[PATCH 3/7] x86/mm/init: pass unconverted symbol addresses to free_init_pages()

From: Dave Hansen
Date: Thu Aug 02 2018 - 18:58:56 EST

From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

The x86 code has several places where it frees parts of kernel image:

1. Unused SMP alternative
2. __init code
3. The hole between text and rodata
4. The hole between rodata and data

We call free_init_pages() to do this. Strangely, we convert the
symbol addresses to kernel direct map addresses in some cases
(#3, #4) but not others (#1, #2).

The virt_to_page() and the other code in free_reserved_area() now
works fine for for symbol addresses on x86, so don't bother
converting the addresses to direct map addresses before freeing

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/mm/init_64.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff -puN arch/x86/mm/init_64.c~x86-init-do-not-convert-symbol-addresses arch/x86/mm/init_64.c
--- a/arch/x86/mm/init_64.c~x86-init-do-not-convert-symbol-addresses 2018-08-02 14:14:48.380483277 -0700
+++ b/arch/x86/mm/init_64.c 2018-08-02 14:14:48.383483277 -0700
@@ -1283,12 +1283,8 @@ void mark_rodata_ro(void)
set_memory_ro(start, (end-start) >> PAGE_SHIFT);

- free_init_pages("unused kernel",
- (unsigned long) __va(__pa_symbol(text_end)),
- (unsigned long) __va(__pa_symbol(rodata_start)));
- free_init_pages("unused kernel",
- (unsigned long) __va(__pa_symbol(rodata_end)),
- (unsigned long) __va(__pa_symbol(_sdata)));
+ free_init_pages("unused kernel", text_end, rodata_start);
+ free_init_pages("unused kernel", rodata_end, _sdata);