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Date: Wed, 17 Feb 2010 19:51:36 GMT
From: tip-bot for Siarhei Liakh <sliakh.lkml@...il.com>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, jmorris@...ei.org,
sliakh.lkml@...il.com, hpa@...or.com, mingo@...hat.com,
arjan@...ux.intel.com, jiang@...ncsu.edu, tglx@...utronix.de
Subject: [tip:x86/mm] x86, mm: NX protection for kernel data
Commit-ID: 01ab31371da90a795b774d87edf2c21bb3a64dda
Gitweb: http://git.kernel.org/tip/01ab31371da90a795b774d87edf2c21bb3a64dda
Author: Siarhei Liakh <sliakh.lkml@...il.com>
AuthorDate: Sun, 31 Jan 2010 18:27:55 -0500
Committer: H. Peter Anvin <hpa@...or.com>
CommitDate: Wed, 17 Feb 2010 10:11:24 -0800
x86, mm: 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 boundary
2. Linker script is adjusted so .rodata and .data always start and
end on a page boundary
3. void mark_nxdata_nx(void) added to arch/x86/mm/init.c with actual
functionality: NX is set for all pages from _etext through _end.
4. mark_nxdata_nx() called from free_initmem() (after init has been released)
5. free_init_pages() sets released memory NX in arch/x86/mm/init.c
V1: initial patch for 2.6.30
V2: patch for 2.6.31-rc7
V3: moved all code into arch/x86, adjusted credits
V4: fixed ifdef, removed credits from CREDITS
V5: fixed an address calculation bug in mark_nxdata_nx()
V6: updated for compatibility with 2.6.33-rc5
Signed-off-by: Siarhei Liakh <sliakh.lkml@...il.com>
Signed-off-by: Xuxian Jiang <jiang@...ncsu.edu>
Acked-by: Arjan van de Ven <arjan@...ux.intel.com>
Reviewed-by: James Morris <jmorris@...ei.org>
LKML-Reference: <817ecb6f1001311527w7914ab20sf15b800dcaa37df7@...l.gmail.com>
Signed-off-by: H. Peter Anvin <hpa@...or.com>
---
arch/x86/kernel/vmlinux.lds.S | 6 +++++-
arch/x86/mm/init.c | 21 ++++++++++++++++++++-
2 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index f92a0da..2cb7369 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -69,7 +69,7 @@ jiffies_64 = jiffies;
PHDRS {
text PT_LOAD FLAGS(5); /* R_E */
- data PT_LOAD FLAGS(7); /* RWE */
+ data PT_LOAD FLAGS(6); /* RW_ */
#ifdef CONFIG_X86_64
user PT_LOAD FLAGS(5); /* R_E */
#ifdef CONFIG_SMP
@@ -108,6 +108,8 @@ SECTIONS
IRQENTRY_TEXT
*(.fixup)
*(.gnu.warning)
+ /* .text should occupy whole number of pages */
+ . = ALIGN(PAGE_SIZE);
/* End of text section */
_etext = .;
} :text = 0x9090
@@ -143,6 +145,8 @@ SECTIONS
/* rarely changed data like cpu maps */
READ_MOSTLY_DATA(INTERNODE_CACHE_BYTES)
+ /* .data should occupy whole number of pages */
+ . = ALIGN(PAGE_SIZE);
/* End of data section */
_edata = .;
} :data
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index d406c52..d613d0a 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -356,9 +356,10 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
/*
* We just marked the kernel text read only above, now that
* we are going to free part of that, we need to make that
- * writeable first.
+ * writeable and non-executable first.
*/
set_memory_rw(begin, (end - begin) >> PAGE_SHIFT);
+ set_memory_nx(begin, (end - begin) >> PAGE_SHIFT);
printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
@@ -373,11 +374,29 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
#endif
}
+void mark_nxdata_nx(void)
+{
+#ifdef CONFIG_DEBUG_RODATA
+ /*
+ * When this called, init has already been executed and released,
+ * so everything past _etext sould be NX.
+ */
+ unsigned long start = PAGE_ALIGN((unsigned long)(&_etext));
+ unsigned long size = PAGE_ALIGN((unsigned long)(&_end)) - start;
+
+ printk(KERN_INFO "NX-protecting the kernel data: %lx, %lu pages\n",
+ start, size >> PAGE_SHIFT);
+ set_memory_nx(start, size >> PAGE_SHIFT);
+#endif
+}
+
void free_initmem(void)
{
free_init_pages("unused kernel memory",
(unsigned long)(&__init_begin),
(unsigned long)(&__init_end));
+ /* Set kernel's data as NX */
+ mark_nxdata_nx();
}
#ifdef CONFIG_BLK_DEV_INITRD
--
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