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Subject[PATCH CPA] [2/28] CPA: Do a simple self test at boot
Date

When CONFIG_DEBUG_RODATA is enabled undo the ro mapping and redo it again.
This gives some simple testing for change_page_attr()

Optional patch, but I find it useful.

Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/x86/Kconfig.debug | 5 +++++
arch/x86/mm/init_32.c | 22 ++++++++++++++++++++++
arch/x86/mm/init_64.c | 10 ++++++++++
3 files changed, 37 insertions(+)

Index: linux/arch/x86/mm/init_64.c
===================================================================
--- linux.orig/arch/x86/mm/init_64.c
+++ linux/arch/x86/mm/init_64.c
@@ -596,6 +596,16 @@ void mark_rodata_ro(void)
* of who is the culprit.
*/
global_flush_tlb();
+
+#ifdef CONFIG_CPA_DEBUG
+ printk("Testing CPA: undo %lx-%lx\n", start, end);
+ change_page_attr_addr(start, (end - start) >> PAGE_SHIFT, PAGE_KERNEL);
+ global_flush_tlb();
+
+ printk("Testing CPA: again\n");
+ change_page_attr_addr(start, (end - start) >> PAGE_SHIFT, PAGE_KERNEL_RO);
+ global_flush_tlb();
+#endif
}
#endif

Index: linux/arch/x86/mm/init_32.c
===================================================================
--- linux.orig/arch/x86/mm/init_32.c
+++ linux/arch/x86/mm/init_32.c
@@ -792,6 +792,18 @@ void mark_rodata_ro(void)
change_page_attr(virt_to_page(start),
size >> PAGE_SHIFT, PAGE_KERNEL_RX);
printk("Write protecting the kernel text: %luk\n", size >> 10);
+
+#ifdef CONFIG_CPA_DEBUG
+ global_flush_tlb();
+
+ printk("Testing CPA: undo %lx-%lx\n", start, start+size);
+ change_page_attr(virt_to_page(start), size>>PAGE_SHIFT, PAGE_KERNEL_EXEC);
+ global_flush_tlb();
+
+ printk("Testing CPA: write protecting again\n");
+ change_page_attr(virt_to_page(start),size>>PAGE_SHIFT,PAGE_KERNEL_RX);
+ global_flush_tlb();
+#endif
}
#endif
start += size;
@@ -808,6 +820,16 @@ void mark_rodata_ro(void)
* of who is the culprit.
*/
global_flush_tlb();
+
+#ifdef CONFIG_CPA_DEBUG
+ printk("Testing CPA: undo %lx-%lx\n", start, start + size);
+ change_page_attr(virt_to_page(start), size >> PAGE_SHIFT, PAGE_KERNEL);
+ global_flush_tlb();
+
+ printk("Testing CPA: write protecting again\n");
+ change_page_attr(virt_to_page(start), size >> PAGE_SHIFT, PAGE_KERNEL_RO);
+ global_flush_tlb();
+#endif
}
#endif

Index: linux/arch/x86/Kconfig.debug
===================================================================
--- linux.orig/arch/x86/Kconfig.debug
+++ linux/arch/x86/Kconfig.debug
@@ -185,4 +185,9 @@ config DEFAULT_IO_DELAY_TYPE
default IO_DELAY_TYPE_NONE
endif

+config CPA_DEBUG
+ bool "CPA self test code"
+ help
+ Do change_page_attr self tests at boot.
+
endmenu

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