[PATCH 0/6] kexec: A new system call to allow in kernel loading

Vivek Goyal vgoyal at redhat.com
Wed Nov 20 12:50:45 EST 2013

Current proposed secureboot implementation disables kexec/kdump because
it can allow unsigned kernel to run on a secureboot platform. Intial
idea was to sign /sbin/kexec binary and let that binary do the kernel
signature verification. I had posted RFC patches for this apparoach


Later we had discussion at Plumbers and most of the people thought
that signing and trusting /sbin/kexec is becoming complex. So a 
better idea might be let kernel do the signature verification of
new kernel being loaded. This calls for implementing a new system call
and moving lot of user space code in kernel.

kexec_load() system call allows loading a kexec/kdump kernel and jump
to that kernel at right time. Though a lot of processing is done in
user space which prepares a list of segments/buffers to be loaded and
kexec_load() works on that list of segments. It does not know what's
contained in those segments.

Now a new system call kexec_file_load() is implemented which takes
kernel fd and initrd fd as parameters. Now kernel should be able
to verify signature of newly loaded kernel. 

This is an early RFC patchset. I have not done signature handling
part yet. This is more of a minimal patch to show how new system
call and functionality will look like. Right now it can only handle
bzImage with 64bit entry point on x86_64. No EFI, no x86_32  or any
other architecture. Rest of the things can be added slowly as need
arises. In first iteration, I have tried to address most common use case
for us.

Any feedback is welcome.

Vivek Goyal (6):
  kexec: Export vmcoreinfo note size properly
  kexec: Move segment verification code in a separate function
  resource: Provide new functions to walk through resources
  kexec: A new system call, kexec_file_load, for in kernel kexec
  kexec-bzImage: Support for loading bzImage using 64bit entry
  kexec: Support for Kexec on panic using new system call

 arch/x86/include/asm/crash.h         |    9 +
 arch/x86/include/asm/kexec-bzimage.h |   12 +
 arch/x86/include/asm/kexec.h         |   43 ++
 arch/x86/kernel/Makefile             |    2 +
 arch/x86/kernel/crash.c              |  585 +++++++++++++++++++++++++++
 arch/x86/kernel/kexec-bzimage.c      |  420 +++++++++++++++++++
 arch/x86/kernel/machine_kexec_64.c   |   60 +++-
 arch/x86/kernel/purgatory_entry_64.S |  119 ++++++
 arch/x86/syscalls/syscall_64.tbl     |    1 +
 include/linux/ioport.h               |    6 +
 include/linux/kexec.h                |   57 +++
 include/linux/syscalls.h             |    3 +
 include/uapi/linux/kexec.h           |    4 +
 kernel/kexec.c                       |  731 ++++++++++++++++++++++++++++++----
 kernel/ksysfs.c                      |    2 +-
 kernel/resource.c                    |  108 +++++-
 kernel/sys_ni.c                      |    1 +
 17 files changed, 2074 insertions(+), 89 deletions(-)
 create mode 100644 arch/x86/include/asm/crash.h
 create mode 100644 arch/x86/include/asm/kexec-bzimage.h
 create mode 100644 arch/x86/kernel/kexec-bzimage.c
 create mode 100644 arch/x86/kernel/purgatory_entry_64.S


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