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authorRafael J. Wysocki <rjw@sisk.pl>2005-10-09 21:19:40 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-10 08:36:46 -0700
commit3dd083255ddcfa87751fa8e32f61a9547a15a541 (patch)
tree9767ee9d882e57037d8423ea06205f6f0139bfea
parent52a2d3e45e06012a662f627177729d3196ba8903 (diff)
[PATCH] x86_64: Set up safe page tables during resume
The following patch makes swsusp avoid the possible temporary corruption of page translation tables during resume on x86-64. This is achieved by creating a copy of the relevant page tables that will not be modified by swsusp and can be safely used by it on resume. The problem is that during resume on x86-64 swsusp may temporarily corrupt the page tables used for the direct mapping of RAM. If that happens, a page fault occurs and cannot be handled properly, which leads to the solid hang of the affected system. This leads to the loss of the system's state from before suspend and may result in the loss of data or the corruption of filesystems, so it is a serious issue. Also, it appears to happen quite often (for me, as often as 50% of the time). The problem is related to the fact that (at least) one of the PMD entries used in the direct memory mapping (starting at PAGE_OFFSET) points to a page table the physical address of which is much greater than the physical address of the PMD entry itself. Moreover, unfortunately, the physical address of the page table before suspend (i.e. the one stored in the suspend image) happens to be different to the physical address of the corresponding page table used during resume (i.e. the one that is valid right before swsusp_arch_resume() in arch/x86_64/kernel/suspend_asm.S is executed). Thus while the image is restored, the "offending" PMD entry gets overwritten, so it does not point to the right physical address any more (i.e. there's no page table at the address pointed to by it, because it points to the address the page table has been at during suspend). Consequently, if the PMD entry is used later on, and it _is_ used in the process of copying the image pages, a page fault occurs, but it cannot be handled in the normal way and the system hangs. In principle we can call create_resume_mapping() from swsusp_arch_resume() (ie. from suspend_asm.S), but then the memory allocations in create_resume_mapping(), resume_pud_mapping(), and resume_pmd_mapping() must be made carefully so that we use _only_ NosaveFree pages in them (the other pages are overwritten by the loop in swsusp_arch_resume()). Additionally, we are in atomic context at that time, so we cannot use GFP_KERNEL. Moreover, if one of the allocations fails, we should free all of the allocated pages, so we need to trace them somehow. All of this is done in the appended patch, except that the functions populating the page tables are located in arch/x86_64/kernel/suspend.c rather than in init.c. It may be done in a more elegan way in the future, with the help of some swsusp patches that are in the works now. [AK: move some externs into headers, renamed a function] Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/x86_64/kernel/suspend.c127
-rw-r--r--arch/x86_64/kernel/suspend_asm.S17
-rw-r--r--include/linux/suspend.h2
-rw-r--r--kernel/power/swsusp.c7
4 files changed, 144 insertions, 9 deletions
diff --git a/arch/x86_64/kernel/suspend.c b/arch/x86_64/kernel/suspend.c
index ebb9abf3ce6d..f066c6ab3618 100644
--- a/arch/x86_64/kernel/suspend.c
+++ b/arch/x86_64/kernel/suspend.c
@@ -11,6 +11,8 @@
#include <linux/smp.h>
#include <linux/suspend.h>
#include <asm/proto.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
struct saved_context saved_context;
@@ -140,4 +142,129 @@ void fix_processor_context(void)
}
+#ifdef CONFIG_SOFTWARE_SUSPEND
+/* Defined in arch/x86_64/kernel/suspend_asm.S */
+extern int restore_image(void);
+pgd_t *temp_level4_pgt;
+
+static void **pages;
+
+static inline void *__add_page(void)
+{
+ void **c;
+
+ c = (void **)get_usable_page(GFP_ATOMIC);
+ if (c) {
+ *c = pages;
+ pages = c;
+ }
+ return c;
+}
+
+static inline void *__next_page(void)
+{
+ void **c;
+
+ c = pages;
+ if (c) {
+ pages = *c;
+ *c = NULL;
+ }
+ return c;
+}
+
+/*
+ * Try to allocate as many usable pages as needed and daisy chain them.
+ * If one allocation fails, free the pages allocated so far
+ */
+static int alloc_usable_pages(unsigned long n)
+{
+ void *p;
+
+ pages = NULL;
+ do
+ if (!__add_page())
+ break;
+ while (--n);
+ if (n) {
+ p = __next_page();
+ while (p) {
+ free_page((unsigned long)p);
+ p = __next_page();
+ }
+ return -ENOMEM;
+ }
+ return 0;
+}
+
+static void res_phys_pud_init(pud_t *pud, unsigned long address, unsigned long end)
+{
+ long i, j;
+
+ i = pud_index(address);
+ pud = pud + i;
+ for (; i < PTRS_PER_PUD; pud++, i++) {
+ unsigned long paddr;
+ pmd_t *pmd;
+
+ paddr = address + i*PUD_SIZE;
+ if (paddr >= end)
+ break;
+
+ pmd = (pmd_t *)__next_page();
+ set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
+ for (j = 0; j < PTRS_PER_PMD; pmd++, j++, paddr += PMD_SIZE) {
+ unsigned long pe;
+
+ if (paddr >= end)
+ break;
+ pe = _PAGE_NX | _PAGE_PSE | _KERNPG_TABLE | paddr;
+ pe &= __supported_pte_mask;
+ set_pmd(pmd, __pmd(pe));
+ }
+ }
+}
+
+static void set_up_temporary_mappings(void)
+{
+ unsigned long start, end, next;
+
+ temp_level4_pgt = (pgd_t *)__next_page();
+
+ /* It is safe to reuse the original kernel mapping */
+ set_pgd(temp_level4_pgt + pgd_index(__START_KERNEL_map),
+ init_level4_pgt[pgd_index(__START_KERNEL_map)]);
+
+ /* Set up the direct mapping from scratch */
+ start = (unsigned long)pfn_to_kaddr(0);
+ end = (unsigned long)pfn_to_kaddr(end_pfn);
+
+ for (; start < end; start = next) {
+ pud_t *pud = (pud_t *)__next_page();
+ next = start + PGDIR_SIZE;
+ if (next > end)
+ next = end;
+ res_phys_pud_init(pud, __pa(start), __pa(next));
+ set_pgd(temp_level4_pgt + pgd_index(start),
+ mk_kernel_pgd(__pa(pud)));
+ }
+}
+
+int swsusp_arch_resume(void)
+{
+ unsigned long n;
+
+ n = ((end_pfn << PAGE_SHIFT) + PUD_SIZE - 1) >> PUD_SHIFT;
+ n += (n + PTRS_PER_PUD - 1) / PTRS_PER_PUD + 1;
+ pr_debug("swsusp_arch_resume(): pages needed = %lu\n", n);
+ if (alloc_usable_pages(n)) {
+ free_eaten_memory();
+ return -ENOMEM;
+ }
+ /* We have got enough memory and from now on we cannot recover */
+ set_up_temporary_mappings();
+ restore_image();
+ return 0;
+}
+#endif /* CONFIG_SOFTWARE_SUSPEND */
diff --git a/arch/x86_64/kernel/suspend_asm.S b/arch/x86_64/kernel/suspend_asm.S
index 4d659e97df10..320b6fb00cca 100644
--- a/arch/x86_64/kernel/suspend_asm.S
+++ b/arch/x86_64/kernel/suspend_asm.S
@@ -39,12 +39,13 @@ ENTRY(swsusp_arch_suspend)
call swsusp_save
ret
-ENTRY(swsusp_arch_resume)
- /* set up cr3 */
- leaq init_level4_pgt(%rip),%rax
- subq $__START_KERNEL_map,%rax
- movq %rax,%cr3
-
+ENTRY(restore_image)
+ /* 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 +70,10 @@ loop:
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
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index f2e96fdfaae0..ad15a54806d8 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -71,5 +71,7 @@ void restore_processor_state(void);
struct saved_context;
void __save_processor_state(struct saved_context *ctxt);
void __restore_processor_state(struct saved_context *ctxt);
+extern unsigned long get_usable_page(unsigned gfp_mask);
+extern void free_eaten_memory(void);
#endif /* _LINUX_SWSUSP_H */
diff --git a/kernel/power/swsusp.c b/kernel/power/swsusp.c
index acf79ac1cb6d..2d5c45676442 100644
--- a/kernel/power/swsusp.c
+++ b/kernel/power/swsusp.c
@@ -1095,7 +1095,7 @@ static inline void eat_page(void *page)
*eaten_memory = c;
}
-static unsigned long get_usable_page(unsigned gfp_mask)
+unsigned long get_usable_page(unsigned gfp_mask)
{
unsigned long m;
@@ -1109,7 +1109,7 @@ static unsigned long get_usable_page(unsigned gfp_mask)
return m;
}
-static void free_eaten_memory(void)
+void free_eaten_memory(void)
{
unsigned long m;
void **c;
@@ -1481,11 +1481,12 @@ static int read_suspend_image(void)
/* 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);

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