diff options
Diffstat (limited to 'drivers/lguest/core.c')
| -rw-r--r-- | drivers/lguest/core.c | 459 |
1 files changed, 13 insertions, 446 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c index ca581ef591e..06869a2d3b4 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. */ |