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authorRusty Russell <rusty@rustcorp.com.au>2007-10-22 11:03:36 +1000
committerRusty Russell <rusty@rustcorp.com.au>2007-10-23 15:49:54 +1000
commit47436aa4ad054c1c7c8231618e86ebd9305308dc (patch)
treea9ba6e0521f9116442144a86e781a3164ec86094 /drivers
parentc18acd73ffc209def08003a1927473096f66c5ad (diff)
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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 <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/lguest/hypercalls.c8
-rw-r--r--drivers/lguest/interrupts_and_traps.c13
-rw-r--r--drivers/lguest/lg.h8
-rw-r--r--drivers/lguest/lguest_user.c11
-rw-r--r--drivers/lguest/page_tables.c47
-rw-r--r--drivers/lguest/x86/core.c7
6 files changed, 62 insertions, 32 deletions
diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c
index 02d0ae2..13b5f2f 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 a57d757..3271c00 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 7408ceb..e4845d7 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);
/* <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 */
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
index b184652..61b177e 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 bfe3650..fe3c757 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -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)
{
diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index a125109..39f64c9 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. */