1/*P:500 2 * Just as userspace programs request kernel operations through a system 3 * call, the Guest requests Host operations through a "hypercall". You might 4 * notice this nomenclature doesn't really follow any logic, but the name has 5 * been around for long enough that we're stuck with it. As you'd expect, this 6 * code is basically a one big switch statement. 7:*/ 8 9/* Copyright (C) 2006 Rusty Russell IBM Corporation 10 11 This program is free software; you can redistribute it and/or modify 12 it under the terms of the GNU General Public License as published by 13 the Free Software Foundation; either version 2 of the License, or 14 (at your option) any later version. 15 16 This program is distributed in the hope that it will be useful, 17 but WITHOUT ANY WARRANTY; without even the implied warranty of 18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 GNU General Public License for more details. 20 21 You should have received a copy of the GNU General Public License 22 along with this program; if not, write to the Free Software 23 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 24*/ 25#include <linux/uaccess.h> 26#include <linux/syscalls.h> 27#include <linux/mm.h> 28#include <linux/ktime.h> 29#include <asm/page.h> 30#include <asm/pgtable.h> 31#include "lg.h" 32 33/*H:120 34 * This is the core hypercall routine: where the Guest gets what it wants. 35 * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. 36 */ 37static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) 38{ 39 switch (args->arg0) { 40 case LHCALL_FLUSH_ASYNC: 41 /* 42 * This call does nothing, except by breaking out of the Guest 43 * it makes us process all the asynchronous hypercalls. 44 */ 45 break; 46 case LHCALL_SEND_INTERRUPTS: 47 /* 48 * This call does nothing too, but by breaking out of the Guest 49 * it makes us process any pending interrupts. 50 */ 51 break; 52 case LHCALL_LGUEST_INIT: 53 /* 54 * You can't get here unless you're already initialized. Don't 55 * do that. 56 */ 57 kill_guest(cpu, "already have lguest_data"); 58 break; 59 case LHCALL_SHUTDOWN: { 60 char msg[128]; 61 /* 62 * Shutdown is such a trivial hypercall that we do it in five 63 * lines right here. 64 * 65 * If the lgread fails, it will call kill_guest() itself; the 66 * kill_guest() with the message will be ignored. 67 */ 68 __lgread(cpu, msg, args->arg1, sizeof(msg)); 69 msg[sizeof(msg)-1] = '\0'; 70 kill_guest(cpu, "CRASH: %s", msg); 71 if (args->arg2 == LGUEST_SHUTDOWN_RESTART) 72 cpu->lg->dead = ERR_PTR(-ERESTART); 73 break; 74 } 75 case LHCALL_FLUSH_TLB: 76 /* FLUSH_TLB comes in two flavors, depending on the argument: */ 77 if (args->arg1) 78 guest_pagetable_clear_all(cpu); 79 else 80 guest_pagetable_flush_user(cpu); 81 break; 82 83 /* 84 * All these calls simply pass the arguments through to the right 85 * routines. 86 */ 87 case LHCALL_NEW_PGTABLE: 88 guest_new_pagetable(cpu, args->arg1); 89 break; 90 case LHCALL_SET_STACK: 91 guest_set_stack(cpu, args->arg1, args->arg2, args->arg3); 92 break; 93 case LHCALL_SET_PTE: 94#ifdef CONFIG_X86_PAE 95 guest_set_pte(cpu, args->arg1, args->arg2, 96 __pte(args->arg3 | (u64)args->arg4 << 32)); 97#else 98 guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3)); 99#endif 100 break; 101 case LHCALL_SET_PGD: 102 guest_set_pgd(cpu->lg, args->arg1, args->arg2); 103 break; 104#ifdef CONFIG_X86_PAE 105 case LHCALL_SET_PMD: 106 guest_set_pmd(cpu->lg, args->arg1, args->arg2); 107 break; 108#endif 109 case LHCALL_SET_CLOCKEVENT: 110 guest_set_clockevent(cpu, args->arg1); 111 break; 112 case LHCALL_TS: 113 /* This sets the TS flag, as we saw used in run_guest(). */ 114 cpu->ts = args->arg1; 115 break; 116 case LHCALL_HALT: 117 /* Similarly, this sets the halted flag for run_guest(). */ 118 cpu->halted = 1; 119 break; 120 default: 121 /* It should be an architecture-specific hypercall. */ 122 if (lguest_arch_do_hcall(cpu, args)) 123 kill_guest(cpu, "Bad hypercall %li\n", args->arg0); 124 } 125} 126 127/*H:124 128 * Asynchronous hypercalls are easy: we just look in the array in the 129 * Guest's "struct lguest_data" to see if any new ones are marked "ready". 130 * 131 * We are careful to do these in order: obviously we respect the order the 132 * Guest put them in the ring, but we also promise the Guest that they will 133 * happen before any normal hypercall (which is why we check this before 134 * checking for a normal hcall). 135 */ 136static void do_async_hcalls(struct lg_cpu *cpu) 137{ 138 unsigned int i; 139 u8 st[LHCALL_RING_SIZE]; 140 141 /* For simplicity, we copy the entire call status array in at once. */ 142 if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st))) 143 return; 144 145 /* We process "struct lguest_data"s hcalls[] ring once. */ 146 for (i = 0; i < ARRAY_SIZE(st); i++) { 147 struct hcall_args args; 148 /* 149 * We remember where we were up to from last time. This makes 150 * sure that the hypercalls are done in the order the Guest 151 * places them in the ring. 152 */ 153 unsigned int n = cpu->next_hcall; 154 155 /* 0xFF means there's no call here (yet). */ 156 if (st[n] == 0xFF) 157 break; 158 159 /* 160 * OK, we have hypercall. Increment the "next_hcall" cursor, 161 * and wrap back to 0 if we reach the end. 162 */ 163 if (++cpu->next_hcall == LHCALL_RING_SIZE) 164 cpu->next_hcall = 0; 165 166 /* 167 * Copy the hypercall arguments into a local copy of the 168 * hcall_args struct. 169 */ 170 if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n], 171 sizeof(struct hcall_args))) { 172 kill_guest(cpu, "Fetching async hypercalls"); 173 break; 174 } 175 176 /* Do the hypercall, same as a normal one. */ 177 do_hcall(cpu, &args); 178 179 /* Mark the hypercall done. */ 180 if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) { 181 kill_guest(cpu, "Writing result for async hypercall"); 182 break; 183 } 184 185 /* 186 * Stop doing hypercalls if they want to notify the Launcher: 187 * it needs to service this first. 188 */ 189 if (cpu->pending.trap) 190 break; 191 } 192} 193 194/* 195 * Last of all, we look at what happens first of all. The very first time the 196 * Guest makes a hypercall, we end up here to set things up: 197 */ 198static void initialize(struct lg_cpu *cpu) 199{ 200 /* 201 * You can't do anything until you're initialized. The Guest knows the 202 * rules, so we're unforgiving here. 203 */ 204 if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) { 205 kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0); 206 return; 207 } 208 209 if (lguest_arch_init_hypercalls(cpu)) 210 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); 211 212 /* 213 * The Guest tells us where we're not to deliver interrupts by putting 214 * the instruction address into "struct lguest_data". 215 */ 216 if (get_user(cpu->lg->noirq_iret, &cpu->lg->lguest_data->noirq_iret)) 217 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); 218 219 /* 220 * We write the current time into the Guest's data page once so it can 221 * set its clock. 222 */ 223 write_timestamp(cpu); 224 225 /* page_tables.c will also do some setup. */ 226 page_table_guest_data_init(cpu); 227 228 /* 229 * This is the one case where the above accesses might have been the 230 * first write to a Guest page. This may have caused a copy-on-write 231 * fault, but the old page might be (read-only) in the Guest 232 * pagetable. 233 */ 234 guest_pagetable_clear_all(cpu); 235} 236/*:*/ 237 238/*M:013 239 * If a Guest reads from a page (so creates a mapping) that it has never 240 * written to, and then the Launcher writes to it (ie. the output of a virtual 241 * device), the Guest will still see the old page. In practice, this never 242 * happens: why would the Guest read a page which it has never written to? But 243 * a similar scenario might one day bite us, so it's worth mentioning. 244 * 245 * Note that if we used a shared anonymous mapping in the Launcher instead of 246 * mapping /dev/zero private, we wouldn't worry about cop-on-write. And we 247 * need that to switch the Launcher to processes (away from threads) anyway. 248:*/ 249 250/*H:100 251 * Hypercalls 252 * 253 * Remember from the Guest, hypercalls come in two flavors: normal and 254 * asynchronous. This file handles both of types. 255 */ 256void do_hypercalls(struct lg_cpu *cpu) 257{ 258 /* Not initialized yet? This hypercall must do it. */ 259 if (unlikely(!cpu->lg->lguest_data)) { 260 /* Set up the "struct lguest_data" */ 261 initialize(cpu); 262 /* Hcall is done. */ 263 cpu->hcall = NULL; 264 return; 265 } 266 267 /* 268 * The Guest has initialized. 269 * 270 * Look in the hypercall ring for the async hypercalls: 271 */ 272 do_async_hcalls(cpu); 273 274 /* 275 * If we stopped reading the hypercall ring because the Guest did a 276 * NOTIFY to the Launcher, we want to return now. Otherwise we do 277 * the hypercall. 278 */ 279 if (!cpu->pending.trap) { 280 do_hcall(cpu, cpu->hcall); 281 /* 282 * Tricky point: we reset the hcall pointer to mark the 283 * hypercall as "done". We use the hcall pointer rather than 284 * the trap number to indicate a hypercall is pending. 285 * Normally it doesn't matter: the Guest will run again and 286 * update the trap number before we come back here. 287 * 288 * However, if we are signalled or the Guest sends I/O to the 289 * Launcher, the run_guest() loop will exit without running the 290 * Guest. When it comes back it would try to re-run the 291 * hypercall. Finding that bug sucked. 292 */ 293 cpu->hcall = NULL; 294 } 295} 296 297/* 298 * This routine supplies the Guest with time: it's used for wallclock time at 299 * initial boot and as a rough time source if the TSC isn't available. 300 */ 301void write_timestamp(struct lg_cpu *cpu) 302{ 303 struct timespec now; 304 ktime_get_real_ts(&now); 305 if (copy_to_user(&cpu->lg->lguest_data->time, 306 &now, sizeof(struct timespec))) 307 kill_guest(cpu, "Writing timestamp"); 308} 309