c6e6aa8850
. helps debugging output; you can see the difference
between parent and child easily (it's sometimes
confusing to see an expected endpoint number with
an unexpected name, i.e. before exec())
. when processes crash after fork and before exec, it's
an instant hint that that's what's going on, instead of
it being the parent (endpoint numbers don't usually convey
this)
. name returns to 'normal' after exec(), so *F isn't visible
normally at all. (Except for for RS which forks apparently.)
137 lines
4.3 KiB
C
137 lines
4.3 KiB
C
/* The kernel call implemented in this file:
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* m_type: SYS_FORK
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*
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* The parameters for this kernel call are:
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* m1_i1: PR_ENDPT (parent, process that forked)
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* m1_i2: PR_SLOT (child's process table slot)
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* m1_p1: PR_MEM_PTR (new memory map for the child)
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* m1_i3: PR_FORK_FLAGS (fork flags)
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*/
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#include "kernel/system.h"
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#include "kernel/vm.h"
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#include <signal.h>
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#include <string.h>
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#include <assert.h>
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#include <minix/endpoint.h>
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#include <minix/u64.h>
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#if USE_FORK
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/*===========================================================================*
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* do_fork *
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*===========================================================================*/
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PUBLIC int do_fork(struct proc * caller, message * m_ptr)
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{
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/* Handle sys_fork(). PR_ENDPT has forked. The child is PR_SLOT. */
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#if (_MINIX_CHIP == _CHIP_INTEL)
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reg_t old_ldt_sel;
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void *old_fpu_save_area_p;
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#endif
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register struct proc *rpc; /* child process pointer */
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struct proc *rpp; /* parent process pointer */
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struct mem_map *map_ptr; /* virtual address of map inside caller (PM) */
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int gen, r;
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int p_proc;
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int namelen;
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if(!isokendpt(m_ptr->PR_ENDPT, &p_proc))
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return EINVAL;
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rpp = proc_addr(p_proc);
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rpc = proc_addr(m_ptr->PR_SLOT);
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if (isemptyp(rpp) || ! isemptyp(rpc)) return(EINVAL);
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assert(!(rpp->p_misc_flags & MF_DELIVERMSG));
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/* needs to be receiving so we know where the message buffer is */
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if(!RTS_ISSET(rpp, RTS_RECEIVING)) {
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printf("kernel: fork not done synchronously?\n");
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return EINVAL;
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}
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map_ptr= (struct mem_map *) m_ptr->PR_MEM_PTR;
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/* make sure that the FPU context is saved in parent before copy */
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save_fpu(rpp);
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/* Copy parent 'proc' struct to child. And reinitialize some fields. */
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gen = _ENDPOINT_G(rpc->p_endpoint);
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#if (_MINIX_CHIP == _CHIP_INTEL)
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old_ldt_sel = rpc->p_seg.p_ldt_sel; /* backup local descriptors */
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old_fpu_save_area_p = rpc->p_fpu_state.fpu_save_area_p;
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#endif
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*rpc = *rpp; /* copy 'proc' struct */
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#if (_MINIX_CHIP == _CHIP_INTEL)
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rpc->p_seg.p_ldt_sel = old_ldt_sel; /* restore descriptors */
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rpc->p_fpu_state.fpu_save_area_p = old_fpu_save_area_p;
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if(proc_used_fpu(rpp))
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memcpy(rpc->p_fpu_state.fpu_save_area_p,
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rpp->p_fpu_state.fpu_save_area_p,
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FPU_XFP_SIZE);
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#endif
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if(++gen >= _ENDPOINT_MAX_GENERATION) /* increase generation */
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gen = 1; /* generation number wraparound */
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rpc->p_nr = m_ptr->PR_SLOT; /* this was obliterated by copy */
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rpc->p_endpoint = _ENDPOINT(gen, rpc->p_nr); /* new endpoint of slot */
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rpc->p_reg.retreg = 0; /* child sees pid = 0 to know it is child */
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rpc->p_user_time = 0; /* set all the accounting times to 0 */
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rpc->p_sys_time = 0;
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rpc->p_reg.psw &= ~TRACEBIT; /* clear trace bit */
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rpc->p_misc_flags &=
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~(MF_VIRT_TIMER | MF_PROF_TIMER | MF_SC_TRACE | MF_SPROF_SEEN);
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rpc->p_virt_left = 0; /* disable, clear the process-virtual timers */
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rpc->p_prof_left = 0;
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/* Mark process name as being a forked copy */
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namelen = strlen(rpc->p_name);
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#define FORKSTR "*F"
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if(namelen+strlen(FORKSTR) < sizeof(rpc->p_name))
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strcat(rpc->p_name, FORKSTR);
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/* the child process is not runnable until it's scheduled. */
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RTS_SET(rpc, RTS_NO_QUANTUM);
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reset_proc_accounting(rpc);
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make_zero64(rpc->p_cpu_time_left);
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make_zero64(rpc->p_cycles);
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make_zero64(rpc->p_kcall_cycles);
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make_zero64(rpc->p_kipc_cycles);
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/* If the parent is a privileged process, take away the privileges from the
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* child process and inhibit it from running by setting the NO_PRIV flag.
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* The caller should explicitely set the new privileges before executing.
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*/
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if (priv(rpp)->s_flags & SYS_PROC) {
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rpc->p_priv = priv_addr(USER_PRIV_ID);
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rpc->p_rts_flags |= RTS_NO_PRIV;
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}
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/* Calculate endpoint identifier, so caller knows what it is. */
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m_ptr->PR_ENDPT = rpc->p_endpoint;
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m_ptr->PR_FORK_MSGADDR = (char *) rpp->p_delivermsg_vir;
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/* Install new map */
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r = newmap(caller, rpc, map_ptr);
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/* Don't schedule process in VM mode until it has a new pagetable. */
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if(m_ptr->PR_FORK_FLAGS & PFF_VMINHIBIT) {
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RTS_SET(rpc, RTS_VMINHIBIT);
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}
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/*
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* Only one in group should have RTS_SIGNALED, child doesn't inherit tracing.
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*/
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RTS_UNSET(rpc, (RTS_SIGNALED | RTS_SIG_PENDING | RTS_P_STOP));
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(void) sigemptyset(&rpc->p_pending);
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rpc->p_seg.p_cr3 = 0;
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rpc->p_seg.p_cr3_v = NULL;
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return r;
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}
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#endif /* USE_FORK */
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