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Date: Tue, 15 Jan 2019 14:01:06 -0500
From: Ruslan Nikolaev <nruslan_devel@...oo.com>
To: kernel-hardening@...ts.openwall.com
Cc: thgarnie@...gle.com, x86@...nel.org, kstewart@...uxfoundation.org,
gregkh@...uxfoundation.org, keescook@...omium.org
Subject: [PATCH v1 04/06]: The PLT stub for PIC modules
The PLT stub for PIC modules
The patch is by Hassan Nadeem and Ruslan Nikolaev. This extends
the prior PIE kernel patch (by Thomas Garnier) to also support
position-independent modules that can be placed anywhere in the
48/64-bit address space (for better KASLR).
Signed-off-by: Ruslan Nikolaev <nruslan_devel@...oo.com>
---
Makefile | 3 ++-
module-plt-stub.S | 23 +++++++++++++++++++++++
2 files changed, 25 insertions(+), 1 deletion(-)
diff -uprN a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
--- a/arch/x86/kernel/Makefile 2019-01-15 11:20:45.271168382 -0500
+++ b/arch/x86/kernel/Makefile 2019-01-15 11:30:12.576999665 -0500
@@ -104,7 +104,8 @@ obj-$(CONFIG_KEXEC_CORE) += relocate_ker
obj-$(CONFIG_KEXEC_FILE) += kexec-bzimage64.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o
obj-y += kprobes/
-obj-$(CONFIG_MODULES) += module.o
+obj-$(CONFIG_MODULES) += module.o module-plt-stub.o
+OBJECT_FILES_NON_STANDARD_module-plt-stub.o := y
obj-$(CONFIG_DOUBLEFAULT) += doublefault.o
obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_VM86) += vm86_32.o
diff -uprN a/arch/x86/kernel/module-plt-stub.S
b/arch/x86/kernel/module-plt-stub.S
--- a/arch/x86/kernel/module-plt-stub.S 1969-12-31 19:00:00.000000000 -0500
+++ b/arch/x86/kernel/module-plt-stub.S 2019-01-15 11:30:12.580999706 -0500
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/stringify.h>
+#include <linux/linkage.h>
+#include <asm/dwarf2.h>
+#include <asm/cpufeatures.h>
+#include <asm/alternative-asm.h>
+#include <asm/export.h>
+#include <asm/nospec-branch.h>
+
+/* The following code is used for PLT generation only
+ and should never be executed directly. */
+.section .rodata
+.globl __THUNK_FOR_PLT
+.globl __THUNK_FOR_PLT_SIZE
+__THUNK_FOR_PLT:
+#ifdef CONFIG_RETPOLINE
+ movq 0(%rip), %rax
+ JMP_NOSPEC %rax
+#else
+ jmpq *0(%rip)
+#endif
+__THUNK_FOR_PLT_SIZE: .long . - __THUNK_FOR_PLT
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