linux-kernel - [PATCH 3/7] x86/mm/init: pass unconverted symbol addresses to free_init

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Message-Id: <20180802225828.89B2D0E2@viggo.jf.intel.com>
Date:   Thu, 02 Aug 2018 15:58:28 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>, keescook@...gle.com,
        tglx@...utronix.de, mingo@...nel.org, aarcange@...hat.com,
        jgross@...e.com, jpoimboe@...hat.com, gregkh@...uxfoundation.org,
        peterz@...radead.org, hughd@...gle.com,
        torvalds@...ux-foundation.org, bp@...en8.de, luto@...nel.org,
        ak@...ux.intel.com
Subject: [PATCH 3/7] x86/mm/init: pass unconverted symbol addresses to free_init_pages()


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

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
them.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Kees Cook <keescook@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Andi Kleen <ak@...ux.intel.com>
---

 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);
 #endif
 
-	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);
 
 	debug_checkwx();
 
_