Re: [PATCH] Support for booting ELF images.

[Antony Pavlov <antonynpavlov@gmail.com>]

On Thu, 26 Jun 2014 16:09:35 -0700
Owen Kirby <osk@exegin.com> wrote:

> 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 

Yes, my kexec series have not been checked in.
I can fix it this weekend.

The main problem of my series is that it's a MIPS series but barebox is essentially a ARM bootloader.
It seems that I have to add kexec ARM support :)

Which hardware platform do you use?

> of loading  the images, but it seems like quite a large patch set just 
> to support another image format.

My series consist of three parts:

  * MIPS cache memory stuff (patches 1-4);
  * common (not ELF) kexec code (patches 5-6);
  * common ELF support (patches 7-8);
  * MIPS ELF support (patch 9);
  * MIPS malta machine-specific stuff (patch 10).

So only patches 7-9 are actually used to support ELF 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.

It uses relocator so somebody has to port kexec relocator code from linux kernel
to use barebox kexec on another architecture.

I know how to run linux on qemu-versatile virtual hardware so I can port ARM kexec stuff.
 
> 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@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@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@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@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@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@lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/barebox
> >
> 


-- 
-- 
Best regards,
  Antony Pavlov

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