FYI, it looks like the following patch (committed in
8fc5b4d4121c95482b2583) adds a new requirement to use at least gcc
4.4 to build the kernel?
On Thu, Jun 26, 2014 at 04:33:40PM -0400, Vivek Goyal wrote:
> Create a stand alone relocatable object purgatory which runs between two
> kernels. This name, concept and some code has been taken from kexec-tools.
> Idea is that this code runs after a crash and it runs in minimal environment.
> So keep it separate from rest of the kernel and in long term we will have
> to practically do no maintenance of this code.
>
> This code also has the logic to do verify sha256 hashes of various
> segments which have been loaded into memory. So first we verify that
> the kernel we are jumping to is fine and has not been corrupted and
> make progress only if checsums are verified.
>
> This code also takes care of copying some memory contents to backup region.
>
> Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
> ---
> arch/x86/Kbuild | 4 ++
> arch/x86/Makefile | 8 +++
> arch/x86/purgatory/Makefile | 30 +++++++++++
> arch/x86/purgatory/entry64.S | 101 ++++++++++++++++++++++++++++++++++++++
> arch/x86/purgatory/purgatory.c | 72 +++++++++++++++++++++++++++
> arch/x86/purgatory/setup-x86_64.S | 58 ++++++++++++++++++++++
> arch/x86/purgatory/stack.S | 19 +++++++
> arch/x86/purgatory/string.c | 13 +++++
> 8 files changed, 305 insertions(+)
> create mode 100644 arch/x86/purgatory/Makefile
> create mode 100644 arch/x86/purgatory/entry64.S
> create mode 100644 arch/x86/purgatory/purgatory.c
> create mode 100644 arch/x86/purgatory/setup-x86_64.S
> create mode 100644 arch/x86/purgatory/stack.S
> create mode 100644 arch/x86/purgatory/string.c
>
[snip]
> diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
> new file mode 100644
> index 0000000..e5829dd
> --- /dev/null
> +++ b/arch/x86/purgatory/Makefile
> @@ -0,0 +1,30 @@
> +purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string.o
> +
> +targets += $(purgatory-y)
> +PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
> +
> +LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
> +targets += purgatory.ro
> +
> +# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
> +# in turn leaves some undefined symbols like __fentry__ in purgatory and not
> +# sure how to relocate those. Like kexec-tools, use custom flags.
> +
> +KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -MD -Os -mcmodel=large
The above "-mcmodel=large" compiler flag produces the following output on GCC 4.1.2.
$ make modules_prepare ; gcc --version
CHK include/config/kernel.release
CHK include/generated/uapi/linux/version.h
CHK include/generated/utsrelease.h
CC arch/x86/purgatory/purgatory.o
arch/x86/purgatory/purgatory.c:1: sorry, unimplemented: code model ?large? not supported yet
make[1]: *** [arch/x86/purgatory/purgatory.o] Error 1
make: *** [archprepare] Error 2
gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-54)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
I did a quick search for a discussion the indicates this compiler is now
officially too old to build the kernel but did not find one.
If this is required, maybe Documentation/Changes needs to be updated
with the new minimum required version?
Cheers,
Shaun
