Re: [PATCH 4/4] kexec/xen: directly load images images into Xen

Simon Horman
2013-11-19T01:20:38Z

On Wed, Nov 06, 2013 at 02:55:22PM +0000, David Vrabel wrote:
> From: David Vrabel <david.vrabel@citrix.com>
>
> Xen 4.4 has an improvided kexec hypercall ABI that allows images to be
> loaded and executed without any kernel involvement. Use the API
> provided by libxc to load images when running in a Xen guest.
>
> Support for loading images via the kexec_load syscall in non-upstream
> ("classic") Xen kernels is no longer supported.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
> ---
> kexec/Makefile | 1 +
> kexec/arch/i386/crashdump-x86.c | 20 +++++-
> kexec/crashdump-xen.c | 34 ++++++++++
> kexec/crashdump.h | 3 +-
> kexec/kexec-xen.c | 139 +++++++++++++++++++++++++++++++++++++++
> kexec/kexec.c | 24 +++++--
> kexec/kexec.h | 5 ++
> 7 files changed, 218 insertions(+), 8 deletions(-)
> create mode 100644 kexec/kexec-xen.c
>

[snip]

> diff --git a/kexec/kexec-xen.c b/kexec/kexec-xen.c
> new file mode 100644
> index 0000000..77f65c0
> --- /dev/null
> +++ b/kexec/kexec-xen.c
> @@ -0,0 +1,139 @@
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <string.h>
> +#include <stdlib.h>
> +#include <elf.h>
> +#include "kexec.h"
> +#include "kexec-syscall.h"
> +#include "crashdump.h"
> +
> +#include "config.h"
> +
> +#ifdef HAVE_LIBXENCTRL
> +#include <xenctrl.h>
> +
> +#include "crashdump.h"
> +
> +int xen_kexec_load(struct kexec_info *info)
> +{
> + uint32_t nr_segments = info->nr_segments;
> + struct kexec_segment *segments = info->segment;
> + xc_interface *xch;
> + xc_hypercall_buffer_array_t *array = NULL;
> + uint8_t type;
> + uint8_t arch;
> + xen_kexec_segment_t *xen_segs;
> + int s;
> + int ret = -1;
> +
> + xch = xc_interface_open(NULL, NULL, 0);
> + if (!xch)
> + return -1;
> +
> + xen_segs = calloc(nr_segments + 1, sizeof(*xen_segs));
> + if (!xen_segs)
> + goto out;
> +
> + array = xc_hypercall_buffer_array_create(xch, nr_segments);
> + if (array == NULL)
> + goto out;
> +
> + for (s = 0; s < nr_segments; s++) {
> + DECLARE_HYPERCALL_BUFFER(void, seg_buf);
> +
> + seg_buf = xc_hypercall_buffer_array_alloc(xch, array, s,
> + seg_buf, segments[s].bufsz);
> + if (seg_buf == NULL)
> + goto out;
> + memcpy(seg_buf, segments[s].buf, segments[s].bufsz);
> +
> + set_xen_guest_handle(xen_segs[s].buf.h, seg_buf);
> + xen_segs[s].buf_size = segments[s].bufsz;
> + xen_segs[s].dest_maddr = (uint64_t)segments[s].mem;
> + xen_segs[s].dest_size = segments[s].memsz;
> + }
> +
> + /*
> + * Ensure 0 - 1 MiB is mapped and accessible by the image.
> + *
> + * This allows access to the VGA memory and the region
> + * purgatory copies in the crash case.
> + */
> + set_xen_guest_handle(xen_segs[s].buf.h, HYPERCALL_BUFFER_NULL);
> + xen_segs[s].buf_size = 0;
> + xen_segs[s].dest_maddr = 0;
> + xen_segs[s].dest_size = 1 * 1024 * 1024;
> + nr_segments++;
> +
> + type = (info->kexec_flags & KEXEC_ON_CRASH) ? KEXEC_TYPE_CRASH
> + : KEXEC_TYPE_DEFAULT;
> +
> + arch = (info->kexec_flags & KEXEC_ARCH_MASK) >> 16;
> +#if defined(_i386__) || defined(__x86_64__)
> + if (!arch)
> + arch = EM_386;
> +#endif
> +
> + ret = xc_kexec_load(xch, type, arch, (uint64_t)info->entry,
> + nr_segments, xen_segs);
> +
> +out:
> + xc_hypercall_buffer_array_destroy(xch, array);
> + free(xen_segs);
> + xc_interface_close(xch);
> +
> + return ret;
> +}
> +
> +int xen_kexec_unload(uint64_t kexec_flags)
> +{
> + xc_interface *xch;
> + uint8_t type;
> + int ret;
> +
> + xch = xc_interface_open(NULL, NULL, 0);
> + if (!xch)
> + return -1;
> +
> + type = (kexec_flags & KEXEC_ON_CRASH) ? KEXEC_TYPE_CRASH
> + : KEXEC_TYPE_DEFAULT;
> +
> + ret = xc_kexec_unload(xch, type);
> +
> + xc_interface_close(xch);
> +
> + return ret;
> +}
> +
> +void xen_kexec_exec(void)
> +{
> + xc_interface *xch;
> +
> + xch = xc_interface_open(NULL, NULL, 0);
> + if (!xch)
> + return;
> +
> + xc_kexec_exec(xch, KEXEC_TYPE_DEFAULT);
> +
> + xc_interface_close(xch);
> +}
> +
> +#else /* ! HAVE_LIBXENCTRL */
> +
> +int xen_kexec_load(uint64_t entry,
> + uint32_t nr_segments, struct kexec_segment *segments,
> + uint64_t kexec_flags)
> +{
> + return -1;
> +}
> +
> +int xen_kexec_unload(uin64_t kexec_flags);
> +{
> + return -1;
> +}
> +
> +void xen_kexec_exec(void)
> +{
> +}
> +
> +#endif

[snip]

I have applied the following follow-up patch to resolves some errors.
Let me know if I messed it up.

From: Simon Horman <horms@verge.net.au>

[PATCH] kexec/xen: Correct some compile errors

Correct various problems introduced by
08cf823704b0fa3b ("kexec/xen: directly load images images into Xen").

These all relate to the case here HAVE_LIBXENCTRL is not set.

Signed-off-by: Simon Horman <horms@verge.net.au>
---
kexec/kexec-xen.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kexec/kexec-xen.c b/kexec/kexec-xen.c
index 77f65c0..e885246 100644
--- a/kexec/kexec-xen.c
+++ b/kexec/kexec-xen.c
@@ -2,6 +2,7 @@
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
+#include <stdlib.h>
#include <elf.h>
#include "kexec.h"
#include "kexec-syscall.h"
@@ -120,14 +121,12 @@ void xen_kexec_exec(void)

#else /* ! HAVE_LIBXENCTRL */

-int xen_kexec_load(uint64_t entry,
- uint32_t nr_segments, struct kexec_segment *segments,
- uint64_t kexec_flags)
+int xen_kexec_load(struct kexec_info *UNUSED(info))
{
return -1;
}

-int xen_kexec_unload(uin64_t kexec_flags);
+int xen_kexec_unload(uint64_t kexec_flags)
{
return -1;
}
--
1.8.4