x86/mm/init: Add helper for freeing kernel image pages

When chunks of the kernel image are freed, free_init_pages() is used
directly.  Consolidate the three sites that do this.  Also update the
string to give an incrementally better description of that memory versus
what was there before.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: keescook@google.com
Cc: aarcange@redhat.com
Cc: jgross@suse.com
Cc: jpoimboe@redhat.com
Cc: gregkh@linuxfoundation.org
Cc: peterz@infradead.org
Cc: hughd@google.com
Cc: torvalds@linux-foundation.org
Cc: bp@alien8.de
Cc: luto@kernel.org
Cc: ak@linux.intel.com
Cc: Kees Cook <keescook@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Link: https://lkml.kernel.org/r/20180802225829.FE0E32EA@viggo.jf.intel.com

arch/x86/include/asm/processor.h

@@ -966,6 +966,7 @@ static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
 
 extern unsigned long arch_align_stack(unsigned long sp);
 extern void free_init_pages(char *what, unsigned long begin, unsigned long end);
+extern void free_kernel_image_pages(void *begin, void *end);
 
 void default_idle(void);
 #ifdef	CONFIG_XEN

arch/x86/mm/init.c

@@ -773,13 +773,22 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
 	}
 }
 
+/*
+ * begin/end can be in the direct map or the "high kernel mapping"
+ * used for the kernel image only.  free_init_pages() will do the
+ * right thing for either kind of address.
+ */
+void free_kernel_image_pages(void *begin, void *end)
+{
+	free_init_pages("unused kernel image",
+			(unsigned long)begin, (unsigned long)end);
+}
+
 void __ref free_initmem(void)
 {
 	e820__reallocate_tables();
 
-	free_init_pages("unused kernel",
-			(unsigned long)(&__init_begin),
-			(unsigned long)(&__init_end));
+	free_kernel_image_pages(&__init_begin, &__init_end);
 }
 
 #ifdef CONFIG_BLK_DEV_INITRD

arch/x86/mm/init_64.c

@@ -1283,8 +1283,8 @@ void mark_rodata_ro(void)
 	set_memory_ro(start, (end-start) >> PAGE_SHIFT);
 #endif
 
-	free_init_pages("unused kernel", text_end, rodata_start);
-	free_init_pages("unused kernel", rodata_end, _sdata);
+	free_kernel_image_pages((void *)text_end, (void *)rodata_start);
+	free_kernel_image_pages((void *)rodata_end, (void *)_sdata);
 
 	debug_checkwx();