Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=6fb14755a676282a4e6caa05a08c92db8e45cfff
Commit:     6fb14755a676282a4e6caa05a08c92db8e45cfff
Parent:     d01ad8dd56527be72947b4b9997bb2c05783c3ed
Author:     Jan Beulich <[EMAIL PROTECTED]>
AuthorDate: Wed May 2 19:27:10 2007 +0200
Committer:  Andi Kleen <[EMAIL PROTECTED]>
CommitDate: Wed May 2 19:27:10 2007 +0200

    [PATCH] x86: tighten kernel image page access rights
    
    On x86-64, kernel memory freed after init can be entirely unmapped instead
    of just getting 'poisoned' by overwriting with a debug pattern.
    
    On i386 and x86-64 (under CONFIG_DEBUG_RODATA), kernel text and bug table
    can also be write-protected.
    
    Compared to the first version, this one prevents re-creating deleted
    mappings in the kernel image range on x86-64, if those got removed
    previously. This, together with the original changes, prevents temporarily
    having inconsistent mappings when cacheability attributes are being
    changed on such pages (e.g. from AGP code). While on i386 such duplicate
    mappings don't exist, the same change is done there, too, both for
    consistency and because checking pte_present() before using various other
    pte_XXX functions is a requirement anyway. At once, i386 code gets
    adjusted to use pte_huge() instead of open coding this.
    
    AK: split out cpa() changes
    
    Signed-off-by: Jan Beulich <[EMAIL PROTECTED]>
    Signed-off-by: Andi Kleen <[EMAIL PROTECTED]>
---
 arch/i386/kernel/vmlinux.lds.S   |    4 ++--
 arch/i386/mm/init.c              |   25 +++++++++++++++++++------
 arch/x86_64/kernel/head.S        |    1 -
 arch/x86_64/kernel/vmlinux.lds.S |    5 +++--
 arch/x86_64/mm/init.c            |   25 ++++++++++++++++---------
 include/linux/poison.h           |    3 ---
 6 files changed, 40 insertions(+), 23 deletions(-)

diff --git a/arch/i386/kernel/vmlinux.lds.S b/arch/i386/kernel/vmlinux.lds.S
index 6f38f81..f4ec722 100644
--- a/arch/i386/kernel/vmlinux.lds.S
+++ b/arch/i386/kernel/vmlinux.lds.S
@@ -61,8 +61,6 @@ SECTIONS
        __stop___ex_table = .;
   }
 
-  RODATA
-
   BUG_TABLE
 
   . = ALIGN(4);
@@ -72,6 +70,8 @@ SECTIONS
        __tracedata_end = .;
   }
 
+  RODATA
+
   /* writeable */
   . = ALIGN(4096);
   .data : AT(ADDR(.data) - LOAD_OFFSET) {      /* Data */
diff --git a/arch/i386/mm/init.c b/arch/i386/mm/init.c
index 23be1b0..bd5ef37 100644
--- a/arch/i386/mm/init.c
+++ b/arch/i386/mm/init.c
@@ -22,6 +22,7 @@
 #include <linux/init.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
+#include <linux/pfn.h>
 #include <linux/poison.h>
 #include <linux/bootmem.h>
 #include <linux/slab.h>
@@ -751,13 +752,25 @@ static int noinline do_test_wp_bit(void)
 
 void mark_rodata_ro(void)
 {
-       unsigned long addr = (unsigned long)__start_rodata;
+       unsigned long start = PFN_ALIGN(_text);
+       unsigned long size = PFN_ALIGN(_etext) - start;
 
-       for (; addr < (unsigned long)__end_rodata; addr += PAGE_SIZE)
-               change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RO);
+#ifdef CONFIG_HOTPLUG_CPU
+       /* It must still be possible to apply SMP alternatives. */
+       if (num_possible_cpus() <= 1)
+#endif
+       {
+               change_page_attr(virt_to_page(start),
+                                size >> PAGE_SHIFT, PAGE_KERNEL_RX);
+               printk("Write protecting the kernel text: %luk\n", size >> 10);
+       }
 
-       printk("Write protecting the kernel read-only data: %uk\n",
-                       (__end_rodata - __start_rodata) >> 10);
+       start += size;
+       size = (unsigned long)__end_rodata - start;
+       change_page_attr(virt_to_page(start),
+                        size >> PAGE_SHIFT, PAGE_KERNEL_RO);
+       printk("Write protecting the kernel read-only data: %luk\n",
+              size >> 10);
 
        /*
         * change_page_attr() requires a global_flush_tlb() call after it.
@@ -781,7 +794,7 @@ void free_init_pages(char *what, unsigned long begin, 
unsigned long end)
                __free_page(page);
                totalram_pages++;
        }
-       printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
+       printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
 }
 
 void free_initmem(void)
diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index 36aa98a..fd9fdfd 100644
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -280,7 +280,6 @@ early_idt_ripmsg:
 
 .balign PAGE_SIZE
 ENTRY(stext)
-ENTRY(_stext)
 
 #define NEXT_PAGE(name) \
        .balign PAGE_SIZE; \
diff --git a/arch/x86_64/kernel/vmlinux.lds.S b/arch/x86_64/kernel/vmlinux.lds.S
index 5176ecf..3bdeb88 100644
--- a/arch/x86_64/kernel/vmlinux.lds.S
+++ b/arch/x86_64/kernel/vmlinux.lds.S
@@ -29,6 +29,7 @@ SECTIONS
   .text :  AT(ADDR(.text) - LOAD_OFFSET) {
        /* First the code that has to be first for bootstrapping */
        *(.bootstrap.text)
+       _stext = .;
        /* Then all the functions that are "hot" in profiles, to group them
            onto the same hugetlb entry */
        #include "functionlist"
@@ -50,10 +51,10 @@ SECTIONS
   __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { *(__ex_table) }
   __stop___ex_table = .;
 
-  RODATA
-
   BUG_TABLE
 
+  RODATA
+
   . = ALIGN(PAGE_SIZE);        /* Align data segment to page size boundary */
                                /* Data */
   .data : AT(ADDR(.data) - LOAD_OFFSET) {
diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index 69e22d3..e3134bc 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -22,6 +22,7 @@
 #include <linux/bootmem.h>
 #include <linux/proc_fs.h>
 #include <linux/pci.h>
+#include <linux/pfn.h>
 #include <linux/poison.h>
 #include <linux/dma-mapping.h>
 #include <linux/module.h>
@@ -563,21 +564,23 @@ void free_init_pages(char *what, unsigned long begin, 
unsigned long end)
        if (begin >= end)
                return;
 
-       printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
+       printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
        for (addr = begin; addr < end; addr += PAGE_SIZE) {
                struct page *page = pfn_to_page(addr >> PAGE_SHIFT);
                ClearPageReserved(page);
                init_page_count(page);
                memset(page_address(page), POISON_FREE_INITMEM, PAGE_SIZE);
+               if (addr >= __START_KERNEL_map)
+                       change_page_attr_addr(addr, 1, __pgprot(0));
                __free_page(page);
                totalram_pages++;
        }
+       if (addr > __START_KERNEL_map)
+               global_flush_tlb();
 }
 
 void free_initmem(void)
 {
-       memset(__initdata_begin, POISON_FREE_INITDATA,
-               __initdata_end - __initdata_begin);
        free_init_pages("unused kernel memory",
                        __pa_symbol(&__init_begin),
                        __pa_symbol(&__init_end));
@@ -587,14 +590,18 @@ void free_initmem(void)
 
 void mark_rodata_ro(void)
 {
-       unsigned long addr = (unsigned long)__va(__pa_symbol(&__start_rodata));
-       unsigned long end  = (unsigned long)__va(__pa_symbol(&__end_rodata));
+       unsigned long start = PFN_ALIGN(__va(__pa_symbol(&_stext))), size;
 
-       for (; addr < end; addr += PAGE_SIZE)
-               change_page_attr_addr(addr, 1, PAGE_KERNEL_RO);
+#ifdef CONFIG_HOTPLUG_CPU
+       /* It must still be possible to apply SMP alternatives. */
+       if (num_possible_cpus() > 1)
+               start = PFN_ALIGN(__va(__pa_symbol(&_etext)));
+#endif
+       size = (unsigned long)__va(__pa_symbol(&__end_rodata)) - start;
+       change_page_attr_addr(start, size >> PAGE_SHIFT, PAGE_KERNEL_RO);
 
-       printk ("Write protecting the kernel read-only data: %luk\n",
-                       (__end_rodata - __start_rodata) >> 10);
+       printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
+              size >> 10);
 
        /*
         * change_page_attr_addr() requires a global_flush_tlb() call after it.
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 3e628f9..89580b7 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -26,9 +26,6 @@
 /********** arch/$ARCH/mm/init.c **********/
 #define POISON_FREE_INITMEM    0xcc
 
-/********** arch/x86_64/mm/init.c **********/
-#define        POISON_FREE_INITDATA    0xba
-
 /********** arch/ia64/hp/common/sba_iommu.c **********/
 /*
  * arch/ia64/hp/common/sba_iommu.c uses a 16-byte poison string with a
-
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