Instructions for porting top to other architectures. This is still a preliminary document. Suggestions for improvement are most welcome. Before you embark on a port, please send me a mail message telling me what platform you are porting top to. There are three reasons for this: (1) I may already have a port, (2) module naming needs to be centralized, (3) I want to loosely track the various porting efforts. You do not need to wait for an "okay", but I do want to know that you are working on it. And of course, once it is finished, please send me the module files so that I can add them to the main distribution! ---------- There is one set of functions which extract all the information that top needs for display. These functions are collected in to one file. To make top work on a different architecture simply requires a different implementation of these functions. The functions for a given architecture "foo" are stored in a file called "m_foo.c". The Configure script looks for these files and lets the configurer choose one of them. This file is called a "module". The idea is that making top work on a different machine only requires one additional file and does not require changes to any existing files. A module template is included in the distribution, called "m-template". To write your own module, it is a good idea to start with this template. If you architecture is similar to one for which a module already exists, then you can start with that module instead. If you do so, remember to change the "AUTHOR" section at the top! The first comment in a module contains information which is extracted and used by Configure. This information is marked with words in all capitals (such as "SYNOPSIS:" and "LIBS:"). Go look at m-template: it is fairly self-explanatory. The text after "LIBS:" (on the same line) is extracted and included in the LIBS definition of the Makefile so that extra libraries which may be necessary on some machines (such as "-lkvm") can be specified in the module. The text after "CFLAGS:" (on the same line) is extracted and included as flags in the "CFLAGS" definition of the Makefile (thus in every compilation step). This is used for rare circumstances only: please don't abuse this hook. Some operating systems have idiosyncrasies which will affect the form and/or content of the information top displays. You may wish to document such anomalies in the top man page. This can be done by adding a file called m_{modulename}.man (where {modulename} is replaced with the name of the module). Configure will automatically add this file to the end of the man page. See m_sunos4.man for an example. A module is concerned with two structures: The statics struct is filled in by machine_init. Each item is a pointer to a list of character pointers. The list is terminated with a null pointer. struct statics { char **procstate_names; /* process state names */ char **cpustate_names; /* cpu state names */ char **memory_names; /* memory information names */ }; The system_info struct is filled in by get_system_info and get_process_info. struct system_info { int last_pid; /* last pid assigned (0 means non-sequential assignment) */ double load_avg[NUM_AVERAGES]; /* see below */ int p_total; /* total number of processes */ int p_active; /* number of procs considered "active" */ int *procstates; /* array of process state counters */ int *cpustates; /* array of cpustate counters */ int *memory; /* memory information */ }; The last three pointers each point to an array of integers. The length of the array is determined by the length of the corresponding _names array in the statics structure. Furthermore, if an entry in a _names array is the empty string ("") then the corresponding value in the value array will be skipped over. The display routine displays, for example, the string procstate_names[0] then the number procstates[0], then procstate_names[1], procstates[1], etc. until procstate_names[N] == NULL. This allows for a tremendous amount of flexibility in labeling the displayed values. "procstates" and "memory" are displayed as straight integer values. Values in "cpustates" are displayed as a percentage * 10. For example, the (integer) value 105 is displayed as 10.5%. These routines must be defined by the machine dependent module. int machine_init(struct statics *) returns 0 on success and -1 on failure, prints error messages char *format_header(char *) Returns a string which should be used as the header for the process display area. The argument is a string used to label the username column (either "USERNAME" or "UID") and is always 8 characters in length. void get_system_info(struct system_info *) caddr_t get_process_info(struct system_info *, int, int, int (*func)()) returns a handle to use with format_next_process char *format_next_process(caddr_t, char *(*func)()) returns string which describes next process int proc_compare(caddr_t, caddr_t) qsort comparison function uid_t proc_owner(pid_t) Returns the uid owner of the process specified by the pid argument. This function is VERY IMPORTANT. If it fails to do its job, then top may pose a security risk. get_process_info is called immediately after get_system_info. In fact, the two functions could be rolled in to one. The reason they are not is mostly historical. Top relies on the existence of a function called "setpriority" to change a process's priority. This exists as a kernel call on most 4.3 BSD derived Unixes. If neither your operating system nor your C library supplies such a function, then you will need to add one to the module. It is defined as follows: int setpriority (int dummy, int who, int niceval) For the purposes of top, the first argument is meaningless. The second is the pid and the third is the new nice value. This function should behave just like a kernel call, setting errno and returning -1 in case of an error. This function MUST check to make sure that a non-root user does not specify a nice value less than the process's current value. If it detects such a condition, it should set errno to EACCES and return -1. Other possible ERRNO values: ESRCH when pid "who" does not exist, EPERM when the invoker is not root and not the same as the process owner. Note that top checks process ownership and should never call setpriority when the invoker's uid is not root and not the same as the process's owner uid. The file "machine.h" contains definitions which are useful to modules and to top.c (such as the structure definitions). You SHOULD NOT need to change it when porting to a new platform. Porting to a new platform should NOT require any changes to existing files. You should only need to add m_ files. If you feel you need a change in one of the existing files, please contact me so that we can discuss the details. I want to keep such changes as general as possible. -------- Changes were made to the module interface between 3.5 and 3.6. Here are the changes that need to be made to port a 3.5 module to 3.6: The array that stores memory statistics and is passed back in the system information structure as "memory" must now be an array of (signed) longs. This was done to more easily accomodate systems that have gigabytes of memory. Since the numbers are supposed to be kilobytes, a long can still represent up to 2 terabytes. Look for "int memory_stats[X]" (where "X" is some arbitrary number) and change it to "long memory_stats[X]". If the module support reporting swap information on a separate line, then its "swap_stats" array also needs to be an array of longs. The argument to proc_owner should be an int, as in "int pid". When it is used in proc_owner it should be cast as necessary. Many operating systems will require it to be cast to a pid_t before being compared to the appropriate element in the proc structure. In the function format_next_process, the last argument in the main call to sprintf is the string that contains the command for the process. Make sure that this last argument is enclosed in a call to "printable". For example: "printable(MPP(pp, p_comm))". The third argument to "get_process_info" needs to be changed to an integer, typically "int compare_index". The call to qsort in get_process_info may be guarded by "if (compare != NULL)". If it is, remove the if statement. The other changes to get_process_info depends on whether or not the module supports multiple sort orders. To support multiple keys: Create an array int (*proc_compares[])() and assign to it the list of comparison functions, NULL terminated. For example: int (*proc_compares[])() = { compare_cpu, compare_size, compare_res, compare_time, NULL }; In get_process_info there is a call to qsort which uses one of the functions in proc_compares. It should be changed so that its fourth argument is "proc_compares[compare_index]". If the module contains the function "proc_compare", it should be removed. There should also be a NULL-terminated array of strings which list the names for the sort keys, for example: char *ordernames[] = {"cpu", "size", "res", "time", NULL}; To indicate that this module supports multiple sort keys, add the following line in machine_init: statics->order_names = ordernames; If there is no support for multiple keys: Leave statics->order_names alone and call the comparison function of your choice in get_process_info, ignoring the third argument.