x86/kexec: Use typedef for relocate_kernel_fn function prototype

Both i386 and x86_64 now copy the relocate_kernel() function into the control
page and execute it from there, using an open-coded function pointer.

Use a typedef for it instead.

  [ bp: Put relocate_kernel_ptr ptr arithmetic on a single line. ]

Signed-off-by: David Woodhouse <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: dwmw2

arch/x86/include/asm/kexec.h

@@ -111,21 +111,21 @@ static inline void crash_setup_regs(struct pt_regs *newregs,
 }
 
 #ifdef CONFIG_X86_32
-asmlinkage unsigned long
-relocate_kernel(unsigned long indirection_page,
-		unsigned long control_page,
-		unsigned long start_address,
-		unsigned int has_pae,
-		unsigned int preserve_context);
+typedef asmlinkage unsigned long
+relocate_kernel_fn(unsigned long indirection_page,
+		   unsigned long control_page,
+		   unsigned long start_address,
+		   unsigned int has_pae,
+		   unsigned int preserve_context);
 #else
-unsigned long
-relocate_kernel(unsigned long indirection_page,
-		unsigned long pa_control_page,
-		unsigned long start_address,
-		unsigned int preserve_context,
-		unsigned int host_mem_enc_active);
+typedef unsigned long
+relocate_kernel_fn(unsigned long indirection_page,
+		   unsigned long pa_control_page,
+		   unsigned long start_address,
+		   unsigned int preserve_context,
+		   unsigned int host_mem_enc_active);
 #endif
-
+extern relocate_kernel_fn relocate_kernel;
 #define ARCH_HAS_KIMAGE_ARCH
 
 #ifdef CONFIG_X86_32

arch/x86/kernel/machine_kexec_32.c

@@ -160,15 +160,10 @@ void machine_kexec_cleanup(struct kimage *image)
  */
 void machine_kexec(struct kimage *image)
 {
+	relocate_kernel_fn *relocate_kernel_ptr;
 	unsigned long page_list[PAGES_NR];
 	void *control_page;
 	int save_ftrace_enabled;
-	asmlinkage unsigned long
-		(*relocate_kernel_ptr)(unsigned long indirection_page,
-				       unsigned long control_page,
-				       unsigned long start_address,
-				       unsigned int has_pae,
-				       unsigned int preserve_context);
 
 #ifdef CONFIG_KEXEC_JUMP
 	if (image->preserve_context)

arch/x86/kernel/machine_kexec_64.c

@@ -344,12 +344,8 @@ void machine_kexec_cleanup(struct kimage *image)
  */
 void __nocfi machine_kexec(struct kimage *image)
 {
-	unsigned long (*relocate_kernel_ptr)(unsigned long indirection_page,
-					     unsigned long pa_control_page,
-					     unsigned long start_address,
-					     unsigned int preserve_context,
-					     unsigned int host_mem_enc_active);
 	unsigned long reloc_start = (unsigned long)__relocate_kernel_start;
+	relocate_kernel_fn *relocate_kernel_ptr;
 	unsigned int host_mem_enc_active;
 	int save_ftrace_enabled;
 	void *control_page;
@@ -391,8 +387,7 @@ void __nocfi machine_kexec(struct kimage *image)
 	 * Allow for the possibility that relocate_kernel might not be at
 	 * the very start of the page.
 	 */
-	relocate_kernel_ptr = control_page + (unsigned long)relocate_kernel -
-		reloc_start;
+	relocate_kernel_ptr = control_page + (unsigned long)relocate_kernel - reloc_start;
 
 	/*
 	 * The segment registers are funny things, they have both a