litmus-rt.git - The LITMUS^RT kernel.

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Diffstat (limited to 'lib/string.c')

0 files changed, 0 insertions, 0 deletions

/*P:400 This contains run_guest() which actually calls into the Host<->Guest * Switcher and analyzes the return, such as determining if the Guest wants the * Host to do something. This file also contains useful helper routines, and a * couple of non-obvious setup and teardown pieces which were implemented after * days of debugging pain. :*/ #include <linux/module.h> #include <linux/stringify.h> #include <linux/stddef.h> #include <linux/io.h> #include <linux/mm.h> #include <linux/vmalloc.h> #include <linux/cpu.h> #include <linux/freezer.h> #include <linux/highmem.h> #include <asm/paravirt.h> #include <asm/pgtable.h> #include <asm/uaccess.h> #include <asm/poll.h> #include <asm/asm-offsets.h> #include "lg.h" static struct vm_struct *switcher_vma; static struct page **switcher_page; /* This One Big lock protects all inter-guest data structures. */ DEFINE_MUTEX(lguest_lock); /*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 * CPU to run the Guest, and then changes back to the Host when a trap or * interrupt happens. * * The Switcher code must be at the same virtual address in the Guest as 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. */ static __init int map_switcher(void) { int i, err; struct page **pagep; /* * Map the Switcher in to high memory. * * It turns out that if we choose the address 0xFFC00000 (4MB under the * top virtual address), it makes setting up the page tables really * easy. */ /* We allocate an array of "struct page"s. map_vm_area() wants the * pages in this form, rather than just an array of pointers. */ switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES, GFP_KERNEL); if (!switcher_page) { err = -ENOMEM; goto out; } /* Now we actually allocate the pages. The Guest will see these pages, * so we make sure they're zeroed. */ for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { unsigned long addr = get_zeroed_page(GFP_KERNEL); if (!addr) { err = -ENOMEM; goto free_some_pages; } switcher_page[i] = virt_to_page(addr); } /* Now we reserve the "virtual memory area" we want: 0xFFC00000 * (SWITCHER_ADDR). We might not get it in theory, but in practice * it's worked so far. */ switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE, VM_ALLOC, SWITCHER_ADDR, VMALLOC_END); if (!switcher_vma) { err = -ENOMEM; printk("lguest: could not map switcher pages high\n"); goto free_pages; } /* This code actually sets up the pages we've allocated to appear at * SWITCHER_ADDR. map_vm_area() takes the vma we allocated above, the * kind of pages we're mapping (kernel pages), and a pointer to our * array of struct pages. It increments that pointer, but we don't * care. */ pagep = switcher_page; err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep); if (err) { printk("lguest: map_vm_area failed: %i\n", 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 <arch>_switcher.S). */ memcpy(switcher_vma->addr, start_switcher_text, end_switcher_text - start_switcher_text); printk(KERN_INFO "lguest: mapped switcher at %p\n", switcher_vma->addr); /* And we succeeded... */ return 0; free_vma: vunmap(switcher_vma->addr); free_pages: i = TOTAL_SWITCHER_PAGES; free_some_pages: for (--i; i >= 0; i--) __free_pages(switcher_page[i], 0); kfree(switcher_page); out: return err; } /*:*/ /* Cleaning up the mapping when the module is unloaded is almost... * too easy. */ static void unmap_switcher(void) { unsigned int i; /* vunmap() undoes *both* map_vm_area() and __get_vm_area(). */ vunmap(switcher_vma->addr); /* Now we just need to free the pages we copied the switcher into */ for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) __free_pages(switcher_page[i], 0); } /*H:032 * Dealing With Guest Memory. * * Before we go too much further into the Host, we need to grok the routines * we use to deal with Guest memory. * * When the Guest gives us (what it thinks is) a physical address, we can use * the normal copy_from_user() & copy_to_user() on the corresponding place in * the memory region allocated by the Launcher. * * But we can't trust the Guest: it might be trying to access the Launcher * code. We have to check that the range is below the pfn_limit the Launcher * gave us. We have to make sure that addr + len doesn't give us a false * positive by overflowing, too. */ int lguest_address_ok(const struct lguest *lg, unsigned long addr, unsigned long len) { return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr); } /* This routine copies memory from the Guest. Here we can see how useful the * kill_lguest() routine we met in the Launcher can be: we return a random * value (all zeroes) instead of needing to return an error. */ void __lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes) { if (!lguest_address_ok(lg, addr, bytes) || copy_from_user(b, lg->mem_base + addr, bytes) != 0) { /* copy_from_user should do this, but as we rely on it... */ memset(b, 0, bytes); kill_guest(lg, "bad read address %#lx len %u", addr, bytes); } } /* This is the write (copy into guest) version. */ void __lgwrite(struct lguest *lg, unsigned long addr, const void *b, unsigned bytes) { if (!lguest_address_ok(lg, addr, bytes) || copy_to_user(lg->mem_base + addr, b, bytes) != 0) kill_guest(lg, "bad write address %#lx len %u", addr, bytes); } /*:*/ /*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. */ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) { struct lguest *lg = cpu->lg; /* We stop running once the Guest is dead. */ while (!lg->dead) { /* First we run any hypercalls the Guest wants done. */ if (lg->hcall) do_hypercalls(lg); /* It's possible the Guest did a NOTIFY hypercall to the * Launcher, in which case we return from the read() now. */ if (lg->pending_notify) { if (put_user(lg->pending_notify, user)) return -EFAULT; return sizeof(lg->pending_notify); } /* Check for signals */ if (signal_pending(current)) return -ERESTARTSYS; /* If Waker set break_out, return to Launcher. */ if (lg->break_out) return -EAGAIN; /* Check if there are any interrupts which can be delivered * now: if so, this sets up the hander to be executed when we * next run the Guest. */ maybe_do_interrupt(lg); /* All long-lived kernel loops need to check with this horrible * thing called the freezer. If the Host is trying to suspend, * it stops us. */ try_to_freeze(); /* Just make absolutely sure the Guest is still alive. One of * those hypercalls could have been fatal, for example. */ if (lg->dead) break; /* If the Guest asked to be stopped, we sleep. The Guest's * clock timer or LHCALL_BREAK from the Waker will wake us. */ if (lg->halted) { set_current_state(TASK_INTERRUPTIBLE); schedule(); continue; } /* OK, now we're ready to jump into the Guest. First we put up * the "Do Not Disturb" sign: */ local_irq_disable(); /* Actually run the Guest until something happens. */ lguest_arch_run_guest(cpu); /* Now we're ready to be interrupted or moved to other CPUs */ local_irq_enable(); /* Now we deal with whatever happened to the Guest. */ lguest_arch_handle_trap(lg); } if (lg->dead == ERR_PTR(-ERESTART)) return -ERESTART; /* The Guest is dead => "No such file or directory" */ return -ENOENT; } /*H:000 * Welcome to the Host! * * By this point your brain has been tickled by the Guest code and numbed by * the Launcher code; prepare for it to be stretched by the Host code. This is * the heart. Let's begin at the initialization routine for the Host's lg * module. */ static int __init init(void) { int err; /* Lguest can't run under Xen, VMI or itself. It does Tricky Stuff. */ if (paravirt_enabled()) { printk("lguest is afraid of being a guest\n"); return -EPERM; } /* First we put the Switcher up in very high virtual memory. */ err = map_switcher(); if (err) goto out; /* Now we set up the pagetable implementation for the Guests. */ err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES); if (err) goto unmap; /* We might need to reserve an interrupt vector. */ err = init_interrupts(); if (err) goto free_pgtables; /* /dev/lguest needs to be registered. */ err = lguest_device_init(); if (err) goto free_interrupts; /* Finally we do some architecture-specific setup. */ lguest_arch_host_init(); /* All good! */ return 0; free_interrupts: free_interrupts(); free_pgtables: free_pagetables(); unmap: unmap_switcher(); out: return err; } /* Cleaning up is just the same code, backwards. With a little French. */ static void __exit fini(void) { lguest_device_remove(); free_interrupts(); free_pagetables(); unmap_switcher(); lguest_arch_host_fini(); } /*:*/ /* The Host side of lguest can be a module. This is a nice way for people to * play with it. */ module_init(init); module_exit(fini); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");


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