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Message-Id: <20170903120757.14968-21-ard.biesheuvel@linaro.org>
Date: Sun, 3 Sep 2017 13:07:48 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: linux-arm-kernel@...ts.infradead.org,
kernel-hardening@...ts.openwall.com
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Arnd Bergmann <arnd@...db.de>,
Nicolas Pitre <nico@...aro.org>,
Russell King <linux@...linux.org.uk>,
Kees Cook <keescook@...omium.org>,
Thomas Garnier <thgarnie@...gle.com>,
Marc Zyngier <marc.zyngier@....com>,
Mark Rutland <mark.rutland@....com>,
Tony Lindgren <tony@...mide.com>,
Matt Fleming <matt@...eblueprint.co.uk>,
Dave Martin <dave.martin@....com>
Subject: [PATCH v2 20/29] ARM: kernel: use PC-relative symbol references in MMU switch code
To prepare for adding support for KASLR, which relocates all absolute
symbol references at runtime after the caches have been enabled,
update the MMU switch code to avoid using absolute symbol references
where possible. This ensures these quantities are invariant under
runtime relocation.
Cc: Russell King <linux@...linux.org.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
arch/arm/kernel/head-common.S | 39 ++++++++------------
1 file changed, 15 insertions(+), 24 deletions(-)
diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 06035488130c..b74477507a12 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -79,9 +79,10 @@ ENDPROC(__vet_atags)
*/
__INIT
__mmap_switched:
- adr r3, __mmap_switched_data
-
- ldmia r3!, {r4, r5, r6, r7}
+ adr_l r4, __data_loc
+ adr_l r5, _sdata
+ adr_l r6, __bss_start
+ adr_l r7, _end
cmp r4, r5 @ Copy data segment if needed
1: cmpne r5, r6
ldrne fp, [r4], #4
@@ -93,9 +94,17 @@ __mmap_switched:
strcc fp, [r6],#4
bcc 1b
- ARM( ldmia r3, {r4, r5, r6, r7, sp})
- THUMB( ldmia r3, {r4, r5, r6, r7} )
- THUMB( ldr sp, [r3, #16] )
+ adr_l r3, init_thread_union + THREAD_START_SP
+ mov sp, r3
+ adr_l r4, processor_id
+ adr_l r5, __machine_arch_type
+ adr_l r6, __atags_pointer
+#ifdef CONFIG_CPU_CP15
+ adr_l r7, cr_alignment
+#else
+ mov r7, #0
+#endif
+
str r9, [r4] @ Save processor ID
str r1, [r5] @ Save machine type
str r2, [r6] @ Save atags pointer
@@ -104,24 +113,6 @@ __mmap_switched:
b start_kernel
ENDPROC(__mmap_switched)
- .align 2
- .type __mmap_switched_data, %object
-__mmap_switched_data:
- .long __data_loc @ r4
- .long _sdata @ r5
- .long __bss_start @ r6
- .long _end @ r7
- .long processor_id @ r4
- .long __machine_arch_type @ r5
- .long __atags_pointer @ r6
-#ifdef CONFIG_CPU_CP15
- .long cr_alignment @ r7
-#else
- .long 0 @ r7
-#endif
- .long init_thread_union + THREAD_START_SP @ sp
- .size __mmap_switched_data, . - __mmap_switched_data
-
/*
* This provides a C-API version of __lookup_processor_type
*/
--
2.11.0
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