Bug 679271

+++ This bug was initially created as a clone of Bug #679270 +++

Description of problem:
1) x86: Add NX protection for kernel data

This patch expands functionality of CONFIG_DEBUG_RODATA to set main (static) kernel data area as NX.
    
The following steps are taken to achieve this:  
     1. Linker script is adjusted so .text always starts and ends on a page bound
     2. Linker script is adjusted so .rodata always start and end on a page boundary
     3. NX is set for all pages from _etext through _end in mark_rodata_ro.
     4. free_init_pages() sets released memory NX in arch/x86/mm/init.c
     5. bios rom is set to x when pcibios is used.

http://git.kernel.org/linus/5bd5a452662bc37c54fb6828db1a3faf87e6511c

2) x86: Add RO/NX protection for loadable kernel modules

This patch is a logical extension of the protection provided by CONFIG_DEBUG_RODATA to LKMs. The protection is provided by splitting module_core and module_init into three logical parts each and setting appropriate page access permissions for each individual section:    
     1. Code: RO+X
     2. RO data: RO+NX
     3. RW data: RW+NX
    
In order to achieve proper protection, layout_sections() have been modified to align each of the three parts mentioned above onto page boundary. Next, the corresponding page access permissions are set right before successful exit from load_module(). Further, free_module() and sys_init_module have been modified to set module_core and module_init as RW+NX right before calling module_free().
    
By default, the original section layout and access flags are preserved. When compiled with CONFIG_DEBUG_SET_MODULE_RONX=y, the patch will page-align each group of sections to ensure that each page contains only one type of content and will enforce RO/NX for each group of pages.

http://git.kernel.org/linus/84e1c6bb38eb318e456558b610396d9f1afaabf0

3) x86: Fix jump label with RO/NX module protection crash
    
If we use jump table in module init, there are marked as removed in __jump_table section after init is done.
    
But we already applied ro permissions on the module, so we can't modify a read only section (crash in remove_jump_label_module_init).
    
Make the __jump_table section rw.

http://git.kernel.org/linus/8969691343354bdd80eff5405a0f879edbf013d6