xref: /illumos-gate/usr/src/uts/intel/syscall/lwp_private.c (revision f0089e391b2bc4be2755f1a1b51fb4cd9b8f3988)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
23  * Use is subject to license terms.
24  * Copyright (c) 2018, Joyent, Inc.
25  */
26 
27 #include <sys/param.h>
28 #include <sys/types.h>
29 #include <sys/disp.h>
30 #include <sys/sysmacros.h>
31 #include <sys/cpuvar.h>
32 #include <sys/systm.h>
33 #include <sys/thread.h>
34 #include <sys/lwp.h>
35 #include <sys/segments.h>
36 #include <sys/privregs.h>
37 #include <sys/cmn_err.h>
38 
39 int
lwp_setprivate(klwp_t * lwp,int which,uintptr_t base)40 lwp_setprivate(klwp_t *lwp, int which, uintptr_t base)
41 {
42 	pcb_t *pcb = &lwp->lwp_pcb;
43 	struct regs *rp = lwptoregs(lwp);
44 	kthread_t *t = lwptot(lwp);
45 	int thisthread = t == curthread;
46 	int rval;
47 
48 	if (thisthread)
49 		kpreempt_disable();
50 
51 
52 	/*
53 	 * 32-bit compatibility processes point to the per-cpu GDT segment
54 	 * descriptors that are virtualized to the lwp.  That allows 32-bit
55 	 * programs to mess with %fs and %gs; in particular it allows
56 	 * things like this:
57 	 *
58 	 *	movw	%gs, %ax
59 	 *	...
60 	 *	movw	%ax, %gs
61 	 *
62 	 * to work, which is needed by emulators for legacy application
63 	 * environments ..
64 	 *
65 	 * 64-bit processes may also point to a per-cpu GDT segment descriptor
66 	 * virtualized to the lwp.  However the descriptor base is forced
67 	 * to zero (because we can't express the full 64-bit address range
68 	 * in a long mode descriptor), so don't reload segment registers
69 	 * in a 64-bit program! 64-bit processes must have selector values
70 	 * of zero for %fs and %gs to use the 64-bit fs_base and gs_base
71 	 * respectively.
72 	 */
73 	if (!PCB_NEED_UPDATE_SEGS(pcb)) {
74 		pcb->pcb_ds = rp->r_ds;
75 		pcb->pcb_es = rp->r_es;
76 		pcb->pcb_fs = rp->r_fs;
77 		pcb->pcb_gs = rp->r_gs;
78 		PCB_SET_UPDATE_SEGS(pcb);
79 		t->t_post_sys = 1;
80 	}
81 	ASSERT(t->t_post_sys);
82 
83 	switch (which) {
84 	case _LWP_FSBASE:
85 		if (lwp_getdatamodel(lwp) == DATAMODEL_NATIVE) {
86 			set_usegd(&pcb->pcb_fsdesc, SDP_LONG, 0, 0,
87 			    SDT_MEMRWA, SEL_UPL, SDP_BYTES, SDP_OP32);
88 			rval = pcb->pcb_fs = 0;	/* null gdt descriptor */
89 		} else {
90 			set_usegd(&pcb->pcb_fsdesc, SDP_SHORT, (void *)base, -1,
91 			    SDT_MEMRWA, SEL_UPL, SDP_PAGES, SDP_OP32);
92 			rval = pcb->pcb_fs = LWPFS_SEL;
93 		}
94 		if (thisthread)
95 			gdt_update_usegd(GDT_LWPFS, &pcb->pcb_fsdesc);
96 
97 		pcb->pcb_fsbase = base;
98 		break;
99 	case _LWP_GSBASE:
100 		if (lwp_getdatamodel(lwp) == DATAMODEL_NATIVE) {
101 			set_usegd(&pcb->pcb_gsdesc, SDP_LONG, 0, 0,
102 			    SDT_MEMRWA, SEL_UPL, SDP_BYTES, SDP_OP32);
103 			rval = pcb->pcb_gs = 0;	/* null gdt descriptor */
104 		} else {
105 			set_usegd(&pcb->pcb_gsdesc, SDP_SHORT, (void *)base, -1,
106 			    SDT_MEMRWA, SEL_UPL, SDP_PAGES, SDP_OP32);
107 			rval = pcb->pcb_gs = LWPGS_SEL;
108 		}
109 		if (thisthread)
110 			gdt_update_usegd(GDT_LWPGS, &pcb->pcb_gsdesc);
111 
112 		pcb->pcb_gsbase = base;
113 		break;
114 	default:
115 		rval = -1;
116 		break;
117 	}
118 
119 	if (thisthread)
120 		kpreempt_enable();
121 	return (rval);
122 }
123 
124 static int
lwp_getprivate(klwp_t * lwp,int which,uintptr_t base)125 lwp_getprivate(klwp_t *lwp, int which, uintptr_t base)
126 {
127 	pcb_t *pcb = &lwp->lwp_pcb;
128 	struct regs *rp = lwptoregs(lwp);
129 	uintptr_t sbase;
130 	int error = 0;
131 
132 	ASSERT(lwptot(lwp) == curthread);
133 
134 	kpreempt_disable();
135 	switch (which) {
136 	case _LWP_FSBASE:
137 		if ((sbase = pcb->pcb_fsbase) != 0) {
138 			if (lwp_getdatamodel(lwp) == DATAMODEL_NATIVE) {
139 				if (PCB_NEED_UPDATE_SEGS(pcb)) {
140 					if (pcb->pcb_fs == 0)
141 						break;
142 				} else {
143 					if (rp->r_fs == 0)
144 						break;
145 				}
146 			} else {
147 				if (PCB_NEED_UPDATE_SEGS(pcb)) {
148 					if (pcb->pcb_fs == LWPFS_SEL)
149 						break;
150 				} else {
151 					if (rp->r_fs == LWPFS_SEL)
152 						break;
153 				}
154 			}
155 		}
156 		error = EINVAL;
157 		break;
158 	case _LWP_GSBASE:
159 		if ((sbase = pcb->pcb_gsbase) != 0) {
160 			if (lwp_getdatamodel(lwp) == DATAMODEL_NATIVE) {
161 				if (PCB_NEED_UPDATE_SEGS(pcb)) {
162 					if (pcb->pcb_gs == 0)
163 						break;
164 				} else {
165 					if (rp->r_gs == 0)
166 						break;
167 				}
168 			} else {
169 				if (PCB_NEED_UPDATE_SEGS(pcb)) {
170 					if (pcb->pcb_gs == LWPGS_SEL)
171 						break;
172 				} else {
173 					if (rp->r_gs == LWPGS_SEL)
174 						break;
175 				}
176 			}
177 		}
178 		error = EINVAL;
179 		break;
180 
181 
182 	default:
183 		error = ENOTSUP;
184 		break;
185 	}
186 	kpreempt_enable();
187 
188 	if (error != 0)
189 		return (error);
190 
191 	if (lwp_getdatamodel(lwp) == DATAMODEL_NATIVE) {
192 		if (sulword((void *)base, sbase) == -1)
193 			error = EFAULT;
194 #if defined(_SYSCALL32_IMPL)
195 	} else {
196 		if (suword32((void *)base, (uint32_t)sbase) == -1)
197 			error = EFAULT;
198 #endif
199 	}
200 	return (error);
201 }
202 
203 /*
204  * libc-private syscall for managing per-lwp %gs and %fs segment base values.
205  */
206 int
syslwp_private(int cmd,int which,uintptr_t base)207 syslwp_private(int cmd, int which, uintptr_t base)
208 {
209 	klwp_t *lwp = ttolwp(curthread);
210 	int res, error;
211 
212 	switch (cmd) {
213 	case _LWP_SETPRIVATE:
214 		res = lwp_setprivate(lwp, which, base);
215 		return (res < 0 ? set_errno(ENOTSUP) : res);
216 	case _LWP_GETPRIVATE:
217 		error = lwp_getprivate(lwp, which, base);
218 		return (error != 0 ? set_errno(error) : error);
219 	default:
220 		return (set_errno(ENOTSUP));
221 	}
222 }
223