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ocaml/libs: Implement a dynamically-loaded plugin for Xenctrl.domain_getinfo
This plugin intends to hide the unstable Xenctrl interface under a stable one. In case of the change in the interface, a V2 of this plugin would need to be produced, but V1 with the old interface would need to be kept (with potential change in the implementation) in the meantime. To reduce the need for such changes in the future, this plugin only provides the absolute minimum functionality that Oxenstored uses - only three fields of the domaininfo struct are used and presented here. Oxenstored currently uses the single-domain domain_getinfo function, whereas domain_getinfolist is a potentially more efficient option. Both of these are provided in the plugin to allow a transition from one to the other without modifying the interface in the future. Both return identical structures and rely on the same fields in xenctrl, thus if one of them breaks, both will break, and a new version of the interface would need to be issued. Signed-off-by: Andrii Sultanov <andrii.sultanov@cloud.com> Acked-by: Christian Lindig <christian.lindig@cloud.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
This commit is contained in:
Andrii Sultanov authored and Andrew Cooper committed
1 parent
0a15b7695b
commit
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11 files changed
+358
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@@ -29,6 +29,7 @@ build-tools-oxenstored:
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$(MAKE) -s -C libs/mmap
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$(MAKE) -s -C libs/xb
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$(MAKE) -s -C libs/xc
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$(MAKE) -s -C libs/xsd_glue
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$(MAKE) -C xenstored
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.PHONY: format
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@@ -4,7 +4,7 @@ include $(XEN_ROOT)/tools/Rules.mk
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SUBDIRS= \
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mmap \
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eventchn xc \
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xb xs
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xb xs xsd_glue
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.PHONY: all
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all: subdirs-all
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@@ -0,0 +1,4 @@
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version = "@VERSION@"
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description = "A small library on top of unstable Xenctrl interfaces used by Oxenstored"
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archive(byte) = "plugin_interface_v1.cma"
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archive(native) = "plugin_interface_v1.cmxa"
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@@ -0,0 +1,46 @@
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OCAML_TOPLEVEL=$(CURDIR)/../..
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XEN_ROOT=$(OCAML_TOPLEVEL)/../..
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include $(OCAML_TOPLEVEL)/common.make
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SUBDIRS= domain_getinfo_plugin_v1
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CFLAGS += $(CFLAGS_xeninclude)
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OCAMLOPTFLAGS += -opaque
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OBJS = plugin_interface_v1
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INTF = $(foreach obj, $(OBJS),$(obj).cmi)
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LIBS = plugin_interface_v1.cma plugin_interface_v1.cmxa
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LIBS_plugin_interface_v1 =
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plugin_interface_v1_OBJS=$(OBJS)
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.PHONY: all
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all: $(INTF) $(LIBS) $(PROGRAMS) subdirs-all
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bins: $(PROGRAMS)
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libs: $(LIBS)
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plugin_interface_v1 = $(OBJS)
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OCAML_NOC_LIBRARY = plugin_interface_v1
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.PHONY: install
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install: $(LIBS) META subdirs-install
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mkdir -p $(OCAMLDESTDIR)
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$(OCAMLFIND) remove -destdir $(OCAMLDESTDIR) xsd_glue
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$(OCAMLFIND) install -destdir $(OCAMLDESTDIR) -ldconf ignore xsd_glue META $(INTF) $(LIBS)
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$(OCAMLFIND) remove -destdir $(OCAMLDESTDIR) xsd_glue_dev
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$(OCAMLFIND) install -destdir $(OCAMLDESTDIR) -ldconf ignore xsd_glue_dev META $(INTF) $(LIBS) *.ml *.mli
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.PHONY: uninstall
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uninstall: subdirs-uninstall
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$(OCAMLFIND) remove -destdir $(OCAMLDESTDIR) xsd_glue
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$(OCAMLFIND) remove -destdir $(OCAMLDESTDIR) xsd_glue_dev
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.PHONY: clean
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clean: subdirs-clean
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.PHONY: distclean
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distclean: subdirs-distclean
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include $(OCAML_TOPLEVEL)/Makefile.rules
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@@ -0,0 +1,5 @@
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version = "@VERSION@"
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description = "Xenstored plugin for Xenctrl.domain_getinfo unstable interface - V1"
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requires = "plugin_interface_v1"
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archive(byte) = "domain_getinfo_v1.cma"
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archive(native) = "domain_getinfo_v1.cmxa"
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@@ -0,0 +1,37 @@
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OCAML_TOPLEVEL=$(CURDIR)/../../..
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XEN_ROOT=$(OCAML_TOPLEVEL)/../..
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include $(OCAML_TOPLEVEL)/common.make
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CFLAGS += -I $(OCAML_TOPLEVEL)/libs -I $(OCAML_TOPLEVEL)/libs/xsd_glue
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CFLAGS += $(CFLAGS_libxenctrl) $(CFLAGS_xeninclude) $(APPEND_CFLAGS)
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OCAMLOPTFLAGS += -opaque
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OCAMLINCLUDE += -I ./ -I ../
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OBJS = domain_getinfo_v1
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INTF = $(foreach obj, $(OBJS),$(obj).cmi)
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LIBS = domain_getinfo_v1.cmxa domain_getinfo_v1.cmxs
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LIBS_xsd_glue = $(call xenlibs-ldflags-ldlibs,xenctrl)
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all: $(INTF) $(LIBS) $(PROGRAMS)
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bins: $(PROGRAMS)
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libs: $(LIBS)
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domain_getinfo_v1_OBJS = $(OBJS)
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domain_getinfo_v1 = $(OBJS)
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domain_getinfo_v1_C_OBJS = domain_getinfo_stubs_v1
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OCAML_DYN_LIBRARY = domain_getinfo_v1
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.PHONY: install
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install: $(LIBS) META
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$(INSTALL_DIR) $(DESTDIR)$(LIBEXEC)/ocaml/xsd_glue/xenctrl_plugin
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$(INSTALL_PROG) domain_getinfo_v1.cmxs $(DESTDIR)$(LIBEXEC)/ocaml/xsd_glue/xenctrl_plugin
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.PHONY: uninstall
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uninstall:
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rm -f $(DESTDIR)$(LIBEXEC)/ocaml/xsd_glue/xenctrl_plugin/domain_getinfo_v1.cmxs
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include $(OCAML_TOPLEVEL)/Makefile.rules
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@@ -0,0 +1,160 @@
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/* SPDX-License-Identifier: LGPL-2.1-only WITH OCaml-LGPL-linking-exception */
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#define _GNU_SOURCE
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#define CAML_NAME_SPACE
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#include <caml/alloc.h>
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#include <caml/memory.h>
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#include <caml/signals.h>
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#include <caml/fail.h>
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#include <caml/callback.h>
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#include <caml/custom.h>
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#include <xen-tools/common-macros.h>
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#include <xenctrl.h>
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#include "xen-caml-compat.h"
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static inline xc_interface *xsd_glue_xch_of_val(value v)
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{
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xc_interface *xch = *(xc_interface **)Data_custom_val(v);
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return xch;
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}
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static void xsd_glue_xenctrl_finalize(value v)
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{
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xc_interface *xch = xsd_glue_xch_of_val(v);
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xc_interface_close(xch);
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}
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static struct custom_operations xsd_glue_xenctrl_ops = {
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.identifier = "xsd_glue.domain_getinfo_v1.xenctrl",
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.finalize = xsd_glue_xenctrl_finalize,
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.compare = custom_compare_default, /* Can't compare */
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.hash = custom_hash_default, /* Can't hash */
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.serialize = custom_serialize_default, /* Can't serialize */
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.deserialize = custom_deserialize_default, /* Can't deserialize */
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.compare_ext = custom_compare_ext_default, /* Can't compare */
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};
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static void Noreturn xsd_glue_failwith(
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xc_interface *xch, const char *func, unsigned int line)
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{
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CAMLparam0();
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CAMLlocal1(msg);
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const xc_error *error = xch ? xc_get_last_error(xch) : NULL;
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char *str = NULL;
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#define ERR (error && error->code != XC_ERROR_NONE)
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int ret = asprintf(&str,
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"%d: %s%s%s - called from %s:%u",
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ERR ? error->code : errno,
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ERR ? xc_error_code_to_desc(error->code) : strerror(errno),
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ERR ? ": " : "",
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ERR ? error->message : "",
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func, line);
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#undef ERR
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if (!*str || (ret == -1))
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caml_raise_out_of_memory();
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msg = caml_copy_string(str);
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free(str);
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caml_raise_with_arg(*caml_named_value("xsg.error_v1"), msg);
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}
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#define xsd_glue_failwith(xch) xsd_glue_failwith(xch, __func__, __LINE__)
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CAMLprim value stub_xsd_glue_xc_interface_open(value unit)
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{
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CAMLparam1(unit);
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CAMLlocal1(result);
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xc_interface *xch;
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result = caml_alloc_custom(&xsd_glue_xenctrl_ops, sizeof(xch), 0, 1);
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caml_enter_blocking_section();
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xch = xc_interface_open(NULL, NULL, 0);
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caml_leave_blocking_section();
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if (!xch)
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xsd_glue_failwith(xch);
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*(xc_interface **)Data_custom_val(result) = xch;
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CAMLreturn(result);
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}
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static value xsd_glue_alloc_domaininfo(const xc_domaininfo_t *info)
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{
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CAMLparam0();
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CAMLlocal1(result);
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result = caml_alloc_tuple(4);
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Store_field(result, 0, Val_int(info->domain));
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Store_field(result, 1, Val_bool(info->flags & XEN_DOMINF_dying));
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Store_field(result, 2, Val_bool(info->flags & XEN_DOMINF_shutdown));
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Store_field(result, 3, Val_int(MASK_EXTR(info->flags, XEN_DOMINF_shutdownmask)));
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CAMLreturn(result);
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}
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CAMLprim value stub_xsd_glue_xc_domain_getinfo(value xch_val, value domid)
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{
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CAMLparam2(xch_val, domid);
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CAMLlocal1(result);
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xc_interface *xch = xsd_glue_xch_of_val(xch_val);
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xc_domaininfo_t info;
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int ret;
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int domid_c = Int_val(domid);
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caml_enter_blocking_section();
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ret = xc_domain_getinfo_single(xch, domid_c, &info);
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caml_leave_blocking_section();
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if (ret < 0)
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xsd_glue_failwith(xch);
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result = xsd_glue_alloc_domaininfo(&info);
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CAMLreturn(result);
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}
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CAMLprim value stub_xsd_glue_xc_domain_getinfolist(value xch_val)
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{
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CAMLparam1(xch_val);
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CAMLlocal1(result);
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xc_interface *xch = xsd_glue_xch_of_val(xch_val);
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xc_domaininfo_t *info;
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int i, retval;
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/* get the minimum number of allocate byte we need and bump it up to page boundary */
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info = malloc(sizeof(xc_domaininfo_t) * DOMID_FIRST_RESERVED);
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if (!info)
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caml_raise_out_of_memory();
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caml_enter_blocking_section();
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retval = xc_domain_getinfolist(xch, 0, DOMID_FIRST_RESERVED, info);
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caml_leave_blocking_section();
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if (retval <= 0) {
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free(info);
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xsd_glue_failwith(xch);
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}
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result = caml_alloc(retval, 0);
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for (i = 0; i < retval; i++) {
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caml_modify(&Field(result, i), xsd_glue_alloc_domaininfo(info + i));
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}
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free(info);
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CAMLreturn(result);
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}
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@@ -0,0 +1,35 @@
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(* SPDX-License-Identifier: LGPL-2.1-only WITH OCaml-LGPL-linking-exception *)
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(** Minimal interface on top of unstable Xenctrl for Oxenstored's usage *)
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module P = Plugin_interface_v1
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module M : P.Domain_getinfo_V1 = struct
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exception Error of string
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type domid = int
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type handle
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type domaininfo = {
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domid : domid;
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dying : bool;
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shutdown : bool;
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shutdown_code : int;
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}
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external interface_open : unit -> handle = "stub_xsd_glue_xc_interface_open"
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external domain_getinfo : handle -> domid -> domaininfo
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= "stub_xsd_glue_xc_domain_getinfo"
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external domain_getinfolist : handle -> domaininfo array
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= "stub_xsd_glue_xc_domain_getinfolist"
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let _ = Callback.register_exception "xsg.error_v1" (Error "register_callback")
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end
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let () =
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Printf.ksprintf !P.logging_function "Registration of %s plugin started\n%!"
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__MODULE__;
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P.register_plugin_v1 (module M : P.Domain_getinfo_V1);
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Printf.ksprintf !P.logging_function "Registration of %s plugin successful\n%!"
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__MODULE__
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@@ -0,0 +1 @@
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(* SPDX-License-Identifier: LGPL-2.1-only WITH OCaml-LGPL-linking-exception *)
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@@ -0,0 +1,30 @@
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(* SPDX-License-Identifier: LGPL-2.1-only WITH OCaml-LGPL-linking-exception *)
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module type Domain_getinfo_V1 = sig
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exception Error of string
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type domid = int
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type handle
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type domaininfo = {
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domid : domid;
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dying : bool;
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shutdown : bool;
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shutdown_code : int;
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}
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val interface_open : unit -> handle
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val domain_getinfo : handle -> domid -> domaininfo
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val domain_getinfolist : handle -> domaininfo array
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end
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let ignore_logging : string -> unit = ignore
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let logging_function = ref ignore_logging
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let register_logging_function func = logging_function := func
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let plugin_implementation_v1 : (module Domain_getinfo_V1) option ref = ref None
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let register_plugin_v1 m = plugin_implementation_v1 := Some m
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let get_plugin_v1 () : (module Domain_getinfo_V1) =
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match !plugin_implementation_v1 with
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| Some s -> s
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| None -> failwith "No plugin loaded"
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@@ -0,0 +1,38 @@
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(* SPDX-License-Identifier: LGPL-2.1-only WITH OCaml-LGPL-linking-exception *)
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(** To avoid breaking the plugin interface, this module needs to be
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standalone and can't rely on any other Xen library. Even unrelated
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changes in the interfaces of those modules would change the hash
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of this interface and break the plugin system.
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It can only depend on Stdlib, therefore all of the types (domid,
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domaininfo etc.) are redefined here instead of using alternatives
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defined elsewhere.
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NOTE: The signature of this interface should not be changed (no
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functions or types can be added, modified, or removed). If
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underlying Xenctrl changes require a new interface, a V2 with a
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corresponding plugin should be created.
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*)
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module type Domain_getinfo_V1 = sig
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exception Error of string
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type domid = int
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type handle
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type domaininfo = {
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domid : domid;
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dying : bool;
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shutdown : bool;
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shutdown_code : int;
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}
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val interface_open : unit -> handle
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val domain_getinfo : handle -> domid -> domaininfo
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val domain_getinfolist : handle -> domaininfo array
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end
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val register_logging_function : (string -> unit) -> unit
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val logging_function : (string -> unit) ref
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val register_plugin_v1 : (module Domain_getinfo_V1) -> unit
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val get_plugin_v1 : unit -> (module Domain_getinfo_V1)
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