diff options
Diffstat (limited to 'drivers/lguest')
| -rw-r--r-- | drivers/lguest/Makefile | 2 | ||||
| -rw-r--r-- | drivers/lguest/core.c | 459 | ||||
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 18 | ||||
| -rw-r--r-- | drivers/lguest/lg.h | 63 | ||||
| -rw-r--r-- | drivers/lguest/segments.c | 26 | ||||
| -rw-r--r-- | drivers/lguest/x86/core.c | 476 | ||||
| -rw-r--r-- | drivers/lguest/x86/switcher_32.S | 3 |
7 files changed, 525 insertions, 522 deletions
diff --git a/drivers/lguest/Makefile b/drivers/lguest/Makefile index a4567c99991b..d330f5b8c456 100644 --- a/drivers/lguest/Makefile +++ b/drivers/lguest/Makefile @@ -6,7 +6,7 @@ obj-$(CONFIG_LGUEST) += lg.o lg-y = core.o hypercalls.o page_tables.o interrupts_and_traps.o \ segments.o io.o lguest_user.o -lg-$(CONFIG_X86_32) += x86/switcher_32.o +lg-$(CONFIG_X86_32) += x86/switcher_32.o x86/core.o Preparation Preparation!: PREFIX=P Guest: PREFIX=G diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c index ca581ef591e8..06869a2d3b40 100644 --- a/drivers/lguest/core.c +++ b/drivers/lguest/core.c @@ -11,54 +11,20 @@ #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 @@ -69,9 +35,7 @@ static struct lguest_pages *lguest_pages(unsigned int cpu) * 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; @@ -128,90 +92,11 @@ static __init int map_switcher(void) 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... */ @@ -243,80 +128,6 @@ static void unmap_switcher(void) __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. * @@ -380,104 +191,6 @@ void lgwrite(struct lguest *lg, unsigned long addr, const void *b, } /* (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. */ @@ -485,11 +198,6 @@ int run_guest(struct lguest *lg, unsigned long __user *user) { /* 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). */ @@ -538,132 +246,20 @@ int run_guest(struct lguest *lg, unsigned long __user *user) * 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! * @@ -705,31 +301,8 @@ static int __init init(void) 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; @@ -742,15 +315,9 @@ static void __exit fini(void) 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. */ diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 0dfb0903aa69..fdefc0afc38c 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -165,7 +165,7 @@ void maybe_do_interrupt(struct lguest *lg) /* Look at the IDT entry the Guest gave us for this interrupt. The * first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip * over them. */ - idt = &lg->idt[FIRST_EXTERNAL_VECTOR+irq]; + idt = &lg->arch.idt[FIRST_EXTERNAL_VECTOR+irq]; /* If they don't have a handler (yet?), we just ignore it */ if (idt_present(idt->a, idt->b)) { /* OK, mark it no longer pending and deliver it. */ @@ -197,14 +197,14 @@ int deliver_trap(struct lguest *lg, unsigned int num) { /* Trap numbers are always 8 bit, but we set an impossible trap number * for traps inside the Switcher, so check that here. */ - if (num >= ARRAY_SIZE(lg->idt)) + if (num >= ARRAY_SIZE(lg->arch.idt)) return 0; /* Early on the Guest hasn't set the IDT entries (or maybe it put a * bogus one in): if we fail here, the Guest will be killed. */ - if (!idt_present(lg->idt[num].a, lg->idt[num].b)) + if (!idt_present(lg->arch.idt[num].a, lg->arch.idt[num].b)) return 0; - set_guest_interrupt(lg, lg->idt[num].a, lg->idt[num].b, has_err(num)); + set_guest_interrupt(lg, lg->arch.idt[num].a, lg->arch.idt[num].b, has_err(num)); return 1; } @@ -341,10 +341,10 @@ void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi) lg->changed |= CHANGED_IDT; /* Check that the Guest doesn't try to step outside the bounds. */ - if (num >= ARRAY_SIZE(lg->idt)) + if (num >= ARRAY_SIZE(lg->arch.idt)) kill_guest(lg, "Setting idt entry %u", num); else - set_trap(lg, &lg->idt[num], num, lo, hi); + set_trap(lg, &lg->arch.idt[num], num, lo, hi); } /* The default entry for each interrupt points into the Switcher routines which @@ -387,7 +387,7 @@ void copy_traps(const struct lguest *lg, struct desc_struct *idt, /* We can simply copy the direct traps, otherwise we use the default * ones in the Switcher: they will return to the Host. */ - for (i = 0; i < ARRAY_SIZE(lg->idt); i++) { + for (i = 0; i < ARRAY_SIZE(lg->arch.idt); i++) { /* If no Guest can ever override this trap, leave it alone. */ if (!direct_trap(i)) continue; @@ -396,8 +396,8 @@ void copy_traps(const struct lguest *lg, struct desc_struct *idt, * Interrupt gates (type 14) disable interrupts as they are * entered, which we never let the Guest do. Not present * entries (type 0x0) also can't go direct, of course. */ - if (idt_type(lg->idt[i].a, lg->idt[i].b) == 0xF) - idt[i] = lg->idt[i]; + if (idt_type(lg->arch.idt[i].a, lg->arch.idt[i].b) == 0xF) + idt[i] = lg->arch.idt[i]; else /* Reset it to the default. */ default_idt_entry(&idt[i], i, def[i]); diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index c1ca127ddece..203d3100c3b4 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -1,13 +1,6 @@ #ifndef _LGUEST_H #define _LGUEST_H -#include <asm/desc.h> - -#define GDT_ENTRY_LGUEST_CS 10 -#define GDT_ENTRY_LGUEST_DS 11 -#define LGUEST_CS (GDT_ENTRY_LGUEST_CS * 8) -#define LGUEST_DS (GDT_ENTRY_LGUEST_DS * 8) - #ifndef __ASSEMBLY__ #include <linux/types.h> #include <linux/init.h> @@ -18,34 +11,12 @@ #include <linux/wait.h> #include <linux/err.h> #include <asm/semaphore.h> -#include "irq_vectors.h" - -#define GUEST_PL 1 -struct lguest_regs -{ - /* Manually saved part. */ - unsigned long ebx, ecx, edx; - unsigned long esi, edi, ebp; - unsigned long gs; - unsigned long eax; - unsigned long fs, ds, es; - unsigned long trapnum, errcode; - /* Trap pushed part */ - unsigned long eip; - unsigned long cs; - unsigned long eflags; - unsigned long esp; - unsigned long ss; -}; +#include <asm/lguest.h> void free_pagetables(void); int init_pagetables(struct page **switcher_page, unsigned int pages); -/* Full 4G segment descriptors, suitable for CS and DS. */ -#define FULL_EXEC_SEGMENT ((struct desc_struct){0x0000ffff, 0x00cf9b00}) -#define FULL_SEGMENT ((struct desc_struct){0x0000ffff, 0x00cf9300}) - struct lguest_dma_info { struct list_head list; @@ -98,23 +69,6 @@ struct pgdir spgd_t *pgdir; }; -/* This is a guest-specific page (mapped ro) into the guest. */ -struct lguest_ro_state -{ - /* Host information we need to restore when we switch back. */ - u32 host_cr3; - struct Xgt_desc_struct host_idt_desc; - struct Xgt_desc_struct host_gdt_desc; - u32 host_sp; - - /* Fields which are used when guest is running. */ - struct Xgt_desc_struct guest_idt_desc; - struct Xgt_desc_struct guest_gdt_desc; - struct i386_hw_tss guest_tss; - struct desc_struct guest_idt[IDT_ENTRIES]; - struct desc_struct guest_gdt[GDT_ENTRIES]; -}; - /* We have two pages shared with guests, per cpu. */ struct lguest_pages { @@ -180,11 +134,7 @@ struct lguest /* Dead? */ const char *dead; - /* The GDT entries copied into lguest_ro_state when running. */ - struct desc_struct gdt[GDT_ENTRIES]; - - /* The IDT entries: some copied into lguest_ro_state when running. */ - struct desc_struct idt[IDT_ENTRIES]; + struct lguest_arch arch; /* Virtual clock device */ struct hrtimer hrt; @@ -239,6 +189,15 @@ void map_switcher_in_guest(struct lguest *lg, struct lguest_pages *pages); int demand_page(struct lguest *info, unsigned long cr2, int errcode); void pin_page(struct lguest *lg, unsigned long vaddr); +/* <arch>/core.c: */ +void lguest_arch_host_init(void); +void lguest_arch_host_fini(void); +void lguest_arch_run_guest(struct lguest *lg); +void lguest_arch_handle_trap(struct lguest *lg); + +/* <arch>/switcher.S: */ +extern char start_switcher_text[], end_switcher_text[], switch_to_guest[]; + /* lguest_user.c: */ int lguest_device_init(void); void lguest_device_remove(void); diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c index 9b81119f46e9..95eb9cf297bf 100644 --- a/drivers/lguest/segments.c +++ b/drivers/lguest/segments.c @@ -73,14 +73,14 @@ static void fixup_gdt_table(struct lguest *lg, unsigned start, unsigned end) /* Segment descriptors contain a privilege level: the Guest is * sometimes careless and leaves this as 0, even though it's * running at privilege level 1. If so, we fix it here. */ - if ((lg->gdt[i].b & 0x00006000) == 0) - lg->gdt[i].b |= (GUEST_PL << 13); + if ((lg->arch.gdt[i].b & 0x00006000) == 0) + lg->arch.gdt[i].b |= (GUEST_PL << 13); /* Each descriptor has an "accessed" bit. If we don't set it * now, the CPU will try to set it when the Guest first loads * that entry into a segment register. But the GDT isn't * writable by the Guest, so bad things can happen. */ - lg->gdt[i].b |= 0x00000100; + lg->arch.gdt[i].b |= 0x00000100; } } @@ -106,12 +106,12 @@ void setup_default_gdt_entries(struct lguest_ro_state *state) void setup_guest_gdt(struct lguest *lg) { /* Start with full 0-4G segments... */ - lg->gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT; - lg->gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT; + lg->arch.gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT; + lg->arch.gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT; /* ...except the Guest is allowed to use them, so set the privilege * level appropriately in the flags. */ - lg->gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13); - lg->gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13); + lg->arch.gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13); + lg->arch.gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13); } /* Like the IDT, we never simply use the GDT the Guest gives us. We set up the @@ -126,7 +126,7 @@ void copy_gdt_tls(const struct lguest *lg, struct desc_struct *gdt) unsigned int i; for (i = GDT_ENTRY_TLS_MIN; i <= GDT_ENTRY_TLS_MAX; i++) - gdt[i] = lg->gdt[i]; + gdt[i] = lg->arch.gdt[i]; } /* This is the full version */ @@ -138,7 +138,7 @@ void copy_gdt(const struct lguest *lg, struct desc_struct *gdt) * replaced. See ignored_gdt() above. */ for (i = 0; i < GDT_ENTRIES; i++) if (!ignored_gdt(i)) - gdt[i] = lg->gdt[i]; + gdt[i] = lg->arch.gdt[i]; } /* This is where the Guest asks us to load a new GDT (LHCALL_LOAD_GDT). */ @@ -146,12 +146,12 @@ void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num) { /* We assume the Guest has the same number of GDT entries as the * Host, otherwise we'd have to dynamically allocate the Guest GDT. */ - if (num > ARRAY_SIZE(lg->gdt)) + if (num > ARRAY_SIZE(lg->arch.gdt)) kill_guest(lg, "too many gdt entries %i", num); /* We read the whole thing in, then fix it up. */ - lgread(lg, lg->gdt, table, num * sizeof(lg->gdt[0])); - fixup_gdt_table(lg, 0, ARRAY_SIZE(lg->gdt)); + lgread(lg, lg->arch.gdt, table, num * sizeof(lg->arch.gdt[0])); + fixup_gdt_table(lg, 0, ARRAY_SIZE(lg->arch.gdt)); /* Mark that the GDT changed so the core knows it has to copy it again, * even if the Guest is run on the same CPU. */ lg->changed |= CHANGED_GDT; @@ -159,7 +159,7 @@ void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num) void guest_load_tls(struct lguest *lg, unsigned long gtls) { - struct desc_struct *tls = &lg->gdt[GDT_ENTRY_TLS_MIN]; + struct desc_struct *tls = &lg->arch.gdt[GDT_ENTRY_TLS_MIN]; lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES); fixup_gdt_table(lg, GDT_ENTRY_TLS_MIN, GDT_ENTRY_TLS_MAX+1); diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c new file mode 100644 index 000000000000..e2f46b16ce31 --- /dev/null +++ b/drivers/lguest/x86/core.c @@ -0,0 +1,476 @@ +/* + * Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation. + * Copyright (C) 2007, Jes Sorensen <jes@sgi.com> SGI. + * + * 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, GOOD TITLE or + * NON INFRINGEMENT. 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., 675 Mass Ave, Cambridge, MA 02139, USA. + */ +#include <linux/kernel.h> +#include <linux/start_kernel.h> +#include <linux/string.h> +#include <linux/console.h> +#include <linux/screen_info.h> +#include <linux/irq.h> +#include <linux/interrupt.h> +#include <linux/clocksource.h> +#include <linux/clockchips.h> +#include <linux/cpu.h> +#include <linux/lguest.h> +#include <linux/lguest_launcher.h> +#include <linux/lguest_bus.h> +#include <asm/paravirt.h> +#include <asm/param.h> +#include <asm/page.h> +#include <asm/pgtable.h> +#include <asm/desc.h> +#include <asm/setup.h> +#include <asm/lguest.h> +#include <asm/uaccess.h> +#include <asm/i387.h> +#include "../lg.h" + +static int cpu_had_pge; + +static struct { + unsigned long offset; + unsigned short segment; +} lguest_entry; + +/* 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]); +} + +static DEFINE_PER_CPU(struct lguest *, last_guest); + +/*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:040 This is the i386-specific code to setup and run the Guest. Interrupts + * are disabled: we own the CPU. */ +void lguest_arch_run_guest(struct lguest *lg) +{ + /* 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) + lguest_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) + lg->arch.last_pagefault = 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); +} + +/*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; +} + +/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */ +void lguest_arch_handle_trap(struct lguest *lg) +{ + 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)) + return; + } + 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, lg->arch.last_pagefault, lg->regs->errcode)) + return; + + /* 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(lg->arch.last_pagefault, &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) + return; + 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 before re-entering Guest */ + return; + } + + /* We didn't handle the trap, so it needs to go to the Guest. */ + if (!deliver_trap(lg, lg->regs->trapnum)) + /* 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 ? lg->arch.last_pagefault + : lg->regs->errcode); +} + +/* 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:020 Now the Switcher is mapped and every thing else is ready, we need to do + * some more i386-specific initialization. */ +void __init lguest_arch_host_init(void) +{ + int i; + + /* Most of the i386/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; + + /* 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(); +}; +/*:*/ + +void __exit lguest_arch_host_fini(void) +{ + /* 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(); +} diff --git a/drivers/lguest/x86/switcher_32.S b/drivers/lguest/x86/switcher_32.S index a3d23f79cba4..e66cec5ac240 100644 --- a/drivers/lguest/x86/switcher_32.S +++ b/drivers/lguest/x86/switcher_32.S @@ -48,7 +48,8 @@ #include <linux/linkage.h> #include <asm/asm-offsets.h> #include <asm/page.h> -#include "../lg.h" +#include <asm/segment.h> +#include <asm/lguest.h> // We mark the start of the code to copy // It's placed in .text tho it's never run here |