Patchwork [2/2] qga: add windows implementation for guest-set-time

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Submitter Lei Li
Date March 6, 2013, 1:45 p.m.
Message ID <1362577504-7994-3-git-send-email-lilei@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/225494/
State New
Headers show

Comments

Lei Li - March 6, 2013, 1:45 p.m.
Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 qga/commands-win32.c |   35 +++++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+), 0 deletions(-)
Eric Blake - March 6, 2013, 3:05 p.m.
On 03/06/2013 06:45 AM, Lei Li wrote:
> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> ---
>  qga/commands-win32.c |   35 +++++++++++++++++++++++++++++++++++
>  1 files changed, 35 insertions(+), 0 deletions(-)
> 
> diff --git a/qga/commands-win32.c b/qga/commands-win32.c
> index 4febec7..1a90aa7 100644
> --- a/qga/commands-win32.c
> +++ b/qga/commands-win32.c
> @@ -136,6 +136,41 @@ int64_t qmp_guest_get_time(Error **errp)
>     return time_ns;
>  }
>  
> +void qmp_guest_set_time(int64_t time_ns, Error **errp)
> +{
> +    SYSTEMTIME ts;
> +    FILETIME tf;
> +    LONGLONG time;
> +
> +    /* year-2038 will overflow in case time_t is 32bit */
> +    if (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
> +        error_setg(errp, "Time %" PRId64 " is too large", time_ns);
> +        return;
> +    }

Do you really need this?  That is, don't you already know what size
time_t is on windows; not to mention that on Windows, you aren't going
through time_t, but directly to tf.dwHighDateTime.

> +
> +    acquire_privilege(SE_SYSTEMTIME_NAME, errp);
> +    if (error_is_set(errp)) {
> +        error_setg(errp, "Failed to acquire privilege");
> +        return;
> +    }
> +
> +    time = time_ns / 100 + _W32_FT_OFFSET;

On the other hand, _this_ operation can overflow, so you should be
checking that time_ns doesn't result in an unexpected time value.

> +
> +    tf.dwLowDateTime = (DWORD) time;
> +    tf.dwHighDateTime = (DWORD) (time >> 32);
> +
> +    if (!FileTimeToSystemTime(&tf, &ts)) {
> +        error_setg(errp, "Failed to convert system time");
> +        return;
> +    }
> +
> +    if (!SetSystemTime(&ts)) {
> +        slog("guest-set-time failed: %d", GetLastError());
> +        error_setg_errno(errp, errno, "Failed to set time to guest");
> +        return;
> +    }   

Trailing whitespace.  Run your submission through scripts/checkpatch.pl.

Should you relinquish the SE_SYSTEMTIME_NAME privilege when exiting this
function, instead of leaving it always enabled for the remaining life of
the agent service?
Lei Li - March 7, 2013, 8:04 a.m.
On 03/06/2013 11:05 PM, Eric Blake wrote:
> On 03/06/2013 06:45 AM, Lei Li wrote:
>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
>> ---
>>   qga/commands-win32.c |   35 +++++++++++++++++++++++++++++++++++
>>   1 files changed, 35 insertions(+), 0 deletions(-)
>>
>> diff --git a/qga/commands-win32.c b/qga/commands-win32.c
>> index 4febec7..1a90aa7 100644
>> --- a/qga/commands-win32.c
>> +++ b/qga/commands-win32.c
>> @@ -136,6 +136,41 @@ int64_t qmp_guest_get_time(Error **errp)
>>      return time_ns;
>>   }
>>   
>> +void qmp_guest_set_time(int64_t time_ns, Error **errp)
>> +{
>> +    SYSTEMTIME ts;
>> +    FILETIME tf;
>> +    LONGLONG time;
>> +
>> +    /* year-2038 will overflow in case time_t is 32bit */
>> +    if (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
>> +        error_setg(errp, "Time %" PRId64 " is too large", time_ns);
>> +        return;
>> +    }
> Do you really need this?  That is, don't you already know what size
> time_t is on windows; not to mention that on Windows, you aren't going
> through time_t, but directly to tf.dwHighDateTime.

You are right.

>
>> +
>> +    acquire_privilege(SE_SYSTEMTIME_NAME, errp);
>> +    if (error_is_set(errp)) {
>> +        error_setg(errp, "Failed to acquire privilege");
>> +        return;
>> +    }
>> +
>> +    time = time_ns / 100 + _W32_FT_OFFSET;
> On the other hand, _this_ operation can overflow, so you should be
> checking that time_ns doesn't result in an unexpected time value.

OK.

>> +
>> +    tf.dwLowDateTime = (DWORD) time;
>> +    tf.dwHighDateTime = (DWORD) (time >> 32);
>> +
>> +    if (!FileTimeToSystemTime(&tf, &ts)) {
>> +        error_setg(errp, "Failed to convert system time");
>> +        return;
>> +    }
>> +
>> +    if (!SetSystemTime(&ts)) {
>> +        slog("guest-set-time failed: %d", GetLastError());
>> +        error_setg_errno(errp, errno, "Failed to set time to guest");
>> +        return;
>> +    }
> Trailing whitespace.  Run your submission through scripts/checkpatch.pl.

Yes.

> Should you relinquish the SE_SYSTEMTIME_NAME privilege when exiting this
> function, instead of leaving it always enabled for the remaining life of
> the agent service?

According to the remarks on msdn, this SetSystemTime function will
disables the SE_SYSTEMTIME_NAME privilege before returning.

Patch

diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 4febec7..1a90aa7 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -136,6 +136,41 @@  int64_t qmp_guest_get_time(Error **errp)
    return time_ns;
 }
 
+void qmp_guest_set_time(int64_t time_ns, Error **errp)
+{
+    SYSTEMTIME ts;
+    FILETIME tf;
+    LONGLONG time;
+
+    /* year-2038 will overflow in case time_t is 32bit */
+    if (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
+        error_setg(errp, "Time %" PRId64 " is too large", time_ns);
+        return;
+    }
+
+    acquire_privilege(SE_SYSTEMTIME_NAME, errp);
+    if (error_is_set(errp)) {
+        error_setg(errp, "Failed to acquire privilege");
+        return;
+    }
+
+    time = time_ns / 100 + _W32_FT_OFFSET;
+
+    tf.dwLowDateTime = (DWORD) time;
+    tf.dwHighDateTime = (DWORD) (time >> 32);
+
+    if (!FileTimeToSystemTime(&tf, &ts)) {
+        error_setg(errp, "Failed to convert system time");
+        return;
+    }
+
+    if (!SetSystemTime(&ts)) {
+        slog("guest-set-time failed: %d", GetLastError());
+        error_setg_errno(errp, errno, "Failed to set time to guest");
+        return;
+    }   
+}
+
 int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode, Error **err)
 {
     error_set(err, QERR_UNSUPPORTED);