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 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 *
25 * Copyright 2018 Joyent, Inc.
26 */
27
28 /*
29 * Management of KMDB's IDT, which is installed upon KMDB activation.
30 *
31 * Debugger activation has two flavors, which cover the cases where KMDB is
32 * loaded at boot, and when it is loaded after boot. In brief, in both cases,
33 * the KDI needs to interpose upon several handlers in the IDT. When
34 * mod-loaded KMDB is deactivated, we undo the IDT interposition, restoring the
35 * handlers to what they were before we started.
36 *
37 * We also take over the entirety of IDT (except the double-fault handler) on
38 * the active CPU when we're in kmdb so we can handle things like page faults
39 * sensibly.
40 *
41 * Boot-loaded KMDB
42 *
43 * When we're first activated, we're running on boot's IDT. We need to be able
44 * to function in this world, so we'll install our handlers into boot's IDT.
45 * This is a little complicated: we're using the fake cpu_t set up by
46 * boot_kdi_tmpinit(), so we can't access cpu_idt directly. Instead,
47 * kdi_idt_write() notices that cpu_idt is NULL, and works around this problem.
48 *
49 * Later, when we're about to switch to the kernel's IDT, it'll call us via
50 * kdi_idt_sync(), allowing us to add our handlers to the new IDT. While
51 * boot-loaded KMDB can't be unloaded, we still need to save the descriptors we
52 * replace so we can pass traps back to the kernel as necessary.
53 *
54 * The last phase of boot-loaded KMDB activation occurs at non-boot CPU
55 * startup. We will be called on each non-boot CPU, thus allowing us to set up
56 * any watchpoints that may have been configured on the boot CPU and interpose
57 * on the given CPU's IDT. We don't save the interposed descriptors in this
58 * case -- see kdi_cpu_init() for details.
59 *
60 * Mod-loaded KMDB
61 *
62 * This style of activation is much simpler, as the CPUs are already running,
63 * and are using their own copy of the kernel's IDT. We simply interpose upon
64 * each CPU's IDT. We save the handlers we replace, both for deactivation and
65 * for passing traps back to the kernel. Note that for the hypervisors'
66 * benefit, we need to xcall to the other CPUs to do this, since we need to
67 * actively set the trap entries in its virtual IDT from that vcpu's context
68 * rather than just modifying the IDT table from the CPU running kdi_activate().
69 */
70
71 #include <sys/types.h>
72 #include <sys/segments.h>
73 #include <sys/trap.h>
74 #include <sys/cpuvar.h>
75 #include <sys/reboot.h>
76 #include <sys/sunddi.h>
77 #include <sys/archsystm.h>
78 #include <sys/kdi_impl.h>
79 #include <sys/x_call.h>
80 #include <ia32/sys/psw.h>
81
82 #define KDI_GATE_NVECS 3
83
84 #define KDI_IDT_NOSAVE 0
85 #define KDI_IDT_SAVE 1
86
87 #define KDI_IDT_DTYPE_KERNEL 0
88 #define KDI_IDT_DTYPE_BOOT 1
89
90 kdi_cpusave_t *kdi_cpusave;
91 int kdi_ncpusave;
92
93 static kdi_main_t kdi_kmdb_main;
94
95 kdi_drreg_t kdi_drreg;
96
97 #ifndef __amd64
98 /* Used to track the current set of valid kernel selectors. */
99 uint32_t kdi_cs;
100 uint32_t kdi_ds;
101 uint32_t kdi_fs;
102 uint32_t kdi_gs;
103 #endif
104
105 uintptr_t kdi_kernel_handler;
106
107 int kdi_trap_switch;
108
109 #define KDI_MEMRANGES_MAX 2
110
111 kdi_memrange_t kdi_memranges[KDI_MEMRANGES_MAX];
112 int kdi_nmemranges;
113
114 typedef void idt_hdlr_f(void);
115
116 extern idt_hdlr_f kdi_trap0, kdi_trap1, kdi_int2, kdi_trap3, kdi_trap4;
117 extern idt_hdlr_f kdi_trap5, kdi_trap6, kdi_trap7, kdi_trap9;
118 extern idt_hdlr_f kdi_traperr10, kdi_traperr11, kdi_traperr12;
119 extern idt_hdlr_f kdi_traperr13, kdi_traperr14, kdi_trap16, kdi_trap17;
120 extern idt_hdlr_f kdi_trap18, kdi_trap19, kdi_trap20, kdi_ivct32;
121 extern idt_hdlr_f kdi_invaltrap;
122 extern size_t kdi_ivct_size;
123
124 typedef struct kdi_gate_spec {
125 uint_t kgs_vec;
126 uint_t kgs_dpl;
127 } kdi_gate_spec_t;
128
129 /*
130 * Beware: kdi_pass_to_kernel() has unpleasant knowledge of this list.
131 */
132 static const kdi_gate_spec_t kdi_gate_specs[KDI_GATE_NVECS] = {
133 { T_SGLSTP, TRP_KPL },
134 { T_BPTFLT, TRP_UPL },
135 { T_DBGENTR, TRP_KPL }
136 };
137
138 static gate_desc_t kdi_kgates[KDI_GATE_NVECS];
139
140 gate_desc_t kdi_idt[NIDT];
141
142 struct idt_description {
143 uint_t id_low;
144 uint_t id_high;
145 idt_hdlr_f *id_basehdlr;
146 size_t *id_incrp;
147 } idt_description[] = {
148 { T_ZERODIV, 0, kdi_trap0, NULL },
149 { T_SGLSTP, 0, kdi_trap1, NULL },
150 { T_NMIFLT, 0, kdi_int2, NULL },
151 { T_BPTFLT, 0, kdi_trap3, NULL },
152 { T_OVFLW, 0, kdi_trap4, NULL },
153 { T_BOUNDFLT, 0, kdi_trap5, NULL },
154 { T_ILLINST, 0, kdi_trap6, NULL },
155 { T_NOEXTFLT, 0, kdi_trap7, NULL },
156 #if !defined(__xpv)
157 { T_DBLFLT, 0, syserrtrap, NULL },
158 #endif
159 { T_EXTOVRFLT, 0, kdi_trap9, NULL },
160 { T_TSSFLT, 0, kdi_traperr10, NULL },
161 { T_SEGFLT, 0, kdi_traperr11, NULL },
162 { T_STKFLT, 0, kdi_traperr12, NULL },
163 { T_GPFLT, 0, kdi_traperr13, NULL },
164 { T_PGFLT, 0, kdi_traperr14, NULL },
165 { 15, 0, kdi_invaltrap, NULL },
166 { T_EXTERRFLT, 0, kdi_trap16, NULL },
167 { T_ALIGNMENT, 0, kdi_trap17, NULL },
168 { T_MCE, 0, kdi_trap18, NULL },
169 { T_SIMDFPE, 0, kdi_trap19, NULL },
170 { T_DBGENTR, 0, kdi_trap20, NULL },
171 { 21, 31, kdi_invaltrap, NULL },
172 { 32, 255, kdi_ivct32, &kdi_ivct_size },
173 { 0, 0, NULL },
174 };
175
176 void
177 kdi_idt_init(selector_t sel)
178 {
179 struct idt_description *id;
180 int i;
181
182 for (id = idt_description; id->id_basehdlr != NULL; id++) {
183 uint_t high = id->id_high != 0 ? id->id_high : id->id_low;
184 size_t incr = id->id_incrp != NULL ? *id->id_incrp : 0;
185
186 for (i = id->id_low; i <= high; i++) {
187 caddr_t hdlr = (caddr_t)id->id_basehdlr +
188 incr * (i - id->id_low);
189 set_gatesegd(&kdi_idt[i], (void (*)())hdlr, sel,
190 SDT_SYSIGT, TRP_KPL, i);
191 }
192 }
193 }
194
195 static void
196 kdi_idt_gates_install(selector_t sel, int saveold)
197 {
198 gate_desc_t gates[KDI_GATE_NVECS];
199 int i;
200
201 bzero(gates, sizeof (*gates));
202
203 for (i = 0; i < KDI_GATE_NVECS; i++) {
204 const kdi_gate_spec_t *gs = &kdi_gate_specs[i];
205 uintptr_t func = GATESEG_GETOFFSET(&kdi_idt[gs->kgs_vec]);
206 set_gatesegd(&gates[i], (void (*)())func, sel, SDT_SYSIGT,
207 gs->kgs_dpl, gs->kgs_vec);
208 }
209
210 for (i = 0; i < KDI_GATE_NVECS; i++) {
211 uint_t vec = kdi_gate_specs[i].kgs_vec;
212
213 if (saveold)
214 kdi_kgates[i] = CPU->cpu_m.mcpu_idt[vec];
215
216 kdi_idt_write(&gates[i], vec);
217 }
218 }
219
220 static void
221 kdi_idt_gates_restore(void)
222 {
223 int i;
224
225 for (i = 0; i < KDI_GATE_NVECS; i++)
226 kdi_idt_write(&kdi_kgates[i], kdi_gate_specs[i].kgs_vec);
227 }
228
229 /*
230 * Called when we switch to the kernel's IDT. We need to interpose on the
231 * kernel's IDT entries and stop using KMDBCODE_SEL.
232 */
233 void
234 kdi_idt_sync(void)
235 {
236 kdi_idt_init(KCS_SEL);
237 kdi_idt_gates_install(KCS_SEL, KDI_IDT_SAVE);
238 }
239
240 void
241 kdi_update_drreg(kdi_drreg_t *drreg)
242 {
243 kdi_drreg = *drreg;
244 }
245
246 void
247 kdi_memrange_add(caddr_t base, size_t len)
248 {
249 kdi_memrange_t *mr = &kdi_memranges[kdi_nmemranges];
250
251 ASSERT(kdi_nmemranges != KDI_MEMRANGES_MAX);
252
253 mr->mr_base = base;
254 mr->mr_lim = base + len - 1;
255 kdi_nmemranges++;
256 }
257
258 void
259 kdi_idt_switch(kdi_cpusave_t *cpusave)
260 {
261 if (cpusave == NULL)
262 kdi_idtr_set(kdi_idt, sizeof (kdi_idt) - 1);
263 else
264 kdi_idtr_set(cpusave->krs_idt, (sizeof (*idt0) * NIDT) - 1);
265 }
266
267 /*
268 * Activation for CPUs other than the boot CPU, called from that CPU's
269 * mp_startup(). We saved the kernel's descriptors when we initialized the
270 * boot CPU, so we don't want to do it again. Saving the handlers from this
271 * CPU's IDT would actually be dangerous with the CPU initialization method in
272 * use at the time of this writing. With that method, the startup code creates
273 * the IDTs for slave CPUs by copying the one used by the boot CPU, which has
274 * already been interposed upon by KMDB. Were we to interpose again, we'd
275 * replace the kernel's descriptors with our own in the save area. By not
276 * saving, but still overwriting, we'll work in the current world, and in any
277 * future world where the IDT is generated from scratch.
278 */
279 void
280 kdi_cpu_init(void)
281 {
282 kdi_idt_gates_install(KCS_SEL, KDI_IDT_NOSAVE);
283 /* Load the debug registers. */
284 kdi_cpu_debug_init(&kdi_cpusave[CPU->cpu_id]);
285 }
286
287 /*
288 * Activation for all CPUs for mod-loaded kmdb, i.e. a kmdb that wasn't
289 * loaded at boot.
290 */
291 static int
292 kdi_cpu_activate(void)
293 {
294 kdi_idt_gates_install(KCS_SEL, KDI_IDT_SAVE);
295 return (0);
296 }
297
298 void
299 kdi_activate(kdi_main_t main, kdi_cpusave_t *cpusave, uint_t ncpusave)
300 {
301 int i;
302 cpuset_t cpuset;
303
304 CPUSET_ALL(cpuset);
305
306 kdi_cpusave = cpusave;
307 kdi_ncpusave = ncpusave;
308
309 kdi_kmdb_main = main;
310
311 for (i = 0; i < kdi_ncpusave; i++) {
312 kdi_cpusave[i].krs_cpu_id = i;
313
314 kdi_cpusave[i].krs_curcrumb =
315 &kdi_cpusave[i].krs_crumbs[KDI_NCRUMBS - 1];
316 kdi_cpusave[i].krs_curcrumbidx = KDI_NCRUMBS - 1;
317 }
318
319 if (boothowto & RB_KMDB)
320 kdi_idt_init(KMDBCODE_SEL);
321 else
322 kdi_idt_init(KCS_SEL);
323
324 /* The initial selector set. Updated by the debugger-entry code */
325 #ifndef __amd64
326 kdi_cs = B32CODE_SEL;
327 kdi_ds = kdi_fs = kdi_gs = B32DATA_SEL;
328 #endif
329
330 kdi_memranges[0].mr_base = kdi_segdebugbase;
331 kdi_memranges[0].mr_lim = kdi_segdebugbase + kdi_segdebugsize - 1;
332 kdi_nmemranges = 1;
333
334 kdi_drreg.dr_ctl = KDIREG_DRCTL_RESERVED;
335 kdi_drreg.dr_stat = KDIREG_DRSTAT_RESERVED;
336
337 if (boothowto & RB_KMDB) {
338 kdi_idt_gates_install(KMDBCODE_SEL, KDI_IDT_NOSAVE);
339 } else {
340 xc_call(0, 0, 0, CPUSET2BV(cpuset),
341 (xc_func_t)kdi_cpu_activate);
342 }
343 }
344
345 static int
346 kdi_cpu_deactivate(void)
347 {
348 kdi_idt_gates_restore();
349 return (0);
350 }
351
352 void
353 kdi_deactivate(void)
354 {
355 cpuset_t cpuset;
356 CPUSET_ALL(cpuset);
357
358 xc_call(0, 0, 0, CPUSET2BV(cpuset), (xc_func_t)kdi_cpu_deactivate);
359 kdi_nmemranges = 0;
360 }
361
362 /*
363 * We receive all breakpoints and single step traps. Some of them,
364 * including those from userland and those induced by DTrace providers,
365 * are intended for the kernel, and must be processed there. We adopt
366 * this ours-until-proven-otherwise position due to the painful
367 * consequences of sending the kernel an unexpected breakpoint or
368 * single step. Unless someone can prove to us that the kernel is
369 * prepared to handle the trap, we'll assume there's a problem and will
370 * give the user a chance to debug it.
371 */
372 int
373 kdi_trap_pass(kdi_cpusave_t *cpusave)
374 {
375 greg_t tt = cpusave->krs_gregs[KDIREG_TRAPNO];
376 greg_t pc = cpusave->krs_gregs[KDIREG_PC];
377 greg_t cs = cpusave->krs_gregs[KDIREG_CS];
378
379 if (USERMODE(cs))
380 return (1);
381
382 if (tt != T_BPTFLT && tt != T_SGLSTP)
383 return (0);
384
385 if (tt == T_BPTFLT && kdi_dtrace_get_state() ==
386 KDI_DTSTATE_DTRACE_ACTIVE)
387 return (1);
388
389 /*
390 * See the comments in the kernel's T_SGLSTP handler for why we need to
391 * do this.
392 */
393 if (tt == T_SGLSTP &&
394 (pc == (greg_t)sys_sysenter || pc == (greg_t)brand_sys_sysenter))
395 return (1);
396
397 return (0);
398 }
399
400 /*
401 * State has been saved, and all CPUs are on the CPU-specific stacks. All
402 * CPUs enter here, and head off into the debugger proper.
403 */
404 void
405 kdi_debugger_entry(kdi_cpusave_t *cpusave)
406 {
407 /*
408 * BPTFLT gives us control with %eip set to the instruction *after*
409 * the int 3. Back it off, so we're looking at the instruction that
410 * triggered the fault.
411 */
412 if (cpusave->krs_gregs[KDIREG_TRAPNO] == T_BPTFLT)
413 cpusave->krs_gregs[KDIREG_PC]--;
414
415 kdi_kmdb_main(cpusave);
416 }