Xen project Mailing List

Re: [Xen-devel] disable qemu PCI devices in HVM domains

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>

From: Steven Smith <steven.smith@xxxxxxxxxxxxx>

Date: Mon, 15 Dec 2008 17:10:59 +0000

Cc: James Harper <james.harper@xxxxxxxxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx

Delivery-date: Mon, 15 Dec 2008 09:11:55 -0800

List-id: Xen developer discussion <xen-devel.lists.xensource.com>

> >> I like the principle of disabling the drivers via an instruction to > >> qemu rather than by attempting to wrestle with the Windows driver > >> machinery to try to hide the devices. But couldn't we simulate a PCI > >> unplug or a medium change or something instead ? Then you could do it > >> later in the boot after your own drivers have properly bound. > >> > > > > Is the 'pci unplug' as simple as making a call somewhere like > > pci_unplug(id of ide adapter)? I'm concerned that Windows may not like > > this. > My own opinion is that the ioports are fine, but they should be offsets from > the xen-platform-pci device's ioport bar. Also we ought to document the > ports in xen-platform-pci's source file, as it's going to start getting > messy in there. > > I'm not sure if the approach taken by the Citrix drivers could be at all > useful. Cc'ing Steven Smith in case he has any comments to make. I can't see any reason why the approach we take in our closed-source drivers wouldn't work here as well. I've attached the appropriate patches from our product qemu patchqueue, tidied up and stripped of the most obviously XenServer-specific bits, and made to apply to current ioemu-remote. The protocol covers three basic things: -- Disconnecting emulated devices. -- Getting log messages out of the drivers and into dom0. -- Allowing dom0 to block the loading of specific drivers. This is intended as a backwards-compatibility thing: if we discover a bug in some old version of the drivers, then rather than working around it in Xen, we have the option of just making those drivers fall back to emulated mode. The current protocol works like this (from the point of view of drivers): 1) When the drivers first come up, they check whether the unplug logic is available by reading a two-byte magic number from IO port 0x10. These should be 0x49d2. If the magic number doesn't match, the drivers don't do anything. 2) The drivers read a one-byte protocol version from IO port 0x12. If this is 0, skip to 6. 3) The drivers write a two-byte product number to IO port 0x12. At the moment, the only drivers using this protocol are our closed-source ones, which use product number 1. 4) The drivers write a four-byte build number to IO port 0x10. 5) The drivers check the magic number by reading two bytes from 0x10 again. If it's changed from 0x49d2, the drivers are blacklisted and should not load. 6) The drivers write a two-byte bitmask of devices to unplug to IO port 0x10. The defined fields are: 1 -- All IDE disks (not including CD drives) 2 -- All emulated NICs 4 -- All IDE disks except for the primary master (not including CD drives) The relevant emulated devices then disappear from the relevant buses. For most guest operating systems, you want to do this before device enumeration happens. ...) Once the drivers have checked the magic number (and the blacklist, if appropriate), they can send log messages to qemu which will be logged to wherever qemu's logs go (/var/log/xen/qemu-dm.log on normal Xen, dom0 syslog on XenServer). These messages are written to IO port 0x12 a byte at a time, and are terminated by newlines. There's a fairly aggressive rate limiter on these messages, so they shouldn't be used for anything even vaguely high-volume, but they're rather useful for debugging and support. This isn't exactly a pretty protocol, but it does solve the problem. The blacklist is, from qemu's point of view, handled mostly through xenstore. A driver version is considered to be blacklisted if /mh/driver-blacklist/{product_name}/{build_number} exists and is readable, where {build_number} is the build number from step 4 as a decimal number. {product_name} is a string corresponding to the product number in step 3; at present, the only product number is 1, which has a product_name of xensource-windows. A previous version of the protocol put the IO ports on the PCI platform device. Unfortunately, that makes it difficult to get at them before PCI bus enumeration happens, which complicates removal of the emulated NICs. It is possible to work around these but (at least on Windows) it's complicated and messy, and generally best avoided. Steven.

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Index: ioemu-remote/hw/ide.c =================================================================== --- ioemu-remote.orig/hw/ide.c 2008-12-15 16:02:19.000000000 +0000 +++ ioemu-remote/hw/ide.c 2008-12-15 16:02:35.000000000 +0000 @@ -484,6 +484,7 @@ int type; /* see IDE_TYPE_xxx */ } PCIIDEState; +static PCIIDEState *principal_ide_controller; #if defined(__ia64__) #include <xen/hvm/ioreq.h> @@ -2778,6 +2779,47 @@ s->media_changed = 0; } +/* Unplug all of the IDE hard disks, starting at index @start in the + table. */ +static void _ide_unplug_harddisks(int start) +{ + IDEState *s; + int i, j; + + if (!principal_ide_controller) { + fprintf(stderr, "No principal controller?\n"); + return; + } + for (i = start; i < 4; i++) { + s = principal_ide_controller->ide_if + i; + if (!s->bs) + continue; /* drive not present */ + if (s->is_cdrom) + continue; /* cdrom */ + /* Is a hard disk, unplug it. */ + for (j = 0; j < nb_drives; j++) + if (drives_table[j].bdrv == s->bs) + drives_table[j].bdrv = NULL; + bdrv_close(s->bs); + s->bs = NULL; + ide_reset(s); + } +} + +/* Unplug all hard disks except for the primary master (which will + almost always be the boot device). */ +void ide_unplug_aux_harddisks(void) +{ + _ide_unplug_harddisks(1); +} + +/* Unplug all hard disks, including the boot device. */ +void ide_unplug_harddisks(void) +{ + _ide_unplug_harddisks(0); +} + + struct partition { uint8_t boot_ind; /* 0x80 - active */ uint8_t head; /* starting head */ @@ -3290,6 +3332,9 @@ sizeof(PCIIDEState), -1, NULL, NULL); + if (principal_ide_controller) + abort(); + principal_ide_controller = d; d->type = IDE_TYPE_CMD646; pci_conf = d->dev.config; pci_conf[0x00] = 0x95; // CMD646 @@ -3419,6 +3464,9 @@ sizeof(PCIIDEState), devfn, NULL, NULL); + if (principal_ide_controller) + abort(); + principal_ide_controller = d; d->type = IDE_TYPE_PIIX3; pci_conf = d->dev.config; Index: ioemu-remote/hw/pci.c =================================================================== --- ioemu-remote.orig/hw/pci.c 2008-12-15 16:02:19.000000000 +0000 +++ ioemu-remote/hw/pci.c 2008-12-15 16:02:22.000000000 +0000 @@ -26,6 +26,9 @@ #include "console.h" #include "net.h" +#include "exec-all.h" +#include "qemu-xen.h" + //#define DEBUG_PCI struct PCIBus { @@ -648,6 +651,46 @@ } } +void pci_unplug_netifs(void) +{ + PCIBus *bus; + PCIDevice *dev; + PCIIORegion *region; + int x; + int i; + + /* We only support one PCI bus */ + for (bus = first_bus; bus; bus = NULL) { + for (x = 0; x < 256; x++) { + dev = bus->devices[x]; + if (dev && + dev->config[0xa] == 0 && + dev->config[0xb] == 2) { + /* Found a netif. Remove it from the bus. Note that + we don't free it here, since there could still be + references to it floating around. There are only + ever one or two structures leaked, and it's not + worth finding them all. */ + bus->devices[x] = NULL; + for (i = 0; i < PCI_NUM_REGIONS; i++) { + region = &dev->io_regions[i]; + if (region->addr == (uint32_t)-1 || + region->size == 0) + continue; + fprintf(logfile, "region type %d at [%x,%x).\n", + region->type, region->addr, + region->addr+region->size); + if (region->type == PCI_ADDRESS_SPACE_IO) { + isa_unassign_ioport(region->addr, region->size); + } else if (region->type == PCI_ADDRESS_SPACE_MEM) { + unregister_iomem(region->addr); + } + } + } + } + } +} + typedef struct { PCIDevice dev; PCIBus *bus; Index: ioemu-remote/qemu-xen.h =================================================================== --- ioemu-remote.orig/qemu-xen.h 2008-12-15 16:02:19.000000000 +0000 +++ ioemu-remote/qemu-xen.h 2008-12-15 16:02:22.000000000 +0000 @@ -26,8 +26,11 @@ void xen_vga_vram_map(uint64_t vram_addr, int copy); #endif - +void ide_unplug_harddisks(void); +void net_tap_shutdown_all(void); +void pci_unplug_netifs(void); void destroy_hvm_domain(void); +void unregister_iomem(target_phys_addr_t start); #ifdef __ia64__ static inline void xc_domain_shutdown_hook(int xc_handle, uint32_t domid) Index: ioemu-remote/vl.c =================================================================== --- ioemu-remote.orig/vl.c 2008-12-15 16:02:19.000000000 +0000 +++ ioemu-remote/vl.c 2008-12-15 16:02:22.000000000 +0000 @@ -262,6 +262,20 @@ #include "xen-vl-extra.c" +typedef struct IOHandlerRecord { + int fd; + IOCanRWHandler *fd_read_poll; + IOHandler *fd_read; + IOHandler *fd_write; + int deleted; + void *opaque; + /* temporary data */ + struct pollfd *ufd; + struct IOHandlerRecord *next; +} IOHandlerRecord; + +static IOHandlerRecord *first_io_handler; + /***********************************************************/ /* x86 ISA bus support */ @@ -4055,6 +4069,7 @@ typedef struct TAPState { VLANClientState *vc; int fd; + struct TAPState *next; char down_script[1024]; char script_arg[1024]; } TAPState; @@ -4092,6 +4107,34 @@ } } +static TAPState *head_net_tap; + +void net_tap_shutdown_all(void) +{ + struct IOHandlerRecord **pioh, *ioh; + + while (head_net_tap) { + pioh = &first_io_handler; + for (;;) { + ioh = *pioh; + if (ioh == NULL) + break; + if (ioh->fd == head_net_tap->fd) { + *pioh = ioh->next; + qemu_free(ioh); + break; + } + pioh = &ioh->next; + } + if (!ioh) + fprintf(stderr, + "warning: can't find iohandler for %d to close it properly.\n", + head_net_tap->fd); + close(head_net_tap->fd); + head_net_tap = head_net_tap->next; + } +} + /* fd support */ static TAPState *net_tap_fd_init(VLANState *vlan, int fd) @@ -4103,6 +4146,8 @@ return NULL; s->fd = fd; s->vc = qemu_new_vlan_client(vlan, tap_receive, NULL, s); + s->next = head_net_tap; + head_net_tap = s; qemu_set_fd_handler(s->fd, tap_send, NULL, s); snprintf(s->vc->info_str, sizeof(s->vc->info_str), "tap: fd=%d", fd); return s; @@ -5666,20 +5711,6 @@ #define MAX_IO_HANDLERS 64 -typedef struct IOHandlerRecord { - int fd; - IOCanRWHandler *fd_read_poll; - IOHandler *fd_read; - IOHandler *fd_write; - int deleted; - void *opaque; - /* temporary data */ - struct pollfd *ufd; - struct IOHandlerRecord *next; -} IOHandlerRecord; - -static IOHandlerRecord *first_io_handler; - /* XXX: fd_read_poll should be suppressed, but an API change is necessary in the character devices to suppress fd_can_read(). */ int qemu_set_fd_handler2(int fd, Index: ioemu-remote/block-raw-posix.c =================================================================== --- ioemu-remote.orig/block-raw-posix.c 2008-12-15 16:02:19.000000000 +0000 +++ ioemu-remote/block-raw-posix.c 2008-12-15 16:02:22.000000000 +0000 @@ -55,6 +55,7 @@ #include <sys/ioctl.h> #include <linux/cdrom.h> #include <linux/fd.h> +#include <sys/mount.h> #endif #ifdef __FreeBSD__ #include <sys/disk.h> @@ -125,6 +126,10 @@ return ret; } s->fd = fd; +#ifndef CONFIG_STUBDOM + /* Invalidate buffer cache for this device. */ + ioctl(s->fd, BLKFLSBUF, 0); +#endif return 0; } @@ -505,6 +510,10 @@ { BDRVRawState *s = bs->opaque; if (s->fd >= 0) { +#ifndef CONFIG_STUBDOM + /* Invalidate buffer cache for this device. */ + ioctl(s->fd, BLKFLSBUF, 0); +#endif close(s->fd); s->fd = -1; } Index: ioemu-remote/i386-dm/exec-dm.c =================================================================== --- ioemu-remote.orig/i386-dm/exec-dm.c 2008-12-15 16:02:19.000000000 +0000 +++ ioemu-remote/i386-dm/exec-dm.c 2008-12-15 16:02:22.000000000 +0000 @@ -267,7 +267,7 @@ /* XXX: Simple implementation. Fix later */ #define MAX_MMIO 32 -struct mmio_space { +static struct mmio_space { target_phys_addr_t start; unsigned long size; unsigned long io_index; @@ -413,6 +413,17 @@ return 0; } +void unregister_iomem(target_phys_addr_t start) +{ + int index = iomem_index(start); + if (index) { + fprintf(logfile, "squash iomem [%lx, %lx).\n", mmio[index].start, + mmio[index].start + mmio[index].size); + mmio[index].start = mmio[index].size = 0; + } +} + + #if defined(__i386__) || defined(__x86_64__) #define phys_ram_addr(x) (qemu_map_cache(x)) #elif defined(__ia64__) Index: ioemu-remote/hw/xen_platform.c =================================================================== --- ioemu-remote.orig/hw/xen_platform.c 2008-12-15 16:02:19.000000000 +0000 +++ ioemu-remote/hw/xen_platform.c 2008-12-15 16:02:35.000000000 +0000 @@ -24,6 +24,7 @@ */ #include "hw.h" +#include "pc.h" #include "pci.h" #include "irq.h" #include "qemu-xen.h" @@ -163,6 +164,52 @@ cpu_register_physical_memory(addr, 0x1000000, mmio_io_addr); } +#define UNPLUG_ALL_IDE_DISKS 1 +#define UNPLUG_ALL_NICS 2 +#define UNPLUG_AUX_IDE_DISKS 4 + +static void platform_fixed_ioport_write2(void *opaque, uint32_t addr, uint32_t val) +{ + switch (addr - 0x10) { + case 0: + /* Unplug devices. Value is a bitmask of which devices to + unplug, with bit 0 the IDE devices, bit 1 the network + devices, and bit 2 the non-primary-master IDE devices. */ + if (val & UNPLUG_ALL_IDE_DISKS) + ide_unplug_harddisks(); + if (val & UNPLUG_ALL_NICS) { + pci_unplug_netifs(); + net_tap_shutdown_all(); + } + if (val & UNPLUG_AUX_IDE_DISKS) { + ide_unplug_aux_harddisks(); + } + break; + } +} + +static uint32_t platform_fixed_ioport_read2(void *opaque, uint32_t addr) +{ + switch (addr - 0x10) { + case 0: + return 0x49d2; /* Magic value so that you can identify the + interface. */ + default: + return 0xffff; + } +} + +static uint32_t platform_fixed_ioport_read1(void *opaque, uint32_t addr) +{ + switch (addr - 0x10) { + case 2: + /* Version number */ + return 0; + default: + return 0xff; + } +} + struct pci_config_header { uint16_t vendor_id; uint16_t device_id; @@ -255,4 +302,7 @@ register_savevm("platform", 0, 2, xen_pci_save, xen_pci_load, d); printf("Done register platform.\n"); + register_ioport_write(0x10, 16, 2, platform_fixed_ioport_write2, NULL); + register_ioport_read(0x10, 16, 2, platform_fixed_ioport_read2, NULL); + register_ioport_read(0x10, 16, 1, platform_fixed_ioport_read1, NULL); } Index: ioemu-remote/hw/pc.h =================================================================== --- ioemu-remote.orig/hw/pc.h 2008-12-15 16:02:19.000000000 +0000 +++ ioemu-remote/hw/pc.h 2008-12-15 16:02:35.000000000 +0000 @@ -146,6 +146,8 @@ qemu_irq *pic); void pci_piix4_ide_init(PCIBus *bus, BlockDriverState **hd_table, int devfn, qemu_irq *pic); +void ide_unplug_harddisks(void); +void ide_unplug_aux_harddisks(void); /* ne2000.c */

Index: ioemu-remote/hw/xen_platform.c =================================================================== --- ioemu-remote.orig/hw/xen_platform.c 2008-12-15 15:02:53.000000000 +0000 +++ ioemu-remote/hw/xen_platform.c 2008-12-15 15:03:34.000000000 +0000 @@ -29,8 +29,10 @@ #include "irq.h" #include "qemu-xen.h" +#include <assert.h> #include <xenguest.h> +static int throttling_disabled; extern FILE *logfile; static char log_buffer[4096]; static int log_buffer_off; @@ -44,6 +46,88 @@ uint64_t vga_stolen_ram; } PCIXenPlatformState; +/* We throttle access to dom0 syslog, to avoid DOS attacks. This is + modelled as a token bucket, with one token for every byte of log. + The bucket size is 128KB (->1024 lines of 128 bytes each) and + refills at 256B/s. It starts full. The guest is blocked if no + tokens are available when it tries to generate a log message. */ +#define BUCKET_MAX_SIZE (128*1024) +#define BUCKET_FILL_RATE 256 + +static void throttle(unsigned count) +{ + static unsigned available; + static struct timespec last_refil; + static int started; + static int warned; + + struct timespec waiting_for, now; + double delay; + struct timespec ts; + + if (throttling_disabled) + return; + + if (!started) { + clock_gettime(CLOCK_MONOTONIC, &last_refil); + available = BUCKET_MAX_SIZE; + started = 1; + } + + if (count > BUCKET_MAX_SIZE) { + fprintf(logfile, "tried to get %d tokens, but bucket size is %d\n", + BUCKET_MAX_SIZE, count); + exit(1); + } + + if (available < count) { + /* The bucket is empty. Refil it */ + + /* When will it be full enough to handle this request? */ + delay = (double)(count - available) / BUCKET_FILL_RATE; + waiting_for = last_refil; + waiting_for.tv_sec += delay; + waiting_for.tv_nsec += (delay - (int)delay) * 1e9; + if (waiting_for.tv_nsec >= 1000000000) { + waiting_for.tv_nsec -= 1000000000; + waiting_for.tv_sec++; + } + + /* How long do we have to wait? (might be negative) */ + clock_gettime(CLOCK_MONOTONIC, &now); + ts.tv_sec = waiting_for.tv_sec - now.tv_sec; + ts.tv_nsec = waiting_for.tv_nsec - now.tv_nsec; + if (ts.tv_nsec < 0) { + ts.tv_sec--; + ts.tv_nsec += 1000000000; + } + + /* Wait for it. */ + if (ts.tv_sec > 0 || + (ts.tv_sec == 0 && ts.tv_nsec > 0)) { + if (!warned) { + fprintf(logfile, "throttling guest access to syslog"); + warned = 1; + } + while (nanosleep(&ts, &ts) < 0 && errno == EINTR) + ; + } + + /* Refil */ + clock_gettime(CLOCK_MONOTONIC, &now); + delay = (now.tv_sec - last_refil.tv_sec) + + (now.tv_nsec - last_refil.tv_nsec) * 1.0e-9; + available += BUCKET_FILL_RATE * delay; + if (available > BUCKET_MAX_SIZE) + available = BUCKET_MAX_SIZE; + last_refil = now; + } + + assert(available >= count); + + available -= count; +} + static uint32_t xen_platform_ioport_readb(void *opaque, uint32_t addr) { PCIXenPlatformState *s = opaque; @@ -76,6 +160,7 @@ if (val == '\n' || log_buffer_off == sizeof(log_buffer) - 1) { /* Flush buffer */ log_buffer[log_buffer_off] = 0; + throttle(log_buffer_off); fprintf(logfile, "%s\n", log_buffer); log_buffer_off = 0; break; @@ -278,6 +363,7 @@ if (val == '\n' || log_buffer_off == sizeof(log_buffer) - 1) { /* Flush buffer */ log_buffer[log_buffer_off] = 0; + throttle(log_buffer_off); fprintf(logfile, "%s\n", log_buffer); log_buffer_off = 0; break; @@ -302,6 +388,7 @@ { PCIXenPlatformState *d; struct pci_config_header *pch; + struct stat stbuf; printf("Register xen platform.\n"); d = (PCIXenPlatformState *)pci_register_device( @@ -337,4 +424,8 @@ register_ioport_write(0x10, 16, 1, platform_fixed_ioport_write1, NULL); register_ioport_read(0x10, 16, 2, platform_fixed_ioport_read2, NULL); register_ioport_read(0x10, 16, 1, platform_fixed_ioport_read1, NULL); + + if (stat("/etc/disable-guest-log-throttle", &stbuf) == 0) + throttling_disabled = 1; + }

Index: ioemu-remote/hw/xen_platform.c =================================================================== --- ioemu-remote.orig/hw/xen_platform.c 2008-12-15 15:03:34.000000000 +0000 +++ ioemu-remote/hw/xen_platform.c 2008-12-15 15:06:08.000000000 +0000 @@ -32,6 +32,8 @@ #include <assert.h> #include <xenguest.h> +static int drivers_blacklisted; +static uint16_t driver_product_version; static int throttling_disabled; extern FILE *logfile; static char log_buffer[4096]; @@ -341,6 +343,42 @@ ide_unplug_aux_harddisks(); } break; + case 2: + switch (val) { + case 1: + fprintf(logfile, "Citrix Windows PV drivers loaded in guest\n"); + break; + case 0: + fprintf(logfile, "Guest claimed to be running PV product 0?\n"); + break; + default: + fprintf(logfile, "Unknown PV product %d loaded in guest\n", val); + break; + } + driver_product_version = val; + break; + } +} + +static void platform_fixed_ioport_write4(void *opaque, uint32_t addr, + uint32_t val) +{ + switch (addr - 0x10) { + case 0: + /* PV driver version */ + if (driver_product_version == 0) { + fprintf(logfile, + "Drivers tried to set their version number (%d) before setting the product number?\n", + val); + return; + } + fprintf(logfile, "PV driver build %d\n", val); + if (xenstore_pv_driver_build_blacklisted(driver_product_version, + val)) { + fprintf(logfile, "Drivers are blacklisted!\n"); + drivers_blacklisted = 1; + } + break; } } @@ -348,8 +386,14 @@ { switch (addr - 0x10) { case 0: - return 0x49d2; /* Magic value so that you can identify the - interface. */ + if (drivers_blacklisted) { + /* The drivers will recognise this magic number and refuse + * to do anything. */ + return 0xd249; + } else { + /* Magic value so that you can identify the interface. */ + return 0x49d2; + } default: return 0xffff; } @@ -378,7 +422,7 @@ switch (addr - 0x10) { case 2: /* Version number */ - return 0; + return 1; default: return 0xff; } @@ -420,6 +464,7 @@ register_savevm("platform", 0, 2, xen_pci_save, xen_pci_load, d); printf("Done register platform.\n"); + register_ioport_write(0x10, 16, 4, platform_fixed_ioport_write4, NULL); register_ioport_write(0x10, 16, 2, platform_fixed_ioport_write2, NULL); register_ioport_write(0x10, 16, 1, platform_fixed_ioport_write1, NULL); register_ioport_read(0x10, 16, 2, platform_fixed_ioport_read2, NULL); Index: ioemu-remote/qemu-xen.h =================================================================== --- ioemu-remote.orig/qemu-xen.h 2008-12-15 15:02:53.000000000 +0000 +++ ioemu-remote/qemu-xen.h 2008-12-15 15:06:39.000000000 +0000 @@ -91,6 +91,8 @@ char *xenstore_device_model_read(int domid, char *key, unsigned int *len); char *xenstore_read_battery_data(int battery_status); int xenstore_refresh_battery_status(void); +int xenstore_pv_driver_build_blacklisted(uint16_t product_number, + uint32_t build_nr); /* xenfbfront.c */ int xenfb_pv_display_init(DisplayState *ds); Index: ioemu-remote/xenstore.c =================================================================== --- ioemu-remote.orig/xenstore.c 2008-12-15 14:30:47.000000000 +0000 +++ ioemu-remote/xenstore.c 2008-12-15 15:06:08.000000000 +0000 @@ -782,6 +782,34 @@ free(path); } +int +xenstore_pv_driver_build_blacklisted(uint16_t product_nr, + uint32_t build_nr) +{ + char *buf = NULL; + char *tmp; + const char *product; + + switch (product_nr) { + case 1: + product = "xensource-windows"; + break; + default: + /* Don't know what product this is -> we can't blacklist + * it. */ + return 0; + } + if (asprintf(&buf, "/mh/driver-blacklist/%s/%d", product, build_nr) < 0) + return 0; + tmp = xs_read(xsh, XBT_NULL, buf, NULL); + free(tmp); + free(buf); + if (tmp == NULL) + return 0; + else + return 1; +} + void xenstore_record_dm_state(char *state) { xenstore_record_dm("state", state);

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