Win32 Programming Lesson 8a: Jobs

Where are we?  Grouping processes into logical groups: Jobs  However, processes don’t retain a parent- child relationship which can make life difficult… very difficult

Jobs  Introduced in Windows 2000  Based upon the Job Kernel Object  Ability to add restrictions to processes (and groups of processes)

CreateJobObject  HANDLE CreateJobObject( PSECURITY_ATTRIBUTES psa, PCTSTR pszName);  Like most calls, we first name our Job Object… can also open an existing object: HANDLE OpenJobObject( DWORD dwDesiredAccess, BOOL bInheritHandle, PCTSTR pszName);

Placing Restrictions on a Job  Jobs can be restricted in several ways Resource Limits UI Limits Security limits (registry, subkeys, files etc.)  Set by: BOOL SetInformationJobObject( HANDLE hJob, JOBOBJECTINFOCLASS JobObjectInformationClass, PVOID pJobObjectInformation, DWORD cbJobObjectInformationLength);

JobObjectInfoClass  Enumerated type setting the limit type Basic Limit Extended Basic Limit Basic UI Restrictions Security Limit  Defines the type of the 3 rd Parameter in the call

Basic Limits  typedef struct _JOBOBJECT_BASIC_LIMIT_INFORMATI ON { LARGE_INTEGER PerProcessUserTimeLimit; LARGE_INTEGER PerJobUserTimeLimit; DWORD LimitFlags; DWORD MinimumWorkingSetSize; DWORD MaximumWorkingSetSize; DWORD ActiveProcessLimit; DWORD_PTR Affinity; DWORD PriorityClass; DWORD SchedulingClass; } JOBOBJECT_BASIC_LIMIT_INFORMATION, *PJOBO BJECT_BASIC_LIMIT_INFORMATION;

Extended Limits  typedef struct _JOBOBJECT_EXTENDED_LIMIT_ INFORMATION { JOBOBJECT_BASIC_LIMIT_INFORMATION BasicLimitInformation; IO_COUNTERS IoInfo; SIZE_T ProcessMemoryLimit; SIZE_T JobMemoryLimit; SIZE_T PeakProcessMemoryUsed; SIZE_T PeakJobMemoryUsed; } JOBOBJECT_EXTENDED_LIMIT_INFORMAT ION, *PJOBOBJECT_EXTENDED_LIMIT_INFO RMATION;

UI Limits JOB_OBJECT_UILIMIT_EXITWINDOWS Prevents processes from logging off, shutting down, rebooting, or powering off the system via the ExitWindowsEx function JOB_OBJECT_UILIMIT_READCLIPBOARDPrevents processes from reading the clipboard JOB_OBJECT_UILIMIT_WRITECLIPBOARDPrevents processes from erasing the clipboard JOB_OBJECT_UILIMIT_SYSTEMPARAMETERSPrevents processes from changing system parameters via the SystemParametersInfo function JOB_OBJECT_UILIMIT_DISPLAYSETTINGSPrevents processes from changing the display settings via the ChangeDisplaySettings function JOB_OBJECT_UILIMIT_GLOBALATOMSGives the job its own global atom table and restricts processes in the job to accessing only the job's table JOB_OBJECT_UILIMIT_DESKTOPPrevents processes from creating or switching desktops using the CreateDesktop or SwitchDesktop function JOB_OBJECT_UILIMIT_HANDLESPrevents processes in a job from using USER objects (such as HWNDs) created by processes outside the same job

Placing a Process in a Job  BOOL AssignProcessToJobObject( HANDLE hJob, HANDLE hProcess);  Create the job…  Place restrictions on the job…  CreateProcess with CREATE_SUSPENDED  Call AssignProcessToJob New processes spawned by a job are automatically part of the job

Terminating All Processes in A Job  Simple! BOOL TerminateJobObject( HANDLE hJob, UINT uExitCode);

Job Accounting  Fairly simple Uses JOBOBJECT_BASIC_ACCOUNTING_INFORMATIO N  See brary/en-us/dllproc/base/isprocessinjob.asp brary/en-us/dllproc/base/isprocessinjob.asp

Notifications  It is possible to receive notifications from jobs as they complete, but it’s somewhat complicated  Should be aware of the I/O Completion Port Kernel Object  Example: JobLab example application