[PATCH] Support for booting ELF images.
Owen Kirby
osk at exegin.com
Thu Jun 26 16:09:35 PDT 2014
I had not seen that patch series. It doesn't seem to have been checked
in, are you still working on it? kexec seems like a really fancy method
of loading the images, but it seems like quite a large patch set just
to support another image format. I guess this means that kexec would
need to be added for any other architectures that want to boot from an
ELF image.
I'm afraid I am guilty as charged of following the U-boot practice,
that's where I got the initial idea from, I'll look at reworking my
changes to use bootm instead.
Thanks,
Owen
On 14-06-26 03:06 PM, Antony Pavlov wrote:
> On Thu, 26 Jun 2014 14:11:32 -0700
> Owen Kirby <osk at exegin.com> wrote:
>
> Have you seen the '[RFC 00/10] MIPS: use kexec to load ELF linux images' series?
> http://lists.infradead.org/pipermail/barebox/2014-April/018651.html
>
> This series is kexec-based so it has relocator.
> The relocator make it possible to load ELF files that overlap current barebox adresses.
>
> Also there is no need to add new 'bootelf' command for new file format support.
> Adding new command for every new file format or new hardware interface is vicious U-boot practice.
> In barebox we already have the 'filetype' mechanism for supporting new file formats, so
> we can load ELF files using conventional 'bootm' command.
>
>> 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
>>
>>
>>
>> _______________________________________________
>> barebox mailing list
>> barebox at lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/barebox
>
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