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authorGerald Schaefer <geraldsc@de.ibm.com>2007-02-05 21:18:17 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2007-02-05 21:18:17 +0100
commitc1821c2e9711adc3cd298a16b7237c92a2cee78d (patch)
tree9155b089db35a37d95863125ea4c5f918bd7801b /arch/s390/kernel/compat_linux.h
parent86aa9fc2456d8a662f299a70bdb70987209170f0 (diff)
[S390] noexec protection
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 <geraldsc@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/compat_linux.h')
-rw-r--r--arch/s390/kernel/compat_linux.h31
1 files changed, 0 insertions, 31 deletions
diff --git a/arch/s390/kernel/compat_linux.h b/arch/s390/kernel/compat_linux.h
index 1a18e29668ef..e89f8c0c42a0 100644
--- a/arch/s390/kernel/compat_linux.h
+++ b/arch/s390/kernel/compat_linux.h
@@ -115,37 +115,6 @@ typedef struct
__u32 addr;
} _psw_t32 __attribute__ ((aligned(8)));
-#define PSW32_MASK_PER 0x40000000UL
-#define PSW32_MASK_DAT 0x04000000UL
-#define PSW32_MASK_IO 0x02000000UL
-#define PSW32_MASK_EXT 0x01000000UL
-#define PSW32_MASK_KEY 0x00F00000UL
-#define PSW32_MASK_MCHECK 0x00040000UL
-#define PSW32_MASK_WAIT 0x00020000UL
-#define PSW32_MASK_PSTATE 0x00010000UL
-#define PSW32_MASK_ASC 0x0000C000UL
-#define PSW32_MASK_CC 0x00003000UL
-#define PSW32_MASK_PM 0x00000f00UL
-
-#define PSW32_ADDR_AMODE31 0x80000000UL
-#define PSW32_ADDR_INSN 0x7FFFFFFFUL
-
-#define PSW32_BASE_BITS 0x00080000UL
-
-#define PSW32_ASC_PRIMARY 0x00000000UL
-#define PSW32_ASC_ACCREG 0x00004000UL
-#define PSW32_ASC_SECONDARY 0x00008000UL
-#define PSW32_ASC_HOME 0x0000C000UL
-
-#define PSW32_USER_BITS (PSW32_BASE_BITS | PSW32_MASK_DAT | PSW32_ASC_HOME | \
- PSW32_MASK_IO | PSW32_MASK_EXT | PSW32_MASK_MCHECK | \
- PSW32_MASK_PSTATE)
-
-#define PSW32_MASK_MERGE(CURRENT,NEW) \
- (((CURRENT) & ~(PSW32_MASK_CC|PSW32_MASK_PM)) | \
- ((NEW) & (PSW32_MASK_CC|PSW32_MASK_PM)))
-
-
typedef struct
{
_psw_t32 psw;