Move xen patchset to new version's subdir.

[ipfire-2.x.git] / src / patches / suse-2.6.27.31 / patches.suse / x86-mark_rodata_rw.patch

From: Nick Piggin <npiggin@novell.com>
Subject: Add mark_rodata_rw() to un-protect read-only kernel code pages
References: bnc#439348

CONFIG_RODATA presents a problem for antivirus vendors who do not have a
clean user-space interface for getting virus scanning triggered, and
currently resort to patching the kernel code instead (presumably the
ystem call table). With CONFIG_RODATA enabled, the kernel rejects such
write accesses.

Add a new mark_rodata_rw() function to un-protect the read-only kernel code
pages for now, and export mark_rodata_ro() and mark_rodata_rw() to modules.

This is not meant as a permanent workaround, and will be removed again in the
next release!

Acked-by: Andres Gruenbacher <agruen@suse.de>

---
 arch/x86/mm/init_32.c        |   22 ++++++++++++++++++++++
 arch/x86/mm/init_64.c        |   17 +++++++++++++++++
 arch/x86/mm/pageattr.c       |   30 ++++++++++++++++++++++++++++--
 include/asm-x86/cacheflush.h |    3 +++
 4 files changed, 70 insertions(+), 2 deletions(-)

--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -1073,6 +1073,28 @@ void mark_rodata_ro(void)
 	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
 #endif
 }
+EXPORT_SYMBOL(mark_rodata_ro);
+
+void mark_rodata_rw(void)
+{
+	unsigned long start = PFN_ALIGN(_text);
+	unsigned long size = PFN_ALIGN(_etext) - start;
+
+#ifndef CONFIG_DYNAMIC_FTRACE
+	/* Dynamic tracing modifies the kernel text section */
+	set_pages_rw_force(virt_to_page(start), size >> PAGE_SHIFT);
+	printk(KERN_INFO "Write enabling the kernel text: %luk\n",
+		size >> 10);
+
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+	start += size;
+	size = (unsigned long)__end_rodata - start;
+	set_pages_rw_force(virt_to_page(start), size >> PAGE_SHIFT);
+	printk(KERN_INFO "Write enabling the kernel read-only data: %luk\n",
+		size >> 10);
+}
+EXPORT_SYMBOL(mark_rodata_rw);
 #endif
 
 void free_init_pages(char *what, unsigned long begin, unsigned long end)
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -896,7 +896,24 @@ void mark_rodata_ro(void)
 	set_memory_ro(start, (end-start) >> PAGE_SHIFT);
 #endif
 }
+EXPORT_SYMBOL(mark_rodata_ro);
 
+void mark_rodata_rw(void)
+{
+	unsigned long start = PFN_ALIGN(_stext), end = PFN_ALIGN(__end_rodata);
+	unsigned long rodata_start =
+		((unsigned long)__start_rodata + PAGE_SIZE - 1) & PAGE_MASK;
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+	/* Dynamic tracing modifies the kernel text section */
+	start = rodata_start;
+#endif
+
+	printk(KERN_INFO "Write enabling the kernel read-only data: %luk\n",
+	       (end - start) >> 10);
+	set_memory_rw_force(start, (end - start) >> PAGE_SHIFT);
+}
+EXPORT_SYMBOL(mark_rodata_rw);
 #endif
 
 #ifdef CONFIG_BLK_DEV_INITRD
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -190,6 +190,8 @@ static void cpa_flush_range(unsigned lon
 	}
 }
 
+static int static_protections_allow_rodata __read_mostly;
+
 /*
  * Certain areas of memory on x86 require very specific protection flags,
  * for example the BIOS area or kernel text. Callers don't always get this
@@ -221,8 +223,10 @@ static inline pgprot_t static_protection
 	 * catches all aliases.
 	 */
 	if (within(pfn, __pa((unsigned long)__start_rodata) >> PAGE_SHIFT,
-		   __pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
-		pgprot_val(forbidden) |= _PAGE_RW;
+		   __pa((unsigned long)__end_rodata) >> PAGE_SHIFT)) {
+		if (!static_protections_allow_rodata)
+			pgprot_val(forbidden) |= _PAGE_RW;
+	}
 
 	prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
 
@@ -956,6 +960,21 @@ int set_memory_rw(unsigned long addr, in
 	return change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
 }
 
+/* hack: bypass kernel rodata section static_protections check. */
+int set_memory_rw_force(unsigned long addr, int numpages)
+{
+	static DEFINE_MUTEX(lock);
+	int ret;
+
+	mutex_lock(&lock);
+	static_protections_allow_rodata = 1;
+	ret = change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
+	static_protections_allow_rodata = 0;
+	mutex_unlock(&lock);
+
+	return ret;
+}
+
 int set_memory_np(unsigned long addr, int numpages)
 {
 	return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_PRESENT));
@@ -1013,6 +1032,13 @@ int set_pages_rw(struct page *page, int
 	return set_memory_rw(addr, numpages);
 }
 
+int set_pages_rw_force(struct page *page, int numpages)
+{
+	unsigned long addr = (unsigned long)page_address(page);
+
+	return set_memory_rw_force(addr, numpages);
+}
+
 #ifdef CONFIG_DEBUG_PAGEALLOC
 
 static int __set_pages_p(struct page *page, int numpages)
--- a/include/asm-x86/cacheflush.h
+++ b/include/asm-x86/cacheflush.h
@@ -63,6 +63,7 @@ int set_memory_x(unsigned long addr, int
 int set_memory_nx(unsigned long addr, int numpages);
 int set_memory_ro(unsigned long addr, int numpages);
 int set_memory_rw(unsigned long addr, int numpages);
+int set_memory_rw_force(unsigned long addr, int numpages);
 int set_memory_np(unsigned long addr, int numpages);
 int set_memory_4k(unsigned long addr, int numpages);
 
@@ -92,6 +93,7 @@ int set_pages_x(struct page *page, int n
 int set_pages_nx(struct page *page, int numpages);
 int set_pages_ro(struct page *page, int numpages);
 int set_pages_rw(struct page *page, int numpages);
+int set_pages_rw_force(struct page *page, int numpages);
 
 
 void clflush_cache_range(void *addr, unsigned int size);
@@ -100,6 +102,7 @@ void cpa_init(void);
 
 #ifdef CONFIG_DEBUG_RODATA
 void mark_rodata_ro(void);
+void mark_rodata_rw(void);
 extern const int rodata_test_data;
 #endif