From b3e0423c4e76b19f04799e01b6443949f5fecbbc Mon Sep 17 00:00:00 2001
From: Vasily Gorbik <gor@linux.ibm.com>
Date: Wed, 15 Mar 2023 13:54:14 +0100
Subject: [PATCH] s390/kaslr: randomize amode31 base address
When the KASLR is enabled, randomize the base address of the amode31 image
within the first 2 GB, similar to the approach taken for the vmlinux
image. This makes it harder to predict the location of amode31 data
and code.
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
---
arch/s390/boot/startup.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index 638a6cf8a075b..64bd7ac3e35d1 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -278,7 +278,7 @@ void startup_kernel(void)
{
unsigned long max_physmem_end;
unsigned long vmlinux_lma = 0;
- unsigned long amode31_lma;
+ unsigned long amode31_lma = 0;
unsigned long asce_limit;
unsigned long safe_addr;
void *img;
@@ -338,7 +338,9 @@ void startup_kernel(void)
/* vmlinux decompression is done, shrink reserved low memory */
physmem_reserve(RR_DECOMPRESSOR, 0, (unsigned long)_decompressor_end);
- amode31_lma = vmlinux.default_lma - vmlinux.amode31_size;
+ if (kaslr_enabled())
+ amode31_lma = randomize_within_range(vmlinux.amode31_size, PAGE_SIZE, 0, SZ_2G);
+ amode31_lma = amode31_lma ?: vmlinux.default_lma - vmlinux.amode31_size;
physmem_reserve(RR_AMODE31, amode31_lma, vmlinux.amode31_size);
/*
--
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