kernel.git/include/asm-s390/pgtable.h, branch linux-2.6.21.y

[S390] noexec protection

2007-02-05T20:18:17Z

This provides a noexec protection on s390 hardware. Our hardware does not have any bits left in the pte for a hw noexec bit, so this is a different approach using shadow page tables and a special addressing mode that allows separate address spaces for code and data. As a special feature of our "secondary-space" addressing mode, separate page tables can be specified for the translation of data addresses (storage operands) and instruction addresses. The shadow page table is used for the instruction addresses and the standard page table for the data addresses. The shadow page table is linked to the standard page table by a pointer in page->lru.next of the struct page corresponding to the page that contains the standard page table (since page->private is not really private with the pte_lock and the page table pages are not in the LRU list). Depending on the software bits of a pte, it is either inserted into both page tables or just into the standard (data) page table. Pages of a vma that does not have the VM_EXEC bit set get mapped only in the data address space. Any try to execute code on such a page will cause a page translation exception. The standard reaction to this is a SIGSEGV with two exceptions: the two system call opcodes 0x0a77 (sys_sigreturn) and 0x0aad (sys_rt_sigreturn) are allowed. They are stored by the kernel to the signal stack frame. Unfortunately, the signal return mechanism cannot be modified to use an SA_RESTORER because the exception unwinding code depends on the system call opcode stored behind the signal stack frame. This feature requires that user space is executed in secondary-space mode and the kernel in home-space mode, which means that the addressing modes need to be switched and that the noexec protection only works for user space. After switching the addressing modes, we cannot use the mvcp/mvcs instructions anymore to copy between kernel and user space. A new mvcos instruction has been added to the z9 EC/BC hardware which allows to copy between arbitrary address spaces, but on older hardware the page tables need to be walked manually. Signed-off-by: Gerald Schaefer Signed-off-by: Martin Schwidefsky

[S390] Get rid of a lot of sparse warnings.

2007-02-05T20:16:47Z

Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

[S390] Virtual memmap for s390.

2006-12-08T14:56:07Z

Virtual memmap support for s390. Inspired by the ia64 implementation. Unlike ia64 we need a mechanism which allows us to dynamically attach shared memory regions. These memory regions are accessed via the dcss device driver. dcss implements the 'direct_access' operation, which requires struct pages for every single shared page. Therefore this implementation provides an interface to attach/detach shared memory: int add_shared_memory(unsigned long start, unsigned long size); int remove_shared_memory(unsigned long start, unsigned long size); The purpose of the add_shared_memory function is to add the given memory range to the 1:1 mapping and to make sure that the corresponding range in the vmemmap is backed with physical pages. It also initialises the new struct pages. remove_shared_memory in turn only invalidates the page table entries in the 1:1 mapping. The page tables and the memory used for struct pages in the vmemmap are currently not freed. They will be reused when the next segment will be attached. Given that the maximum size of a shared memory region is 2GB and in addition all regions must reside below 2GB this is not too much of a restriction, but there is room for improvement. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

[S390] Memory detection fixes.

2006-12-04T14:40:56Z

VMALLOC_END on 31bit should be 0x8000000UL instead of 0x7fffffffL. The page mask which is used to make sure memory_end is on 4MB/2MB boundary is wrong and not needed. Therefore remove it. Make sure a vmalloc area does also exist and work on (future) machines with 4TB and more memory. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

[S390] Fix pte type checking.

2006-10-18T16:30:51Z

handle_pte_fault uses pte_present, pte_none and pte_file to find out the type of a pte. That is done without holding the page table lock. This clashes with the way how ptep_clear_flush removes active page table entries from the system. First the ipte instruction is used to invalidate the pte and remove all plt entries for the page. The ipte sets the hardware invalid bit without changing any other bit. After the ipte finished the pte is cleared. A concurrent fault can observe the the previously valid pte with the invalid bit set. With the current encoding of the different pte types an invalidated read-only pte can be misinterpreted as a swap-pte. Signed-off-by: Martin Schwidefsky

[S390] Remove open-coded mem_map usage.

2006-10-04T18:02:23Z

Use page_to_phys and pfn_to_page to avoid open-coded mem_map usage. Signed-off-by: Heiko Carstens

[PATCH] convert s390 page handling macros to functions

2006-09-29T16:18:03Z

Convert s390 page handling macros to functions. In particular this fixes a problem with s390's SetPageUptodate macro which uses its input parameter twice which again can cause subtle bugs. [akpm@osdl.org: build fix] Cc: Martin Schwidefsky Signed-off-by: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[S390] Inline assembly cleanup.

2006-09-28T14:56:43Z

Major cleanup of all s390 inline assemblies. They now have a common coding style. Quite a few have been shortened, mainly by using register asm variables. Use of the EX_TABLE macro helps as well. The atomic ops, bit ops and locking inlines new use the Q-constraint if a newer gcc is used. That results in slightly better code. Thanks to Christian Borntraeger for proof reading the changes. Signed-off-by: Martin Schwidefsky

[PATCH] Standardize pxx_page macros

2006-09-26T15:48:51Z

One of the changes necessary for shared page tables is to standardize the pxx_page macros. pte_page and pmd_page have always returned the struct page associated with their entry, while pte_page_kernel and pmd_page_kernel have returned the kernel virtual address. pud_page and pgd_page, on the other hand, return the kernel virtual address. Shared page tables needs pud_page and pgd_page to return the actual page structures. There are very few actual users of these functions, so it is simple to standardize their usage. Since this is basic cleanup, I am submitting these changes as a standalone patch. Per Hugh Dickins' comments about it, I am also changing the pxx_page_kernel macros to pxx_page_vaddr to clarify their meaning. Signed-off-by: Dave McCracken Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[S390] Cleanup in page table related code.

2006-09-20T13:59:37Z

Changed and simplified some page table related #defines and code. Signed-off-by: Gerald Schaefer Signed-off-by: Martin Schwidefsky