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Message-Id: <1451301654-32019-9-git-send-email-ard.biesheuvel@linaro.org>
Date: Mon, 28 Dec 2015 12:20:52 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: linux-arm-kernel@...ts.infradead.org,
kernel-hardening@...ts.openwall.com,
will.deacon@....com,
catalin.marinas@....com,
mark.rutland@....com,
leif.lindholm@...aro.org,
keescook@...omium.org,
lkml@...r.kernel.org
Cc: stuart.yoder@...escale.com,
bhupesh.sharma@...escale.com,
Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [RFC PATCH 08/10] arm64: avoid dynamic relocations in early boot code
Before implementing KASLR for arm64 by building a self-relocating PIE
executable, we have to ensure that values we use before the relocation
routine is executed are not subject to dynamic relocation themselves.
This applies not only to virtual addresses, but also to values that are
supplied by the linker at build time and relocated using R_AARCH64_ABS64
relocations.
So instead, use assemble time constants, or force the use of static
relocations by folding the constants into the instructions.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
arch/arm64/kernel/efi-entry.S | 2 +-
arch/arm64/kernel/head.S | 12 +++++++++---
2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S
index a773db92908b..f82036e02485 100644
--- a/arch/arm64/kernel/efi-entry.S
+++ b/arch/arm64/kernel/efi-entry.S
@@ -61,7 +61,7 @@ ENTRY(entry)
*/
mov x20, x0 // DTB address
ldr x0, [sp, #16] // relocated _text address
- ldr x21, =stext_offset
+ movz x21, #:abs_g0:stext_offset
add x21, x0, x21
/*
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index a03ffffd84cb..4f086e247eea 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -227,11 +227,13 @@ ENTRY(stext)
* On return, the CPU will be ready for the MMU to be turned on and
* the TCR will have been set.
*/
- ldr x27, =__mmap_switched // address to jump to after
+ ldr x27, 0f // address to jump to after
// MMU has been enabled
adr_l lr, __enable_mmu // return (PIC) address
b __cpu_setup // initialise processor
ENDPROC(stext)
+ .align 3
+0: .quad __mmap_switched - (_head - TEXT_OFFSET) + KIMAGE_VADDR
/*
* Preserve the arguments passed by the bootloader in x0 .. x3
@@ -341,7 +343,7 @@ __create_page_tables:
cmp x0, x6
b.lo 1b
- ldr x7, =SWAPPER_MM_MMUFLAGS
+ mov x7, SWAPPER_MM_MMUFLAGS
/*
* Create the identity mapping.
@@ -399,7 +401,8 @@ __create_page_tables:
mov x0, x26 // swapper_pg_dir
ldr x5, =KIMAGE_VADDR
create_pgd_entry x0, x5, x3, x6
- ldr x6, =KERNEL_END // __va(KERNEL_END)
+ ldr w6, kernel_img_size
+ add x6, x6, x5
mov x3, x24 // phys offset
create_block_map x0, x7, x3, x5, x6
@@ -416,6 +419,9 @@ __create_page_tables:
mov lr, x27
ret
ENDPROC(__create_page_tables)
+
+kernel_img_size:
+ .long _end - (_head - TEXT_OFFSET)
.ltorg
/*
--
2.5.0
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