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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 4/4] kexec/xen: directly load images images into Xen
On Fri, Sep 20, 2013 at 02:16:38PM +0100, David Vrabel wrote:
> From: David Vrabel <david.vrabel@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
[...]
> diff --git a/kexec/kexec-xen.c b/kexec/kexec-xen.c
> new file mode 100644
> index 0000000..0e47e68
> --- /dev/null
> +++ b/kexec/kexec-xen.c
> @@ -0,0 +1,134 @@
> +#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;
> + }
> +
> + if (info->kexec_flags & KEXEC_ON_CRASH) {
> + set_xen_guest_handle(xen_segs[s].buf.h, HYPERCALL_BUFFER_NULL);
> + xen_segs[s].buf_size = 0;
> + xen_segs[s].dest_maddr = info->backup_src_start;
> + xen_segs[s].dest_size = info->backup_src_size;
> + 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_TYPE_CRASH;
Why? Could not we unload normal kexec images?
> + 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
> diff --git a/kexec/kexec.c b/kexec/kexec.c
> index 21ff0e7..13b568f 100644
> --- a/kexec/kexec.c
> +++ b/kexec/kexec.c
> @@ -764,8 +764,12 @@ static int my_load(const char *type, int fileind, int
> argc, char **argv,
> if (kexec_debug)
> print_segments(stderr, &info);
>
> - result = kexec_load(
> - info.entry, info.nr_segments, info.segment, info.kexec_flags);
> + if (xen_present())
> + result = xen_kexec_load(&info);
> + else
> + result = kexec_load(info.entry,
> + info.nr_segments, info.segment,
> + info.kexec_flags);
> if (result != 0) {
> /* The load failed, print some debugging information */
> fprintf(stderr, "kexec_load failed: %s\n",
> @@ -789,10 +793,13 @@ static int k_unload (unsigned long kexec_flags)
> }
> kexec_flags |= native_arch;
>
> - result = kexec_load(NULL, 0, NULL, kexec_flags);
> + if (xen_present())
> + result = xen_kexec_unload(kexec_flags);
> + else
> + result = kexec_load(NULL, 0, NULL, kexec_flags);
> if (result != 0) {
> /* The unload failed, print some debugging information */
> - fprintf(stderr, "kexec_load (0 segments) failed: %s\n",
> + fprintf(stderr, "kexec unload failed: %s\n",
> strerror(errno));
> }
> return result;
> @@ -823,7 +830,10 @@ static int my_shutdown(void)
> */
> static int my_exec(void)
> {
> - reboot(LINUX_REBOOT_CMD_KEXEC);
> + if (xen_present())
> + xen_kexec_exec();
> + else
> + reboot(LINUX_REBOOT_CMD_KEXEC);
> /* I have failed if I make it here */
> fprintf(stderr, "kexec failed: %s\n",
> strerror(errno));
> @@ -928,6 +938,10 @@ static int kexec_loaded(void)
> char *p;
> char line[3];
>
> + /* No way to tell if an image is loaded under Xen, assume it is. */
> + if (xen_present())
> + return 1;
> +
Why? I think that we should have relevant machanism to do that.
Please take into account Konrad's comments too
(http://lists.xenproject.org/archives/html/xen-devel/2013-09/msg02364.html).
Daniel
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