xiaomi-sm8450/android_kernel_xiaomi_sm8450
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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
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47
drivers/lguest/page_tables.c
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@@ -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)
{