Re: [PATCH v5 06/10] powerpc/fsl_booke/32: implement KASLR infrastructure

On 2019/8/7 21:04, Michael Ellerman wrote:

Jason Yan [off-list ref] writes:

quoted

This patch add support to boot kernel from places other than KERNELBASE.
Since CONFIG_RELOCATABLE has already supported, what we need to do is
map or copy kernel to a proper place and relocate. Freescale Book-E
parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1
entries are not suitable to map the kernel directly in a randomized
region, so we chose to copy the kernel to a proper place and restart to
relocate.

So to be 100% clear you are randomising the location of the kernel in
virtual and physical space, by the same amount, and retaining the 1:1
linear mapping.

100% right :)

quoted

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 77f6ebf97113..755378887912 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -548,6 +548,17 @@ config RELOCATABLE
  	  setting can still be useful to bootwrappers that need to know the
  	  load address of the kernel (eg. u-boot/mkimage).
  
+config RANDOMIZE_BASE
+	bool "Randomize the address of the kernel image"
+	depends on (FSL_BOOKE && FLATMEM && PPC32)
+	select RELOCATABLE

I think this should depend on RELOCATABLE, rather than selecting it.

quoted

diff --git a/arch/powerpc/kernel/kaslr_booke.c b/arch/powerpc/kernel/kaslr_booke.c
new file mode 100644
index 000000000000..30f84c0321b2
--- /dev/null
+++ b/arch/powerpc/kernel/kaslr_booke.c

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019 Jason Yan <yanaijie@huawei.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.

You don't need that paragraph now that you have the SPDX tag.

Rather than using a '//' comment followed by a single line block comment
you can format it as:

// SPDX-License-Identifier: GPL-2.0-only
//
// Copyright (C) 2019 Jason Yan [off-list ref]

quoted

+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/stddef.h>
+#include <linux/vmalloc.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/highmem.h>
+#include <linux/memblock.h>
+#include <asm/pgalloc.h>
+#include <asm/prom.h>
+#include <asm/io.h>
+#include <asm/mmu_context.h>
+#include <asm/pgtable.h>
+#include <asm/mmu.h>
+#include <linux/uaccess.h>
+#include <asm/smp.h>
+#include <asm/machdep.h>
+#include <asm/setup.h>
+#include <asm/paca.h>
+#include <mm/mmu_decl.h>

Do you really need all those headers?

I will remove useless headers.

quoted

+extern int is_second_reloc;

That should be in a header.

Any reason why it isn't a bool?

Oh yes, it should be in a header. This variable is already defined before and also used in assembly code. I think it was not defined as a bool just because there is no 'bool' in assembly code.

cheers


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