/*P:500 Just as userspace programs request kernel operations through a system * call, the Guest requests Host operations through a "hypercall". You might * notice this nomenclature doesn't really follow any logic, but the name has * been around for long enough that we're stuck with it. As you'd expect, this * code is basically a one big switch statement. :*/ /* Copyright (C) 2006 Rusty Russell IBM Corporation This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ #include #include #include #include #include #include #include "lg.h" /*H:120 This is the core hypercall routine: where the Guest gets what it * wants. Or gets killed. Or, in the case of LHCALL_CRASH, both. * * Remember from the Guest: %eax == which call to make, and the arguments are * packed into %edx, %ebx and %ecx if needed. */ static void do_hcall(struct lguest *lg, struct lguest_regs *regs) { switch (regs->eax) { case LHCALL_FLUSH_ASYNC: /* This call does nothing, except by breaking out of the Guest * it makes us process all the asynchronous hypercalls. */ break; case LHCALL_LGUEST_INIT: /* You can't get here unless you're already initialized. Don't * do that. */ kill_guest(lg, "already have lguest_data"); break; case LHCALL_CRASH: { /* Crash is such a trivial hypercall that we do it in four * lines right here. */ char msg[128]; /* If the lgread fails, it will call kill_guest() itself; the * kill_guest() with the message will be ignored. */ lgread(lg, msg, regs->edx, sizeof(msg)); msg[sizeof(msg)-1] = '\0'; kill_guest(lg, "CRASH: %s", msg); break; } case LHCALL_FLUSH_TLB: /* FLUSH_TLB comes in two flavors, depending on the * argument: */ if (regs->edx) guest_pagetable_clear_all(lg); else guest_pagetable_flush_user(lg); break; case LHCALL_BIND_DMA: /* BIND_DMA really wants four arguments, but it's the only call * which does. So the Guest packs the number of buffers and * the interrupt number into the final argument, and we decode * it here. This can legitimately fail, since we currently * place a limit on the number of DMA pools a Guest can have. * So we return true or false from this call. */ regs->eax = bind_dma(lg, regs->edx, regs->ebx, regs->ecx >> 8, regs->ecx & 0xFF); break; /* All these calls simply pass the arguments through to the right * routines. */ case LHCALL_SEND_DMA: send_dma(lg, regs->edx, regs->ebx); break; case LHCALL_LOAD_GDT: load_guest_gdt(lg, regs->edx, regs->ebx); break; case LHCALL_LOAD_IDT_ENTRY: load_guest_idt_entry(lg, regs->edx, regs->ebx, regs->ecx); break; case LHCALL_NEW_PGTABLE: guest_new_pagetable(lg, regs->edx); break; case LHCALL_SET_STACK: guest_set_stack(lg, regs->edx, regs->ebx, regs->ecx); break; case LHCALL_SET_PTE: guest_set_pte(lg, regs->edx, regs->ebx, mkgpte(regs->ecx)); break; case LHCALL_SET_PMD: guest_set_pmd(lg, regs->edx, regs->ebx); break; case LHCALL_LOAD_TLS: guest_load_tls(lg, regs->edx); break; case LHCALL_SET_CLOCKEVENT: guest_set_clockevent(lg, regs->edx); break; case LHCALL_TS: /* This sets the TS flag, as we saw used in run_guest(). */ lg->ts = regs->edx; break; case LHCALL_HALT: /* Similarly, this sets the halted flag for run_guest(). */ lg->halted = 1; break; default: kill_guest(lg, "Bad hypercall %li\n", regs->eax); } } /* Asynchronous hypercalls are easy: we just look in the array in the Guest's * "struct lguest_data" and see if there are any new ones marked "ready". * * We are careful to do these in order: obviously we respect the order the * Guest put them in the ring, but we also promise the Guest that they will * happen before any normal hypercall (which is why we check this before * checking for a normal hcall). */ static void do_async_hcalls(struct lguest *lg) { unsigned int i; u8 st[LHCALL_RING_SIZE]; /* For simplicity, we copy the entire call status array in at once. */ if (copy_from_user(&st, &lg->lguest_data->hcall_status, sizeof(st))) return; /* We process "struct lguest_data"s hcalls[] ring once. */ for (i = 0; i < ARRAY_SIZE(st); i++) { struct lguest_regs regs; /* We remember where we were up to from last time. This makes * sure that the hypercalls are done in the order the Guest * places them in the ring. */ unsigned int n = lg->next_hcall; /* 0xFF means there's no call here (yet). */ if (st[n] == 0xFF) break; /* OK, we have hypercall. Increment the "next_hcall" cursor, * and wrap back to 0 if we reach the end. */ if (++lg->next_hcall == LHCALL_RING_SIZE) lg->next_hcall = 0; /* We copy the hypercall arguments into a fake register * structure. This makes life simple for do_hcall(). */ if (get_user(regs.eax, &lg->lguest_data->hcalls[n].eax) || get_user(regs.edx, &lg->lguest_data->hcalls[n].edx) || get_user(regs.ecx, &lg->lguest_data->hcalls[n].ecx) || get_user(regs.ebx, &lg->lguest_data->hcalls[n].ebx)) { kill_guest(lg, "Fetching async hypercalls"); break; } /* Do the hypercall, same as a normal one. */ do_hcall(lg, ®s); /* Mark the hypercall done. */ if (put_user(0xFF, &lg->lguest_data->hcall_status[n])) { kill_guest(lg, "Writing result for async hypercall"); break; } /* Stop doing hypercalls if we've just done a DMA to the * Launcher: it needs to service this first. */ if (lg->dma_is_pending) break; } } /* Last of all, we look at what happens first of all. The very first time the * Guest makes a hypercall, we end up here to set things up: */ static void initialize(struct lguest *lg) { u32 tsc_speed; /* You can't do anything until you're initialized. The Guest knows the * rules, so we're unforgiving here. */ if (lg->regs->eax != LHCALL_LGUEST_INIT) { kill_guest(lg, "hypercall %li before LGUEST_INIT", lg->regs->eax); return; } /* We insist that the Time Stamp Counter exist and doesn't change with * cpu frequency. Some devious chip manufacturers decided that TSC * changes could be handled in software. I decided that time going * backwards might be good for benchmarks, but it's bad for users. * * We also insist that the TSC be stable: the kernel detects unreliable * TSCs for its own purposes, and we use that here. */ if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable()) tsc_speed = tsc_khz; else tsc_speed = 0; /* The pointer to the Guest's "struct lguest_data" is the only * argument. */ lg->lguest_data = (struct lguest_data __user *)lg->regs->edx; /* If we check the address they gave is OK now, we can simply * copy_to_user/from_user from now on rather than using lgread/lgwrite. * I put this in to show that I'm not immune to writing stupid * optimizations. */ if (!lguest_address_ok(lg, lg->regs->edx, sizeof(*lg->lguest_data))) { kill_guest(lg, "bad guest page %p", lg->lguest_data); return; } /* The Guest tells us where we're not to deliver interrupts by putting * the range of addresses into "struct lguest_data". */ if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start) || get_user(lg->noirq_end, &lg->lguest_data->noirq_end) /* We tell the Guest that it can't use the top 4MB of virtual * addresses used by the Switcher. */ || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem) || put_user(tsc_speed, &lg->lguest_data->tsc_khz) /* We also give the Guest a unique id, as used in lguest_net.c. */ || put_user(lg->guestid, &lg->lguest_data->guestid)) kill_guest(lg, "bad guest page %p", lg->lguest_data); /* We write the current time into the Guest's data page once now. */ write_timestamp(lg); /* This is the one case where the above accesses might have been the * first write to a Guest page. This may have caused a copy-on-write * fault, but the Guest might be referring to the old (read-only) * page. */ guest_pagetable_clear_all(lg); } /* Now we've examined the hypercall code; our Guest can make requests. There * is one other way we can do things for the Guest, as we see in * emulate_insn(). */ /*H:110 Tricky point: we mark the hypercall as "done" once we've done it. * Normally we don't need to do this: the Guest will run again and update the * trap number before we come back around the run_guest() loop to * do_hypercalls(). * * However, if we are signalled or the Guest sends DMA to the Launcher, that * loop will exit without running the Guest. When it comes back it would try * to re-run the hypercall. */ static void clear_hcall(struct lguest *lg) { lg->regs->trapnum = 255; } /*H:100 * Hypercalls * * Remember from the Guest, hypercalls come in two flavors: normal and * asynchronous. This file handles both of types. */ void do_hypercalls(struct lguest *lg) { /* Not initialized yet? */ if (unlikely(!lg->lguest_data)) { /* Did the Guest make a hypercall? We might have come back for * some other reason (an interrupt, a different trap). */ if (lg->regs->trapnum == LGUEST_TRAP_ENTRY) { /* Set up the "struct lguest_data" */ initialize(lg); /* The hypercall is done. */ clear_hcall(lg); } return; } /* The Guest has initialized. * * Look in the hypercall ring for the async hypercalls: */ do_async_hcalls(lg); /* If we stopped reading the hypercall ring because the Guest did a * SEND_DMA to the Launcher, we want to return now. Otherwise if the * Guest asked us to do a hypercall, we do it. */ if (!lg->dma_is_pending && lg->regs->trapnum == LGUEST_TRAP_ENTRY) { do_hcall(lg, lg->regs); /* The hypercall is done. */ clear_hcall(lg); } } /* This routine supplies the Guest with time: it's used for wallclock time at * initial boot and as a rough time source if the TSC isn't available. */ void write_timestamp(struct lguest *lg) { struct timespec now; ktime_get_real_ts(&now); if (put_user(now, &lg->lguest_data->time)) kill_guest(lg, "Writing timestamp"); }