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      1 /*	$NetBSD: syscall.c,v 1.22 2023/10/05 19:41:06 ad Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1998, 2000, 2009 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Charles M. Hannum.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 __KERNEL_RCSID(0, "$NetBSD: syscall.c,v 1.22 2023/10/05 19:41:06 ad Exp $");
     34 
     35 #include <sys/param.h>
     36 #include <sys/systm.h>
     37 #include <sys/proc.h>
     38 #include <sys/signal.h>
     39 #include <sys/ktrace.h>
     40 #include <sys/syscall.h>
     41 #include <sys/syscallvar.h>
     42 #include <sys/syscall_stats.h>
     43 
     44 #include <uvm/uvm_extern.h>
     45 
     46 #include <machine/cpu.h>
     47 #include <machine/psl.h>
     48 #include <machine/userret.h>
     49 
     50 #include "opt_dtrace.h"
     51 
     52 #ifndef __x86_64__
     53 int		x86_copyargs(void *, void *, size_t);
     54 #endif
     55 
     56 void		syscall_intern(struct proc *);
     57 static void	syscall(struct trapframe *);
     58 
     59 void
     60 md_child_return(struct lwp *l)
     61 {
     62 	struct trapframe *tf = l->l_md.md_regs;
     63 
     64 	X86_TF_RAX(tf) = 0;
     65 	X86_TF_RFLAGS(tf) &= ~PSL_C;
     66 
     67 	userret(l);
     68 }
     69 
     70 /*
     71  * Process the tail end of a posix_spawn() for the child.
     72  */
     73 void
     74 cpu_spawn_return(struct lwp *l)
     75 {
     76 
     77 	userret(l);
     78 }
     79 
     80 /*
     81  * syscall(frame):
     82  *	System call request from POSIX system call gate interface to kernel.
     83  *	Like trap(), argument is call by reference.
     84  */
     85 #ifdef KDTRACE_HOOKS
     86 void syscall(struct trapframe *);
     87 #else
     88 static
     89 #endif
     90 void
     91 syscall(struct trapframe *frame)
     92 {
     93 	const struct sysent *callp;
     94 	struct proc *p;
     95 	struct lwp *l;
     96 	int error;
     97 	register_t code, rval[2];
     98 #ifdef __x86_64__
     99 	/* Verify that the syscall args will fit in the trapframe space */
    100 	CTASSERT(offsetof(struct trapframe, tf_arg9) >=
    101 	    sizeof(register_t) * (2 + SYS_MAXSYSARGS - 1));
    102 #define args (&frame->tf_rdi)
    103 #else
    104 	register_t args[2 + SYS_MAXSYSARGS];
    105 #endif
    106 
    107 	l = curlwp;
    108 	p = l->l_proc;
    109 
    110 	code = X86_TF_RAX(frame) & (SYS_NSYSENT - 1);
    111 	callp = p->p_emul->e_sysent + code;
    112 
    113 	SYSCALL_COUNT(syscall_counts, code);
    114 	SYSCALL_TIME_SYS_ENTRY(l, syscall_times, code);
    115 
    116 #ifdef __x86_64__
    117 	/*
    118 	 * The first 6 syscall args are passed in rdi, rsi, rdx, r10, r8 and r9
    119 	 * (rcx gets copied to r10 in the libc stub because the syscall
    120 	 * instruction overwrites %cx) and are together in the trap frame
    121 	 * with space following for 4 more entries.
    122 	 */
    123 	if (__predict_false(callp->sy_argsize > 6 * 8)) {
    124 		error = copyin((register_t *)frame->tf_rsp + 1,
    125 		    &frame->tf_arg6, callp->sy_argsize - 6 * 8);
    126 		if (error != 0)
    127 			goto bad;
    128 	}
    129 #else
    130 	if (callp->sy_argsize) {
    131 		error = x86_copyargs((char *)frame->tf_esp + sizeof(int), args,
    132 			    callp->sy_argsize);
    133 		if (__predict_false(error != 0))
    134 			goto bad;
    135 	}
    136 #endif
    137 	error = sy_invoke(callp, l, args, rval, code);
    138 
    139 	if (__predict_true(error == 0)) {
    140 		X86_TF_RAX(frame) = rval[0];
    141 		X86_TF_RDX(frame) = rval[1];
    142 		X86_TF_RFLAGS(frame) &= ~PSL_C;	/* carry bit */
    143 	} else {
    144 		switch (error) {
    145 		case ERESTART:
    146 			/*
    147 			 * The offset to adjust the PC by depends on whether we
    148 			 * entered the kernel through the trap or call gate.
    149 			 * We saved the instruction size in tf_err on entry.
    150 			 */
    151 			X86_TF_RIP(frame) -= frame->tf_err;
    152 			break;
    153 		case EJUSTRETURN:
    154 			/* nothing to do */
    155 			break;
    156 		default:
    157 		bad:
    158 			X86_TF_RAX(frame) = error;
    159 			X86_TF_RFLAGS(frame) |= PSL_C;	/* carry bit */
    160 			break;
    161 		}
    162 	}
    163 
    164 	SYSCALL_TIME_SYS_EXIT(l);
    165 	userret(l);
    166 }
    167 
    168 void
    169 syscall_intern(struct proc *p)
    170 {
    171 
    172 	p->p_md.md_syscall = syscall;
    173 }
    174