[Lguest] [PATCH 1/3] lguest: move the initial guest page table creation code to the host
Matias Zabaljauregui
zabaljauregui at gmail.com
Sat Sep 27 09:51:21 EST 2008
This patch moves the initial guest page table creation code to the host.
Signed-off-by: Matias Zabaljauregui <zabaljauregui at gmail.com>
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 7228369..6c641b6 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -481,51 +481,6 @@ static unsigned long load_initrd(const char
*name, unsigned long mem)
/* We return the initrd size. */
return len;
}
-
-/* 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 here). */
-static unsigned long setup_pagetables(unsigned long mem,
- unsigned long initrd_size)
-{
- unsigned long *pgdir, *linear;
- unsigned int mapped_pages, i, linear_pages;
- unsigned int ptes_per_page = getpagesize()/sizeof(void *);
-
- 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;
-
- /* We put the toplevel page directory page at the top of memory. */
- 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();
-
- /* Linear mapping is easy: put every page's address into the mapping in
- * order. PAGE_PRESENT contains the flags Present, Writable and
- * Executable. */
- for (i = 0; i < mapped_pages; i++)
- linear[i] = ((i * getpagesize()) | PAGE_PRESENT);
-
- /* The top level points to the linear page table pages above. */
- for (i = 0; i < mapped_pages; i += ptes_per_page) {
- pgdir[i/ptes_per_page]
- = ((to_guest_phys(linear) + i*sizeof(void *))
- | PAGE_PRESENT);
- }
-
- 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 to_guest_phys(pgdir);
-}
/*:*/
/* Simple routine to roll all the commandline arguments together with spaces
@@ -550,11 +505,11 @@ static void concat(char *dst, char *args[])
* 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 and the entry point for the Guest. */
-static int tell_kernel(unsigned long pgdir, unsigned long start)
+static int tell_kernel(unsigned long start)
{
unsigned long args[] = { LHREQ_INITIALIZE,
(unsigned long)guest_base,
- guest_limit / getpagesize(), pgdir, start };
+ guest_limit / getpagesize(), start };
int fd;
verbose("Guest: %p - %p (%#lx)\n",
@@ -1941,7 +1896,7 @@ int main(int argc, char *argv[])
{
/* Memory, top-level pagetable, code startpoint and size of the
* (optional) initrd. */
- unsigned long mem = 0, pgdir, start, initrd_size = 0;
+ unsigned long mem = 0, start, initrd_size = 0;
/* Two temporaries and the /dev/lguest file descriptor. */
int i, c, lguest_fd;
/* The boot information for the Guest. */
@@ -2040,9 +1995,6 @@ int main(int argc, char *argv[])
boot->hdr.type_of_loader = 0xFF;
}
- /* Set up the initial linear pagetables, starting below the initrd. */
- pgdir = setup_pagetables(mem, initrd_size);
-
/* The Linux boot header contains an "E820" memory map: ours is a
* simple, single region. */
boot->e820_entries = 1;
@@ -2064,7 +2016,7 @@ 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);
+ lguest_fd = tell_kernel(start);
/* We clone off a thread, which wakes the Launcher whenever one of the
* input file descriptors needs attention. We call this the Waker, and
diff --git a/arch/x86/lguest/i386_head.S b/arch/x86/lguest/i386_head.S
index 5c7cef3..10b9bd3 100644
--- a/arch/x86/lguest/i386_head.S
+++ b/arch/x86/lguest/i386_head.S
@@ -30,21 +30,6 @@ ENTRY(lguest_entry)
movl $lguest_data - __PAGE_OFFSET, %edx
int $LGUEST_TRAP_ENTRY
- /* The Host put the toplevel pagetable in lguest_data.pgdir. The movsl
- * instruction uses %esi implicitly as the source for the copy we're
- * about to do. */
- 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
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index 5faefea..f2c641e 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -164,7 +164,7 @@ void copy_gdt(const struct lg_cpu *cpu, struct
desc_struct *gdt);
void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt);
/* page_tables.c: */
-int init_guest_pagetable(struct lguest *lg, unsigned long pgtable);
+int init_guest_pagetable(struct lguest *lg);
void free_guest_pagetable(struct lguest *lg);
void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable);
void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 i);
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
index e73a000..34bc017 100644
--- a/drivers/lguest/lguest_user.c
+++ b/drivers/lguest/lguest_user.c
@@ -146,7 +146,7 @@ static int lg_cpu_start(struct lg_cpu *cpu,
unsigned id, unsigned long start_ip)
return 0;
}
-/*L:020 The initialization write supplies 4 pointer sized (32 or 64 bit)
+/*L:020 The initialization write supplies 3 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.
@@ -155,9 +155,6 @@ static int lg_cpu_start(struct lg_cpu *cpu,
unsigned id, unsigned long start_ip)
* allowed to access. The Guest memory lives inside the Launcher, so it sets
* this to ensure the Guest can only reach its own memory.
*
- * pgdir: The (Guest-physical) address of the top of the initial Guest
- * pagetables (which are set up by the Launcher).
- *
* start: The first instruction to execute ("eip" in x86-speak).
*/
static int initialize(struct file *file, const unsigned long __user *input)
@@ -166,7 +163,7 @@ static int initialize(struct file *file, const
unsigned long __user *input)
* Guest. */
struct lguest *lg;
int err;
- unsigned long args[4];
+ unsigned long args[3];
/* We grab the Big Lguest lock, which protects against multiple
* simultaneous initializations. */
@@ -192,14 +189,14 @@ static int initialize(struct file *file, const
unsigned long __user *input)
lg->mem_base = (void __user *)args[0];
lg->pfn_limit = args[1];
- /* This is the first cpu (cpu 0) and it will start booting at args[3] */
- err = lg_cpu_start(&lg->cpus[0], 0, args[3]);
+ /* This is the first cpu (cpu 0) and it will start booting at args[2] */
+ err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
if (err)
goto release_guest;
/* Initialize the Guest's shadow page tables, using the toplevel
* address the Launcher gave us. This allocates memory, so can fail. */
- err = init_guest_pagetable(lg, args[2]);
+ err = init_guest_pagetable(lg);
if (err)
goto free_regs;
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index 81d0c60..99b6f66 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -14,6 +14,7 @@
#include <linux/percpu.h>
#include <asm/tlbflush.h>
#include <asm/uaccess.h>
+#include <asm/bootparam.h>
#include "lg.h"
/*M:008 We hold reference to pages, which prevents them from being swapped.
@@ -581,15 +582,71 @@ void guest_set_pmd(struct lguest *lg, unsigned
long gpgdir, u32 idx)
release_pgd(lg, lg->pgdirs[pgdir].pgdir + idx);
}
+/* Once we know how much memory we have we can construct simple identity
+ * (which set virtual == physical) and linear mappings
+ * 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 here). */
+static unsigned long setup_pagetables(unsigned long mem,
+ unsigned long initrd_size,
+ unsigned long mem_base)
+{
+ pgd_t *pgdir;
+ pte_t *linear;
+ unsigned int mapped_pages, i, linear_pages, phys_linear;
+
+ /* We have mapped_pages frames to map, so we need
+ * linear_pages page tables to map them. */
+ mapped_pages = mem / PAGE_SIZE;
+ linear_pages = (mapped_pages + PTRS_PER_PTE - 1) / PTRS_PER_PTE;
+
+ /* We put the toplevel page directory page at the top of memory. */
+ pgdir = (pgd_t *) (mem + mem_base - initrd_size - PAGE_SIZE);
+
+ /* Now we use the next linear_pages pages as pte pages */
+ linear = (void *)pgdir - linear_pages * PAGE_SIZE;
+
+ /* Linear mapping is easy: put every page's address into the
+ * mapping in order. */
+ for (i = 0; i < mapped_pages; i++)
+ set_pte(&linear[i], pfn_pte(i,
+ __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_USER)));
+
+ /* The top level points to the linear page table pages above.
+ * We setup the identity and linear mappings here. */
+ phys_linear = (unsigned long)linear - mem_base;
+ for (i = 0; i < mapped_pages; i += PTRS_PER_PTE)
+ pgdir[i / PTRS_PER_PTE] =
+ pgdir[pgd_index(PAGE_OFFSET) + i / PTRS_PER_PTE] =
+ __pgd((phys_linear + i * sizeof(pte_t)) |
+ (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER));
+
+ /* We return the top level (guest-physical) address: the kernel needs
+ * to know where it is. */
+ return (unsigned long)pgdir - mem_base;
+}
+
/*H:500 (vii) Setting up the page tables initially.
*
* When a Guest is first created, the Launcher tells us where the toplevel of
* its first page table is. We set some things up here: */
-int init_guest_pagetable(struct lguest *lg, unsigned long pgtable)
+int init_guest_pagetable(struct lguest *lg)
{
+ unsigned long initrd_size = 0, mem = 0;
+ struct boot_params *boot = (struct boot_params *) lg->mem_base;
+
+ /* Get the guest memory size and the ramdisk size
+ * from the boot header located at lg->mem_base*/
+ if (copy_from_user(&mem, &boot->e820_map[0].size, 8))
+ kill_guest(&lg->cpus[0], "Error reading from user space");
+ if (get_user(initrd_size, &boot->hdr.ramdisk_size))
+ kill_guest(&lg->cpus[0], "Error reading from user space");
+
/* We start on the first shadow page table, and give it a blank PGD
* page. */
- lg->pgdirs[0].gpgdir = pgtable;
+ lg->pgdirs[0].gpgdir = setup_pagetables(mem,
+ initrd_size, (unsigned long) lg->mem_base);
lg->pgdirs[0].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL);
if (!lg->pgdirs[0].pgdir)
return -ENOMEM;
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