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[RFC,v3,24/27] x86/mm: Make the x86 GOT read-only

Message ID 20171004212003.28296-25-thgarnie@google.com (mailing list archive)
State New, archived
Headers show

Commit Message

Thomas Garnier Oct. 4, 2017, 9:20 p.m. UTC 
The GOT is changed during early boot when relocations are applied. Make
it read-only directly. This table exists only for PIE binary.

Position Independent Executable (PIE) support will allow to extended the
KASLR randomization range below the -2G memory limit.

Signed-off-by: Thomas Garnier <thgarnie@google.com>
---
 include/asm-generic/vmlinux.lds.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)
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Patch

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e549bff87c5b..a2301c292e26 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -279,6 +279,17 @@ 
 	VMLINUX_SYMBOL(__end_ro_after_init) = .;
 #endif
 
+#ifdef CONFIG_X86_PIE
+#define RO_GOT_X86							\
+	.got        : AT(ADDR(.got) - LOAD_OFFSET) {			\
+		VMLINUX_SYMBOL(__start_got) = .;			\
+		*(.got);						\
+		VMLINUX_SYMBOL(__end_got) = .;				\
+	}
+#else
+#define RO_GOT_X86
+#endif
+
 /*
  * Read only Data
  */
@@ -335,6 +346,7 @@ 
 		VMLINUX_SYMBOL(__end_builtin_fw) = .;			\
 	}								\
 									\
+	RO_GOT_X86							\
 	TRACEDATA							\
 									\
 	/* Kernel symbol table: Normal symbols */			\