diff options
Diffstat (limited to 'Documentation/lguest')
| -rw-r--r-- | Documentation/lguest/Makefile | 26 | ||||
| -rw-r--r-- | Documentation/lguest/lguest.c | 189 |
2 files changed, 113 insertions, 102 deletions
diff --git a/Documentation/lguest/Makefile b/Documentation/lguest/Makefile index 526c15fd83a..bac037eb1cd 100644 --- a/Documentation/lguest/Makefile +++ b/Documentation/lguest/Makefile @@ -1,28 +1,8 @@ # This creates the demonstration utility "lguest" which runs a Linux guest. - -# For those people that have a separate object dir, look there for .config -KBUILD_OUTPUT := ../.. -ifdef O - ifeq ("$(origin O)", "command line") - KBUILD_OUTPUT := $(O) - endif -endif -# We rely on CONFIG_PAGE_OFFSET to know where to put lguest binary. -include $(KBUILD_OUTPUT)/.config -LGUEST_GUEST_TOP := ($(CONFIG_PAGE_OFFSET) - 0x08000000) - -CFLAGS:=-Wall -Wmissing-declarations -Wmissing-prototypes -O3 -I../../include -Wl,-T,lguest.lds +CFLAGS:=-Wall -Wmissing-declarations -Wmissing-prototypes -O3 -I../../include LDLIBS:=-lz -# Removing this works for some versions of ld.so (eg. Ubuntu Feisty) and -# not others (eg. FC7). -LDFLAGS+=-static -all: lguest.lds lguest -# The linker script on x86 is so complex the only way of creating one -# which will link our binary in the right place is to mangle the -# default one. -lguest.lds: - $(LD) --verbose | awk '/^==========/ { PRINT=1; next; } /SIZEOF_HEADERS/ { gsub(/0x[0-9A-F]*/, "$(LGUEST_GUEST_TOP)") } { if (PRINT) print $$0; }' > $@ +all: lguest clean: - rm -f lguest.lds lguest + rm -f lguest diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c index 401d26b464f..140bd98a841 100644 --- a/Documentation/lguest/lguest.c +++ b/Documentation/lguest/lguest.c @@ -1,10 +1,7 @@ /*P:100 This is the Launcher code, a simple program which lays out the * "physical" memory for the new Guest by mapping the kernel image and the * virtual devices, then reads repeatedly from /dev/lguest to run the Guest. - * - * The only trick: the Makefile links it at a high address so it will be clear - * of the guest memory region. It means that each Guest cannot have more than - * about 2.5G of memory on a normally configured Host. :*/ +:*/ #define _LARGEFILE64_SOURCE #define _GNU_SOURCE #include <stdio.h> @@ -56,6 +53,8 @@ typedef uint8_t u8; #ifndef SIOCBRADDIF #define SIOCBRADDIF 0x89a2 /* add interface to bridge */ #endif +/* We can have up to 256 pages for devices. */ +#define DEVICE_PAGES 256 /*L:120 verbose is both a global flag and a macro. The C preprocessor allows * this, and although I wouldn't recommend it, it works quite nicely here. */ @@ -66,8 +65,10 @@ static bool verbose; /* The pipe to send commands to the waker process */ static int waker_fd; -/* The top of guest physical memory. */ -static u32 top; +/* The pointer to the start of guest memory. */ +static void *guest_base; +/* The maximum guest physical address allowed, and maximum possible. */ +static unsigned long guest_limit, guest_max; /* This is our list of devices. */ struct device_list @@ -111,6 +112,29 @@ struct device void *priv; }; +/*L:100 The Launcher code itself takes us out into userspace, that scary place + * where pointers run wild and free! Unfortunately, like most userspace + * programs, it's quite boring (which is why everyone likes to hack on the + * kernel!). Perhaps if you make up an Lguest Drinking Game at this point, it + * will get you through this section. Or, maybe not. + * + * The Launcher sets up a big chunk of memory to be the Guest's "physical" + * memory and stores it in "guest_base". In other words, Guest physical == + * Launcher virtual with an offset. + * + * This can be tough to get your head around, but usually it just means that we + * use these trivial conversion functions when the Guest gives us it's + * "physical" addresses: */ +static void *from_guest_phys(unsigned long addr) +{ + return guest_base + addr; +} + +static unsigned long to_guest_phys(const void *addr) +{ + return (addr - guest_base); +} + /*L:130 * Loading the Kernel. * @@ -124,33 +148,40 @@ static int open_or_die(const char *name, int flags) return fd; } -/* map_zeroed_pages() takes a (page-aligned) address and a number of pages. */ -static void *map_zeroed_pages(unsigned long addr, unsigned int num) +/* map_zeroed_pages() takes a number of pages. */ +static void *map_zeroed_pages(unsigned int num) { - /* We cache the /dev/zero file-descriptor so we only open it once. */ - static int fd = -1; - - if (fd == -1) - fd = open_or_die("/dev/zero", O_RDONLY); + int fd = open_or_die("/dev/zero", O_RDONLY); + void *addr; /* We use a private mapping (ie. if we write to the page, it will be - * copied), and obviously we insist that it be mapped where we ask. */ - if (mmap((void *)addr, getpagesize() * num, - PROT_READ|PROT_WRITE|PROT_EXEC, MAP_FIXED|MAP_PRIVATE, fd, 0) - != (void *)addr) - err(1, "Mmaping %u pages of /dev/zero @%p", num, (void *)addr); - - /* Returning the address is just a courtesy: can simplify callers. */ - return (void *)addr; + * copied). */ + addr = mmap(NULL, getpagesize() * num, + PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0); + if (addr == MAP_FAILED) + err(1, "Mmaping %u pages of /dev/zero", num); + + return addr; +} + +/* Get some more pages for a device. */ +static void *get_pages(unsigned int num) +{ + void *addr = from_guest_phys(guest_limit); + + guest_limit += num * getpagesize(); + if (guest_limit > guest_max) + errx(1, "Not enough memory for devices"); + return addr; } /* To find out where to start we look for the magic Guest string, which marks * the code we see in lguest_asm.S. This is a hack which we are currently * plotting to replace with the normal Linux entry point. */ -static unsigned long entry_point(void *start, void *end, +static unsigned long entry_point(const void *start, const void *end, unsigned long page_offset) { - void *p; + const void *p; /* The scan gives us the physical starting address. We want the * virtual address in this case, and fortunately, we already figured @@ -158,7 +189,8 @@ static unsigned long entry_point(void *start, void *end, * "page_offset". */ for (p = start; p < end; p++) if (memcmp(p, "GenuineLguest", strlen("GenuineLguest")) == 0) - return (long)p + strlen("GenuineLguest") + page_offset; + return to_guest_phys(p + strlen("GenuineLguest")) + + page_offset; errx(1, "Is this image a genuine lguest?"); } @@ -201,9 +233,9 @@ static void map_at(int fd, void *addr, unsigned long offset, unsigned long len) static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr, unsigned long *page_offset) { + void *start = (void *)-1, *end = NULL; Elf32_Phdr phdr[ehdr->e_phnum]; unsigned int i; - unsigned long start = -1UL, end = 0; /* Sanity checks on the main ELF header: an x86 executable with a * reasonable number of correctly-sized program headers. */ @@ -246,17 +278,17 @@ static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr, /* We track the first and last address we mapped, so we can * tell entry_point() where to scan. */ - if (phdr[i].p_paddr < start) - start = phdr[i].p_paddr; - if (phdr[i].p_paddr + phdr[i].p_filesz > end) - end = phdr[i].p_paddr + phdr[i].p_filesz; + if (from_guest_phys(phdr[i].p_paddr) < start) + start = from_guest_phys(phdr[i].p_paddr); + if (from_guest_phys(phdr[i].p_paddr) + phdr[i].p_filesz > end) + end=from_guest_phys(phdr[i].p_paddr)+phdr[i].p_filesz; /* We map this section of the file at its physical address. */ - map_at(elf_fd, (void *)phdr[i].p_paddr, + map_at(elf_fd, from_guest_phys(phdr[i].p_paddr), phdr[i].p_offset, phdr[i].p_filesz); } - return entry_point((void *)start, (void *)end, *page_offset); + return entry_point(start, end, *page_offset); } /*L:170 Prepare to be SHOCKED and AMAZED. And possibly a trifle nauseated. @@ -307,7 +339,7 @@ static unsigned long unpack_bzimage(int fd, unsigned long *page_offset) * actually configurable as CONFIG_PHYSICAL_START, but as the comment * there says, "Don't change this unless you know what you are doing". * Indeed. */ - void *img = (void *)0x100000; + void *img = from_guest_phys(0x100000); /* gzdopen takes our file descriptor (carefully placed at the start of * the GZIP header we found) and returns a gzFile. */ @@ -421,7 +453,7 @@ static unsigned long load_initrd(const char *name, unsigned long mem) /* We map the initrd at the top of memory, but mmap wants it to be * page-aligned, so we round the size up for that. */ len = page_align(st.st_size); - map_at(ifd, (void *)mem - len, 0, st.st_size); + map_at(ifd, from_guest_phys(mem - len), 0, st.st_size); /* Once a file is mapped, you can close the file descriptor. It's a * little odd, but quite useful. */ close(ifd); @@ -431,9 +463,9 @@ static unsigned long load_initrd(const char *name, unsigned long mem) return len; } -/* Once we know how much memory we have, and the address the Guest kernel - * expects, we can construct simple linear page tables which will get the Guest - * far enough into the boot to create its own. +/* Once we know the address the Guest kernel expects, we can construct simple + * linear page tables for all of memory which will get the Guest far enough + * into the boot to create its own. * * We lay them out of the way, just below the initrd (which is why we need to * know its size). */ @@ -457,7 +489,7 @@ static unsigned long setup_pagetables(unsigned long mem, linear_pages = (mapped_pages + ptes_per_page-1)/ptes_per_page; /* We put the toplevel page directory page at the top of memory. */ - pgdir = (void *)mem - initrd_size - getpagesize(); + pgdir = from_guest_phys(mem) - initrd_size - getpagesize(); /* Now we use the next linear_pages pages as pte pages */ linear = (void *)pgdir - linear_pages*getpagesize(); @@ -473,15 +505,16 @@ static unsigned long setup_pagetables(unsigned long mem, * continue from there. */ for (i = 0; i < mapped_pages; i += ptes_per_page) { pgdir[(i + page_offset/getpagesize())/ptes_per_page] - = (((u32)linear + i*sizeof(u32)) | PAGE_PRESENT); + = ((to_guest_phys(linear) + i*sizeof(u32)) + | PAGE_PRESENT); } - verbose("Linear mapping of %u pages in %u pte pages at %p\n", - mapped_pages, linear_pages, linear); + verbose("Linear mapping of %u pages in %u pte pages at %#lx\n", + mapped_pages, linear_pages, to_guest_phys(linear)); /* We return the top level (guest-physical) address: the kernel needs * to know where it is. */ - return (unsigned long)pgdir; + return to_guest_phys(pgdir); } /* Simple routine to roll all the commandline arguments together with spaces @@ -501,14 +534,19 @@ static void concat(char *dst, char *args[]) /* This is where we actually tell the kernel to initialize the Guest. We saw * the arguments it expects when we looked at initialize() in lguest_user.c: - * the top physical page to allow, the top level pagetable, the entry point and - * the page_offset constant for the Guest. */ + * the base of guest "physical" memory, the top physical page to allow, the + * top level pagetable, the entry point and the page_offset constant for the + * Guest. */ static int tell_kernel(u32 pgdir, u32 start, u32 page_offset) { u32 args[] = { LHREQ_INITIALIZE, - top/getpagesize(), pgdir, start, page_offset }; + (unsigned long)guest_base, + guest_limit / getpagesize(), + pgdir, start, page_offset }; int fd; + verbose("Guest: %p - %p (%#lx)\n", + guest_base, guest_base + guest_limit, guest_limit); fd = open_or_die("/dev/lguest", O_RDWR); if (write(fd, args, sizeof(args)) < 0) err(1, "Writing to /dev/lguest"); @@ -605,11 +643,11 @@ static void *_check_pointer(unsigned long addr, unsigned int size, { /* We have to separately check addr and addr+size, because size could * be huge and addr + size might wrap around. */ - if (addr >= top || addr + size >= top) + if (addr >= guest_limit || addr + size >= guest_limit) errx(1, "%s:%i: Invalid address %li", __FILE__, line, addr); /* We return a pointer for the caller's convenience, now we know it's * safe to use. */ - return (void *)addr; + return from_guest_phys(addr); } /* A macro which transparently hands the line number to the real function. */ #define check_pointer(addr,size) _check_pointer(addr, size, __LINE__) @@ -646,7 +684,7 @@ static u32 *dma2iov(unsigned long dma, struct iovec iov[], unsigned *num) static u32 *get_dma_buffer(int fd, void *key, struct iovec iov[], unsigned int *num, u32 *irq) { - u32 buf[] = { LHREQ_GETDMA, (u32)key }; + u32 buf[] = { LHREQ_GETDMA, to_guest_phys(key) }; unsigned long udma; u32 *res; @@ -998,11 +1036,11 @@ new_dev_desc(struct lguest_device_desc *descs, descs[i].features = features; descs[i].num_pages = num_pages; /* If they said the device needs memory, we allocate - * that now, bumping up the top of Guest memory. */ + * that now. */ if (num_pages) { - map_zeroed_pages(top, num_pages); - descs[i].pfn = top/getpagesize(); - top += num_pages*getpagesize(); + unsigned long pa; + pa = to_guest_phys(get_pages(num_pages)); + descs[i].pfn = pa / getpagesize(); } return &descs[i]; } @@ -1040,9 +1078,9 @@ static struct device *new_device(struct device_list *devices, if (handle_input) set_fd(dev->fd, devices); dev->desc = new_dev_desc(devices->descs, type, features, num_pages); - dev->mem = (void *)(dev->desc->pfn * getpagesize()); + dev->mem = from_guest_phys(dev->desc->pfn * getpagesize()); dev->handle_input = handle_input; - dev->watch_key = (unsigned long)dev->mem + watch_off; + dev->watch_key = to_guest_phys(dev->mem) + watch_off; dev->handle_output = handle_output; return dev; } @@ -1382,21 +1420,7 @@ static void usage(void) "<mem-in-mb> vmlinux [args...]"); } -/*L:100 The Launcher code itself takes us out into userspace, that scary place - * where pointers run wild and free! Unfortunately, like most userspace - * programs, it's quite boring (which is why everyone like to hack on the - * kernel!). Perhaps if you make up an Lguest Drinking Game at this point, it - * will get you through this section. Or, maybe not. - * - * The Launcher binary sits up high, usually starting at address 0xB8000000. - * Everything below this is the "physical" memory for the Guest. For example, - * if the Guest were to write a "1" at physical address 0, we would see a "1" - * in the Launcher at "(int *)0". Guest physical == Launcher virtual. - * - * This can be tough to get your head around, but usually it just means that we - * don't need to do any conversion when the Guest gives us it's "physical" - * addresses. - */ +/*L:105 The main routine is where the real work begins: */ int main(int argc, char *argv[]) { /* Memory, top-level pagetable, code startpoint, PAGE_OFFSET and size @@ -1406,8 +1430,8 @@ int main(int argc, char *argv[]) int i, c, lguest_fd; /* The list of Guest devices, based on command line arguments. */ struct device_list device_list; - /* The boot information for the Guest: at guest-physical address 0. */ - void *boot = (void *)0; + /* The boot information for the Guest. */ + void *boot; /* If they specify an initrd file to load. */ const char *initrd_name = NULL; @@ -1427,9 +1451,16 @@ int main(int argc, char *argv[]) * of memory now. */ for (i = 1; i < argc; i++) { if (argv[i][0] != '-') { - mem = top = atoi(argv[i]) * 1024 * 1024; - device_list.descs = map_zeroed_pages(top, 1); - top += getpagesize(); + mem = atoi(argv[i]) * 1024 * 1024; + /* We start by mapping anonymous pages over all of + * guest-physical memory range. This fills it with 0, + * and ensures that the Guest won't be killed when it + * tries to access it. */ + guest_base = map_zeroed_pages(mem / getpagesize() + + DEVICE_PAGES); + guest_limit = mem; + guest_max = mem + DEVICE_PAGES*getpagesize(); + device_list.descs = get_pages(1); break; } } @@ -1462,18 +1493,18 @@ int main(int argc, char *argv[]) if (optind + 2 > argc) usage(); + verbose("Guest base is at %p\n", guest_base); + /* We always have a console device */ setup_console(&device_list); - /* We start by mapping anonymous pages over all of guest-physical - * memory range. This fills it with 0, and ensures that the Guest - * won't be killed when it tries to access it. */ - map_zeroed_pages(0, mem / getpagesize()); - /* Now we load the kernel */ start = load_kernel(open_or_die(argv[optind+1], O_RDONLY), &page_offset); + /* Boot information is stashed at physical address 0 */ + boot = from_guest_phys(0); + /* Map the initrd image if requested (at top of physical memory) */ if (initrd_name) { initrd_size = load_initrd(initrd_name, mem); @@ -1495,7 +1526,7 @@ int main(int argc, char *argv[]) = ((struct e820entry) { 0, mem, E820_RAM }); /* The boot header contains a command line pointer: we put the command * line after the boot header (at address 4096) */ - *(void **)(boot + 0x228) = boot + 4096; + *(u32 *)(boot + 0x228) = 4096; concat(boot + 4096, argv+optind+2); /* The guest type value of "1" tells the Guest it's under lguest. */ |