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

Dave Hansen
2018-08-02T22:58:42Z

From: Dave Hansen <dave.hansen@linux.intel.com>

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>
Cc: Kees Cook <keescook@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
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>
---

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
_