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authorRafael J. Wysocki <rjw@sisk.pl>2005-10-09 15:19:40 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-10 11:36:46 -0400
commit3dd083255ddcfa87751fa8e32f61a9547a15a541 (patch)
tree9767ee9d882e57037d8423ea06205f6f0139bfea /arch/x86_64/kernel/suspend_asm.S
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>
Diffstat (limited to 'arch/x86_64/kernel/suspend_asm.S')
-rw-r--r--arch/x86_64/kernel/suspend_asm.S17
1 files changed, 11 insertions, 6 deletions
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)
39 call swsusp_save 39 call swsusp_save
40 ret 40 ret
41 41
42ENTRY(swsusp_arch_resume) 42ENTRY(restore_image)
43 /* set up cr3 */ 43 /* switch to temporary page tables */
44 leaq init_level4_pgt(%rip),%rax 44 movq $__PAGE_OFFSET, %rdx
45 subq $__START_KERNEL_map,%rax 45 movq temp_level4_pgt(%rip), %rax
46 movq %rax,%cr3 46 subq %rdx, %rax
47 47 movq %rax, %cr3
48 /* Flush TLB */
48 movq mmu_cr4_features(%rip), %rax 49 movq mmu_cr4_features(%rip), %rax
49 movq %rax, %rdx 50 movq %rax, %rdx
50 andq $~(1<<7), %rdx # PGE 51 andq $~(1<<7), %rdx # PGE
@@ -69,6 +70,10 @@ loop:
69 movq pbe_next(%rdx), %rdx 70 movq pbe_next(%rdx), %rdx
70 jmp loop 71 jmp loop
71done: 72done:
73 /* go back to the original page tables */
74 leaq init_level4_pgt(%rip), %rax
75 subq $__START_KERNEL_map, %rax
76 movq %rax, %cr3
72 /* Flush TLB, including "global" things (vmalloc) */ 77 /* Flush TLB, including "global" things (vmalloc) */
73 movq mmu_cr4_features(%rip), %rax 78 movq mmu_cr4_features(%rip), %rax
74 movq %rax, %rdx 79 movq %rax, %rdx