", "None"); break;
+ case ELFCLASS32: printf(ELF_FMT "%s\n", "Class:", "ELF32"); break;
+ case ELFCLASS64: printf(ELF_FMT "%s\n", "Class:", "ELF64"); break;
+ default: printf(ELF_FMT "%s\n", "Class:", "Invalid"); break;
+ } /* switch */
+ switch (ident[EI_DATA]) {
+ case ELFDATANONE: printf(ELF_FMT "%s\n", "Data:", "None"); break;
+ case ELFDATA2LSB: printf(ELF_FMT "%s\n", "Data:", "2's compliment, litte endian"); break;
+ case ELFDATA2MSB: printf(ELF_FMT "%s\n", "Data:", "2's compliment, big endian"); break;
+ default: printf(ELF_FMT "%s\n", "Data:", "Invalid"); break;
+ } /* switch */
+ printf(ELF_FMT "0x%x\n", "Version:", ident[EI_VERSION]);
+ /* TODO: OS/ABI */
+
+ if (ident[EI_CLASS] == ELFCLASS32) {
+ const Elf32_Ehdr *elf32 = (const Elf32_Ehdr *)hdr;
+ if (elf32->e_type <= ARRAY_SIZE(elf_types))
+ printf(ELF_FMT "%s\n", "Type:", elf_types[elf32->e_type]);
+ else
+ printf(ELF_FMT "0x%x\n", "Type:", elf32->e_type);
+ printf(ELF_FMT "0x%x\n", "Machine:", elf32->e_machine);
+ printf(ELF_FMT "0x%x\n", "Version:", elf32->e_version);
+ printf(ELF_FMT "0x%lx\n", "Entry point:", (unsigned long)elf32->e_entry);
+ printf(ELF_FMT "0x%08x\n", "Flags:", elf32->e_flags);
+ }
+ else if (ident[EI_CLASS] == ELFCLASS64) {
+ const Elf64_Ehdr *elf64 = (const Elf64_Ehdr *)hdr;
+ if (elf64->e_type <= ARRAY_SIZE(elf_types))
+ printf(ELF_FMT "%s\n", "Type:", elf_types[elf64->e_type]);
+ else
+ printf(ELF_FMT "0x%x\n", "Type:", elf64->e_type);
+ printf(ELF_FMT "0x%x\n", "Machine:", elf64->e_machine);
+ printf(ELF_FMT "0x%x\n", "Version:", elf64->e_version);
+ printf(ELF_FMT "0x%llx\n", "Entry point:", (unsigned long long)elf64->e_entry);
+ printf(ELF_FMT "0x%08x\n", "Flags:", elf64->e_flags);
+ }
+ /* TODO: Print the section/program header offsets. */
+} /* elf_print_header */
+EXPORT_SYMBOL(elf_print_header);
+
+static void *elf32_load_sections(int fd, Elf32_Ehdr *hdr)
+{
+ unsigned long off;
+ unsigned char *strtab = NULL;
+ size_t strtabsz = 0;
+ Elf32_Shdr shdr;
+ int i;
+
+ /* We can only load executable images. */
+ if (hdr->e_type != ET_EXEC) {
+ printf("ELF image is not executable\n");
+ return NULL;
+ }
+
+ /* Find the string table from among the section headers. */
+ off = hdr->e_shoff + (hdr->e_shstrndx * sizeof(shdr));
+ if ((lseek(fd, off, SEEK_SET) < 0) || (read(fd, &shdr, sizeof(shdr)) < 0)) {
+ printf("could not read string section header: %s\n", errno_str());
+ return NULL;
+ }
+ if ((shdr.sh_type == SHT_STRTAB) && (shdr.sh_size)) {
+ strtabsz = shdr.sh_size;
+ strtab = xzalloc(shdr.sh_size);
+ if (!strtab) {
+ printf("could not allocate memory for string table\n");
+ return NULL;
+ }
+ if ((lseek(fd, shdr.sh_offset, SEEK_SET) < 0) || (read(fd, strtab, shdr.sh_size) < 0)) {
+ printf("could not read string table section: %s\n", errno_str());
+ free(strtab);
+ return NULL;
+ }
+ }
+
+ /* Load the program sections. */
+ for (i = 0; i < hdr->e_shnum; i++) {
+ /* Read the next section header */
+ off = hdr->e_shoff + (i * sizeof(shdr));
+ if ((lseek(fd, off, SEEK_SET) < 0) || (read(fd, &shdr, sizeof(shdr)) < 0)) {
+ printf("could not read section header: %s\n", errno_str());
+ free(strtab);
+ return NULL;
+ }
+ /* Ignore unallocated or empty sections. */
+ if (!(shdr.sh_flags & SHF_ALLOC)) continue;
+ if (!shdr.sh_addr || !shdr.sh_size) continue;
+
+ /* Inform the user. */
+ if (strtab) {
+ printf("%sing %s @ 0x%08lx (%ld bytes)\n",
+ (shdr.sh_type == SHT_NOBITS) ? "Clear" : "Load",
+ &strtab[shdr.sh_name],
+ (unsigned long) shdr.sh_addr,
+ (long) shdr.sh_size);
+ }
+
+ /* Program the section. */
+ if (shdr.sh_type == SHT_NOBITS) {
+ memset((void *)shdr.sh_addr, 0, shdr.sh_size);
+ } else {
+ if ((lseek(fd, shdr.sh_offset, SEEK_SET) < 0) ||
+ (read(fd, (void *)shdr.sh_addr, shdr.sh_size) < 0)) {
+ printf("could not read section data: %s\n", errno_str());
+ free(strtab);
+ return NULL;
+ }
+ }
+ } /* for */
+
+ /* Success. */
+ free(strtab);
+ return (void *)hdr->e_entry;
+} /* elf32_load_sections */
+
+void *elf_load_sections(int fd)
+{
+ unsigned char *hdr;
+ void *entry;
+
+ /* Load the ELF header. */
+ hdr = elf_load_header(fd);
+ if (!hdr) return NULL;
+ if (hdr[EI_CLASS] == ELFCLASS32) {
+ entry = elf32_load_sections(fd, (Elf32_Ehdr *)hdr);
+ }
+ else {
+ printf("Unsupported ELF image class\n");
+ entry = NULL;
+ }
+ free(hdr);
+ return entry;
+} /* elf_load_sections */
+EXPORT_SYMBOL(elf_load_sections);
+
diff --git a/common/filetype.c b/common/filetype.c
index 0b5da30..0f46fda 100644
--- a/common/filetype.c
+++ b/common/filetype.c
@@ -52,6 +52,7 @@ static const struct filetype_str filetype_str[] = {
[filetype_ext] = { "ext filesystem", "ext" },
[filetype_gpt] = { "GUID Partition Table", "gpt" },
[filetype_bpk] = { "Binary PacKage", "bpk" },
+ [filetype_elf] = { "executable and linkable file", "elf" },
[filetype_barebox_env] = { "barebox environment file", "bbenv" },
};
@@ -227,6 +228,8 @@ enum filetype file_detect_type(const void *_buf, size_t bufsize)
return filetype_mips_barebox;
if (buf[0] == be32_to_cpu(0x534F4659))
return filetype_bpk;
+ if (strncmp(buf8, "\177ELF", 4) == 0)
+ return filetype_elf;
if (bufsize < 64)
return filetype_unknown;
diff --git a/include/elf.h b/include/elf.h
index 6d4addf..357814f 100644
--- a/include/elf.h
+++ b/include/elf.h
@@ -397,4 +397,8 @@ static inline void arch_write_notes(struct file *file) { }
#define ELF_CORE_WRITE_EXTRA_NOTES arch_write_notes(file)
#endif /* ARCH_HAVE_EXTRA_ELF_NOTES */
+void *elf_load_header(int fd);
+void elf_print_header(const void *hdr);
+void *elf_load_sections(int fd);
+
#endif /* _LINUX_ELF_H */
diff --git a/include/filetype.h b/include/filetype.h
index c20a4f9..c4f776f 100644
--- a/include/filetype.h
+++ b/include/filetype.h
@@ -30,6 +30,7 @@ enum filetype {
filetype_ubifs,
filetype_bpk,
filetype_barebox_env,
+ filetype_elf,
filetype_max,
};
--
1.7.9.5
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