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-rw-r--r--arch/x86/entry/entry.S21
1 files changed, 21 insertions, 0 deletions
diff --git a/arch/x86/entry/entry.S b/arch/x86/entry/entry.S
index d9feadffa972..b7ea3e8e9ecc 100644
--- a/arch/x86/entry/entry.S
+++ b/arch/x86/entry/entry.S
@@ -9,6 +9,8 @@
#include <asm/unwind_hints.h>
#include <asm/segment.h>
#include <asm/cache.h>
+#include <asm/cpufeatures.h>
+#include <asm/nospec-branch.h>
#include "calling.h"
@@ -19,6 +21,9 @@ SYM_FUNC_START(entry_ibpb)
movl $PRED_CMD_IBPB, %eax
xorl %edx, %edx
wrmsr
+
+ /* Make sure IBPB clears return stack preductions too. */
+ FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_BUG_IBPB_NO_RET
RET
SYM_FUNC_END(entry_ibpb)
/* For KVM */
@@ -46,3 +51,19 @@ EXPORT_SYMBOL_GPL(mds_verw_sel);
.popsection
THUNK warn_thunk_thunk, __warn_thunk
+
+#ifndef CONFIG_X86_64
+/*
+ * Clang's implementation of TLS stack cookies requires the variable in
+ * question to be a TLS variable. If the variable happens to be defined as an
+ * ordinary variable with external linkage in the same compilation unit (which
+ * amounts to the whole of vmlinux with LTO enabled), Clang will drop the
+ * segment register prefix from the references, resulting in broken code. Work
+ * around this by avoiding the symbol used in -mstack-protector-guard-symbol=
+ * entirely in the C code, and use an alias emitted by the linker script
+ * instead.
+ */
+#ifdef CONFIG_STACKPROTECTOR
+EXPORT_SYMBOL(__ref_stack_chk_guard);
+#endif
+#endif