tools/misc: xen-hvmcrash: New tool to attempt to crash HVM guests

This tool reads the CPU save records, overwrites RIP with a bogus
value, and then restores them. This is, of course, not guaranteed
to crash the guest (since the CPUs may not be executing in kernel
at the time) but it's good for breaking into some tight loops that
would be hard to debug otherwise.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

2 files changed, 146 insertions, 3 deletions

diff --git a/tools/misc/Makefile b/tools/misc/Makefile
index 843de9d3ec..22fd42300a 100644
--- a/tools/misc/Makefile
+++ b/tools/misc/Makefile
@@ -11,7 +11,7 @@ CFLAGS   += $(INCLUDES)
 HDRS     = $(wildcard *.h)
 
 TARGETS-y := xenperf xenpm xen-tmem-list-parse gtraceview gtracestat xenlockprof xenwatchdogd
-TARGETS-$(CONFIG_X86) += xen-detect xen-hvmctx
+TARGETS-$(CONFIG_X86) += xen-detect xen-hvmctx xen-hvmcrash
 TARGETS-$(CONFIG_MIGRATE) += xen-hptool
 TARGETS := $(TARGETS-y)
 
@@ -24,7 +24,7 @@ INSTALL_BIN-$(CONFIG_X86) += xen-detect
 INSTALL_BIN := $(INSTALL_BIN-y)
 
 INSTALL_SBIN-y := xm xen-bugtool xen-python-path xend xenperf xsview xenpm xen-tmem-list-parse gtraceview gtracestat xenlockprof xenwatchdogd
-INSTALL_SBIN-$(CONFIG_X86) += xen-hvmctx
+INSTALL_SBIN-$(CONFIG_X86) += xen-hvmctx xen-hvmcrash
 INSTALL_SBIN-$(CONFIG_MIGRATE) += xen-hptool
 INSTALL_SBIN := $(INSTALL_SBIN-y)
 
@@ -51,7 +51,7 @@ clean:
 %.o: %.c $(HDRS) Makefile
 	$(CC) -c $(CFLAGS) -o $@ $<
 
-xen-hvmctx xenperf xenpm gtracestat xenlockprof xen-hptool xenwatchdogd: %: %.o Makefile
+xen-hvmctx xen-hvmcrash xenperf xenpm gtracestat xenlockprof xen-hptool xenwatchdogd: %: %.o Makefile
 	$(CC) $(CFLAGS) -o $@ $< $(LDFLAGS) $(LDFLAGS_libxenctrl) $(LDFLAGS_libxenguest) $(LDFLAGS_libxenstore)
 
 gtraceview: %: %.o Makefile
diff --git a/tools/misc/xen-hvmcrash.c b/tools/misc/xen-hvmcrash.c
new file mode 100644
index 0000000000..4f0dabcb18
--- /dev/null
+++ b/tools/misc/xen-hvmcrash.c
@@ -0,0 +1,143 @@
+/* 
+ * xen-hvmcrash.c
+ *
+ * Attempt to crash an HVM guest by overwriting RIP/EIP with a bogus value
+ * 
+ * Copyright (c) 2010 Citrix Systems, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <limits.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <arpa/inet.h>
+
+#include <xenctrl.h>
+#include <xen/xen.h>
+#include <xen/domctl.h>
+#include <xen/hvm/save.h>
+
+int
+main(int argc, char **argv)
+{
+    int domid;
+    xc_interface *xch;
+    xc_dominfo_t dominfo;
+    int ret;
+    uint32_t len;
+    uint8_t *buf;
+    uint32_t off;
+    struct hvm_save_descriptor *descriptor;
+
+    if (argc != 2 || !argv[1] || (domid = atoi(argv[1])) < 0) {
+        fprintf(stderr, "usage: %s <domid>\n", argv[0]);
+        exit(1);
+    }
+
+    xch = xc_interface_open(0, 0, 0);
+    if (!xch) {
+        fprintf(stderr, "error: can't open libxc handle\n");
+        exit(1);
+    }
+
+    ret = xc_domain_getinfo(xch, domid, 1, &dominfo);
+    if (ret < 0) {
+        perror("xc_domain_getinfo");
+        exit(1);
+    }
+
+    if (!dominfo.hvm) {
+        fprintf(stderr, "domain %d is not HVM\n", domid);
+        exit(1);
+    }
+
+    ret = xc_domain_pause(xch, domid);
+    if (ret < 0) {
+        perror("xc_domain_pause");
+        exit(-1);
+    }
+
+    /*
+     * Calling with zero buffer length should return the buffer length
+     * required.
+     */
+    ret = xc_domain_hvm_getcontext(xch, domid, 0, 0);
+    if (ret < 0) {
+        perror("xc_domain_hvm_getcontext");
+        exit(1);
+    }
+    
+    len = ret;
+    buf = malloc(len);
+    if (buf == NULL) {
+        perror("malloc");
+        exit(1);
+    }
+
+    ret = xc_domain_hvm_getcontext(xch, domid, buf, len);
+    if (ret < 0) {
+        perror("xc_domain_hvm_getcontext");
+        exit(1);
+    }
+
+    off = 0;
+
+    while (off < len) {
+        descriptor = (struct hvm_save_descriptor *)(buf + off);
+
+        off += sizeof (struct hvm_save_descriptor);
+
+        if (descriptor->typecode == HVM_SAVE_CODE(CPU)) {
+            HVM_SAVE_TYPE(CPU) *cpu;
+
+            /* Overwrite EIP/RIP with some recognisable but bogus value */
+            cpu = (HVM_SAVE_TYPE(CPU) *)(buf + off);
+            printf("CPU[%d]: RIP = %" PRIx64 "\n", descriptor->instance, cpu->rip);
+            cpu->rip = 0xf001;
+        } else if (descriptor->typecode == HVM_SAVE_CODE(END)) {
+            break;
+        }
+
+        off += descriptor->length;
+    }
+
+    ret = xc_domain_hvm_setcontext(xch, domid, buf, len);
+    if (ret < 0) {
+        perror("xc_domain_hvm_setcontext");
+        exit(1);
+    }
+
+    ret = xc_domain_unpause(xch, domid);
+    if (ret < 0) {
+        perror("xc_domain_unpause");
+        exit(1);
+    }
+
+    return 0;
+}