#include <linux/vmalloc.h>
#include <linux/cpu.h>
#include <linux/freezer.h>
+#include <linux/highmem.h>
#include <asm/paravirt.h>
-#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/poll.h>
-#include <asm/highmem.h>
#include <asm/asm-offsets.h>
-#include <asm/i387.h>
#include "lg.h"
-/* Found in switcher.S */
-extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
-extern unsigned long default_idt_entries[];
-
-/* Every guest maps the core switcher code. */
-#define SHARED_SWITCHER_PAGES \
- DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE)
-/* Pages for switcher itself, then two pages per cpu */
-#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS)
-
-/* We map at -4M for ease of mapping into the guest (one PTE page). */
-#define SWITCHER_ADDR 0xFFC00000
static struct vm_struct *switcher_vma;
static struct page **switcher_page;
-static int cpu_had_pge;
-static struct {
- unsigned long offset;
- unsigned short segment;
-} lguest_entry;
-
/* This One Big lock protects all inter-guest data structures. */
DEFINE_MUTEX(lguest_lock);
-static DEFINE_PER_CPU(struct lguest *, last_guest);
-
-/* Offset from where switcher.S was compiled to where we've copied it */
-static unsigned long switcher_offset(void)
-{
- return SWITCHER_ADDR - (unsigned long)start_switcher_text;
-}
-
-/* This cpu's struct lguest_pages. */
-static struct lguest_pages *lguest_pages(unsigned int cpu)
-{
- return &(((struct lguest_pages *)
- (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]);
-}
/*H:010 We need to set up the Switcher at a high virtual address. Remember the
* Switcher is a few hundred bytes of assembler code which actually changes the
* Host since it will be running as the switchover occurs.
*
* Trying to map memory at a particular address is an unusual thing to do, so
- * it's not a simple one-liner. We also set up the per-cpu parts of the
- * Switcher here.
- */
+ * it's not a simple one-liner. */
static __init int map_switcher(void)
{
int i, err;
goto free_vma;
}
- /* Now the switcher is mapped at the right address, we can't fail!
- * Copy in the compiled-in Switcher code (from switcher.S). */
+ /* Now the Switcher is mapped at the right address, we can't fail!
+ * Copy in the compiled-in Switcher code (from <arch>_switcher.S). */
memcpy(switcher_vma->addr, start_switcher_text,
end_switcher_text - start_switcher_text);
- /* Most of the switcher.S doesn't care that it's been moved; on Intel,
- * jumps are relative, and it doesn't access any references to external
- * code or data.
- *
- * The only exception is the interrupt handlers in switcher.S: their
- * addresses are placed in a table (default_idt_entries), so we need to
- * update the table with the new addresses. switcher_offset() is a
- * convenience function which returns the distance between the builtin
- * switcher code and the high-mapped copy we just made. */
- for (i = 0; i < IDT_ENTRIES; i++)
- default_idt_entries[i] += switcher_offset();
-
- /*
- * Set up the Switcher's per-cpu areas.
- *
- * Each CPU gets two pages of its own within the high-mapped region
- * (aka. "struct lguest_pages"). Much of this can be initialized now,
- * but some depends on what Guest we are running (which is set up in
- * copy_in_guest_info()).
- */
- for_each_possible_cpu(i) {
- /* lguest_pages() returns this CPU's two pages. */
- struct lguest_pages *pages = lguest_pages(i);
- /* This is a convenience pointer to make the code fit one
- * statement to a line. */
- struct lguest_ro_state *state = &pages->state;
-
- /* The Global Descriptor Table: the Host has a different one
- * for each CPU. We keep a descriptor for the GDT which says
- * where it is and how big it is (the size is actually the last
- * byte, not the size, hence the "-1"). */
- state->host_gdt_desc.size = GDT_SIZE-1;
- state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
-
- /* All CPUs on the Host use the same Interrupt Descriptor
- * Table, so we just use store_idt(), which gets this CPU's IDT
- * descriptor. */
- store_idt(&state->host_idt_desc);
-
- /* The descriptors for the Guest's GDT and IDT can be filled
- * out now, too. We copy the GDT & IDT into ->guest_gdt and
- * ->guest_idt before actually running the Guest. */
- state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
- state->guest_idt_desc.address = (long)&state->guest_idt;
- state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
- state->guest_gdt_desc.address = (long)&state->guest_gdt;
-
- /* We know where we want the stack to be when the Guest enters
- * the switcher: in pages->regs. The stack grows upwards, so
- * we start it at the end of that structure. */
- state->guest_tss.esp0 = (long)(&pages->regs + 1);
- /* And this is the GDT entry to use for the stack: we keep a
- * couple of special LGUEST entries. */
- state->guest_tss.ss0 = LGUEST_DS;
-
- /* x86 can have a finegrained bitmap which indicates what I/O
- * ports the process can use. We set it to the end of our
- * structure, meaning "none". */
- state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
-
- /* Some GDT entries are the same across all Guests, so we can
- * set them up now. */
- setup_default_gdt_entries(state);
- /* Most IDT entries are the same for all Guests, too.*/
- setup_default_idt_entries(state, default_idt_entries);
-
- /* The Host needs to be able to use the LGUEST segments on this
- * CPU, too, so put them in the Host GDT. */
- get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
- get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
- }
-
- /* In the Switcher, we want the %cs segment register to use the
- * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so
- * it will be undisturbed when we switch. To change %cs and jump we
- * need this structure to feed to Intel's "lcall" instruction. */
- lguest_entry.offset = (long)switch_to_guest + switcher_offset();
- lguest_entry.segment = LGUEST_CS;
-
printk(KERN_INFO "lguest: mapped switcher at %p\n",
switcher_vma->addr);
/* And we succeeded... */
__free_pages(switcher_page[i], 0);
}
-/*H:130 Our Guest is usually so well behaved; it never tries to do things it
- * isn't allowed to. Unfortunately, Linux's paravirtual infrastructure isn't
- * quite complete, because it doesn't contain replacements for the Intel I/O
- * instructions. As a result, the Guest sometimes fumbles across one during
- * the boot process as it probes for various things which are usually attached
- * to a PC.
- *
- * When the Guest uses one of these instructions, we get trap #13 (General
- * Protection Fault) and come here. We see if it's one of those troublesome
- * instructions and skip over it. We return true if we did. */
-static int emulate_insn(struct lguest *lg)
-{
- u8 insn;
- unsigned int insnlen = 0, in = 0, shift = 0;
- /* The eip contains the *virtual* address of the Guest's instruction:
- * guest_pa just subtracts the Guest's page_offset. */
- unsigned long physaddr = guest_pa(lg, lg->regs->eip);
-
- /* The guest_pa() function only works for Guest kernel addresses, but
- * that's all we're trying to do anyway. */
- if (lg->regs->eip < lg->page_offset)
- return 0;
-
- /* Decoding x86 instructions is icky. */
- lgread(lg, &insn, physaddr, 1);
-
- /* 0x66 is an "operand prefix". It means it's using the upper 16 bits
- of the eax register. */
- if (insn == 0x66) {
- shift = 16;
- /* The instruction is 1 byte so far, read the next byte. */
- insnlen = 1;
- lgread(lg, &insn, physaddr + insnlen, 1);
- }
-
- /* We can ignore the lower bit for the moment and decode the 4 opcodes
- * we need to emulate. */
- switch (insn & 0xFE) {
- case 0xE4: /* in <next byte>,%al */
- insnlen += 2;
- in = 1;
- break;
- case 0xEC: /* in (%dx),%al */
- insnlen += 1;
- in = 1;
- break;
- case 0xE6: /* out %al,<next byte> */
- insnlen += 2;
- break;
- case 0xEE: /* out %al,(%dx) */
- insnlen += 1;
- break;
- default:
- /* OK, we don't know what this is, can't emulate. */
- return 0;
- }
-
- /* If it was an "IN" instruction, they expect the result to be read
- * into %eax, so we change %eax. We always return all-ones, which
- * traditionally means "there's nothing there". */
- if (in) {
- /* Lower bit tells is whether it's a 16 or 32 bit access */
- if (insn & 0x1)
- lg->regs->eax = 0xFFFFFFFF;
- else
- lg->regs->eax |= (0xFFFF << shift);
- }
- /* Finally, we've "done" the instruction, so move past it. */
- lg->regs->eip += insnlen;
- /* Success! */
- return 1;
-}
-/*:*/
-
/*L:305
* Dealing With Guest Memory.
*
}
/* (end of memory access helper routines) :*/
-static void set_ts(void)
-{
- u32 cr0;
-
- cr0 = read_cr0();
- if (!(cr0 & 8))
- write_cr0(cr0|8);
-}
-
-/*S:010
- * We are getting close to the Switcher.
- *
- * Remember that each CPU has two pages which are visible to the Guest when it
- * runs on that CPU. This has to contain the state for that Guest: we copy the
- * state in just before we run the Guest.
- *
- * Each Guest has "changed" flags which indicate what has changed in the Guest
- * since it last ran. We saw this set in interrupts_and_traps.c and
- * segments.c.
- */
-static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages)
-{
- /* Copying all this data can be quite expensive. We usually run the
- * same Guest we ran last time (and that Guest hasn't run anywhere else
- * meanwhile). If that's not the case, we pretend everything in the
- * Guest has changed. */
- if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) {
- __get_cpu_var(last_guest) = lg;
- lg->last_pages = pages;
- lg->changed = CHANGED_ALL;
- }
-
- /* These copies are pretty cheap, so we do them unconditionally: */
- /* Save the current Host top-level page directory. */
- pages->state.host_cr3 = __pa(current->mm->pgd);
- /* Set up the Guest's page tables to see this CPU's pages (and no
- * other CPU's pages). */
- map_switcher_in_guest(lg, pages);
- /* Set up the two "TSS" members which tell the CPU what stack to use
- * for traps which do directly into the Guest (ie. traps at privilege
- * level 1). */
- pages->state.guest_tss.esp1 = lg->esp1;
- pages->state.guest_tss.ss1 = lg->ss1;
-
- /* Copy direct-to-Guest trap entries. */
- if (lg->changed & CHANGED_IDT)
- copy_traps(lg, pages->state.guest_idt, default_idt_entries);
-
- /* Copy all GDT entries which the Guest can change. */
- if (lg->changed & CHANGED_GDT)
- copy_gdt(lg, pages->state.guest_gdt);
- /* If only the TLS entries have changed, copy them. */
- else if (lg->changed & CHANGED_GDT_TLS)
- copy_gdt_tls(lg, pages->state.guest_gdt);
-
- /* Mark the Guest as unchanged for next time. */
- lg->changed = 0;
-}
-
-/* Finally: the code to actually call into the Switcher to run the Guest. */
-static void run_guest_once(struct lguest *lg, struct lguest_pages *pages)
-{
- /* This is a dummy value we need for GCC's sake. */
- unsigned int clobber;
-
- /* Copy the guest-specific information into this CPU's "struct
- * lguest_pages". */
- copy_in_guest_info(lg, pages);
-
- /* Set the trap number to 256 (impossible value). If we fault while
- * switching to the Guest (bad segment registers or bug), this will
- * cause us to abort the Guest. */
- lg->regs->trapnum = 256;
-
- /* Now: we push the "eflags" register on the stack, then do an "lcall".
- * This is how we change from using the kernel code segment to using
- * the dedicated lguest code segment, as well as jumping into the
- * Switcher.
- *
- * The lcall also pushes the old code segment (KERNEL_CS) onto the
- * stack, then the address of this call. This stack layout happens to
- * exactly match the stack of an interrupt... */
- asm volatile("pushf; lcall *lguest_entry"
- /* This is how we tell GCC that %eax ("a") and %ebx ("b")
- * are changed by this routine. The "=" means output. */
- : "=a"(clobber), "=b"(clobber)
- /* %eax contains the pages pointer. ("0" refers to the
- * 0-th argument above, ie "a"). %ebx contains the
- * physical address of the Guest's top-level page
- * directory. */
- : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))
- /* We tell gcc that all these registers could change,
- * which means we don't have to save and restore them in
- * the Switcher. */
- : "memory", "%edx", "%ecx", "%edi", "%esi");
-}
-/*:*/
-
/*H:030 Let's jump straight to the the main loop which runs the Guest.
* Remember, this is called by the Launcher reading /dev/lguest, and we keep
* going around and around until something interesting happens. */
{
/* We stop running once the Guest is dead. */
while (!lg->dead) {
- /* We need to initialize this, otherwise gcc complains. It's
- * not (yet) clever enough to see that it's initialized when we
- * need it. */
- unsigned int cr2 = 0; /* Damn gcc */
-
/* First we run any hypercalls the Guest wants done: either in
* the hypercall ring in "struct lguest_data", or directly by
* using int 31 (LGUEST_TRAP_ENTRY). */
* the "Do Not Disturb" sign: */
local_irq_disable();
- /* Remember the awfully-named TS bit? If the Guest has asked
- * to set it we set it now, so we can trap and pass that trap
- * to the Guest if it uses the FPU. */
- if (lg->ts)
- set_ts();
-
- /* SYSENTER is an optimized way of doing system calls. We
- * can't allow it because it always jumps to privilege level 0.
- * A normal Guest won't try it because we don't advertise it in
- * CPUID, but a malicious Guest (or malicious Guest userspace
- * program) could, so we tell the CPU to disable it before
- * running the Guest. */
- if (boot_cpu_has(X86_FEATURE_SEP))
- wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
-
- /* Now we actually run the Guest. It will pop back out when
- * something interesting happens, and we can examine its
- * registers to see what it was doing. */
- run_guest_once(lg, lguest_pages(raw_smp_processor_id()));
-
- /* The "regs" pointer contains two extra entries which are not
- * really registers: a trap number which says what interrupt or
- * trap made the switcher code come back, and an error code
- * which some traps set. */
-
- /* If the Guest page faulted, then the cr2 register will tell
- * us the bad virtual address. We have to grab this now,
- * because once we re-enable interrupts an interrupt could
- * fault and thus overwrite cr2, or we could even move off to a
- * different CPU. */
- if (lg->regs->trapnum == 14)
- cr2 = read_cr2();
- /* Similarly, if we took a trap because the Guest used the FPU,
- * we have to restore the FPU it expects to see. */
- else if (lg->regs->trapnum == 7)
- math_state_restore();
-
- /* Restore SYSENTER if it's supposed to be on. */
- if (boot_cpu_has(X86_FEATURE_SEP))
- wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
+ /* Actually run the Guest until something happens. */
+ lguest_arch_run_guest(lg);
/* Now we're ready to be interrupted or moved to other CPUs */
local_irq_enable();
- /* OK, so what happened? */
- switch (lg->regs->trapnum) {
- case 13: /* We've intercepted a GPF. */
- /* Check if this was one of those annoying IN or OUT
- * instructions which we need to emulate. If so, we
- * just go back into the Guest after we've done it. */
- if (lg->regs->errcode == 0) {
- if (emulate_insn(lg))
- continue;
- }
- break;
- case 14: /* We've intercepted a page fault. */
- /* The Guest accessed a virtual address that wasn't
- * mapped. This happens a lot: we don't actually set
- * up most of the page tables for the Guest at all when
- * we start: as it runs it asks for more and more, and
- * we set them up as required. In this case, we don't
- * even tell the Guest that the fault happened.
- *
- * The errcode tells whether this was a read or a
- * write, and whether kernel or userspace code. */
- if (demand_page(lg, cr2, lg->regs->errcode))
- continue;
-
- /* OK, it's really not there (or not OK): the Guest
- * needs to know. We write out the cr2 value so it
- * knows where the fault occurred.
- *
- * Note that if the Guest were really messed up, this
- * could happen before it's done the INITIALIZE
- * hypercall, so lg->lguest_data will be NULL */
- if (lg->lguest_data
- && put_user(cr2, &lg->lguest_data->cr2))
- kill_guest(lg, "Writing cr2");
- break;
- case 7: /* We've intercepted a Device Not Available fault. */
- /* If the Guest doesn't want to know, we already
- * restored the Floating Point Unit, so we just
- * continue without telling it. */
- if (!lg->ts)
- continue;
- break;
- case 32 ... 255:
- /* These values mean a real interrupt occurred, in
- * which case the Host handler has already been run.
- * We just do a friendly check if another process
- * should now be run, then fall through to loop
- * around: */
- cond_resched();
- case LGUEST_TRAP_ENTRY: /* Handled at top of loop */
- continue;
- }
-
- /* If we get here, it's a trap the Guest wants to know
- * about. */
- if (deliver_trap(lg, lg->regs->trapnum))
- continue;
-
- /* If the Guest doesn't have a handler (either it hasn't
- * registered any yet, or it's one of the faults we don't let
- * it handle), it dies with a cryptic error message. */
- kill_guest(lg, "unhandled trap %li at %#lx (%#lx)",
- lg->regs->trapnum, lg->regs->eip,
- lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode);
+ /* Now we deal with whatever happened to the Guest. */
+ lguest_arch_handle_trap(lg);
}
+
/* The Guest is dead => "No such file or directory" */
return -ENOENT;
}
-/* Now we can look at each of the routines this calls, in increasing order of
- * complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(),
- * deliver_trap() and demand_page(). After all those, we'll be ready to
- * examine the Switcher, and our philosophical understanding of the Host/Guest
- * duality will be complete. :*/
-static void adjust_pge(void *on)
-{
- if (on)
- write_cr4(read_cr4() | X86_CR4_PGE);
- else
- write_cr4(read_cr4() & ~X86_CR4_PGE);
-}
-
/*H:000
* Welcome to the Host!
*
return err;
}
- /* Finally, we need to turn off "Page Global Enable". PGE is an
- * optimization where page table entries are specially marked to show
- * they never change. The Host kernel marks all the kernel pages this
- * way because it's always present, even when userspace is running.
- *
- * Lguest breaks this: unbeknownst to the rest of the Host kernel, we
- * switch to the Guest kernel. If you don't disable this on all CPUs,
- * you'll get really weird bugs that you'll chase for two days.
- *
- * I used to turn PGE off every time we switched to the Guest and back
- * on when we return, but that slowed the Switcher down noticibly. */
-
- /* We don't need the complexity of CPUs coming and going while we're
- * doing this. */
- lock_cpu_hotplug();
- if (cpu_has_pge) { /* We have a broader idea of "global". */
- /* Remember that this was originally set (for cleanup). */
- cpu_had_pge = 1;
- /* adjust_pge is a helper function which sets or unsets the PGE
- * bit on its CPU, depending on the argument (0 == unset). */
- on_each_cpu(adjust_pge, (void *)0, 0, 1);
- /* Turn off the feature in the global feature set. */
- clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
- }
- unlock_cpu_hotplug();
+ /* Finally we do some architecture-specific setup. */
+ lguest_arch_host_init();
/* All good! */
return 0;
free_pagetables();
unmap_switcher();
- /* If we had PGE before we started, turn it back on now. */
- lock_cpu_hotplug();
- if (cpu_had_pge) {
- set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
- /* adjust_pge's argument "1" means set PGE. */
- on_each_cpu(adjust_pge, (void *)1, 0, 1);
- }
- unlock_cpu_hotplug();
+ lguest_arch_host_fini();
}
+/*:*/
/* The Host side of lguest can be a module. This is a nice way for people to
* play with it. */
git://bbs.cooldavid.org / net-next-2.6.git / blobdiff