android_kernel_xiaomi_sm8350/arch
Gerald Schaefer c1821c2e97 [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>
2007-02-05 21:18:17 +01:00
..
alpha [PATCH] missing exports of pm_power_off() on alpha and sparc32 2007-01-30 08:39:20 -08:00
arm [ARM] 4117/1: S3C2412: Fix writel() usage in selection code 2007-01-29 10:09:17 +00:00
arm26
avr32 [AVR32] Update ATSTK1000 defconfig: Enable macb by default 2007-01-26 13:19:48 +01:00
cris [PATCH] Change cpu_up and co from __devinit to __cpuinit 2007-01-11 18:18:20 -08:00
frv
h8300
i386 [PATCH] EFI x86: pass firmware call parameters on the stack 2007-02-04 10:27:10 -08:00
ia64 [PATCH] Altix: more ACPI PRT support 2007-02-03 11:26:06 -08:00
m32r [PATCH] Change cpu_up and co from __devinit to __cpuinit 2007-01-11 18:18:20 -08:00
m68k
m68knommu
mips [MIPS] Fix typo of "CONFIG_MT_SMP". 2007-01-30 12:10:48 +00:00
parisc [PATCH] Change cpu_up and co from __devinit to __cpuinit 2007-01-11 18:18:20 -08:00
powerpc Merge branch 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc 2007-01-28 12:45:22 -08:00
ppc Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 2007-01-18 10:34:51 +11:00
s390 [S390] noexec protection 2007-02-05 21:18:17 +01:00
sh
sh64
sparc [PATCH] sanitize sections for sparc32 smp 2007-02-01 16:17:06 -08:00
sparc64 [SPARC64]: Set g4/g5 properly in sun4v dtlb-prot handling. 2007-01-26 18:56:01 -08:00
um [PATCH] uml: fix signal frame alignment 2007-01-30 16:01:35 -08:00
v850
x86_64 [PATCH] x86_64 ia32 vDSO: define arch_vma_name 2007-01-26 13:50:58 -08:00
xtensa