[PATCH v8 7/7] [DO NOT MERGE] x86/kexec: Add CFI type information to relocate_kernel()

[David Woodhouse]

From: David Woodhouse <dwmw@xxxxxxxxxxxx>

A previous commit added __nocfi to machine_kexec() because it makes an
indirect call to relocate_kernel() which lacked CFI type information,
and caused the system to crash.

Use SYM_TYPED_FUNC_START() to ensure that the type information is
present, and remove the __nocfi tag.

I still can't make objtool happy with this in both GCC and Clang builds
at the same time, so not yet for merging; only included in this series
to nerd-snipe the objtool maintainers.

Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
 arch/x86/kernel/machine_kexec_64.c   | 2 +-
 arch/x86/kernel/relocate_kernel_64.S | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 7abc7aa0261b..84f59f18dcb6 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -380,7 +380,7 @@ void machine_kexec_cleanup(struct kimage *image)
  * Do not allocate memory (or fail in any way) in machine_kexec().
  * We are past the point of no return, committed to rebooting now.
  */
-void __nocfi machine_kexec(struct kimage *image)
+void machine_kexec(struct kimage *image)
 {
 	unsigned long reloc_start = (unsigned long)__relocate_kernel_start;
 	relocate_kernel_fn *relocate_kernel_ptr;
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 228301ac66e9..dbcef3430285 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -5,6 +5,7 @@
  */
 
 #include <linux/linkage.h>
+#include <linux/cfi_types.h>
 #include <linux/stringify.h>
 #include <asm/alternative.h>
 #include <asm/page_types.h>
@@ -59,8 +60,9 @@ SYM_DATA_END(kexec_debug_idt)
 
 	.section .text..relocate_kernel,"ax";
 	.code64
-SYM_CODE_START_NOALIGN(relocate_kernel)
+SYM_TYPED_FUNC_START(relocate_kernel)
 	UNWIND_HINT_END_OF_STACK
+	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	/*
 	 * %rdi indirection_page
-- 
2.48.1