cca24d06d8
kernel (sys task). The main reason is that these would have to become cpu local variables on SMP. Once the system task is not a task but a genuine part of the kernel there is even less reason to have these extra variables as proc_ptr will already contain all neccessary information. In addition converting who_e to the process pointer and back again all the time will be avoided. Although proc_ptr will contain all important information, accessing it as a cpu local variable will be fairly expensive, hence the value would be assigned to some on stack local variable. Therefore it is better to add the 'caller' argument to the syscall handlers to pass the value on stack anyway. It also clearly denotes on who's behalf is the syscall being executed. This patch also ANSIfies the syscall function headers. Last but not least, it also fixes a potential bug in virtual_copy_f() in case the check is disabled. So far the function in case of a failure could possible reuse an old who_p in case this function had not been called from the system task. virtual_copy_f() takes the caller as a parameter too. In case the checking is disabled, the caller must be NULL and non NULL if it is enabled as we must be able to suspend the caller.
122 lines
4 KiB
C
122 lines
4 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 "../system.h"
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#include "../vm.h"
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#include <signal.h>
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#include <string.h>
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#include <minix/endpoint.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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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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vmassert(!(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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/* 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(rpp->p_misc_flags & MF_FPU_INITIALIZED)
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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 &= ~(MF_VIRT_TIMER | MF_PROF_TIMER | MF_SC_TRACE);
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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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/* Parent and child have to share the quantum that the forked process had,
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* so that queued processes do not have to wait longer because of the fork.
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* If the time left is odd, the child gets an extra tick.
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*/
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rpc->p_ticks_left = (rpc->p_ticks_left + 1) / 2;
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rpp->p_ticks_left = rpp->p_ticks_left / 2;
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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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FIXLINMSG(rpc);
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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_LOCK_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_LOCK_UNSET(rpc, (RTS_SIGNALED | RTS_SIG_PENDING | RTS_P_STOP));
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sigemptyset(&rpc->p_pending);
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return r;
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}
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#endif /* USE_FORK */
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