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