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minix/kernel/system.c

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/* This task handles the interface between the kernel and user-level servers.
* System services can be accessed by doing a system call. System calls are
* transformed into request messages, which are handled by this task. By
* convention, a sys_call() is transformed in a SYS_CALL request message that
* is handled in a function named do_call().
*
* A private call vector is used to map all system calls to the functions that
* handle them. The actual handler functions are contained in separate files
* to keep this file clean. The call vector is used in the system task's main
* loop to handle all incoming requests.
*
* In addition to the main sys_task() entry point, which starts the main loop,
* there are several other minor entry points:
* get_priv: assign privilege structure to user or system process
* set_sendto_bit: allow a process to send messages to a new target
* unset_sendto_bit: disallow a process from sending messages to a target
* send_sig: send a signal directly to a system process
* cause_sig: take action to cause a signal to occur via a signal mgr
* sig_delay_done: tell PM that a process is not sending
* umap_bios: map virtual address in BIOS_SEG to physical
* get_randomness: accumulate randomness in a buffer
* clear_endpoint: remove a process' ability to send and receive messages
*
* Changes:
* Nov 22, 2009 get_priv supports static priv ids (Cristiano Giuffrida)
* Aug 04, 2005 check if system call is allowed (Jorrit N. Herder)
* Jul 20, 2005 send signal to services with message (Jorrit N. Herder)
* Jan 15, 2005 new, generalized virtual copy function (Jorrit N. Herder)
* Oct 10, 2004 dispatch system calls from call vector (Jorrit N. Herder)
* Sep 30, 2004 source code documentation updated (Jorrit N. Herder)
*/
#include "debug.h"
#include "kernel.h"
#include "system.h"
#include "proc.h"
#include "vm.h"
#include <stdlib.h>
#include <assert.h>
#include <signal.h>
#include <unistd.h>
#include <sys/sigcontext.h>
#include <minix/endpoint.h>
#include <minix/safecopies.h>
/* Declaration of the call vector that defines the mapping of system calls
* to handler functions. The vector is initialized in sys_init() with map(),
* which makes sure the system call numbers are ok. No space is allocated,
* because the dummy is declared extern. If an illegal call is given, the
* array size will be negative and this won't compile.
*/
PUBLIC int (*call_vec[NR_SYS_CALLS])(struct proc * caller, message *m_ptr);
char *callnames[NR_SYS_CALLS];
#define map(call_nr, handler) \
{extern int dummy[NR_SYS_CALLS>(unsigned)(call_nr-KERNEL_CALL) ? 1:-1];} \
callnames[(call_nr-KERNEL_CALL)] = #call_nr; \
call_vec[(call_nr-KERNEL_CALL)] = (handler)
PRIVATE void kernel_call_finish(struct proc * caller, message *msg, int result)
{
if(result == VMSUSPEND) {
/* Special case: message has to be saved for handling
* until VM tells us it's allowed. VM has been notified
* and we must wait for its reply to restart the call.
*/
assert(RTS_ISSET(caller, RTS_VMREQUEST));
assert(caller->p_vmrequest.type == VMSTYPE_KERNELCALL);
caller->p_vmrequest.saved.reqmsg = *msg;
caller->p_misc_flags |= MF_KCALL_RESUME;
} else {
/*
* call is finished, we could have been suspended because of VM,
* remove the request message
*/
caller->p_vmrequest.saved.reqmsg.m_source = NONE;
if (result != EDONTREPLY) {
/* copy the result as a message to the original user buffer */
msg->m_source = SYSTEM;
msg->m_type = result; /* report status of call */
if (copy_msg_to_user(caller, msg,
(message *)caller->p_delivermsg_vir)) {
printf("WARNING wrong user pointer 0x%08x from "
"process %s / %d\n",
caller->p_delivermsg_vir,
caller->p_name,
caller->p_endpoint);
}
}
}
}
PRIVATE int kernel_call_dispatch(struct proc * caller, message *msg)
{
int result = OK;
int call_nr;
call_nr = msg->m_type - KERNEL_CALL;
/* See if the caller made a valid request and try to handle it. */
if (call_nr < 0 || call_nr >= NR_SYS_CALLS) { /* check call number */
printf("SYSTEM: illegal request %d from %d.\n",
call_nr,msg->m_source);
result = EBADREQUEST; /* illegal message type */
}
else if (!GET_BIT(priv(caller)->s_k_call_mask, call_nr)) {
printf("SYSTEM: denied request %d from %d.\n",
call_nr,msg->m_source);
result = ECALLDENIED; /* illegal message type */
} else {
/* handle the system call */
result = (*call_vec[call_nr])(caller, msg);
}
return result;
}
/*===========================================================================*
* kernel_call *
*===========================================================================*/
/*
* this function checks the basic syscall parameters and if accepted it
* dispatches its handling to the right handler
*/
PUBLIC void kernel_call(message *m_user, struct proc * caller)
{
int result = OK;
message msg;
caller->p_delivermsg_vir = (vir_bytes) m_user;
/*
* the ldt and cr3 of the caller process is loaded because it just've trapped
* into the kernel or was already set in schedcheck() before we resume
* execution of an interrupted kernel call
*/
if (copy_msg_from_user(caller, m_user, &msg) == 0) {
msg.m_source = caller->p_endpoint;
result = kernel_call_dispatch(caller, &msg);
}
else {
printf("WARNING wrong user pointer 0x%08x from process %s / %d\n",
m_user, caller->p_name, caller->p_endpoint);
result = EBADREQUEST;
}
kernel_call_finish(caller, &msg, result);
}
/*===========================================================================*
* initialize *
*===========================================================================*/
PUBLIC void system_init(void)
{
register struct priv *sp;
int i;
/* Initialize IRQ handler hooks. Mark all hooks available. */
for (i=0; i<NR_IRQ_HOOKS; i++) {
irq_hooks[i].proc_nr_e = NONE;
}
/* Initialize all alarm timers for all processes. */
for (sp=BEG_PRIV_ADDR; sp < END_PRIV_ADDR; sp++) {
tmr_inittimer(&(sp->s_alarm_timer));
}
/* Initialize the call vector to a safe default handler. Some system calls
* may be disabled or nonexistant. Then explicitely map known calls to their
* handler functions. This is done with a macro that gives a compile error
* if an illegal call number is used. The ordering is not important here.
*/
for (i=0; i<NR_SYS_CALLS; i++) {
call_vec[i] = do_unused;
callnames[i] = "unused";
}
/* Process management. */
map(SYS_FORK, do_fork); /* a process forked a new process */
map(SYS_EXEC, do_exec); /* update process after execute */
map(SYS_CLEAR, do_clear); /* clean up after process exit */
map(SYS_EXIT, do_exit); /* a system process wants to exit */
map(SYS_PRIVCTL, do_privctl); /* system privileges control */
map(SYS_TRACE, do_trace); /* request a trace operation */
map(SYS_SETGRANT, do_setgrant); /* get/set own parameters */
map(SYS_RUNCTL, do_runctl); /* set/clear stop flag of a process */
map(SYS_UPDATE, do_update); /* update a process into another */
map(SYS_STATECTL, do_statectl); /* let a process control its state */
/* Signal handling. */
map(SYS_KILL, do_kill); /* cause a process to be signaled */
map(SYS_GETKSIG, do_getksig); /* signal manager checks for signals */
map(SYS_ENDKSIG, do_endksig); /* signal manager finished signal */
map(SYS_SIGSEND, do_sigsend); /* start POSIX-style signal */
map(SYS_SIGRETURN, do_sigreturn); /* return from POSIX-style signal */
/* Device I/O. */
map(SYS_IRQCTL, do_irqctl); /* interrupt control operations */
map(SYS_DEVIO, do_devio); /* inb, inw, inl, outb, outw, outl */
map(SYS_VDEVIO, do_vdevio); /* vector with devio requests */
/* Memory management. */
map(SYS_NEWMAP, do_newmap); /* set up a process memory map */
map(SYS_SEGCTL, do_segctl); /* add segment and get selector */
map(SYS_MEMSET, do_memset); /* write char to memory area */
map(SYS_VMCTL, do_vmctl); /* various VM process settings */
/* Copying. */
map(SYS_UMAP, do_umap); /* map virtual to physical address */
map(SYS_VIRCOPY, do_vircopy); /* use pure virtual addressing */
map(SYS_PHYSCOPY, do_copy); /* use physical addressing */
map(SYS_SAFECOPYFROM, do_safecopy); /* copy with pre-granted permission */
map(SYS_SAFECOPYTO, do_safecopy); /* copy with pre-granted permission */
map(SYS_VSAFECOPY, do_vsafecopy); /* vectored safecopy */
/* Mapping. */
map(SYS_SAFEMAP, do_safemap); /* map pages from other process */
map(SYS_SAFEREVMAP, do_saferevmap); /* grantor revokes the map grant */
map(SYS_SAFEUNMAP, do_safeunmap); /* requestor unmaps the mapped pages */
/* Clock functionality. */
map(SYS_TIMES, do_times); /* get uptime and process times */
map(SYS_SETALARM, do_setalarm); /* schedule a synchronous alarm */
map(SYS_STIME, do_stime); /* set the boottime */
map(SYS_VTIMER, do_vtimer); /* set or retrieve a virtual timer */
/* System control. */
map(SYS_ABORT, do_abort); /* abort MINIX */
map(SYS_GETINFO, do_getinfo); /* request system information */
map(SYS_SYSCTL, do_sysctl); /* misc system manipulation */
/* Profiling. */
map(SYS_SPROF, do_sprofile); /* start/stop statistical profiling */
map(SYS_CPROF, do_cprofile); /* get/reset call profiling data */
map(SYS_PROFBUF, do_profbuf); /* announce locations to kernel */
/* i386-specific. */
#if _MINIX_CHIP == _CHIP_INTEL
map(SYS_INT86, do_int86); /* real-mode BIOS calls */
map(SYS_READBIOS, do_readbios); /* read from BIOS locations */
map(SYS_IOPENABLE, do_iopenable); /* Enable I/O */
map(SYS_SDEVIO, do_sdevio); /* phys_insb, _insw, _outsb, _outsw */
/* Machine state switching. */
map(SYS_SETMCONTEXT, do_setmcontext); /* set machine context */
map(SYS_GETMCONTEXT, do_getmcontext); /* get machine context */
#endif
/* Scheduling */
map(SYS_SCHEDULE, do_schedule); /* reschedule a process */
map(SYS_SCHEDCTL, do_schedctl); /* change process scheduler */
}
/*===========================================================================*
* get_priv *
*===========================================================================*/
PUBLIC int get_priv(rc, priv_id)
register struct proc *rc; /* new (child) process pointer */
int priv_id; /* privilege id */
{
/* Allocate a new privilege structure for a system process. Privilege ids
* can be assigned either statically or dynamically.
*/
register struct priv *sp; /* privilege structure */
if(priv_id == NULL_PRIV_ID) { /* allocate slot dynamically */
for (sp = BEG_DYN_PRIV_ADDR; sp < END_DYN_PRIV_ADDR; ++sp)
if (sp->s_proc_nr == NONE) break;
if (sp >= END_DYN_PRIV_ADDR) return(ENOSPC);
}
else { /* allocate slot from id */
if(!is_static_priv_id(priv_id)) {
return EINVAL; /* invalid static priv id */
}
if(priv[priv_id].s_proc_nr != NONE) {
return EBUSY; /* slot already in use */
}
sp = &priv[priv_id];
}
rc->p_priv = sp; /* assign new slot */
rc->p_priv->s_proc_nr = proc_nr(rc); /* set association */
return(OK);
}
/*===========================================================================*
* set_sendto_bit *
*===========================================================================*/
PUBLIC void set_sendto_bit(const struct proc *rp, int id)
{
/* Allow a process to send messages to the process(es) associated with the
* system privilege structure with the given ID.
*/
/* Disallow the process from sending to a process privilege structure with no
* associated process, and disallow the process from sending to itself.
*/
if (id_to_nr(id) == NONE || priv_id(rp) == id) {
unset_sys_bit(priv(rp)->s_ipc_to, id);
return;
}
set_sys_bit(priv(rp)->s_ipc_to, id);
/* The process that this process can now send to, must be able to reply (or
* vice versa). Therefore, its send mask should be updated as well. Ignore
* receivers that don't support traps other than RECEIVE, they can't reply
* or send messages anyway.
*/
if (priv_addr(id)->s_trap_mask & ~((1 << RECEIVE)))
set_sys_bit(priv_addr(id)->s_ipc_to, priv_id(rp));
}
/*===========================================================================*
* unset_sendto_bit *
*===========================================================================*/
PUBLIC void unset_sendto_bit(const struct proc *rp, int id)
{
/* Prevent a process from sending to another process. Retain the send mask
* symmetry by also unsetting the bit for the other direction.
*/
unset_sys_bit(priv(rp)->s_ipc_to, id);
unset_sys_bit(priv_addr(id)->s_ipc_to, priv_id(rp));
}
/*===========================================================================*
* send_sig *
*===========================================================================*/
PUBLIC void send_sig(endpoint_t proc_nr, int sig_nr)
{
/* Notify a system process about a signal. This is straightforward. Simply
* set the signal that is to be delivered in the pending signals map and
* send a notification with source SYSTEM.
*/
register struct proc *rp;
if(!isokprocn(proc_nr) || isemptyn(proc_nr))
panic("send_sig to empty process: %d", proc_nr);
rp = proc_addr(proc_nr);
sigaddset(&priv(rp)->s_sig_pending, sig_nr);
mini_notify(proc_addr(SYSTEM), rp->p_endpoint);
}
/*===========================================================================*
* cause_sig *
*===========================================================================*/
PUBLIC void cause_sig(proc_nr, sig_nr)
proc_nr_t proc_nr; /* process to be signalled */
int sig_nr; /* signal to be sent */
{
/* A system process wants to send a signal to a process. Examples are:
* - HARDWARE wanting to cause a SIGSEGV after a CPU exception
* - TTY wanting to cause SIGINT upon getting a DEL
* - FS wanting to cause SIGPIPE for a broken pipe
* Signals are handled by sending a message to the signal manager assigned to
* the process. This function handles the signals and makes sure the signal
* manager gets them by sending a notification. The process being signaled
* is blocked while the signal manager has not finished all signals for it.
* Race conditions between calls to this function and the system calls that
* process pending kernel signals cannot exist. Signal related functions are
* only called when a user process causes a CPU exception and from the kernel
* process level, which runs to completion.
*/
register struct proc *rp;
endpoint_t sig_mgr;
/* Lookup signal manager. */
rp = proc_addr(proc_nr);
sig_mgr = priv(rp)->s_sig_mgr;
/* If the target is the signal manager of itself, send the signal directly. */
if(rp->p_endpoint == sig_mgr) {
if(SIGS_IS_LETHAL(sig_nr)) {
proc_stacktrace(rp);
panic("cause_sig: signal manager gets lethal signal %d for itself",
sig_nr);
}
sigaddset(&priv(rp)->s_sig_pending, sig_nr);
send_sig(rp->p_endpoint, SIGKSIGSM);
return;
}
/* Check if the signal is already pending. Process it otherwise. */
if (! sigismember(&rp->p_pending, sig_nr)) {
sigaddset(&rp->p_pending, sig_nr);
if (! (RTS_ISSET(rp, RTS_SIGNALED))) { /* other pending */
RTS_SET(rp, RTS_SIGNALED | RTS_SIG_PENDING);
send_sig(sig_mgr, SIGKSIG);
}
}
}
/*===========================================================================*
* sig_delay_done *
*===========================================================================*/
PUBLIC void sig_delay_done(struct proc *rp)
{
/* A process is now known not to send any direct messages.
* Tell PM that the stop delay has ended, by sending a signal to the process.
* Used for actual signal delivery.
*/
rp->p_misc_flags &= ~MF_SIG_DELAY;
cause_sig(proc_nr(rp), SIGSNDELAY);
}
#if _MINIX_CHIP == _CHIP_INTEL
/*===========================================================================*
* umap_bios *
*===========================================================================*/
PUBLIC phys_bytes umap_bios(vir_addr, bytes)
vir_bytes vir_addr; /* virtual address in BIOS segment */
vir_bytes bytes; /* # of bytes to be copied */
{
/* Calculate the physical memory address at the BIOS. Note: currently, BIOS
* address zero (the first BIOS interrupt vector) is not considered as an
* error here, but since the physical address will be zero as well, the
* calling function will think an error occurred. This is not a problem,
* since no one uses the first BIOS interrupt vector.
*/
/* Check all acceptable ranges. */
if (vir_addr >= BIOS_MEM_BEGIN && vir_addr + bytes <= BIOS_MEM_END)
return (phys_bytes) vir_addr;
else if (vir_addr >= BASE_MEM_TOP && vir_addr + bytes <= UPPER_MEM_END)
return (phys_bytes) vir_addr;
printf("Warning, error in umap_bios, virtual address 0x%x\n", vir_addr);
return 0;
}
#endif
/*===========================================================================*
* umap_grant *
*===========================================================================*/
PUBLIC phys_bytes umap_grant(rp, grant, bytes)
struct proc *rp; /* pointer to proc table entry for process */
cp_grant_id_t grant; /* grant no. */
vir_bytes bytes; /* size */
{
int proc_nr;
vir_bytes offset, ret;
endpoint_t granter;
/* See if the grant in that process is sensible, and
* find out the virtual address and (optionally) new
* process for that address.
*
* Then convert that process to a slot number.
*/
if(verify_grant(rp->p_endpoint, ANY, grant, bytes, 0, 0,
&offset, &granter) != OK) {
printf("SYSTEM: umap_grant: verify_grant failed\n");
return 0;
}
if(!isokendpt(granter, &proc_nr)) {
printf("SYSTEM: umap_grant: isokendpt failed\n");
return 0;
}
/* Do the mapping from virtual to physical. */
ret = umap_virtual(proc_addr(proc_nr), D, offset, bytes);
if(!ret) {
printf("SYSTEM:umap_grant:umap_virtual failed; grant %s:%d -> %s: vir 0x%lx\n",
rp->p_name, grant,
proc_addr(proc_nr)->p_name, offset);
}
return ret;
}
/*===========================================================================*
* clear_endpoint *
*===========================================================================*/
PUBLIC void clear_endpoint(rc)
register struct proc *rc; /* slot of process to clean up */
{
if(isemptyp(rc)) panic("clear_proc: empty process: %d", rc->p_endpoint);
/* Make sure that the exiting process is no longer scheduled. */
RTS_SET(rc, RTS_NO_ENDPOINT);
if (priv(rc)->s_flags & SYS_PROC)
{
priv(rc)->s_asynsize= 0;
}
/* If the process happens to be queued trying to send a
* message, then it must be removed from the message queues.
*/
clear_ipc(rc);
/* Likewise, if another process was sending or receive a message to or from
* the exiting process, it must be alerted that process no longer is alive.
* Check all processes.
*/
clear_ipc_refs(rc, EDEADSRCDST);
}
/*===========================================================================*
* clear_ipc *
*===========================================================================*/
PUBLIC void clear_ipc(rc)
register struct proc *rc; /* slot of process to clean up */
{
/* Clear IPC data for a given process slot. */
struct proc **xpp; /* iterate over caller queue */
if (RTS_ISSET(rc, RTS_SENDING)) {
int target_proc;
okendpt(rc->p_sendto_e, &target_proc);
xpp = &proc_addr(target_proc)->p_caller_q; /* destination's queue */
while (*xpp) { /* check entire queue */
if (*xpp == rc) { /* process is on the queue */
*xpp = (*xpp)->p_q_link; /* replace by next process */
#if DEBUG_ENABLE_IPC_WARNINGS
printf("endpoint %d / %s removed from queue at %d\n",
rc->p_endpoint, rc->p_name, rc->p_sendto_e);
#endif
break; /* can only be queued once */
}
xpp = &(*xpp)->p_q_link; /* proceed to next queued */
}
rc->p_rts_flags &= ~RTS_SENDING;
}
rc->p_rts_flags &= ~RTS_RECEIVING;
}
/*===========================================================================*
* clear_ipc_refs *
*===========================================================================*/
PUBLIC void clear_ipc_refs(rc, caller_ret)
register struct proc *rc; /* slot of process to clean up */
int caller_ret; /* code to return on callers */
{
/* Clear IPC references for a given process slot. */
struct proc *rp; /* iterate over process table */
for (rp = BEG_PROC_ADDR; rp < END_PROC_ADDR; rp++) {
if(isemptyp(rp))
continue;
/* Unset pending notification bits. */
unset_sys_bit(priv(rp)->s_notify_pending, priv(rc)->s_id);
/* XXX FIXME: Cleanup should be done for senda() as well. For this to be
* done in a realistic way, we need a better implementation of senda
* with a bitmap similar to s_notify_pending for notify() rather than
* a single global MF_ASYNMSG flag. The current arrangement exposes
* several performance issues.
*/
/* Check if process depends on given process. */
if (P_BLOCKEDON(rp) == rc->p_endpoint) {
rp->p_reg.retreg = caller_ret; /* return requested code */
RTS_UNSET(rp, (RTS_RECEIVING|RTS_SENDING)); /* no longer blocking */
}
}
}
/*===========================================================================*
* kernel_call_resume *
*===========================================================================*/
PUBLIC void kernel_call_resume(struct proc *caller)
{
int result;
assert(!RTS_ISSET(caller, RTS_SLOT_FREE));
assert(!RTS_ISSET(caller, RTS_VMREQUEST));
assert(caller->p_vmrequest.saved.reqmsg.m_source == caller->p_endpoint);
/*
printf("KERNEL_CALL restart from %s / %d rts 0x%08x misc 0x%08x\n",
caller->p_name, caller->p_endpoint,
caller->p_rts_flags, caller->p_misc_flags);
*/
/*
* we are resuming the kernel call so we have to remove this flag so it
* can be set again
*/
caller->p_misc_flags &= ~MF_KCALL_RESUME;
result = kernel_call_dispatch(caller, &caller->p_vmrequest.saved.reqmsg);
kernel_call_finish(caller, &caller->p_vmrequest.saved.reqmsg, result);
}
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