The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/vm_machdep.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-4-Clause
    3  *
    4  * Copyright (c) 1982, 1986 The Regents of the University of California.
    5  * Copyright (c) 1989, 1990 William Jolitz
    6  * Copyright (c) 1994 John Dyson
    7  * All rights reserved.
    8  *
    9  * This code is derived from software contributed to Berkeley by
   10  * the Systems Programming Group of the University of Utah Computer
   11  * Science Department, and William Jolitz.
   12  *
   13  * Redistribution and use in source and binary forms, with or without
   14  * modification, are permitted provided that the following conditions
   15  * are met:
   16  * 1. Redistributions of source code must retain the above copyright
   17  *    notice, this list of conditions and the following disclaimer.
   18  * 2. Redistributions in binary form must reproduce the above copyright
   19  *    notice, this list of conditions and the following disclaimer in the
   20  *    documentation and/or other materials provided with the distribution.
   21  * 3. All advertising materials mentioning features or use of this software
   22  *    must display the following acknowledgement:
   23  *      This product includes software developed by the University of
   24  *      California, Berkeley and its contributors.
   25  * 4. Neither the name of the University nor the names of its contributors
   26  *    may be used to endorse or promote products derived from this software
   27  *    without specific prior written permission.
   28  *
   29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   39  * SUCH DAMAGE.
   40  *
   41  *      from: @(#)vm_machdep.c  7.3 (Berkeley) 5/13/91
   42  *      Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
   43  */
   44 
   45 #include <sys/cdefs.h>
   46 __FBSDID("$FreeBSD$");
   47 
   48 #include "opt_isa.h"
   49 #include "opt_cpu.h"
   50 
   51 #include <sys/param.h>
   52 #include <sys/systm.h>
   53 #include <sys/bio.h>
   54 #include <sys/buf.h>
   55 #include <sys/kernel.h>
   56 #include <sys/ktr.h>
   57 #include <sys/lock.h>
   58 #include <sys/malloc.h>
   59 #include <sys/mbuf.h>
   60 #include <sys/mutex.h>
   61 #include <sys/priv.h>
   62 #include <sys/proc.h>
   63 #include <sys/procctl.h>
   64 #include <sys/smp.h>
   65 #include <sys/sysctl.h>
   66 #include <sys/sysent.h>
   67 #include <sys/unistd.h>
   68 #include <sys/vnode.h>
   69 #include <sys/vmmeter.h>
   70 #include <sys/wait.h>
   71 
   72 #include <machine/cpu.h>
   73 #include <machine/md_var.h>
   74 #include <machine/pcb.h>
   75 #include <machine/smp.h>
   76 #include <machine/specialreg.h>
   77 #include <machine/tss.h>
   78 
   79 #include <vm/vm.h>
   80 #include <vm/vm_extern.h>
   81 #include <vm/vm_kern.h>
   82 #include <vm/vm_page.h>
   83 #include <vm/vm_map.h>
   84 #include <vm/vm_param.h>
   85 
   86 _Static_assert(OFFSETOF_MONITORBUF == offsetof(struct pcpu, pc_monitorbuf),
   87     "OFFSETOF_MONITORBUF does not correspond with offset of pc_monitorbuf.");
   88 
   89 void
   90 set_top_of_stack_td(struct thread *td)
   91 {
   92         td->td_md.md_stack_base = td->td_kstack +
   93             td->td_kstack_pages * PAGE_SIZE;
   94 }
   95 
   96 struct savefpu *
   97 get_pcb_user_save_td(struct thread *td)
   98 {
   99         KASSERT(((vm_offset_t)td->td_md.md_usr_fpu_save %
  100             XSAVE_AREA_ALIGN) == 0,
  101             ("Unaligned pcb_user_save area ptr %p td %p",
  102             td->td_md.md_usr_fpu_save, td));
  103         return (td->td_md.md_usr_fpu_save);
  104 }
  105 
  106 struct pcb *
  107 get_pcb_td(struct thread *td)
  108 {
  109 
  110         return (&td->td_md.md_pcb);
  111 }
  112 
  113 struct savefpu *
  114 get_pcb_user_save_pcb(struct pcb *pcb)
  115 {
  116         struct thread *td;
  117 
  118         td = __containerof(pcb, struct thread, td_md.md_pcb);
  119         return (get_pcb_user_save_td(td));
  120 }
  121 
  122 void *
  123 alloc_fpusave(int flags)
  124 {
  125         void *res;
  126         struct savefpu_ymm *sf;
  127 
  128         res = malloc(cpu_max_ext_state_size, M_DEVBUF, flags);
  129         if (use_xsave) {
  130                 sf = (struct savefpu_ymm *)res;
  131                 bzero(&sf->sv_xstate.sx_hd, sizeof(sf->sv_xstate.sx_hd));
  132                 sf->sv_xstate.sx_hd.xstate_bv = xsave_mask;
  133         }
  134         return (res);
  135 }
  136 
  137 /*
  138  * Common code shared between cpu_fork() and cpu_copy_thread() for
  139  * initializing a thread.
  140  */
  141 static void
  142 copy_thread(struct thread *td1, struct thread *td2)
  143 {
  144         struct pcb *pcb2;
  145 
  146         pcb2 = td2->td_pcb;
  147 
  148         /* Ensure that td1's pcb is up to date for user threads. */
  149         if ((td2->td_pflags & TDP_KTHREAD) == 0) {
  150                 MPASS(td1 == curthread);
  151                 fpuexit(td1);
  152                 update_pcb_bases(td1->td_pcb);
  153         }
  154 
  155         /* Copy td1's pcb */
  156         bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
  157 
  158         /* Properly initialize pcb_save */
  159         pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
  160 
  161         /* Kernel threads start with clean FPU and segment bases. */
  162         if ((td2->td_pflags & TDP_KTHREAD) != 0) {
  163                 pcb2->pcb_fsbase = 0;
  164                 pcb2->pcb_gsbase = 0;
  165                 clear_pcb_flags(pcb2, PCB_FPUINITDONE | PCB_USERFPUINITDONE |
  166                     PCB_KERNFPU | PCB_KERNFPU_THR);
  167         } else {
  168                 MPASS((pcb2->pcb_flags & (PCB_KERNFPU | PCB_KERNFPU_THR)) == 0);
  169                 bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2),
  170                     cpu_max_ext_state_size);
  171         }
  172 
  173         td2->td_frame = (struct trapframe *)td2->td_md.md_stack_base - 1;
  174 
  175         /*
  176          * Set registers for trampoline to user mode.  Leave space for the
  177          * return address on stack.  These are the kernel mode register values.
  178          */
  179         pcb2->pcb_r12 = (register_t)fork_return;        /* fork_trampoline argument */
  180         pcb2->pcb_rbp = 0;
  181         pcb2->pcb_rsp = (register_t)td2->td_frame - sizeof(void *);
  182         pcb2->pcb_rbx = (register_t)td2;                /* fork_trampoline argument */
  183         pcb2->pcb_rip = (register_t)fork_trampoline;
  184         /*-
  185          * pcb2->pcb_dr*:       cloned above.
  186          * pcb2->pcb_savefpu:   cloned above.
  187          * pcb2->pcb_flags:     cloned above.
  188          * pcb2->pcb_onfault:   cloned above (always NULL here?).
  189          * pcb2->pcb_[fg]sbase: cloned above
  190          */
  191 
  192         pcb2->pcb_tssp = NULL;
  193 
  194         /* Setup to release spin count in fork_exit(). */
  195         td2->td_md.md_spinlock_count = 1;
  196         td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
  197         pmap_thread_init_invl_gen(td2);
  198 
  199         /*
  200          * Copy the trap frame for the return to user mode as if from a syscall.
  201          * This copies most of the user mode register values.  Some of these
  202          * registers are rewritten by cpu_set_upcall() and linux_set_upcall().
  203          */
  204         if ((td1->td_proc->p_flag & P_KPROC) == 0) {
  205                 bcopy(td1->td_frame, td2->td_frame, sizeof(struct trapframe));
  206 
  207                 /*
  208                  * If the current thread has the trap bit set (i.e. a debugger
  209                  * had single stepped the process to the system call), we need
  210                  * to clear the trap flag from the new frame. Otherwise, the new
  211                  * thread will receive a (likely unexpected) SIGTRAP when it
  212                  * executes the first instruction after returning to userland.
  213                  */
  214                 td2->td_frame->tf_rflags &= ~PSL_T;
  215         }
  216 }
  217 
  218 /*
  219  * Finish a fork operation, with process p2 nearly set up.
  220  * Copy and update the pcb, set up the stack so that the child
  221  * ready to run and return to user mode.
  222  */
  223 void
  224 cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
  225 {
  226         struct proc *p1;
  227         struct pcb *pcb2;
  228         struct mdproc *mdp1, *mdp2;
  229         struct proc_ldt *pldt;
  230 
  231         p1 = td1->td_proc;
  232         if ((flags & RFPROC) == 0) {
  233                 if ((flags & RFMEM) == 0) {
  234                         /* unshare user LDT */
  235                         mdp1 = &p1->p_md;
  236                         mtx_lock(&dt_lock);
  237                         if ((pldt = mdp1->md_ldt) != NULL &&
  238                             pldt->ldt_refcnt > 1 &&
  239                             user_ldt_alloc(p1, 1) == NULL)
  240                                 panic("could not copy LDT");
  241                         mtx_unlock(&dt_lock);
  242                 }
  243                 return;
  244         }
  245 
  246         /* Point the stack and pcb to the actual location */
  247         set_top_of_stack_td(td2);
  248         td2->td_pcb = pcb2 = get_pcb_td(td2);
  249 
  250         copy_thread(td1, td2);
  251 
  252         /* Reset debug registers in the new process */
  253         x86_clear_dbregs(pcb2);
  254 
  255         /* Point mdproc and then copy over p1's contents */
  256         mdp2 = &p2->p_md;
  257         bcopy(&p1->p_md, mdp2, sizeof(*mdp2));
  258 
  259         /* Set child return values. */
  260         p2->p_sysent->sv_set_fork_retval(td2);
  261 
  262         /* As on i386, do not copy io permission bitmap. */
  263         pcb2->pcb_tssp = NULL;
  264 
  265         /* New segment registers. */
  266         set_pcb_flags_raw(pcb2, PCB_FULL_IRET);
  267 
  268         /* Copy the LDT, if necessary. */
  269         mdp1 = &td1->td_proc->p_md;
  270         mdp2 = &p2->p_md;
  271         if (mdp1->md_ldt == NULL) {
  272                 mdp2->md_ldt = NULL;
  273                 return;
  274         }
  275         mtx_lock(&dt_lock);
  276         if (mdp1->md_ldt != NULL) {
  277                 if (flags & RFMEM) {
  278                         mdp1->md_ldt->ldt_refcnt++;
  279                         mdp2->md_ldt = mdp1->md_ldt;
  280                         bcopy(&mdp1->md_ldt_sd, &mdp2->md_ldt_sd, sizeof(struct
  281                             system_segment_descriptor));
  282                 } else {
  283                         mdp2->md_ldt = NULL;
  284                         mdp2->md_ldt = user_ldt_alloc(p2, 0);
  285                         if (mdp2->md_ldt == NULL)
  286                                 panic("could not copy LDT");
  287                         amd64_set_ldt_data(td2, 0, max_ldt_segment,
  288                             (struct user_segment_descriptor *)
  289                             mdp1->md_ldt->ldt_base);
  290                 }
  291         } else
  292                 mdp2->md_ldt = NULL;
  293         mtx_unlock(&dt_lock);
  294 
  295         /*
  296          * Now, cpu_switch() can schedule the new process.
  297          * pcb_rsp is loaded pointing to the cpu_switch() stack frame
  298          * containing the return address when exiting cpu_switch.
  299          * This will normally be to fork_trampoline(), which will have
  300          * %rbx loaded with the new proc's pointer.  fork_trampoline()
  301          * will set up a stack to call fork_return(p, frame); to complete
  302          * the return to user-mode.
  303          */
  304 }
  305 
  306 void
  307 x86_set_fork_retval(struct thread *td)
  308 {
  309         struct trapframe *frame = td->td_frame;
  310 
  311         frame->tf_rax = 0;              /* Child returns zero */
  312         frame->tf_rflags &= ~PSL_C;     /* success */
  313         frame->tf_rdx = 1;              /* System V emulation */
  314 }
  315 
  316 /*
  317  * Intercept the return address from a freshly forked process that has NOT
  318  * been scheduled yet.
  319  *
  320  * This is needed to make kernel threads stay in kernel mode.
  321  */
  322 void
  323 cpu_fork_kthread_handler(struct thread *td, void (*func)(void *), void *arg)
  324 {
  325         /*
  326          * Note that the trap frame follows the args, so the function
  327          * is really called like this:  func(arg, frame);
  328          */
  329         td->td_pcb->pcb_r12 = (long) func;      /* function */
  330         td->td_pcb->pcb_rbx = (long) arg;       /* first arg */
  331 }
  332 
  333 void
  334 cpu_exit(struct thread *td)
  335 {
  336 
  337         /*
  338          * If this process has a custom LDT, release it.
  339          */
  340         if (td->td_proc->p_md.md_ldt != NULL)
  341                 user_ldt_free(td);
  342 }
  343 
  344 void
  345 cpu_thread_exit(struct thread *td)
  346 {
  347         struct pcb *pcb;
  348 
  349         critical_enter();
  350         if (td == PCPU_GET(fpcurthread))
  351                 fpudrop();
  352         critical_exit();
  353 
  354         pcb = td->td_pcb;
  355 
  356         /* Disable any hardware breakpoints. */
  357         if (pcb->pcb_flags & PCB_DBREGS) {
  358                 reset_dbregs();
  359                 clear_pcb_flags(pcb, PCB_DBREGS);
  360         }
  361 }
  362 
  363 void
  364 cpu_thread_clean(struct thread *td)
  365 {
  366         struct pcb *pcb;
  367 
  368         pcb = td->td_pcb;
  369 
  370         /*
  371          * Clean TSS/iomap
  372          */
  373         if (pcb->pcb_tssp != NULL) {
  374                 pmap_pti_remove_kva((vm_offset_t)pcb->pcb_tssp,
  375                     (vm_offset_t)pcb->pcb_tssp + ctob(IOPAGES + 1));
  376                 kmem_free(pcb->pcb_tssp, ctob(IOPAGES + 1));
  377                 pcb->pcb_tssp = NULL;
  378         }
  379 }
  380 
  381 void
  382 cpu_thread_swapin(struct thread *td)
  383 {
  384 }
  385 
  386 void
  387 cpu_thread_swapout(struct thread *td)
  388 {
  389 }
  390 
  391 void
  392 cpu_thread_alloc(struct thread *td)
  393 {
  394         struct pcb *pcb;
  395         struct xstate_hdr *xhdr;
  396 
  397         set_top_of_stack_td(td);
  398         td->td_pcb = pcb = get_pcb_td(td);
  399         td->td_frame = (struct trapframe *)td->td_md.md_stack_base - 1;
  400         td->td_md.md_usr_fpu_save = fpu_save_area_alloc();
  401         pcb->pcb_save = get_pcb_user_save_pcb(pcb);
  402         if (use_xsave) {
  403                 xhdr = (struct xstate_hdr *)(pcb->pcb_save + 1);
  404                 bzero(xhdr, sizeof(*xhdr));
  405                 xhdr->xstate_bv = xsave_mask;
  406         }
  407 }
  408 
  409 void
  410 cpu_thread_free(struct thread *td)
  411 {
  412         cpu_thread_clean(td);
  413 
  414         fpu_save_area_free(td->td_md.md_usr_fpu_save);
  415         td->td_md.md_usr_fpu_save = NULL;
  416 }
  417 
  418 bool
  419 cpu_exec_vmspace_reuse(struct proc *p, vm_map_t map)
  420 {
  421 
  422         return (((curproc->p_md.md_flags & P_MD_KPTI) != 0) ==
  423             (vm_map_pmap(map)->pm_ucr3 != PMAP_NO_CR3));
  424 }
  425 
  426 static void
  427 cpu_procctl_kpti_ctl(struct proc *p, int val)
  428 {
  429 
  430         if (pti && val == PROC_KPTI_CTL_ENABLE_ON_EXEC)
  431                 p->p_md.md_flags |= P_MD_KPTI;
  432         if (val == PROC_KPTI_CTL_DISABLE_ON_EXEC)
  433                 p->p_md.md_flags &= ~P_MD_KPTI;
  434 }
  435 
  436 static void
  437 cpu_procctl_kpti_status(struct proc *p, int *val)
  438 {
  439         *val = (p->p_md.md_flags & P_MD_KPTI) != 0 ?
  440             PROC_KPTI_CTL_ENABLE_ON_EXEC:
  441             PROC_KPTI_CTL_DISABLE_ON_EXEC;
  442         if (vmspace_pmap(p->p_vmspace)->pm_ucr3 != PMAP_NO_CR3)
  443                 *val |= PROC_KPTI_STATUS_ACTIVE;
  444 }
  445 
  446 static int
  447 cpu_procctl_la_ctl(struct proc *p, int val)
  448 {
  449         int error;
  450 
  451         error = 0;
  452         switch (val) {
  453         case PROC_LA_CTL_LA48_ON_EXEC:
  454                 p->p_md.md_flags |= P_MD_LA48;
  455                 p->p_md.md_flags &= ~P_MD_LA57;
  456                 break;
  457         case PROC_LA_CTL_LA57_ON_EXEC:
  458                 if (la57) {
  459                         p->p_md.md_flags &= ~P_MD_LA48;
  460                         p->p_md.md_flags |= P_MD_LA57;
  461                 } else {
  462                         error = ENOTSUP;
  463                 }
  464                 break;
  465         case PROC_LA_CTL_DEFAULT_ON_EXEC:
  466                 p->p_md.md_flags &= ~(P_MD_LA48 | P_MD_LA57);
  467                 break;
  468         }
  469         return (error);
  470 }
  471 
  472 static void
  473 cpu_procctl_la_status(struct proc *p, int *val)
  474 {
  475         int res;
  476 
  477         if ((p->p_md.md_flags & P_MD_LA48) != 0)
  478                 res = PROC_LA_CTL_LA48_ON_EXEC;
  479         else if ((p->p_md.md_flags & P_MD_LA57) != 0)
  480                 res = PROC_LA_CTL_LA57_ON_EXEC;
  481         else
  482                 res = PROC_LA_CTL_DEFAULT_ON_EXEC;
  483         if (p->p_sysent->sv_maxuser == VM_MAXUSER_ADDRESS_LA48)
  484                 res |= PROC_LA_STATUS_LA48;
  485         else
  486                 res |= PROC_LA_STATUS_LA57;
  487         *val = res;
  488 }
  489 
  490 int
  491 cpu_procctl(struct thread *td, int idtype, id_t id, int com, void *data)
  492 {
  493         struct proc *p;
  494         int error, val;
  495 
  496         switch (com) {
  497         case PROC_KPTI_CTL:
  498         case PROC_KPTI_STATUS:
  499         case PROC_LA_CTL:
  500         case PROC_LA_STATUS:
  501                 if (idtype != P_PID) {
  502                         error = EINVAL;
  503                         break;
  504                 }
  505                 if (com == PROC_KPTI_CTL) {
  506                         /* sad but true and not a joke */
  507                         error = priv_check(td, PRIV_IO);
  508                         if (error != 0)
  509                                 break;
  510                 }
  511                 if (com == PROC_KPTI_CTL || com == PROC_LA_CTL) {
  512                         error = copyin(data, &val, sizeof(val));
  513                         if (error != 0)
  514                                 break;
  515                 }
  516                 if (com == PROC_KPTI_CTL &&
  517                     val != PROC_KPTI_CTL_ENABLE_ON_EXEC &&
  518                     val != PROC_KPTI_CTL_DISABLE_ON_EXEC) {
  519                         error = EINVAL;
  520                         break;
  521                 }
  522                 if (com == PROC_LA_CTL &&
  523                     val != PROC_LA_CTL_LA48_ON_EXEC &&
  524                     val != PROC_LA_CTL_LA57_ON_EXEC &&
  525                     val != PROC_LA_CTL_DEFAULT_ON_EXEC) {
  526                         error = EINVAL;
  527                         break;
  528                 }
  529                 error = pget(id, PGET_CANSEE | PGET_NOTWEXIT | PGET_NOTID, &p);
  530                 if (error != 0)
  531                         break;
  532                 switch (com) {
  533                 case PROC_KPTI_CTL:
  534                         cpu_procctl_kpti_ctl(p, val);
  535                         break;
  536                 case PROC_KPTI_STATUS:
  537                         cpu_procctl_kpti_status(p, &val);
  538                         break;
  539                 case PROC_LA_CTL:
  540                         error = cpu_procctl_la_ctl(p, val);
  541                         break;
  542                 case PROC_LA_STATUS:
  543                         cpu_procctl_la_status(p, &val);
  544                         break;
  545                 }
  546                 PROC_UNLOCK(p);
  547                 if (com == PROC_KPTI_STATUS || com == PROC_LA_STATUS)
  548                         error = copyout(&val, data, sizeof(val));
  549                 break;
  550         default:
  551                 error = EINVAL;
  552                 break;
  553         }
  554         return (error);
  555 }
  556 
  557 void
  558 cpu_set_syscall_retval(struct thread *td, int error)
  559 {
  560         struct trapframe *frame;
  561 
  562         frame = td->td_frame;
  563         if (__predict_true(error == 0)) {
  564                 frame->tf_rax = td->td_retval[0];
  565                 frame->tf_rdx = td->td_retval[1];
  566                 frame->tf_rflags &= ~PSL_C;
  567                 return;
  568         }
  569 
  570         switch (error) {
  571         case ERESTART:
  572                 /*
  573                  * Reconstruct pc, we know that 'syscall' is 2 bytes,
  574                  * lcall $X,y is 7 bytes, int 0x80 is 2 bytes.
  575                  * We saved this in tf_err.
  576                  * %r10 (which was holding the value of %rcx) is restored
  577                  * for the next iteration.
  578                  * %r10 restore is only required for freebsd/amd64 processes,
  579                  * but shall be innocent for any ia32 ABI.
  580                  *
  581                  * Require full context restore to get the arguments
  582                  * in the registers reloaded at return to usermode.
  583                  */
  584                 frame->tf_rip -= frame->tf_err;
  585                 frame->tf_r10 = frame->tf_rcx;
  586                 set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
  587                 break;
  588 
  589         case EJUSTRETURN:
  590                 break;
  591 
  592         default:
  593                 frame->tf_rax = error;
  594                 frame->tf_rflags |= PSL_C;
  595                 break;
  596         }
  597 }
  598 
  599 /*
  600  * Initialize machine state, mostly pcb and trap frame for a new
  601  * thread, about to return to userspace.  Put enough state in the new
  602  * thread's PCB to get it to go back to the fork_return(), which
  603  * finalizes the thread state and handles peculiarities of the first
  604  * return to userspace for the new thread.
  605  */
  606 void
  607 cpu_copy_thread(struct thread *td, struct thread *td0)
  608 {
  609         copy_thread(td0, td);
  610 
  611         set_pcb_flags_raw(td->td_pcb, PCB_FULL_IRET);
  612 }
  613 
  614 /*
  615  * Set that machine state for performing an upcall that starts
  616  * the entry function with the given argument.
  617  */
  618 void
  619 cpu_set_upcall(struct thread *td, void (*entry)(void *), void *arg,
  620     stack_t *stack)
  621 {
  622 
  623         /* 
  624          * Do any extra cleaning that needs to be done.
  625          * The thread may have optional components
  626          * that are not present in a fresh thread.
  627          * This may be a recycled thread so make it look
  628          * as though it's newly allocated.
  629          */
  630         cpu_thread_clean(td);
  631 
  632 #ifdef COMPAT_FREEBSD32
  633         if (SV_PROC_FLAG(td->td_proc, SV_ILP32)) {
  634                 /*
  635                  * Set the trap frame to point at the beginning of the entry
  636                  * function.
  637                  */
  638                 td->td_frame->tf_rbp = 0;
  639                 td->td_frame->tf_rsp =
  640                    (((uintptr_t)stack->ss_sp + stack->ss_size - 4) & ~0x0f) - 4;
  641                 td->td_frame->tf_rip = (uintptr_t)entry;
  642 
  643                 /* Return address sentinel value to stop stack unwinding. */
  644                 suword32((void *)td->td_frame->tf_rsp, 0);
  645 
  646                 /* Pass the argument to the entry point. */
  647                 suword32((void *)(td->td_frame->tf_rsp + sizeof(int32_t)),
  648                     (uint32_t)(uintptr_t)arg);
  649 
  650                 return;
  651         }
  652 #endif
  653 
  654         /*
  655          * Set the trap frame to point at the beginning of the uts
  656          * function.
  657          */
  658         td->td_frame->tf_rbp = 0;
  659         td->td_frame->tf_rsp =
  660             ((register_t)stack->ss_sp + stack->ss_size) & ~0x0f;
  661         td->td_frame->tf_rsp -= 8;
  662         td->td_frame->tf_rip = (register_t)entry;
  663         td->td_frame->tf_ds = _udatasel;
  664         td->td_frame->tf_es = _udatasel;
  665         td->td_frame->tf_fs = _ufssel;
  666         td->td_frame->tf_gs = _ugssel;
  667         td->td_frame->tf_flags = TF_HASSEGS;
  668 
  669         /* Return address sentinel value to stop stack unwinding. */
  670         suword((void *)td->td_frame->tf_rsp, 0);
  671 
  672         /* Pass the argument to the entry point. */
  673         td->td_frame->tf_rdi = (register_t)arg;
  674 }
  675 
  676 int
  677 cpu_set_user_tls(struct thread *td, void *tls_base)
  678 {
  679         struct pcb *pcb;
  680 
  681         if ((u_int64_t)tls_base >= VM_MAXUSER_ADDRESS)
  682                 return (EINVAL);
  683 
  684         pcb = td->td_pcb;
  685         set_pcb_flags(pcb, PCB_FULL_IRET);
  686 #ifdef COMPAT_FREEBSD32
  687         if (SV_PROC_FLAG(td->td_proc, SV_ILP32)) {
  688                 pcb->pcb_gsbase = (register_t)tls_base;
  689                 return (0);
  690         }
  691 #endif
  692         pcb->pcb_fsbase = (register_t)tls_base;
  693         return (0);
  694 }

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