lkml.org 
[lkml]   [2014]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 10/11] kexec: Support for loading ELF x86_64 images
    On Mon, Jan 27, 2014 at 01:57:50PM -0500, Vivek Goyal wrote:
    > This patch provides support for kexec for loading ELF x86_64 images. I have
    > tested it with loading vmlinux and it worked.

    Can you please enlighten me what the use case for ELF kernel images is? bzImage
    I understand but what produces ELF images?

    I see that kexec_file_load() can receive ELF segments too but why are we
    doing that?

    > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
    > ---
    > arch/x86/include/asm/kexec-elf.h | 11 ++
    > arch/x86/kernel/Makefile | 1 +
    > arch/x86/kernel/kexec-elf.c | 231 +++++++++++++++++++++++++++++++++++++
    > arch/x86/kernel/machine_kexec_64.c | 2 +
    > 4 files changed, 245 insertions(+)
    > create mode 100644 arch/x86/include/asm/kexec-elf.h
    > create mode 100644 arch/x86/kernel/kexec-elf.c
    >
    > diff --git a/arch/x86/include/asm/kexec-elf.h b/arch/x86/include/asm/kexec-elf.h
    > new file mode 100644
    > index 0000000..afef382
    > --- /dev/null
    > +++ b/arch/x86/include/asm/kexec-elf.h
    > @@ -0,0 +1,11 @@
    > +#ifndef _ASM_KEXEC_ELF_H
    > +#define _ASM_KEXEC_ELF_H
    > +
    > +extern int elf_x86_64_probe(const char *buf, unsigned long len);
    > +extern void *elf_x86_64_load(struct kimage *image, char *kernel,
    > + unsigned long kernel_len, char *initrd,
    > + unsigned long initrd_len, char *cmdline,
    > + unsigned long cmdline_len);
    > +extern int elf_x86_64_cleanup(struct kimage *image);
    > +
    > +#endif /* _ASM_KEXEC_ELF_H */
    > diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
    > index fa9981d..2d77de7 100644
    > --- a/arch/x86/kernel/Makefile
    > +++ b/arch/x86/kernel/Makefile
    > @@ -71,6 +71,7 @@ obj-$(CONFIG_KEXEC) += machine_kexec.o
    > obj-$(CONFIG_KEXEC) += machine_kexec_$(BITS).o
    > obj-$(CONFIG_KEXEC) += relocate_kernel_$(BITS).o crash.o
    > obj-$(CONFIG_KEXEC) += kexec-bzimage.o
    > +obj-$(CONFIG_KEXEC) += kexec-elf.o

    It looks like kexec could slowly grow its own dir now:

    arch/x86/kexec/

    or so.

    > obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o
    > obj-y += kprobes/
    > obj-$(CONFIG_MODULES) += module.o
    > diff --git a/arch/x86/kernel/kexec-elf.c b/arch/x86/kernel/kexec-elf.c
    > new file mode 100644
    > index 0000000..ff1017c
    > --- /dev/null
    > +++ b/arch/x86/kernel/kexec-elf.c
    > @@ -0,0 +1,231 @@
    > +#include <linux/string.h>
    > +#include <linux/printk.h>
    > +#include <linux/errno.h>
    > +#include <linux/slab.h>
    > +#include <linux/kexec.h>
    > +#include <linux/kernel.h>
    > +#include <linux/mm.h>
    > +
    > +#include <asm/bootparam.h>
    > +#include <asm/setup.h>
    > +
    > +#ifdef CONFIG_X86_64
    > +
    > +struct elf_x86_64_data {
    > + /*
    > + * Temporary buffer to hold bootparams buffer. This should be
    > + * freed once the bootparam segment has been loaded.
    > + */
    > + void *bootparams_buf;
    > +};
    > +
    > +int elf_x86_64_probe(const char *buf, unsigned long len)
    > +{
    > + int ret = -ENOEXEC;
    > + Elf_Ehdr *ehdr;
    > +
    > + if (len < sizeof(Elf_Ehdr)) {
    > + pr_debug("File is too short to be an ELF executable.\n");
    > + return ret;
    > + }
    > +
    > + ehdr = (Elf_Ehdr *)buf;
    > +
    > + if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0
    > + || ehdr->e_type != ET_EXEC || !elf_check_arch(ehdr)
    > + || ehdr->e_phentsize != sizeof(Elf_Phdr))
    > + return -ENOEXEC;
    > +
    > + if (ehdr->e_phoff >= len
    > + || (ehdr->e_phnum * sizeof(Elf_Phdr) > len - ehdr->e_phoff))
    > + return -ENOEXEC;
    > +
    > + /* I've got a bzImage */
    > + pr_debug("It's an elf_x86_64 image.\n");
    > + ret = 0;
    > +
    > + return ret;

    I think you can drop 'ret' here and return the error vals directly.

    > +}
    > +
    > +static int elf_exec_load(struct kimage *image, char *kernel)
    > +{
    > + Elf_Ehdr *ehdr;
    > + Elf_Phdr *phdrs;
    > + int i, ret;
    > + size_t filesz;
    > + char *buffer;
    > +
    > + ehdr = (Elf_Ehdr *)kernel;
    > + phdrs = (void *)ehdr + ehdr->e_phoff;
    > +
    > + for (i = 0; i < ehdr->e_phnum; i++) {
    > + if (phdrs[i].p_type != PT_LOAD)
    > + continue;

    newline

    > + filesz = phdrs[i].p_filesz;
    > + if (filesz > phdrs[i].p_memsz)
    > + filesz = phdrs[i].p_memsz;
    > +
    > + buffer = (char *)ehdr + phdrs[i].p_offset;
    > + ret = kexec_add_segment(image, buffer, filesz, phdrs[i].p_memsz,
    > + phdrs[i].p_paddr);
    > + if (ret)
    > + break;
    > + }
    > +
    > + return ret;
    > +}
    > +
    > +/* Fill in fields which are usually present in bzImage */
    > +static int init_linux_parameters(struct boot_params *params)
    > +{
    > + /*
    > + * FIXME: It is odd that the information which comes from kernel
    > + * has to be faked by loading kernel. I guess it is limitation of
    > + * ELF format. Right now keeping it same as kexec-tools
    > + * implementation. But this most likely needs fixing.
    > + */
    > + memcpy(&params->hdr.header, "HdrS", 4);
    > + params->hdr.version = 0x0206;
    > + params->hdr.initrd_addr_max = 0x37FFFFFF;
    > + params->hdr.cmdline_size = 2048;
    > + return 0;
    > +}

    Why a separate function? Its body is small enough to be merged into
    elf_x86_64_load.

    > +
    > +void *elf_x86_64_load(struct kimage *image, char *kernel,
    > + unsigned long kernel_len,
    > + char *initrd, unsigned long initrd_len,
    > + char *cmdline, unsigned long cmdline_len)
    > +{

    Btw, this functionality below looks very similar to the one in
    bzImage64_load(). Can we share some of it?

    --
    Regards/Gruss,
    Boris.

    Sent from a fat crate under my desk. Formatting is fine.
    --


    \
     
     \ /
      Last update: 2014-02-28 17:01    [W:4.422 / U:0.248 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site