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Boot with virtual == physical to get closer to native Linux.

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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 <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2007-10-22 11:03:36 +10:00
parent c18acd73ff
commit 47436aa4ad
12 changed files with 141 additions and 148 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

134
Documentation/lguest/lguest.c
View File

@ -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 <some-address>, %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

1
arch/x86/kernel/asm-offsets_32.c
View File

@ -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);

7
arch/x86/lguest/boot.c
View File

@ -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

41
arch/x86/lguest/i386_head.S
View File

@ -1,5 +1,6 @@
#include <linux/linkage.h>
#include <linux/lguest.h>
#include <asm/lguest_hcall.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/processor-flags.h>
@ -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

8
drivers/lguest/hypercalls.c
View File

@ -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)

13
drivers/lguest/interrupts_and_traps.c
View File

@ -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);

8
drivers/lguest/lg.h
View File

@ -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);
/* <arch>/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 */

11
drivers/lguest/lguest_user.c
View File

@ -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. */

47
drivers/lguest/page_tables.c
View File

@ -13,6 +13,7 @@
#include <linux/random.h>
#include <linux/percpu.h>
#include <asm/tlbflush.h>
#include <asm/uaccess.h>
#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)
{

7
drivers/lguest/x86/core.c
View File

@ -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. */

7
include/asm-x86/lguest_hcall.h
View File

@ -2,8 +2,6 @@
#ifndef _X86_LGUEST_HCALL_H
#define _X86_LGUEST_HCALL_H
#include <asm/hw_irq.h>
#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 <asm/hw_irq.h>
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 */

5
include/linux/lguest.h
View File

@ -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;
};