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Diffstat (limited to 'drivers/lguest/hypercalls.c')
| -rw-r--r-- | drivers/lguest/hypercalls.c | 308 |
1 files changed, 308 insertions, 0 deletions
diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c new file mode 100644 index 000000000..19a322807 --- /dev/null +++ b/drivers/lguest/hypercalls.c @@ -0,0 +1,308 @@ +/*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 <linux/uaccess.h> +#include <linux/syscalls.h> +#include <linux/mm.h> +#include <linux/ktime.h> +#include <asm/page.h> +#include <asm/pgtable.h> +#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_SHUTDOWN, both. + */ +static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) +{ + switch (args->arg0) { + 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_SEND_INTERRUPTS: + /* + * This call does nothing too, but by breaking out of the Guest + * it makes us process any pending interrupts. + */ + break; + case LHCALL_LGUEST_INIT: + /* + * You can't get here unless you're already initialized. Don't + * do that. + */ + kill_guest(cpu, "already have lguest_data"); + break; + case LHCALL_SHUTDOWN: { + char msg[128]; + /* + * Shutdown is such a trivial hypercall that we do it in five + * lines right here. + * + * If the lgread fails, it will call kill_guest() itself; the + * kill_guest() with the message will be ignored. + */ + __lgread(cpu, msg, args->arg1, sizeof(msg)); + msg[sizeof(msg)-1] = '\0'; + kill_guest(cpu, "CRASH: %s", msg); + if (args->arg2 == LGUEST_SHUTDOWN_RESTART) + cpu->lg->dead = ERR_PTR(-ERESTART); + break; + } + case LHCALL_FLUSH_TLB: + /* FLUSH_TLB comes in two flavors, depending on the argument: */ + if (args->arg1) + guest_pagetable_clear_all(cpu); + else + guest_pagetable_flush_user(cpu); + break; + + /* + * All these calls simply pass the arguments through to the right + * routines. + */ + case LHCALL_NEW_PGTABLE: + guest_new_pagetable(cpu, args->arg1); + break; + case LHCALL_SET_STACK: + guest_set_stack(cpu, args->arg1, args->arg2, args->arg3); + break; + case LHCALL_SET_PTE: +#ifdef CONFIG_X86_PAE + guest_set_pte(cpu, args->arg1, args->arg2, + __pte(args->arg3 | (u64)args->arg4 << 32)); +#else + guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3)); +#endif + break; + case LHCALL_SET_PGD: + guest_set_pgd(cpu->lg, args->arg1, args->arg2); + break; +#ifdef CONFIG_X86_PAE + case LHCALL_SET_PMD: + guest_set_pmd(cpu->lg, args->arg1, args->arg2); + break; +#endif + case LHCALL_SET_CLOCKEVENT: + guest_set_clockevent(cpu, args->arg1); + break; + case LHCALL_TS: + /* This sets the TS flag, as we saw used in run_guest(). */ + cpu->ts = args->arg1; + break; + case LHCALL_HALT: + /* Similarly, this sets the halted flag for run_guest(). */ + cpu->halted = 1; + break; + default: + /* It should be an architecture-specific hypercall. */ + if (lguest_arch_do_hcall(cpu, args)) + kill_guest(cpu, "Bad hypercall %li\n", args->arg0); + } +} + +/*H:124 + * Asynchronous hypercalls are easy: we just look in the array in the + * Guest's "struct lguest_data" to see if any new ones are 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 lg_cpu *cpu) +{ + 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, &cpu->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 hcall_args args; + /* + * 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 = cpu->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 (++cpu->next_hcall == LHCALL_RING_SIZE) + cpu->next_hcall = 0; + + /* + * Copy the hypercall arguments into a local copy of the + * hcall_args struct. + */ + if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n], + sizeof(struct hcall_args))) { + kill_guest(cpu, "Fetching async hypercalls"); + break; + } + + /* Do the hypercall, same as a normal one. */ + do_hcall(cpu, &args); + + /* Mark the hypercall done. */ + if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) { + kill_guest(cpu, "Writing result for async hypercall"); + break; + } + + /* + * Stop doing hypercalls if they want to notify the Launcher: + * it needs to service this first. + */ + if (cpu->pending.trap) + 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 lg_cpu *cpu) +{ + /* + * You can't do anything until you're initialized. The Guest knows the + * rules, so we're unforgiving here. + */ + if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) { + kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0); + return; + } + + if (lguest_arch_init_hypercalls(cpu)) + kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); + + /* + * The Guest tells us where we're not to deliver interrupts by putting + * the instruction address into "struct lguest_data". + */ + if (get_user(cpu->lg->noirq_iret, &cpu->lg->lguest_data->noirq_iret)) + kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); + + /* + * We write the current time into the Guest's data page once so it can + * set its clock. + */ + write_timestamp(cpu); + + /* page_tables.c will also do some setup. */ + page_table_guest_data_init(cpu); + + /* + * 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 old page might be (read-only) in the Guest + * pagetable. + */ + guest_pagetable_clear_all(cpu); +} +/*:*/ + +/*M:013 + * If a Guest reads from a page (so creates a mapping) that it has never + * written to, and then the Launcher writes to it (ie. the output of a virtual + * device), the Guest will still see the old page. In practice, this never + * happens: why would the Guest read a page which it has never written to? But + * a similar scenario might one day bite us, so it's worth mentioning. + * + * Note that if we used a shared anonymous mapping in the Launcher instead of + * mapping /dev/zero private, we wouldn't worry about cop-on-write. And we + * need that to switch the Launcher to processes (away from threads) anyway. +:*/ + +/*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 lg_cpu *cpu) +{ + /* Not initialized yet? This hypercall must do it. */ + if (unlikely(!cpu->lg->lguest_data)) { + /* Set up the "struct lguest_data" */ + initialize(cpu); + /* Hcall is done. */ + cpu->hcall = NULL; + return; + } + + /* + * The Guest has initialized. + * + * Look in the hypercall ring for the async hypercalls: + */ + do_async_hcalls(cpu); + + /* + * If we stopped reading the hypercall ring because the Guest did a + * NOTIFY to the Launcher, we want to return now. Otherwise we do + * the hypercall. + */ + if (!cpu->pending.trap) { + do_hcall(cpu, cpu->hcall); + /* + * Tricky point: we reset the hcall pointer to mark the + * hypercall as "done". We use the hcall pointer rather than + * the trap number to indicate a hypercall is pending. + * Normally it doesn't matter: the Guest will run again and + * update the trap number before we come back here. + * + * However, if we are signalled or the Guest sends I/O to the + * Launcher, the run_guest() loop will exit without running the + * Guest. When it comes back it would try to re-run the + * hypercall. Finding that bug sucked. + */ + cpu->hcall = NULL; + } +} + +/* + * 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 lg_cpu *cpu) +{ + struct timespec now; + ktime_get_real_ts(&now); + if (copy_to_user(&cpu->lg->lguest_data->time, + &now, sizeof(struct timespec))) + kill_guest(cpu, "Writing timestamp"); +} |