[PATCH 4/7] x86/mm/init: add helper for freeing kernel image pages

[Dave Hansen]

From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---

 b/arch/x86/include/asm/processor.h |    1 +
 b/arch/x86/mm/init.c               |   15 ++++++++++++---
 b/arch/x86/mm/init_64.c            |    4 ++--
 3 files changed, 15 insertions(+), 5 deletions(-)

diff -puN arch/x86/include/asm/processor.h~x86-mm-init-common-kernel-image-free-helper arch/x86/include/asm/processor.h
--- a/arch/x86/include/asm/processor.h~x86-mm-init-common-kernel-image-free-helper	2018-08-02 14:14:48.891483276 -0700
+++ b/arch/x86/include/asm/processor.h	2018-08-02 14:14:48.901483276 -0700
@@ -966,6 +966,7 @@ static inline uint32_t hypervisor_cpuid_
 
 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
diff -puN arch/x86/mm/init_64.c~x86-mm-init-common-kernel-image-free-helper arch/x86/mm/init_64.c
--- a/arch/x86/mm/init_64.c~x86-mm-init-common-kernel-image-free-helper	2018-08-02 14:14:48.895483276 -0700
+++ b/arch/x86/mm/init_64.c	2018-08-02 14:14:48.902483276 -0700
@@ -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();
 
diff -puN arch/x86/mm/init.c~x86-mm-init-common-kernel-image-free-helper arch/x86/mm/init.c
--- a/arch/x86/mm/init.c~x86-mm-init-common-kernel-image-free-helper	2018-08-02 14:14:48.896483276 -0700
+++ b/arch/x86/mm/init.c	2018-08-02 14:14:48.902483276 -0700
@@ -773,13 +773,22 @@ void free_init_pages(char *what, unsigne
 	}
 }
 
+/*
+ * 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
_