Re: [RFC PATCH 2/2] Makefile: use xxd for converting guest/init

Andreas Herrmann
2015-06-24T09:07:51Z

On Tue, Jun 23, 2015 at 04:06:27PM +0100, Andre Przywara wrote:
> Currently we use ld to convert the static guest/init binary back
> into an object file, which we can embed as a binary blob into our
> lkvm binary. This works fine as long as compiler and linker use the
> same ELF target format, which seems to be not true for most of the
> MIPS toolchains.
> Use a different approach instead, which converts the guest/init
> binary into a C array, from which the compiler generates an .o
> representation. As the compiler is now the same, this naturally links
> together fine on all architectures.
> We use the "xxd" tool for generating a C array representation out of
> the binary file. If this turns out to be not widely installed (it
> seems to be part of the vim package in most distributions), we could
> think about switching to a scripted implementation using "od" or some
> printf trickery.

Works for me. (tested with an octeon-sdk toolchain)

Thanks,
Andreas

> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> Makefile | 4 ++--
> builtin-run.c | 8 ++++----
> builtin-setup.c | 8 ++++----
> 3 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index b9480ff..7f2a0ea 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -365,8 +365,8 @@ $(PROGRAM_ALIAS): $(PROGRAM)
> $(Q) ln -f $< $@
>
> $(GUEST_OBJS): $(GUEST_INIT)
> - $(E) " LINK " $@
> - $(Q) $(LD) $(LDFLAGS) -r -b binary -o $@ $<
> + $(E) " CONVERT " $@
> + $(Q) xxd -i $< | $(CC) -c -x c - -o $@
>
> $(GUEST_INIT): guest/init.c
> $(E) " CC " $@
> diff --git a/builtin-run.c b/builtin-run.c
> index 1ee75ad..0a48663 100644
> --- a/builtin-run.c
> +++ b/builtin-run.c
> @@ -59,8 +59,8 @@ static int kvm_run_wrapper;
>
> bool do_debug_print = false;
>
> -extern char _binary_guest_init_start;
> -extern char _binary_guest_init_size;
> +extern char guest_init;
> +extern char guest_init_len;
>
> static const char * const run_usage[] = {
> "lkvm run [<options>] [<kernel image>]",
> @@ -354,8 +354,8 @@ static int kvm_setup_guest_init(struct kvm *kvm)
> char *data;
>
> /* Setup /virt/init */
> - size = (size_t)&_binary_guest_init_size;
> - data = (char *)&_binary_guest_init_start;
> + size = (size_t)&guest_init_len;
> + data = (char *)&guest_init;
> snprintf(tmp, PATH_MAX, "%s%s/virt/init", kvm__get_dir(), rootfs);
> remove(tmp);
> fd = open(tmp, O_CREAT | O_WRONLY, 0755);
> diff --git a/builtin-setup.c b/builtin-setup.c
> index 8b45c56..fd7ca54 100644
> --- a/builtin-setup.c
> +++ b/builtin-setup.c
> @@ -16,8 +16,8 @@
> #include <sys/mman.h>
> #include <fcntl.h>
>
> -extern char _binary_guest_init_start;
> -extern char _binary_guest_init_size;
> +extern char guest_init;
> +extern char guest_init_len;
>
> static const char *instance_name;
>
> @@ -131,8 +131,8 @@ static int copy_init(const char *guestfs_name)
> int fd, ret;
> char *data;
>
> - size = (size_t)&_binary_guest_init_size;
> - data = (char *)&_binary_guest_init_start;
> + size = (size_t)&guest_init;
> + data = (char *)&guest_init_len;
> snprintf(path, PATH_MAX, "%s%s/virt/init", kvm__get_dir(), guestfs_name);
> remove(path);
> fd = open(path, O_CREAT | O_WRONLY, 0755);
> --
> 2.3.5
>