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minix/kernel/system.c
Ben Gras 9647fbc94e moved type and constants for random data to include file; 
added consistency check in random; added source of randomness
internal to random using timing; only retrieve random bins that are full.
2009-04-02 15:24:44 +00:00

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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
* send_sig: send a signal directly to a system process
* cause_sig: take action to cause a signal to occur via PM
* 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:
* 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 <signal.h>
#include <unistd.h>
#include <string.h>
#include <sys/sigcontext.h>
#include <minix/endpoint.h>
#include <minix/safecopies.h>
#include <minix/u64.h>
#include <sys/vm_i386.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])(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)
FORWARD _PROTOTYPE( void initialize, (void));
FORWARD _PROTOTYPE( void softnotify_check, (void));
FORWARD _PROTOTYPE( struct proc *vmrestart_check, (message *));
/*===========================================================================*
* sys_task *
*===========================================================================*/
PUBLIC void sys_task()
{
/* Main entry point of sys_task. Get the message and dispatch on type. */
static message m;
register int result;
register struct proc *caller_ptr;
int s;
int call_nr;
int n = 0;
/* Initialize the system task. */
initialize();
while (TRUE) {
struct proc *restarting;
restarting = vmrestart_check(&m);
softnotify_check();
if(softnotify)
minix_panic("softnotify non-NULL before receive (1)", NO_NUM);
if(!restarting) {
int r;
/* Get work. Block and wait until a request message arrives. */
if(softnotify)
minix_panic("softnotify non-NULL before receive (2)", NO_NUM);
if((r=receive(ANY, &m)) != OK)
minix_panic("receive() failed", r);
if(m.m_source == SYSTEM)
continue;
if(softnotify)
minix_panic("softnotify non-NULL after receive", NO_NUM);
}
sys_call_code = (unsigned) m.m_type;
call_nr = sys_call_code - KERNEL_CALL;
who_e = m.m_source;
okendpt(who_e, &who_p);
caller_ptr = proc_addr(who_p);
if (caller_ptr->p_endpoint == ipc_stats_target)
sys_stats.total= add64u(sys_stats.total, 1);
/* 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 */
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("SYSTEM: illegal request %d from %d.\n",
call_nr,m.m_source);
#endif
if (caller_ptr->p_endpoint == ipc_stats_target)
sys_stats.bad_req++;
result = EBADREQUEST; /* illegal message type */
}
else if (!GET_BIT(priv(caller_ptr)->s_k_call_mask, call_nr)) {
#if DEBUG_ENABLE_IPC_WARNINGS
static int curr= 0, limit= 100, extra= 20;
if (curr < limit+extra)
{
kprintf("SYSTEM: request %d from %d denied.\n",
call_nr, m.m_source);
} else if (curr == limit+extra)
{
kprintf("sys_task: no debug output for a while\n");
}
else if (curr == 2*limit-1)
limit *= 2;
curr++;
#endif
if (caller_ptr->p_endpoint == ipc_stats_target)
sys_stats.not_allowed++;
result = ECALLDENIED; /* illegal message type */
}
else {
result = (*call_vec[call_nr])(&m); /* handle the system call */
}
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.
*/
memcpy(&caller_ptr->p_vmrequest.saved.reqmsg, &m, sizeof(m));
caller_ptr->p_vmrequest.type = VMSTYPE_SYS_MESSAGE;
} else if (result != EDONTREPLY) {
/* Send a reply, unless inhibited by a handler function.
* Use the kernel function lock_send() to prevent a system
* call trap.
*/
if(restarting)
RTS_LOCK_UNSET(restarting, VMREQUEST);
m.m_type = result; /* report status of call */
if(WILLRECEIVE(caller_ptr, SYSTEM)) {
if (OK != (s=lock_send(m.m_source, &m))) {
kprintf("SYSTEM, reply to %d failed: %d\n",
m.m_source, s);
}
} else {
kprintf("SYSTEM: not replying to %d; not ready\n",
caller_ptr->p_endpoint);
}
}
}
}
/*===========================================================================*
* initialize *
*===========================================================================*/
PRIVATE void initialize(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_EXIT, do_exit); /* clean up after process exit */
map(SYS_NICE, do_nice); /* set scheduling priority */
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 */
/* Signal handling. */
map(SYS_KILL, do_kill); /* cause a process to be signaled */
map(SYS_GETKSIG, do_getksig); /* PM checks for pending signals */
map(SYS_ENDKSIG, do_endksig); /* PM finished processing 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_VM_SETBUF, do_vm_setbuf); /* PM passes buffer for page tables */
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_VIRVCOPY, do_virvcopy); /* vector with copy requests */
map(SYS_PHYSVCOPY, do_vcopy); /* vector with copy requests */
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 */
/* 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 */
/* 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 */
map(SYS_MAPDMA, do_mapdma);
#endif
}
/*===========================================================================*
* get_priv *
*===========================================================================*/
PUBLIC int get_priv(rc, proc_type)
register struct proc *rc; /* new (child) process pointer */
int proc_type; /* system or user process flag */
{
/* Get a privilege structure. All user processes share the same privilege
* structure. System processes get their own privilege structure.
*/
register struct priv *sp; /* privilege structure */
if (proc_type == SYS_PROC) { /* find a new slot */
for (sp = BEG_PRIV_ADDR; sp < END_PRIV_ADDR; ++sp)
if (sp->s_proc_nr == NONE && sp->s_id != USER_PRIV_ID) break;
if (sp >= END_PRIV_ADDR) return(ENOSPC);
rc->p_priv = sp; /* assign new slot */
rc->p_priv->s_proc_nr = proc_nr(rc); /* set association */
rc->p_priv->s_flags = SYS_PROC; /* mark as privileged */
/* Clear some fields */
sp->s_asyntab= -1;
sp->s_asynsize= 0;
} else {
rc->p_priv = &priv[USER_PRIV_ID]; /* use shared slot */
rc->p_priv->s_proc_nr = INIT_PROC_NR; /* set association */
/* s_flags of this shared structure are to be once at system startup. */
}
return(OK);
}
/*===========================================================================*
* send_sig *
*===========================================================================*/
PUBLIC void send_sig(int 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;
static int n;
if(!isokprocn(proc_nr) || isemptyn(proc_nr))
minix_panic("send_sig to empty process", proc_nr);
rp = proc_addr(proc_nr);
sigaddset(&priv(rp)->s_sig_pending, sig_nr);
soft_notify(rp->p_endpoint);
}
/*===========================================================================*
* cause_sig *
*===========================================================================*/
PUBLIC void cause_sig(proc_nr, sig_nr)
int proc_nr; /* process to be signalled */
int sig_nr; /* signal to be sent, 1 to _NSIG */
{
/* 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 PM. This function handles the
* signals and makes sure the PM gets them by sending a notification. The
* process being signaled is blocked while PM 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;
if (proc_nr == PM_PROC_NR)
minix_panic("cause_sig: PM gets signal", NO_NUM);
/* Check if the signal is already pending. Process it otherwise. */
rp = proc_addr(proc_nr);
if (! sigismember(&rp->p_pending, sig_nr)) {
sigaddset(&rp->p_pending, sig_nr);
if (! (RTS_ISSET(rp, SIGNALED))) { /* other pending */
RTS_LOCK_SET(rp, SIGNALED | SIG_PENDING);
send_sig(PM_PROC_NR, SIGKSIG);
}
}
}
#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;
kprintf("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) {
kprintf("SYSTEM: umap_grant: verify_grant failed\n");
return 0;
}
if(!isokendpt(granter, &proc_nr)) {
kprintf("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) {
kprintf("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 */
{
register struct proc *rp; /* iterate over process table */
register struct proc **xpp; /* iterate over caller queue */
struct proc *np;
if(isemptyp(rc)) minix_panic("clear_proc: empty process", rc->p_endpoint);
if(rc->p_endpoint == PM_PROC_NR || rc->p_endpoint == VFS_PROC_NR) {
/* This test is great for debugging system processes dying,
* but as this happens normally on reboot, not good permanent code.
*/
kprintf("process %s / %d died; stack: ", rc->p_name, rc->p_endpoint);
proc_stacktrace(rc);
kprintf("kernel trace: ");
util_stacktrace();
minix_panic("clear_proc: system process died", rc->p_endpoint);
}
/* Make sure that the exiting process is no longer scheduled. */
RTS_LOCK_SET(rc, NO_ENDPOINT);
if (priv(rc)->s_flags & SYS_PROC)
{
if (priv(rc)->s_asynsize) {
kprintf("clear_endpoint: clearing s_asynsize of %s / %d\n",
rc->p_name, rc->p_endpoint);
proc_stacktrace(rc);
}
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.
*/
if (RTS_ISSET(rc, SENDING)) {
int target_proc;
okendpt(rc->p_sendto_e, &target_proc);
xpp = &proc_addr(target_proc)->p_caller_q; /* destination's queue */
while (*xpp != NIL_PROC) { /* 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
kprintf("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 &= ~SENDING;
}
rc->p_rts_flags &= ~RECEIVING;
/* 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.
*/
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);
/* Check if process is receiving from exiting process. */
if (RTS_ISSET(rp, RECEIVING) && rp->p_getfrom_e == rc->p_endpoint) {
rp->p_reg.retreg = ESRCDIED; /* report source died */
RTS_LOCK_UNSET(rp, RECEIVING); /* no longer receiving */
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("endpoint %d / %s receiving from dead src ep %d / %s\n",
rp->p_endpoint, rp->p_name, rc->p_endpoint, rc->p_name);
#endif
}
if (RTS_ISSET(rp, SENDING) &&
rp->p_sendto_e == rc->p_endpoint) {
rp->p_reg.retreg = EDSTDIED; /* report destination died */
RTS_LOCK_UNSET(rp, SENDING);
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("endpoint %d / %s send to dying dst ep %d (%s)\n",
rp->p_endpoint, rp->p_name, rc->p_endpoint, rc->p_name);
#endif
}
}
/* No pending soft notifies. */
for(np = softnotify; np; np = np->next_soft_notify) {
if(np == rc) {
minix_panic("dying proc was on next_soft_notify", np->p_endpoint);
}
}
}
/*===========================================================================*
* umap_verify_grant *
*===========================================================================*/
PUBLIC phys_bytes umap_verify_grant(rp, grantee, grant, offset, bytes, access)
struct proc *rp; /* pointer to proc table entry for process */
endpoint_t grantee; /* who wants to do this */
cp_grant_id_t grant; /* grant no. */
vir_bytes offset; /* offset into grant */
vir_bytes bytes; /* size */
int access; /* does grantee want to CPF_READ or _WRITE? */
{
int proc_nr;
vir_bytes v_offset;
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, grantee, grant, bytes, access, offset,
&v_offset, &granter) != OK
|| !isokendpt(granter, &proc_nr)) {
return 0;
}
/* Do the mapping from virtual to physical. */
return umap_virtual(proc_addr(proc_nr), D, v_offset, bytes);
}
/*===========================================================================*
* softnotify_check *
*===========================================================================*/
PRIVATE void softnotify_check(void)
{
struct proc *np, *nextnp;
if(!softnotify)
return;
for(np = softnotify; np; np = nextnp) {
if(!np->p_softnotified)
minix_panic("softnotify but no p_softnotified", NO_NUM);
lock_notify(SYSTEM, np->p_endpoint);
nextnp = np->next_soft_notify;
np->next_soft_notify = NULL;
np->p_softnotified = 0;
}
softnotify = NULL;
}
/*===========================================================================*
* vmrestart_check *
*===========================================================================*/
PRIVATE struct proc *vmrestart_check(message *m)
{
int type, r;
struct proc *restarting;
/* Anyone waiting to be vm-restarted? */
if(!(restarting = vmrestart))
return NULL;
if(restarting->p_rts_flags & SLOT_FREE)
minix_panic("SYSTEM: VMREQUEST set for empty process", NO_NUM);
type = restarting->p_vmrequest.type;
restarting->p_vmrequest.type = VMSTYPE_SYS_NONE;
vmrestart = restarting->p_vmrequest.nextrestart;
if(!RTS_ISSET(restarting, VMREQUEST))
minix_panic("SYSTEM: VMREQUEST not set for process on vmrestart queue",
restarting->p_endpoint);
switch(type) {
case VMSTYPE_SYS_MESSAGE:
memcpy(m, &restarting->p_vmrequest.saved.reqmsg, sizeof(*m));
if(m->m_source != restarting->p_endpoint)
minix_panic("SYSTEM: vmrestart source doesn't match",
NO_NUM);
/* Original caller could've disappeared in the meantime. */
if(!isokendpt(m->m_source, &who_p)) {
kprintf("SYSTEM: ignoring call %d from dead %d\n",
m->m_type, m->m_source);
return NULL;
}
{ int i;
i = m->m_type - KERNEL_CALL;
if(i >= 0 && i < NR_SYS_CALLS) {
#if 0
kprintf("SYSTEM: restart %s from %d\n",
callnames[i], m->m_source);
#endif
} else {
minix_panic("call number out of range", i);
}
}
return restarting;
case VMSTYPE_SYS_CALL:
kprintf("SYSTEM: restart sys_call\n");
/* Restarting a kernel trap. */
sys_call_restart(restarting);
/* Handled; restart system loop. */
return NULL;
case VMSTYPE_MSGCOPY:
/* Do delayed message copy. */
if((r=data_copy(SYSTEM,
(vir_bytes) &restarting->p_vmrequest.saved.msgcopy.msgbuf,
restarting->p_vmrequest.saved.msgcopy.dst->p_endpoint,
(vir_bytes) restarting->p_vmrequest.saved.msgcopy.dst_v,
sizeof(message))) != OK) {
minix_panic("SYSTEM: delayed msgcopy failed", r);
}
RTS_LOCK_UNSET(restarting, VMREQUEST);
/* Handled; restart system loop. */
return NULL;
default:
minix_panic("strange restart type", type);
}
minix_panic("fell out of switch", NO_NUM);
}
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