| 1 | /* The kernel call implemented in this file:
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| 2 | * m_type: SYS_FORK
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| 3 | *
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| 4 | * The parameters for this kernel call are:
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| 5 | * m1_i1: PR_SLOT (child's process table slot)
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| 6 | * m1_i2: PR_ENDPT (parent, process that forked)
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| 7 | */
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| 8 |
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| 9 | #include "../system.h"
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| 10 | #include <signal.h>
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| 11 | #if (CHIP == INTEL)
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| 12 | #include "../protect.h"
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| 13 | #endif
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| 14 |
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| 15 | #include <minix/endpoint.h>
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| 16 |
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| 17 | #if USE_FORK
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| 18 |
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| 19 | /*===========================================================================*
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| 20 | * do_fork *
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| 21 | *===========================================================================*/
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| 22 | PUBLIC int do_fork(m_ptr)
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| 23 | register message *m_ptr; /* pointer to request message */
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| 24 | {
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| 25 | /* Handle sys_fork(). PR_ENDPT has forked. The child is PR_SLOT. */
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| 26 | #if (CHIP == INTEL)
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| 27 | reg_t old_ldt_sel;
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| 28 | #endif
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| 29 | register struct proc *rpc; /* child process pointer */
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| 30 | struct proc *rpp; /* parent process pointer */
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| 31 | int i, gen;
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| 32 | int p_proc;
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| 33 |
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| 34 | if(!isokendpt(m_ptr->PR_ENDPT, &p_proc))
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| 35 | return EINVAL;
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| 36 | rpp = proc_addr(p_proc);
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| 37 | rpc = proc_addr(m_ptr->PR_SLOT);
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| 38 | if (isemptyp(rpp) || ! isemptyp(rpc)) return(EINVAL);
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| 39 |
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| 40 | /* Copy parent 'proc' struct to child. And reinitialize some fields. */
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| 41 | gen = _ENDPOINT_G(rpc->p_endpoint);
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| 42 | #if (CHIP == INTEL)
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| 43 | old_ldt_sel = rpc->p_ldt_sel; /* backup local descriptors */
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| 44 | *rpc = *rpp; /* copy 'proc' struct */
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| 45 | rpc->p_ldt_sel = old_ldt_sel; /* restore descriptors */
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| 46 | #else
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| 47 | *rpc = *rpp; /* copy 'proc' struct */
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| 48 | #endif
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| 49 | if(++gen >= _ENDPOINT_MAX_GENERATION) /* increase generation */
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| 50 | gen = 1; /* generation number wraparound */
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| 51 | rpc->p_nr = m_ptr->PR_SLOT; /* this was obliterated by copy */
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| 52 | rpc->p_endpoint = _ENDPOINT(gen, rpc->p_nr); /* new endpoint of slot */
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| 53 |
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| 54 | /* Only one in group should have SIGNALED, child doesn't inherit tracing. */
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| 55 | rpc->p_rts_flags |= NO_MAP; /* inhibit process from running */
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| 56 | rpc->p_rts_flags &= ~(SIGNALED | SIG_PENDING | P_STOP);
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| 57 | sigemptyset(&rpc->p_pending);
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| 58 |
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| 59 | rpc->p_reg.retreg = 0; /* child sees pid = 0 to know it is child */
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| 60 | rpc->p_user_time = 0; /* set all the accounting times to 0 */
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| 61 | rpc->p_sys_time = 0;
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| 62 |
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| 63 | /* Parent and child have to share the quantum that the forked process had,
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| 64 | * so that queued processes do not have to wait longer because of the fork.
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| 65 | * If the time left is odd, the child gets an extra tick.
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| 66 | */
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| 67 | rpc->p_ticks_left = (rpc->p_ticks_left + 1) / 2;
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| 68 | rpp->p_ticks_left = rpp->p_ticks_left / 2;
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| 69 |
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| 70 | /* If the parent is a privileged process, take away the privileges from the
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| 71 | * child process and inhibit it from running by setting the NO_PRIV flag.
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| 72 | * The caller should explicitely set the new privileges before executing.
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| 73 | */
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| 74 | if (priv(rpp)->s_flags & SYS_PROC) {
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| 75 | rpc->p_priv = priv_addr(USER_PRIV_ID);
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| 76 | rpc->p_rts_flags |= NO_PRIV;
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| 77 | }
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| 78 |
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| 79 | /* Calculate endpoint identifier, so caller knows what it is. */
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| 80 | m_ptr->PR_ENDPT = rpc->p_endpoint;
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| 81 |
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| 82 | return(OK);
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| 83 | }
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| 84 |
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| 85 | #endif /* USE_FORK */
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| 86 |
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