[PATCH][Fix] Prevent swsusp from corrupting page translation tables during resume on x86-64

[PATCH][Fix] Prevent swsusp from corrupting page translation tables during resume on x86-64

[Rafael J. Wysocki]

Hi,

The following patch fixes Bug #4959.  It creates temporary page translation
tables located in the page frames that are not overwritten by swsusp while copying
the image.

The temporary page translation tables are generally based on the existing ones
with the exception that the mappings using 4KB pages are replaced with the
equivalent mappings that use 2MB pages only.  The temporary page tables are
only used for copying the image.

Please consider for applying.

Greetings,
Rafael


Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>



-- 
- Would you tell me, please, which way I ought to go from here?
- That depends a good deal on where you want to get to.
		-- Lewis Carroll "Alice's Adventures in Wonderland"

[PATCH][Fix] Prevent swsusp from corrupting page translation tables during resume on x86-64

[Rafael J. Wysocki]

[The previous message has been sent accidentally without the patch]

Hi,

The following patch fixes Bug #4959.  It creates temporary page translation
tables located in the page frames that are not overwritten by swsusp while copying
the image.

The temporary page translation tables are generally based on the existing ones
with the exception that the mappings using 4KB pages are replaced with the
equivalent mappings that use 2MB pages only.  The temporary page tables are
only used for copying the image.

Please consider for applying.

Greetings,
Rafael


Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

Index: linux-2.6.14-rc2-git3/arch/x86_64/kernel/suspend.c
===================================================================
--- linux-2.6.14-rc2-git3.orig/arch/x86_64/kernel/suspend.c	2005-09-23 18:20:41.000000000 +0200
+++ linux-2.6.14-rc2-git3/arch/x86_64/kernel/suspend.c	2005-09-23 18:21:48.000000000 +0200
@@ -11,6 +11,17 @@
 #include <linux/smp.h>
 #include <linux/suspend.h>
 #include <asm/proto.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+/* Defined in kernel/power/swsusp.c */
+extern unsigned long get_usable_page(unsigned gfp_mask);
+
+pgd_t *temp_level4_pgt;
+
+#define __PGTABLE_MASK		0x000ffffffffff000UL
+#define __PGTABLE_PSE_MASK	0x000fffffffe00000UL
 
 struct saved_context saved_context;
 
@@ -140,4 +151,69 @@
 
 }
 
+static int __duplicate_page_tables(pgd_t *src_pgd, pgd_t *pgd, unsigned long map_offset)
+{
+	pud_t *src_pud, *pud;
+	pmd_t *src_pmd, *pmd;
+	pte_t *src_pte;
+	int i, j, k;
+
+	pr_debug("Duplicating pagetables for the map 0x%016lx at 0x%016lx\n",
+		map_offset, (unsigned long)src_pgd);
+	i = pgd_index(map_offset);
+	j = pud_index(map_offset);
+	k = pmd_index(map_offset);
+	src_pgd += i;
+	pgd += i;
+	for (; pgd_val(*src_pgd) && i < PTRS_PER_PGD; i++, src_pgd++, pgd++) {
+		pud = (pud_t *)get_usable_page(GFP_ATOMIC);
+		if (!pud)
+			return -ENOMEM;
+		pgd_val(*pgd) = (pgd_val(*src_pgd) & ~__PGTABLE_MASK) |
+			__pa((unsigned long)pud);
+		pud += j;
+		src_pud = (pud_t *)__va(pgd_val(*src_pgd) & __PGTABLE_MASK) + j;
+		for (; pud_val(*src_pud) && j < PTRS_PER_PUD; j++, src_pud++, pud++) {
+			pmd = (pmd_t *)get_usable_page(GFP_ATOMIC);
+			if (!pmd)
+				return -ENOMEM;
+			pud_val(*pud) = (pud_val(*src_pud) & ~__PGTABLE_MASK) |
+				__pa((unsigned long)pmd);
+			pmd += k;
+			src_pmd = (pmd_t *)__va(pud_val(*src_pud) & __PGTABLE_MASK) + k;
+			for (; pmd_val(*src_pmd) && k < PTRS_PER_PMD; k++, src_pmd++, pmd++)
+				if (pmd_val(*src_pmd) & _PAGE_PSE) /* 2MB page */
+					pmd_val(*pmd) = pmd_val(*src_pmd);
+				else { /* 4KB page table -> 2MB page */
+					src_pte = __va(pmd_val(*src_pmd) & __PGTABLE_MASK);
+					pmd_val(*pmd) = ((pmd_val(*src_pmd) & ~__PGTABLE_MASK) |
+						_PAGE_PSE) |
+						(pte_val(*src_pte) & __PGTABLE_PSE_MASK);
+				}
+			k = 0;
+		}
+		j = 0;
+	}
+	return 0;
+}
 
+void duplicate_page_tables(void)
+{
+	int result = 0;
+
+	temp_level4_pgt = (pgd_t *)get_usable_page(GFP_ATOMIC);
+
+	if (!temp_level4_pgt)
+		result = -ENOMEM;
+
+	if (!result)
+		result = __duplicate_page_tables(init_level4_pgt, temp_level4_pgt,
+				PAGE_OFFSET);
+
+	if (!result)
+		result = __duplicate_page_tables(init_level4_pgt, temp_level4_pgt,
+				__START_KERNEL_map);
+
+	if (result)
+		panic("No room for temporary page translation tables!\n");
+}
Index: linux-2.6.14-rc2-git3/kernel/power/swsusp.c
===================================================================
--- linux-2.6.14-rc2-git3.orig/kernel/power/swsusp.c	2005-09-23 18:20:41.000000000 +0200
+++ linux-2.6.14-rc2-git3/kernel/power/swsusp.c	2005-09-23 18:21:48.000000000 +0200
@@ -1092,7 +1092,7 @@
 	*eaten_memory = c;
 }
 
-static unsigned long get_usable_page(unsigned gfp_mask)
+unsigned long get_usable_page(unsigned gfp_mask)
 {
 	unsigned long m;
 
@@ -1478,11 +1478,12 @@
 	/* Allocate memory for the image and read the data from swap */
 
 	error = check_pagedir(pagedir_nosave);
-	free_eaten_memory();
+
 	if (!error)
 		error = data_read(pagedir_nosave);
 
 	if (error) { /* We fail cleanly */
+		free_eaten_memory();
 		for_each_pbe (p, pagedir_nosave)
 			if (p->address) {
 				free_page(p->address);
Index: linux-2.6.14-rc2-git3/arch/x86_64/kernel/suspend_asm.S
===================================================================
--- linux-2.6.14-rc2-git3.orig/arch/x86_64/kernel/suspend_asm.S	2005-09-23 18:20:41.000000000 +0200
+++ linux-2.6.14-rc2-git3/arch/x86_64/kernel/suspend_asm.S	2005-09-23 18:21:48.000000000 +0200
@@ -40,11 +40,14 @@
 	ret
 
 ENTRY(swsusp_arch_resume)
-	/* set up cr3 */	
-	leaq	init_level4_pgt(%rip),%rax
-	subq	$__START_KERNEL_map,%rax
-	movq	%rax,%cr3
+	call	duplicate_page_tables
 
+	/* switch to temporary page tables */
+	movq	$__PAGE_OFFSET, %rdx
+	movq	temp_level4_pgt(%rip), %rax
+	subq	%rdx, %rax
+	movq	%rax, %cr3
+	/* Flush TLB */
 	movq	mmu_cr4_features(%rip), %rax
 	movq	%rax, %rdx
 	andq	$~(1<<7), %rdx	# PGE
@@ -69,6 +72,10 @@
 	movq	pbe_next(%rdx), %rdx
 	jmp	loop
 done:
+	/* go back to the original page tables */
+	leaq	init_level4_pgt(%rip), %rax
+	subq	$__START_KERNEL_map, %rax
+	movq	%rax, %cr3
 	/* Flush TLB, including "global" things (vmalloc) */
 	movq	mmu_cr4_features(%rip), %rax
 	movq	%rax, %rdx


-- 
- Would you tell me, please, which way I ought to go from here?
- That depends a good deal on where you want to get to.
		-- Lewis Carroll "Alice's Adventures in Wonderland"

Re: [PATCH][Fix] Prevent swsusp from corrupting page translation tables during resume on x86-64

[Pavel Machek]

Hi!

> The following patch fixes Bug #4959.  It creates temporary page translation
> tables located in the page frames that are not overwritten by swsusp while copying
> the image.
> 
> The temporary page translation tables are generally based on the existing ones
> with the exception that the mappings using 4KB pages are replaced with the
> equivalent mappings that use 2MB pages only.  The temporary page tables are
> only used for copying the image.

Would not it be simpler to create them from scratch? mm/init.c has
some handy functions, they should be applicable. [init_memory_mapping,
phys_pud_init]. Perhaps even initialize only simple direct mapping,
and place virt_to_phys() at strategic places?
								Pavel

> +static int __duplicate_page_tables(pgd_t *src_pgd, pgd_t *pgd, unsigned long map_offset)
> +{
> +	pud_t *src_pud, *pud;
> +	pmd_t *src_pmd, *pmd;
> +	pte_t *src_pte;
> +	int i, j, k;
> +
> +	pr_debug("Duplicating pagetables for the map 0x%016lx at 0x%016lx\n",
> +		map_offset, (unsigned long)src_pgd);
> +	i = pgd_index(map_offset);
> +	j = pud_index(map_offset);
> +	k = pmd_index(map_offset);
> +	src_pgd += i;
> +	pgd += i;
> +	for (; pgd_val(*src_pgd) && i < PTRS_PER_PGD; i++, src_pgd++, pgd++) {
> +		pud = (pud_t *)get_usable_page(GFP_ATOMIC);
> +		if (!pud)
> +			return -ENOMEM;
> +		pgd_val(*pgd) = (pgd_val(*src_pgd) & ~__PGTABLE_MASK) |
> +			__pa((unsigned long)pud);
> +		pud += j;
> +		src_pud = (pud_t *)__va(pgd_val(*src_pgd) & __PGTABLE_MASK) + j;
> +		for (; pud_val(*src_pud) && j < PTRS_PER_PUD; j++, src_pud++, pud++) {
> +			pmd = (pmd_t *)get_usable_page(GFP_ATOMIC);
> +			if (!pmd)
> +				return -ENOMEM;
> +			pud_val(*pud) = (pud_val(*src_pud) & ~__PGTABLE_MASK) |
> +				__pa((unsigned long)pmd);
> +			pmd += k;
> +			src_pmd = (pmd_t *)__va(pud_val(*src_pud) & __PGTABLE_MASK) + k;
> +			for (; pmd_val(*src_pmd) && k < PTRS_PER_PMD; k++, src_pmd++, pmd++)
> +				if (pmd_val(*src_pmd) & _PAGE_PSE) /* 2MB page */
> +					pmd_val(*pmd) = pmd_val(*src_pmd);
> +				else { /* 4KB page table -> 2MB page */
> +					src_pte = __va(pmd_val(*src_pmd) & __PGTABLE_MASK);
> +					pmd_val(*pmd) = ((pmd_val(*src_pmd) & ~__PGTABLE_MASK) |
> +						_PAGE_PSE) |
> +						(pte_val(*src_pte) & __PGTABLE_PSE_MASK);
> +				}
> +			k = 0;
> +		}
> +		j = 0;
> +	}
> +	return 0;
> +}

-- 
if you have sharp zaurus hardware you don't need... you know my address

Re: [PATCH][Fix] Prevent swsusp from corrupting page translation tables during resume on x86-64

[Rafael J. Wysocki]

Hi,

On Monday, 26 of September 2005 00:07, Pavel Machek wrote:
> Hi!
> 
> > The following patch fixes Bug #4959.  It creates temporary page translation
> > tables located in the page frames that are not overwritten by swsusp while copying
> > the image.
> > 
> > The temporary page translation tables are generally based on the existing ones
> > with the exception that the mappings using 4KB pages are replaced with the
> > equivalent mappings that use 2MB pages only.  The temporary page tables are
> > only used for copying the image.
> 
> Would not it be simpler to create them from scratch? mm/init.c has
> some handy functions, they should be applicable. [init_memory_mapping,
> phys_pud_init]. Perhaps even initialize only simple direct mapping,
> and place virt_to_phys() at strategic places?

Perhaps, but the outcome would be very much the same.  The problem is to what
extent we can use the existing constructs, because I'd rather like to avoid the situation
in which any future changes to the initialization code would have to be replicated
in the swsusp code.  I'll have a look at that, but I'm not sure.  Also I don't really know
what the Andi's preferences are with this respect.

Anyway do you think that creating temporary page tables at the beginning of
swsusp_arch_resume() is a good idea?  If not, where do you think should they be
created?

Greetings,
Rafael

Re: [PATCH][Fix] Prevent swsusp from corrupting page translation tables during resume on x86-64

[Pavel Machek]

Hi!

> > > The following patch fixes Bug #4959.  It creates temporary page translation
> > > tables located in the page frames that are not overwritten by swsusp while copying
> > > the image.
> > > 
> > > The temporary page translation tables are generally based on the existing ones
> > > with the exception that the mappings using 4KB pages are replaced with the
> > > equivalent mappings that use 2MB pages only.  The temporary page tables are
> > > only used for copying the image.
> > 
> > Would not it be simpler to create them from scratch? mm/init.c has
> > some handy functions, they should be applicable. [init_memory_mapping,
> > phys_pud_init]. Perhaps even initialize only simple direct mapping,
> > and place virt_to_phys() at strategic places?
> 
> Perhaps, but the outcome would be very much the same.  The problem is to what
> extent we can use the existing constructs, because I'd rather like to avoid the situation
> in which any future changes to the initialization code would have to be replicated
> in the swsusp code.  I'll have a look at that, but I'm not sure.  Also I don't really know
> what the Andi's preferences are with this respect.
> 
> Anyway do you think that creating temporary page tables at the beginning of
> swsusp_arch_resume() is a good idea?  If not, where do you think should they be
> created?

For i386, I simply let bootup code create them, and create "backup
copy" that is not damaged by any page splits... Result is in
mm/init.c:


#ifdef CONFIG_SOFTWARE_SUSPEND
/*
 * Swap suspend & friends need this for resume because things like the
intel-agp
 * driver might have split up a kernel 4MB mapping.
 */
char __nosavedata swsusp_pg_dir[PAGE_SIZE]
        __attribute__ ((aligned (PAGE_SIZE)));

static inline void save_pg_dir(void)
{
        memcpy(swsusp_pg_dir, swapper_pg_dir, PAGE_SIZE);
}
#else
static inline void save_pg_dir(void)
{
}
#endif

It is probably not as simple for x86-64 case, but some bootup code
reusal still should be neccessary...
								Pavel
-- 
if you have sharp zaurus hardware you don't need... you know my address