6 files changed, 45 insertions, 6 deletions

diff --git a/arch/x86_64/Kconfig.debug b/arch/x86_64/Kconfig.debug
index e2c6e64a85ec..fcb06a50fdd2 100644
--- a/arch/x86_64/Kconfig.debug
+++ b/arch/x86_64/Kconfig.debug
@@ -9,6 +9,16 @@ config INIT_DEBUG
           Fill __init and __initdata at the end of boot. This helps debugging
           illegal uses of __init and __initdata after initialization.
 
+config DEBUG_RODATA
+       bool "Write protect kernel read-only data structures"
+       depends on DEBUG_KERNEL
+       help
+         Mark the kernel read-only data as write-protected in the pagetables,
+         in order to catch accidental (and incorrect) writes to such const data.
+         This option may have a slight performance impact because a portion
+         of the kernel code won't be covered by a 2MB TLB anymore.
+         If in doubt, say "N".
+
 config IOMMU_DEBUG
        depends on GART_IOMMU && DEBUG_KERNEL
        bool "Enable IOMMU debugging"
diff --git a/arch/x86_64/ia32/ia32entry.S b/arch/x86_64/ia32/ia32entry.S
index e0eb0c712fe9..df0773c9bdbe 100644
--- a/arch/x86_64/ia32/ia32entry.S
+++ b/arch/x86_64/ia32/ia32entry.S
@@ -341,7 +341,7 @@ ENTRY(ia32_ptregs_common)
         jmp  ia32_sysret        /* misbalances the return cache */
         CFI_ENDPROC
 
-        .data
+        .section .rodata,"a"
         .align 8
         .globl ia32_sys_call_table
 ia32_sys_call_table:
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c
index 7519fc520eb3..3060ed97b755 100644
--- a/arch/x86_64/kernel/process.c
+++ b/arch/x86_64/kernel/process.c
@@ -157,7 +157,7 @@ EXPORT_SYMBOL_GPL(cpu_idle_wait);
 DECLARE_PER_CPU(int, cpu_state);
 
 #include <asm/nmi.h>
-/* We don't actually take CPU down, just spin without interrupts. */
+/* We halt the CPU with physical CPU hotplug */
 static inline void play_dead(void)
 {
         idle_task_exit();
@@ -166,8 +166,9 @@ static inline void play_dead(void)
         /* Ack it */
         __get_cpu_var(cpu_state) = CPU_DEAD;
 
+        local_irq_disable();
         while (1)
-                safe_halt();
+                halt();
 }
 #else
 static inline void play_dead(void)
diff --git a/arch/x86_64/kernel/syscall.c b/arch/x86_64/kernel/syscall.c
index e263685f864c..7c176b3edde0 100644
--- a/arch/x86_64/kernel/syscall.c
+++ b/arch/x86_64/kernel/syscall.c
@@ -19,7 +19,7 @@ typedef void (*sys_call_ptr_t)(void);
 
 extern void sys_ni_syscall(void);
 
-sys_call_ptr_t sys_call_table[__NR_syscall_max+1] __cacheline_aligned = { 
+const sys_call_ptr_t sys_call_table[__NR_syscall_max+1] = {
         /* Smells like a like a compiler bug -- it doesn't work when the & below is removed. */ 
         [0 ... __NR_syscall_max] = &sys_ni_syscall,
 #include <asm-x86_64/unistd.h>
diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index c016dfe84784..1faae5fc1c01 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -498,6 +498,29 @@ void free_initmem(void)
         printk ("Freeing unused kernel memory: %luk freed\n", (__init_end - __init_begin) >> 10);
 }
 
+#ifdef CONFIG_DEBUG_RODATA
+
+extern char __start_rodata, __end_rodata;
+void mark_rodata_ro(void)
+{
+        unsigned long addr = (unsigned long)&__start_rodata;
+
+        for (; addr < (unsigned long)&__end_rodata; addr += PAGE_SIZE)
+                change_page_attr_addr(addr, 1, PAGE_KERNEL_RO);
+
+        printk ("Write protecting the kernel read-only data: %luk\n",
+                        (&__end_rodata - &__start_rodata) >> 10);
+
+        /*
+         * change_page_attr_addr() requires a global_flush_tlb() call after it.
+         * We do this after the printk so that if something went wrong in the
+         * change, the printk gets out at least to give a better debug hint
+         * of who is the culprit.
+         */
+        global_flush_tlb();
+}
+#endif
+
 #ifdef CONFIG_BLK_DEV_INITRD
 void free_initrd_mem(unsigned long start, unsigned long end)
 {
diff --git a/arch/x86_64/mm/pageattr.c b/arch/x86_64/mm/pageattr.c
index b90e8fe9eeb0..35f1f1aab063 100644
--- a/arch/x86_64/mm/pageattr.c
+++ b/arch/x86_64/mm/pageattr.c
@@ -128,6 +128,7 @@ __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
         pte_t *kpte; 
         struct page *kpte_page;
         unsigned kpte_flags;
+        pgprot_t ref_prot2;
         kpte = lookup_address(address);
         if (!kpte) return 0;
         kpte_page = virt_to_page(((unsigned long)kpte) & PAGE_MASK);
@@ -140,10 +141,14 @@ __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
                          * split_large_page will take the reference for this change_page_attr
                          * on the split page.
                          */
-                        struct page *split = split_large_page(address, prot, ref_prot); 
+
+                        struct page *split;
+                        ref_prot2 = __pgprot(pgprot_val(pte_pgprot(*lookup_address(address))) & ~(1<<_PAGE_BIT_PSE));
+
+                        split = split_large_page(address, prot, ref_prot2);
                         if (!split)
                                 return -ENOMEM;
-                        set_pte(kpte,mk_pte(split, ref_prot));
+                        set_pte(kpte,mk_pte(split, ref_prot2));
                         kpte_page = split;
                 }       
                 get_page(kpte_page);