From 47436aa4ad054c1c7c8231618e86ebd9305308dc Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 22 Oct 2007 11:03:36 +1000 Subject: [PATCH] Boot with virtual == physical to get closer to native Linux. 1) This allows us to get alot closer to booting bzImages. 2) It means we don't have to know page_offset. 3) The Guest needs to modify the boot pagetables to create the PAGE_OFFSET mapping before jumping to C code. 4) guest_pa() walks the page tables rather than using page_offset. 5) We don't use page_offset to figure out whether to emulate: it was always kinda quesationable, and won't work for instructions done before remapping (bzImage unpacking in particular). 6) We still want the kernel address for tlb flushing: have the initial hypercall give us that, too. Signed-off-by: Rusty Russell --- Documentation/lguest/lguest.c | 134 ++++++-------------------- arch/x86/kernel/asm-offsets_32.c | 1 + arch/x86/lguest/boot.c | 7 +- arch/x86/lguest/i386_head.S | 41 +++++++- drivers/lguest/hypercalls.c | 8 +- drivers/lguest/interrupts_and_traps.c | 13 ++- drivers/lguest/lg.h | 8 +- drivers/lguest/lguest_user.c | 11 +-- drivers/lguest/page_tables.c | 47 +++++++-- drivers/lguest/x86/core.c | 7 +- include/asm-x86/lguest_hcall.h | 7 +- include/linux/lguest.h | 5 +- 12 files changed, 141 insertions(+), 148 deletions(-) diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c index 4950b03514..32c2eaf94c 100644 --- a/Documentation/lguest/lguest.c +++ b/Documentation/lguest/lguest.c @@ -178,19 +178,16 @@ static void *get_pages(unsigned int num) /* 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(const void *start, const void *end, - unsigned long page_offset) +static unsigned long entry_point(const void *start, const void *end) { const void *p; - /* The scan gives us the physical starting address. We want the - * virtual address in this case, and fortunately, we already figured - * out the physical-virtual difference and passed it here in - * "page_offset". */ + /* The scan gives us the physical starting address. We boot with + * pagetables set up with virtual and physical the same, so that's + * OK. */ for (p = start; p < end; p++) if (memcmp(p, "GenuineLguest", strlen("GenuineLguest")) == 0) - return to_guest_phys(p + strlen("GenuineLguest")) - + page_offset; + return to_guest_phys(p + strlen("GenuineLguest")); errx(1, "Is this image a genuine lguest?"); } @@ -224,14 +221,11 @@ static void map_at(int fd, void *addr, unsigned long offset, unsigned long len) * by all modern binaries on Linux including the kernel. * * The ELF headers give *two* addresses: a physical address, and a virtual - * address. The Guest kernel expects to be placed in memory at the physical - * address, and the page tables set up so it will correspond to that virtual - * address. We return the difference between the virtual and physical - * addresses in the "page_offset" pointer. + * address. We use the physical address; the Guest will map itself to the + * virtual address. * * We return the starting address. */ -static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr, - unsigned long *page_offset) +static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr) { void *start = (void *)-1, *end = NULL; Elf32_Phdr phdr[ehdr->e_phnum]; @@ -255,9 +249,6 @@ static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr, if (read(elf_fd, phdr, sizeof(phdr)) != sizeof(phdr)) err(1, "Reading program headers"); - /* We don't know page_offset yet. */ - *page_offset = 0; - /* Try all the headers: there are usually only three. A read-only one, * a read-write one, and a "note" section which isn't loadable. */ for (i = 0; i < ehdr->e_phnum; i++) { @@ -268,14 +259,6 @@ static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr, verbose("Section %i: size %i addr %p\n", i, phdr[i].p_memsz, (void *)phdr[i].p_paddr); - /* We expect a simple linear address space: every segment must - * have the same difference between virtual (p_vaddr) and - * physical (p_paddr) address. */ - if (!*page_offset) - *page_offset = phdr[i].p_vaddr - phdr[i].p_paddr; - else if (*page_offset != phdr[i].p_vaddr - phdr[i].p_paddr) - errx(1, "Page offset of section %i different", i); - /* We track the first and last address we mapped, so we can * tell entry_point() where to scan. */ if (from_guest_phys(phdr[i].p_paddr) < start) @@ -288,50 +271,13 @@ static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr, phdr[i].p_offset, phdr[i].p_filesz); } - return entry_point(start, end, *page_offset); -} - -/*L:170 Prepare to be SHOCKED and AMAZED. And possibly a trifle nauseated. - * - * We know that CONFIG_PAGE_OFFSET sets what virtual address the kernel expects - * to be. We don't know what that option was, but we can figure it out - * approximately by looking at the addresses in the code. I chose the common - * case of reading a memory location into the %eax register: - * - * movl , %eax - * - * This gets encoded as five bytes: "0xA1 <4-byte-address>". For example, - * "0xA1 0x18 0x60 0x47 0xC0" reads the address 0xC0476018 into %eax. - * - * In this example can guess that the kernel was compiled with - * CONFIG_PAGE_OFFSET set to 0xC0000000 (it's always a round number). If the - * kernel were larger than 16MB, we might see 0xC1 addresses show up, but our - * kernel isn't that bloated yet. - * - * Unfortunately, x86 has variable-length instructions, so finding this - * particular instruction properly involves writing a disassembler. Instead, - * we rely on statistics. We look for "0xA1" and tally the different bytes - * which occur 4 bytes later (the "0xC0" in our example above). When one of - * those bytes appears three times, we can be reasonably confident that it - * forms the start of CONFIG_PAGE_OFFSET. - * - * This is amazingly reliable. */ -static unsigned long intuit_page_offset(unsigned char *img, unsigned long len) -{ - unsigned int i, possibilities[256] = { 0 }; - - for (i = 0; i + 4 < len; i++) { - /* mov 0xXXXXXXXX,%eax */ - if (img[i] == 0xA1 && ++possibilities[img[i+4]] > 3) - return (unsigned long)img[i+4] << 24; - } - errx(1, "could not determine page offset"); + return entry_point(start, end); } /*L:160 Unfortunately the entire ELF image isn't compressed: the segments * which need loading are extracted and compressed raw. This denies us the * information we need to make a fully-general loader. */ -static unsigned long unpack_bzimage(int fd, unsigned long *page_offset) +static unsigned long unpack_bzimage(int fd) { gzFile f; int ret, len = 0; @@ -352,12 +298,7 @@ static unsigned long unpack_bzimage(int fd, unsigned long *page_offset) verbose("Unpacked size %i addr %p\n", len, img); - /* Without the ELF header, we can't tell virtual-physical gap. This is - * CONFIG_PAGE_OFFSET, and people do actually change it. Fortunately, - * I have a clever way of figuring it out from the code itself. */ - *page_offset = intuit_page_offset(img, len); - - return entry_point(img, img + len, *page_offset); + return entry_point(img, img + len); } /*L:150 A bzImage, unlike an ELF file, is not meant to be loaded. You're @@ -368,7 +309,7 @@ static unsigned long unpack_bzimage(int fd, unsigned long *page_offset) * The bzImage is formed by putting the decompressing code in front of the * compressed kernel code. So we can simple scan through it looking for the * first "gzip" header, and start decompressing from there. */ -static unsigned long load_bzimage(int fd, unsigned long *page_offset) +static unsigned long load_bzimage(int fd) { unsigned char c; int state = 0; @@ -396,7 +337,7 @@ static unsigned long load_bzimage(int fd, unsigned long *page_offset) if (c != 0x03) state = -1; else - return unpack_bzimage(fd, page_offset); + return unpack_bzimage(fd); } } errx(1, "Could not find kernel in bzImage"); @@ -405,7 +346,7 @@ static unsigned long load_bzimage(int fd, unsigned long *page_offset) /*L:140 Loading the kernel is easy when it's a "vmlinux", but most kernels * come wrapped up in the self-decompressing "bzImage" format. With some funky * coding, we can load those, too. */ -static unsigned long load_kernel(int fd, unsigned long *page_offset) +static unsigned long load_kernel(int fd) { Elf32_Ehdr hdr; @@ -415,10 +356,10 @@ static unsigned long load_kernel(int fd, unsigned long *page_offset) /* If it's an ELF file, it starts with "\177ELF" */ if (memcmp(hdr.e_ident, ELFMAG, SELFMAG) == 0) - return map_elf(fd, &hdr, page_offset); + return map_elf(fd, &hdr); /* Otherwise we assume it's a bzImage, and try to unpack it */ - return load_bzimage(fd, page_offset); + return load_bzimage(fd); } /* This is a trivial little helper to align pages. Andi Kleen hated it because @@ -463,27 +404,20 @@ static unsigned long load_initrd(const char *name, unsigned long mem) return len; } -/* 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 +/* Once we know how much memory we have, we can construct simple linear page + * tables which set virtual == physical 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). */ static unsigned long setup_pagetables(unsigned long mem, - unsigned long initrd_size, - unsigned long page_offset) + unsigned long initrd_size) { unsigned long *pgdir, *linear; unsigned int mapped_pages, i, linear_pages; unsigned int ptes_per_page = getpagesize()/sizeof(void *); - /* Ideally we map all physical memory starting at page_offset. - * However, if page_offset is 0xC0000000 we can only map 1G of physical - * (0xC0000000 + 1G overflows). */ - if (mem <= -page_offset) - mapped_pages = mem/getpagesize(); - else - mapped_pages = -page_offset/getpagesize(); + mapped_pages = mem/getpagesize(); /* Each PTE page can map ptes_per_page pages: how many do we need? */ linear_pages = (mapped_pages + ptes_per_page-1)/ptes_per_page; @@ -500,11 +434,9 @@ static unsigned long setup_pagetables(unsigned long mem, for (i = 0; i < mapped_pages; i++) linear[i] = ((i * getpagesize()) | PAGE_PRESENT); - /* The top level points to the linear page table pages above. The - * entry representing page_offset points to the first one, and they - * continue from there. */ + /* The top level points to the linear page table pages above. */ for (i = 0; i < mapped_pages; i += ptes_per_page) { - pgdir[(i + page_offset/getpagesize())/ptes_per_page] + pgdir[i/ptes_per_page] = ((to_guest_phys(linear) + i*sizeof(void *)) | PAGE_PRESENT); } @@ -535,15 +467,12 @@ 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 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(unsigned long pgdir, unsigned long start, - unsigned long page_offset) + * top level pagetable and the entry point for the Guest. */ +static int tell_kernel(unsigned long pgdir, unsigned long start) { unsigned long args[] = { LHREQ_INITIALIZE, (unsigned long)guest_base, - guest_limit / getpagesize(), - pgdir, start, page_offset }; + guest_limit / getpagesize(), pgdir, start }; int fd; verbose("Guest: %p - %p (%#lx)\n", @@ -1424,9 +1353,9 @@ static void usage(void) /*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 - * of the (optional) initrd. */ - unsigned long mem = 0, pgdir, start, page_offset, initrd_size = 0; + /* Memory, top-level pagetable, code startpoint and size of the + * (optional) initrd. */ + unsigned long mem = 0, pgdir, start, initrd_size = 0; /* A temporary and the /dev/lguest file descriptor. */ int i, c, lguest_fd; /* The list of Guest devices, based on command line arguments. */ @@ -1500,8 +1429,7 @@ int main(int argc, char *argv[]) setup_console(&device_list); /* Now we load the kernel */ - start = load_kernel(open_or_die(argv[optind+1], O_RDONLY), - &page_offset); + start = load_kernel(open_or_die(argv[optind+1], O_RDONLY)); /* Boot information is stashed at physical address 0 */ boot = from_guest_phys(0); @@ -1518,7 +1446,7 @@ int main(int argc, char *argv[]) } /* Set up the initial linear pagetables, starting below the initrd. */ - pgdir = setup_pagetables(mem, initrd_size, page_offset); + pgdir = setup_pagetables(mem, initrd_size); /* The Linux boot header contains an "E820" memory map: ours is a * simple, single region. */ @@ -1535,7 +1463,7 @@ int main(int argc, char *argv[]) /* We tell the kernel to initialize the Guest: this returns the open * /dev/lguest file descriptor. */ - lguest_fd = tell_kernel(pgdir, start, page_offset); + lguest_fd = tell_kernel(pgdir, start); /* We fork off a child process, which wakes the Launcher whenever one * of the input file descriptors needs attention. Otherwise we would diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c index f8764716b0..0e45981b2d 100644 --- a/arch/x86/kernel/asm-offsets_32.c +++ b/arch/x86/kernel/asm-offsets_32.c @@ -136,6 +136,7 @@ void foo(void) #ifdef CONFIG_LGUEST_GUEST BLANK(); OFFSET(LGUEST_DATA_irq_enabled, lguest_data, irq_enabled); + OFFSET(LGUEST_DATA_pgdir, lguest_data, pgdir); OFFSET(LGUEST_PAGES_host_gdt_desc, lguest_pages, state.host_gdt_desc); OFFSET(LGUEST_PAGES_host_idt_desc, lguest_pages, state.host_idt_desc); OFFSET(LGUEST_PAGES_host_cr3, lguest_pages, state.host_cr3); diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 3a06b51c98..090f30cbf2 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -86,6 +86,7 @@ struct lguest_data lguest_data = { .hcall_status = { [0 ... LHCALL_RING_SIZE-1] = 0xFF }, .noirq_start = (u32)lguest_noirq_start, .noirq_end = (u32)lguest_noirq_end, + .kernel_address = PAGE_OFFSET, .blocked_interrupts = { 1 }, /* Block timer interrupts */ .syscall_vec = SYSCALL_VECTOR, }; @@ -1033,11 +1034,7 @@ __init void lguest_init(void *boot) /*G:070 Now we've seen all the paravirt_ops, we return to * lguest_init() where the rest of the fairly chaotic boot setup - * occurs. - * - * The Host expects our first hypercall to tell it where our "struct - * lguest_data" is, so we do that first. */ - hcall(LHCALL_LGUEST_INIT, __pa(&lguest_data), 0, 0); + * occurs. */ /* The native boot code sets up initial page tables immediately after * the kernel itself, and sets init_pg_tables_end so they're not diff --git a/arch/x86/lguest/i386_head.S b/arch/x86/lguest/i386_head.S index 6d7a74f07c..ba4282eba5 100644 --- a/arch/x86/lguest/i386_head.S +++ b/arch/x86/lguest/i386_head.S @@ -1,5 +1,6 @@ #include #include +#include #include #include #include @@ -8,18 +9,48 @@ * looks for. The plan is that the Linux boot protocol will be extended with a * "platform type" field which will guide us here from the normal entry point, * but for the moment this suffices. The normal boot code uses %esi for the - * boot header, so we do too. We convert it to a virtual address by adding - * PAGE_OFFSET, and hand it to lguest_init() as its argument (ie. %eax). + * boot header, so we do too. + * + * WARNING: be very careful here! We're running at addresses equal to physical + * addesses (around 0), not above PAGE_OFFSET as most code expectes + * (eg. 0xC0000000). Jumps are relative, so they're OK, but we can't touch any + * data. * * The .section line puts this code in .init.text so it will be discarded after * boot. */ .section .init.text, "ax", @progbits .ascii "GenuineLguest" - /* Set up initial stack. */ - movl $(init_thread_union+THREAD_SIZE),%esp + /* Make initial hypercall now, so we can set up the pagetables. */ + movl $LHCALL_LGUEST_INIT, %eax + movl $lguest_data - __PAGE_OFFSET, %edx + int $LGUEST_TRAP_ENTRY + + /* Set up boot information pointer to hand to lguest_init(): it wants + * a virtual address. */ movl %esi, %eax addl $__PAGE_OFFSET, %eax - jmp lguest_init + + /* The Host put the toplevel pagetable in lguest_data.pgdir. The movsl + * instruction uses %esi, so we needed to save it above. */ + movl lguest_data - __PAGE_OFFSET + LGUEST_DATA_pgdir, %esi + + /* Copy first 32 entries of page directory to __PAGE_OFFSET entries. + * This means the first 128M of kernel memory will be mapped at + * PAGE_OFFSET where the kernel expects to run. This will get it far + * enough through boot to switch to its own pagetables. */ + movl $32, %ecx + movl %esi, %edi + addl $((__PAGE_OFFSET >> 22) * 4), %edi + rep + movsl + + /* Set up the initial stack so we can run C code. */ + movl $(init_thread_union+THREAD_SIZE),%esp + + + /* Jumps are relative, and we're running __PAGE_OFFSET too low at the + * moment. */ + jmp lguest_init+__PAGE_OFFSET /*G:055 We create a macro which puts the assembler code between lgstart_ and * lgend_ markers. These templates are put in the .text section: they can't be diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c index 02d0ae2682..13b5f2f813 100644 --- a/drivers/lguest/hypercalls.c +++ b/drivers/lguest/hypercalls.c @@ -181,15 +181,15 @@ static void initialize(struct lguest *lg) /* The Guest tells us where we're not to deliver interrupts by putting * the range of addresses into "struct lguest_data". */ if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start) - || get_user(lg->noirq_end, &lg->lguest_data->noirq_end) - /* We tell the Guest that it can't use the top 4MB of virtual - * addresses used by the Switcher. */ - || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem)) + || get_user(lg->noirq_end, &lg->lguest_data->noirq_end)) kill_guest(lg, "bad guest page %p", lg->lguest_data); /* We write the current time into the Guest's data page once now. */ write_timestamp(lg); + /* page_tables.c will also do some setup. */ + page_table_guest_data_init(lg); + /* This is the one case where the above accesses might have been the * first write to a Guest page. This may have caused a copy-on-write * fault, but the Guest might be referring to the old (read-only) diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index a57d757eab..3271c0031a 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -62,8 +62,9 @@ static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val) * it). */ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) { - unsigned long gstack; + unsigned long gstack, origstack; u32 eflags, ss, irq_enable; + unsigned long virtstack; /* There are two cases for interrupts: one where the Guest is already * in the kernel, and a more complex one where the Guest is in @@ -71,8 +72,10 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) if ((lg->regs->ss&0x3) != GUEST_PL) { /* The Guest told us their kernel stack with the SET_STACK * hypercall: both the virtual address and the segment */ - gstack = guest_pa(lg, lg->esp1); + virtstack = lg->esp1; ss = lg->ss1; + + origstack = gstack = guest_pa(lg, virtstack); /* We push the old stack segment and pointer onto the new * stack: when the Guest does an "iret" back from the interrupt * handler the CPU will notice they're dropping privilege @@ -81,8 +84,10 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) push_guest_stack(lg, &gstack, lg->regs->esp); } else { /* We're staying on the same Guest (kernel) stack. */ - gstack = guest_pa(lg, lg->regs->esp); + virtstack = lg->regs->esp; ss = lg->regs->ss; + + origstack = gstack = guest_pa(lg, virtstack); } /* Remember that we never let the Guest actually disable interrupts, so @@ -108,7 +113,7 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) /* Now we've pushed all the old state, we change the stack, the code * segment and the address to execute. */ lg->regs->ss = ss; - lg->regs->esp = gstack + lg->page_offset; + lg->regs->esp = virtstack + (gstack - origstack); lg->regs->cs = (__KERNEL_CS|GUEST_PL); lg->regs->eip = idt_address(lo, hi); diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index 7408cebe99..e4845d7f06 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -63,7 +63,7 @@ struct lguest /* This provides the offset to the base of guest-physical * memory in the Launcher. */ void __user *mem_base; - u32 page_offset; + unsigned long kernel_address; u32 cr2; int halted; int ts; @@ -165,6 +165,8 @@ void guest_set_pte(struct lguest *lg, unsigned long gpgdir, 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); +unsigned long guest_pa(struct lguest *lg, unsigned long vaddr); +void page_table_guest_data_init(struct lguest *lg); /* /core.c: */ void lguest_arch_host_init(void); @@ -229,9 +231,5 @@ do { \ } while(0) /* (End of aside) :*/ -static inline unsigned long guest_pa(struct lguest *lg, unsigned long vaddr) -{ - return vaddr - lg->page_offset; -} #endif /* __ASSEMBLY__ */ #endif /* _LGUEST_H */ diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c index b184652e45..61b177e1e6 100644 --- a/drivers/lguest/lguest_user.c +++ b/drivers/lguest/lguest_user.c @@ -111,7 +111,7 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) return run_guest(lg, (unsigned long __user *)user); } -/*L:020 The initialization write supplies 5 pointer sized (32 or 64 bit) +/*L:020 The initialization write supplies 4 pointer sized (32 or 64 bit) * values (in addition to the LHREQ_INITIALIZE value). These are: * * base: The start of the Guest-physical memory inside the Launcher memory. @@ -124,12 +124,6 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) * pagetables (which are set up by the Launcher). * * start: The first instruction to execute ("eip" in x86-speak). - * - * page_offset: The PAGE_OFFSET constant in the Guest kernel. We should - * probably wean the code off this, but it's a very useful constant! Any - * address above this is within the Guest kernel, and any kernel address can - * quickly converted from physical to virtual by adding PAGE_OFFSET. It's - * 0xC0000000 (3G) by default, but it's configurable at kernel build time. */ static int initialize(struct file *file, const unsigned long __user *input) { @@ -137,7 +131,7 @@ static int initialize(struct file *file, const unsigned long __user *input) * Guest. */ struct lguest *lg; int err; - unsigned long args[5]; + unsigned long args[4]; /* We grab the Big Lguest lock, which protects against multiple * simultaneous initializations. */ @@ -162,7 +156,6 @@ static int initialize(struct file *file, const unsigned long __user *input) /* Populate the easy fields of our "struct lguest" */ lg->mem_base = (void __user *)(long)args[0]; lg->pfn_limit = args[1]; - lg->page_offset = args[4]; /* We need a complete page for the Guest registers: they are accessible * to the Guest and we can only grant it access to whole pages. */ diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index bfe3650b28..fe3c757564 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -13,6 +13,7 @@ #include #include #include +#include #include "lg.h" /*M:008 We hold reference to pages, which prevents them from being swapped. @@ -345,7 +346,7 @@ static void flush_user_mappings(struct lguest *lg, int idx) { unsigned int i; /* Release every pgd entry up to the kernel's address. */ - for (i = 0; i < pgd_index(lg->page_offset); i++) + for (i = 0; i < pgd_index(lg->kernel_address); i++) release_pgd(lg, lg->pgdirs[idx].pgdir + i); } @@ -358,6 +359,25 @@ void guest_pagetable_flush_user(struct lguest *lg) } /*:*/ +/* We walk down the guest page tables to get a guest-physical address */ +unsigned long guest_pa(struct lguest *lg, unsigned long vaddr) +{ + pgd_t gpgd; + pte_t gpte; + + /* First step: get the top-level Guest page table entry. */ + gpgd = __pgd(lgread_u32(lg, gpgd_addr(lg, vaddr))); + /* Toplevel not present? We can't map it in. */ + if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) + kill_guest(lg, "Bad address %#lx", vaddr); + + gpte = __pte(lgread_u32(lg, gpte_addr(lg, gpgd, vaddr))); + if (!(pte_flags(gpte) & _PAGE_PRESENT)) + kill_guest(lg, "Bad address %#lx", vaddr); + + return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK); +} + /* We keep several page tables. This is a simple routine to find the page * table (if any) corresponding to this top-level address the Guest has given * us. */ @@ -500,7 +520,7 @@ void guest_set_pte(struct lguest *lg, { /* Kernel mappings must be changed on all top levels. Slow, but * doesn't happen often. */ - if (vaddr >= lg->page_offset) { + if (vaddr >= lg->kernel_address) { unsigned int i; for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) if (lg->pgdirs[i].pgdir) @@ -550,11 +570,6 @@ void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 idx) * its first page table is. We set some things up here: */ int init_guest_pagetable(struct lguest *lg, unsigned long pgtable) { - /* In flush_user_mappings() we loop from 0 to - * "pgd_index(lg->page_offset)". This assumes it won't hit - * the Switcher mappings, so check that now. */ - if (pgd_index(lg->page_offset) >= SWITCHER_PGD_INDEX) - return -EINVAL; /* We start on the first shadow page table, and give it a blank PGD * page. */ lg->pgdidx = 0; @@ -565,6 +580,24 @@ int init_guest_pagetable(struct lguest *lg, unsigned long pgtable) return 0; } +/* When the Guest calls LHCALL_LGUEST_INIT we do more setup. */ +void page_table_guest_data_init(struct lguest *lg) +{ + /* We get the kernel address: above this is all kernel memory. */ + if (get_user(lg->kernel_address, &lg->lguest_data->kernel_address) + /* We tell the Guest that it can't use the top 4MB of virtual + * addresses used by the Switcher. */ + || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem) + || put_user(lg->pgdirs[lg->pgdidx].gpgdir,&lg->lguest_data->pgdir)) + kill_guest(lg, "bad guest page %p", lg->lguest_data); + + /* In flush_user_mappings() we loop from 0 to + * "pgd_index(lg->kernel_address)". This assumes it won't hit the + * Switcher mappings, so check that now. */ + if (pgd_index(lg->kernel_address) >= SWITCHER_PGD_INDEX) + kill_guest(lg, "bad kernel address %#lx", lg->kernel_address); +} + /* When a Guest dies, our cleanup is fairly simple. */ void free_guest_pagetable(struct lguest *lg) { diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c index a125109446..39f64c95de 100644 --- a/drivers/lguest/x86/core.c +++ b/drivers/lguest/x86/core.c @@ -216,9 +216,10 @@ static int emulate_insn(struct lguest *lg) * 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) + /* This must be the Guest kernel trying to do something, not userspace! + * The bottom two bits of the CS segment register are the privilege + * level. */ + if ((lg->regs->cs & 3) != GUEST_PL) return 0; /* Decoding x86 instructions is icky. */ diff --git a/include/asm-x86/lguest_hcall.h b/include/asm-x86/lguest_hcall.h index 8f2a1edc4f..0c553ef362 100644 --- a/include/asm-x86/lguest_hcall.h +++ b/include/asm-x86/lguest_hcall.h @@ -2,8 +2,6 @@ #ifndef _X86_LGUEST_HCALL_H #define _X86_LGUEST_HCALL_H -#include - #define LHCALL_FLUSH_ASYNC 0 #define LHCALL_LGUEST_INIT 1 #define LHCALL_CRASH 2 @@ -36,6 +34,9 @@ * definition of a gentleman: "someone who is only rude intentionally". */ #define LGUEST_TRAP_ENTRY 0x1F +#ifndef __ASSEMBLY__ +#include + static inline unsigned long hcall(unsigned long call, unsigned long arg1, unsigned long arg2, unsigned long arg3) @@ -66,4 +67,6 @@ struct hcall_args /* These map directly onto eax, ebx, ecx, edx in struct lguest_regs */ unsigned long arg0, arg2, arg3, arg1; }; + +#endif /* !__ASSEMBLY__ */ #endif /* _I386_LGUEST_HCALL_H */ diff --git a/include/linux/lguest.h b/include/linux/lguest.h index 083052236d..8beb291346 100644 --- a/include/linux/lguest.h +++ b/include/linux/lguest.h @@ -44,11 +44,14 @@ struct lguest_data unsigned long reserve_mem; /* KHz for the TSC clock. */ u32 tsc_khz; + /* Page where the top-level pagetable is */ + unsigned long pgdir; /* Fields initialized by the Guest at boot: */ /* Instruction range to suppress interrupts even if enabled */ unsigned long noirq_start, noirq_end; - + /* Address above which page tables are all identical. */ + unsigned long kernel_address; /* The vector to try to use for system calls (0x40 or 0x80). */ unsigned int syscall_vec; }; -- 2.39.5