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x86/mm: Always enable CONFIG_DEBUG_RODATA and remove the Kconfig option

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This removes the CONFIG_DEBUG_RODATA option and makes it always enabled.

This simplifies the code and also makes it clearer that read-only mapped
memory is just as fundamental a security feature in kernel-space as it is
in user-space.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Brown <david.brown@linaro.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Krause <minipli@googlemail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-hardening@lists.openwall.com
Cc: linux-arch <linux-arch@vger.kernel.org>
Link: http://lkml.kernel.org/r/1455748879-21872-4-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kees Cook
2016-02-17 14:41:14 -08:00
committed by Ingo Molnar
parent d2aa1acad2
commit 9ccaf77cf0
13 changed files with 25 additions and 61 deletions
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25
arch/x86/kernel/vmlinux.lds.S
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@@ -41,29 +41,28 @@ ENTRY(phys_startup_64)
jiffies_64 = jiffies;
#endif
#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
#if defined(CONFIG_X86_64)
/*
* On 64-bit, align RODATA to 2MB so that even with CONFIG_DEBUG_RODATA
* we retain large page mappings for boundaries spanning kernel text, rodata
* and data sections.
* On 64-bit, align RODATA to 2MB so we retain large page mappings for
* boundaries spanning kernel text, rodata and data sections.
*
* However, kernel identity mappings will have different RWX permissions
* to the pages mapping to text and to the pages padding (which are freed) the
* text section. Hence kernel identity mappings will be broken to smaller
* pages. For 64-bit, kernel text and kernel identity mappings are different,
* so we can enable protection checks that come with CONFIG_DEBUG_RODATA,
* as well as retain 2MB large page mappings for kernel text.
* so we can enable protection checks as well as retain 2MB large page
* mappings for kernel text.
*/
#define X64_ALIGN_DEBUG_RODATA_BEGIN . = ALIGN(HPAGE_SIZE);
#define X64_ALIGN_RODATA_BEGIN . = ALIGN(HPAGE_SIZE);
#define X64_ALIGN_DEBUG_RODATA_END \
#define X64_ALIGN_RODATA_END \
. = ALIGN(HPAGE_SIZE); \
__end_rodata_hpage_align = .;
#else
#define X64_ALIGN_DEBUG_RODATA_BEGIN
#define X64_ALIGN_DEBUG_RODATA_END
#define X64_ALIGN_RODATA_BEGIN
#define X64_ALIGN_RODATA_END
#endif
@@ -112,13 +111,11 @@ SECTIONS
EXCEPTION_TABLE(16) :text = 0x9090
#if defined(CONFIG_DEBUG_RODATA)
/* .text should occupy whole number of pages */
. = ALIGN(PAGE_SIZE);
#endif
X64_ALIGN_DEBUG_RODATA_BEGIN
X64_ALIGN_RODATA_BEGIN
RO_DATA(PAGE_SIZE)
X64_ALIGN_DEBUG_RODATA_END
X64_ALIGN_RODATA_END
/* Data */
.data : AT(ADDR(.data) - LOAD_OFFSET) {