xref: /illumos-gate/usr/src/uts/intel/kdi/kdi_idt.c (revision f0089e39)
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 <sys/psw.h>
81 #include <vm/hat_i86.h>
82 
83 #define	KDI_GATE_NVECS	3
84 
85 #define	KDI_IDT_NOSAVE	0
86 #define	KDI_IDT_SAVE	1
87 
88 #define	KDI_IDT_DTYPE_KERNEL	0
89 #define	KDI_IDT_DTYPE_BOOT	1
90 
91 /* Solely to keep kdiregs_t in the CTF, otherwise unused. */
92 kdiregs_t kdi_regs;
93 
94 kdi_cpusave_t *kdi_cpusave;
95 int kdi_ncpusave;
96 
97 static kdi_main_t kdi_kmdb_main;
98 
99 kdi_drreg_t kdi_drreg;
100 
101 
102 uintptr_t	kdi_kernel_handler;
103 
104 int		kdi_trap_switch;
105 
106 #define	KDI_MEMRANGES_MAX	2
107 
108 kdi_memrange_t	kdi_memranges[KDI_MEMRANGES_MAX];
109 int		kdi_nmemranges;
110 
111 typedef void idt_hdlr_f(void);
112 
113 extern idt_hdlr_f kdi_trap0, kdi_trap1, kdi_int2, kdi_trap3, kdi_trap4;
114 extern idt_hdlr_f kdi_trap5, kdi_trap6, kdi_trap7, kdi_trap9;
115 extern idt_hdlr_f kdi_traperr10, kdi_traperr11, kdi_traperr12;
116 extern idt_hdlr_f kdi_traperr13, kdi_traperr14, kdi_trap16, kdi_traperr17;
117 extern idt_hdlr_f kdi_trap18, kdi_trap19, kdi_trap20, kdi_ivct32;
118 extern idt_hdlr_f kdi_invaltrap;
119 extern size_t kdi_ivct_size;
120 
121 typedef struct kdi_gate_spec {
122 	uint_t kgs_vec;
123 	uint_t kgs_dpl;
124 } kdi_gate_spec_t;
125 
126 /*
127  * Beware: kdi_pass_to_kernel() has unpleasant knowledge of this list.
128  */
129 static const kdi_gate_spec_t kdi_gate_specs[KDI_GATE_NVECS] = {
130 	{ T_SGLSTP, TRP_KPL },
131 	{ T_BPTFLT, TRP_UPL },
132 	{ T_DBGENTR, TRP_KPL }
133 };
134 
135 static gate_desc_t kdi_kgates[KDI_GATE_NVECS];
136 
137 extern gate_desc_t kdi_idt[NIDT];
138 
139 struct idt_description {
140 	uint_t id_low;
141 	uint_t id_high;
142 	idt_hdlr_f *id_basehdlr;
143 	size_t *id_incrp;
144 } idt_description[] = {
145 	{ T_ZERODIV, 0,		kdi_trap0, NULL },
146 	{ T_SGLSTP, 0,		kdi_trap1, NULL },
147 	{ T_NMIFLT, 0,		kdi_int2, NULL },
148 	{ T_BPTFLT, 0,		kdi_trap3, NULL },
149 	{ T_OVFLW, 0,		kdi_trap4, NULL },
150 	{ T_BOUNDFLT, 0,	kdi_trap5, NULL },
151 	{ T_ILLINST, 0,		kdi_trap6, NULL },
152 	{ T_NOEXTFLT, 0,	kdi_trap7, NULL },
153 #if !defined(__xpv)
154 	{ T_DBLFLT, 0,		syserrtrap, NULL },
155 #endif
156 	{ T_EXTOVRFLT, 0,	kdi_trap9, NULL },
157 	{ T_TSSFLT, 0,		kdi_traperr10, NULL },
158 	{ T_SEGFLT, 0,		kdi_traperr11, NULL },
159 	{ T_STKFLT, 0,		kdi_traperr12, NULL },
160 	{ T_GPFLT, 0,		kdi_traperr13, NULL },
161 	{ T_PGFLT, 0,		kdi_traperr14, NULL },
162 	{ 15, 0,		kdi_invaltrap, NULL },
163 	{ T_EXTERRFLT, 0,	kdi_trap16, NULL },
164 	{ T_ALIGNMENT, 0,	kdi_traperr17, NULL },
165 	{ T_MCE, 0,		kdi_trap18, NULL },
166 	{ T_SIMDFPE, 0,		kdi_trap19, NULL },
167 	{ T_DBGENTR, 0,		kdi_trap20, NULL },
168 	{ 21, 31,		kdi_invaltrap, NULL },
169 	{ 32, 255,		kdi_ivct32, &kdi_ivct_size },
170 	{ 0, 0, NULL },
171 };
172 
173 void
kdi_idt_init(selector_t sel)174 kdi_idt_init(selector_t sel)
175 {
176 	struct idt_description *id;
177 	int i;
178 
179 	for (id = idt_description; id->id_basehdlr != NULL; id++) {
180 		uint_t high = id->id_high != 0 ? id->id_high : id->id_low;
181 		size_t incr = id->id_incrp != NULL ? *id->id_incrp : 0;
182 
183 #if !defined(__xpv)
184 		if (kpti_enable && sel == KCS_SEL && id->id_low == T_DBLFLT)
185 			id->id_basehdlr = tr_syserrtrap;
186 #endif
187 
188 		for (i = id->id_low; i <= high; i++) {
189 			caddr_t hdlr = (caddr_t)id->id_basehdlr +
190 			    incr * (i - id->id_low);
191 			set_gatesegd(&kdi_idt[i], (void (*)())hdlr, sel,
192 			    SDT_SYSIGT, TRP_KPL, IST_DBG);
193 		}
194 	}
195 }
196 
197 static void
kdi_idt_gates_install(selector_t sel,int saveold)198 kdi_idt_gates_install(selector_t sel, int saveold)
199 {
200 	gate_desc_t gates[KDI_GATE_NVECS];
201 	int i;
202 
203 	bzero(gates, sizeof (*gates));
204 
205 	for (i = 0; i < KDI_GATE_NVECS; i++) {
206 		const kdi_gate_spec_t *gs = &kdi_gate_specs[i];
207 		uintptr_t func = GATESEG_GETOFFSET(&kdi_idt[gs->kgs_vec]);
208 		set_gatesegd(&gates[i], (void (*)())func, sel, SDT_SYSIGT,
209 		    gs->kgs_dpl, IST_DBG);
210 	}
211 
212 	for (i = 0; i < KDI_GATE_NVECS; i++) {
213 		uint_t vec = kdi_gate_specs[i].kgs_vec;
214 
215 		if (saveold)
216 			kdi_kgates[i] = CPU->cpu_m.mcpu_idt[vec];
217 
218 		kdi_idt_write(&gates[i], vec);
219 	}
220 }
221 
222 static void
kdi_idt_gates_restore(void)223 kdi_idt_gates_restore(void)
224 {
225 	int i;
226 
227 	for (i = 0; i < KDI_GATE_NVECS; i++)
228 		kdi_idt_write(&kdi_kgates[i], kdi_gate_specs[i].kgs_vec);
229 }
230 
231 /*
232  * Called when we switch to the kernel's IDT.  We need to interpose on the
233  * kernel's IDT entries and stop using KMDBCODE_SEL.
234  */
235 void
kdi_idt_sync(void)236 kdi_idt_sync(void)
237 {
238 	kdi_idt_init(KCS_SEL);
239 	kdi_idt_gates_install(KCS_SEL, KDI_IDT_SAVE);
240 }
241 
242 void
kdi_update_drreg(kdi_drreg_t * drreg)243 kdi_update_drreg(kdi_drreg_t *drreg)
244 {
245 	kdi_drreg = *drreg;
246 }
247 
248 void
kdi_memrange_add(caddr_t base,size_t len)249 kdi_memrange_add(caddr_t base, size_t len)
250 {
251 	kdi_memrange_t *mr = &kdi_memranges[kdi_nmemranges];
252 
253 	ASSERT(kdi_nmemranges != KDI_MEMRANGES_MAX);
254 
255 	mr->mr_base = base;
256 	mr->mr_lim = base + len - 1;
257 	kdi_nmemranges++;
258 }
259 
260 void
kdi_idt_switch(kdi_cpusave_t * cpusave)261 kdi_idt_switch(kdi_cpusave_t *cpusave)
262 {
263 	if (cpusave == NULL)
264 		kdi_idtr_set(kdi_idt, sizeof (kdi_idt) - 1);
265 	else
266 		kdi_idtr_set(cpusave->krs_idt, (sizeof (*idt0) * NIDT) - 1);
267 }
268 
269 /*
270  * Activation for CPUs other than the boot CPU, called from that CPU's
271  * mp_startup().  We saved the kernel's descriptors when we initialized the
272  * boot CPU, so we don't want to do it again.  Saving the handlers from this
273  * CPU's IDT would actually be dangerous with the CPU initialization method in
274  * use at the time of this writing.  With that method, the startup code creates
275  * the IDTs for slave CPUs by copying the one used by the boot CPU, which has
276  * already been interposed upon by KMDB.  Were we to interpose again, we'd
277  * replace the kernel's descriptors with our own in the save area.  By not
278  * saving, but still overwriting, we'll work in the current world, and in any
279  * future world where the IDT is generated from scratch.
280  */
281 void
kdi_cpu_init(void)282 kdi_cpu_init(void)
283 {
284 	kdi_idt_gates_install(KCS_SEL, KDI_IDT_NOSAVE);
285 	/* Load the debug registers. */
286 	kdi_cpu_debug_init(&kdi_cpusave[CPU->cpu_id]);
287 }
288 
289 /*
290  * Activation for all CPUs for mod-loaded kmdb, i.e. a kmdb that wasn't
291  * loaded at boot.
292  */
293 static int
kdi_cpu_activate(xc_arg_t arg1 __unused,xc_arg_t arg2 __unused,xc_arg_t arg3 __unused)294 kdi_cpu_activate(xc_arg_t arg1 __unused, xc_arg_t arg2 __unused,
295     xc_arg_t arg3 __unused)
296 {
297 	kdi_idt_gates_install(KCS_SEL, KDI_IDT_SAVE);
298 	return (0);
299 }
300 
301 void
kdi_activate(kdi_main_t main,kdi_cpusave_t * cpusave,uint_t ncpusave)302 kdi_activate(kdi_main_t main, kdi_cpusave_t *cpusave, uint_t ncpusave)
303 {
304 	int i;
305 	cpuset_t cpuset;
306 
307 	CPUSET_ALL(cpuset);
308 
309 	kdi_cpusave = cpusave;
310 	kdi_ncpusave = ncpusave;
311 
312 	kdi_kmdb_main = main;
313 
314 	for (i = 0; i < kdi_ncpusave; i++) {
315 		kdi_cpusave[i].krs_cpu_id = i;
316 
317 		kdi_cpusave[i].krs_curcrumb =
318 		    &kdi_cpusave[i].krs_crumbs[KDI_NCRUMBS - 1];
319 		kdi_cpusave[i].krs_curcrumbidx = KDI_NCRUMBS - 1;
320 	}
321 
322 	if (boothowto & RB_KMDB)
323 		kdi_idt_init(KMDBCODE_SEL);
324 	else
325 		kdi_idt_init(KCS_SEL);
326 
327 	kdi_memranges[0].mr_base = kdi_segdebugbase;
328 	kdi_memranges[0].mr_lim = kdi_segdebugbase + kdi_segdebugsize - 1;
329 	kdi_nmemranges = 1;
330 
331 	kdi_drreg.dr_ctl = KDIREG_DRCTL_RESERVED;
332 	kdi_drreg.dr_stat = KDIREG_DRSTAT_RESERVED;
333 
334 	if (boothowto & RB_KMDB) {
335 		kdi_idt_gates_install(KMDBCODE_SEL, KDI_IDT_NOSAVE);
336 	} else {
337 		xc_call(0, 0, 0, CPUSET2BV(cpuset), kdi_cpu_activate);
338 	}
339 }
340 
341 static int
kdi_cpu_deactivate(xc_arg_t arg1 __unused,xc_arg_t arg2 __unused,xc_arg_t arg3 __unused)342 kdi_cpu_deactivate(xc_arg_t arg1 __unused, xc_arg_t arg2 __unused,
343     xc_arg_t arg3 __unused)
344 {
345 	kdi_idt_gates_restore();
346 	return (0);
347 }
348 
349 void
kdi_deactivate(void)350 kdi_deactivate(void)
351 {
352 	cpuset_t cpuset;
353 	CPUSET_ALL(cpuset);
354 
355 	xc_call(0, 0, 0, CPUSET2BV(cpuset), kdi_cpu_deactivate);
356 	kdi_nmemranges = 0;
357 }
358 
359 /*
360  * We receive all breakpoints and single step traps.  Some of them, including
361  * those from userland and those induced by DTrace providers, are intended for
362  * the kernel, and must be processed there.  We adopt this
363  * ours-until-proven-otherwise position due to the painful consequences of
364  * sending the kernel an unexpected breakpoint or single step.  Unless someone
365  * can prove to us that the kernel is prepared to handle the trap, we'll assume
366  * there's a problem and will give the user a chance to debug it.
367  *
368  * If we return 2, then the calling code should restore the trap-time %cr3: that
369  * is, it really is a kernel-originated trap.
370  */
371 int
kdi_trap_pass(kdi_cpusave_t * cpusave)372 kdi_trap_pass(kdi_cpusave_t *cpusave)
373 {
374 	greg_t tt = cpusave->krs_gregs[KDIREG_TRAPNO];
375 	greg_t pc = cpusave->krs_gregs[KDIREG_PC];
376 	greg_t cs = cpusave->krs_gregs[KDIREG_CS];
377 
378 	if (USERMODE(cs))
379 		return (1);
380 
381 	if (tt != T_BPTFLT && tt != T_SGLSTP)
382 		return (0);
383 
384 	if (tt == T_BPTFLT && kdi_dtrace_get_state() ==
385 	    KDI_DTSTATE_DTRACE_ACTIVE)
386 		return (2);
387 
388 	/*
389 	 * See the comments in the kernel's T_SGLSTP handler for why we need to
390 	 * do this.
391 	 */
392 #if !defined(__xpv)
393 	if (tt == T_SGLSTP &&
394 	    (pc == (greg_t)sys_sysenter || pc == (greg_t)brand_sys_sysenter ||
395 	    pc == (greg_t)tr_sys_sysenter ||
396 	    pc == (greg_t)tr_brand_sys_sysenter)) {
397 #else
398 	if (tt == T_SGLSTP &&
399 	    (pc == (greg_t)sys_sysenter || pc == (greg_t)brand_sys_sysenter)) {
400 #endif
401 		return (1);
402 	}
403 
404 	return (0);
405 }
406 
407 /*
408  * State has been saved, and all CPUs are on the CPU-specific stacks.  All
409  * CPUs enter here, and head off into the debugger proper.
410  */
411 void
412 kdi_debugger_entry(kdi_cpusave_t *cpusave)
413 {
414 	/*
415 	 * BPTFLT gives us control with %eip set to the instruction *after*
416 	 * the int 3.  Back it off, so we're looking at the instruction that
417 	 * triggered the fault.
418 	 */
419 	if (cpusave->krs_gregs[KDIREG_TRAPNO] == T_BPTFLT)
420 		cpusave->krs_gregs[KDIREG_PC]--;
421 
422 	kdi_kmdb_main(cpusave);
423 }
424