s390/boot: fix mem_detect extended area allocation

Allocation of mem_detect extended area was not considered neither
in commit 9641b8cc733f ("s390/ipl: read IPL report at early boot")
nor in commit b2d24b97b2a9 ("s390/kernel: add support for kernel address
space layout randomization (KASLR)"). As a result mem_detect extended
theoretically may overlap with ipl report or randomized kernel image
position. But as mem_detect code will allocate extended area only
upon exceeding 255 online regions (which should alternate with offline
memory regions) it is not seen in practice.

To make sure mem_detect extended area does not overlap with ipl report
or randomized kernel position extend usage of "safe_addr". Make initrd
handling and mem_detect extended area allocation code move it further
right and make KASLR takes in into consideration as well.

Fixes: 9641b8cc733f ("s390/ipl: read IPL report at early boot")
Fixes: b2d24b97b2a9 ("s390/kernel: add support for kernel address space layout randomization (KASLR)")
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 12 insertions, 9 deletions

diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index c9dfd7e09233..577ebec9971b 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -76,16 +76,17 @@ unsigned long mem_safe_offset(void)
 }
 #endif
 
-static void rescue_initrd(unsigned long addr)
+static unsigned long rescue_initrd(unsigned long safe_addr)
 {
 	if (!IS_ENABLED(CONFIG_BLK_DEV_INITRD))
-		return;
+		return safe_addr;
 	if (!initrd_data.start || !initrd_data.size)
-		return;
-	if (addr <= initrd_data.start)
-		return;
-	memmove((void *)addr, (void *)initrd_data.start, initrd_data.size);
-	initrd_data.start = addr;
+		return safe_addr;
+	if (initrd_data.start < safe_addr) {
+		memmove((void *)safe_addr, (void *)initrd_data.start, initrd_data.size);
+		initrd_data.start = safe_addr;
+	}
+	return initrd_data.start + initrd_data.size;
 }
 
 static void copy_bootdata(void)
@@ -275,6 +276,7 @@ static unsigned long reserve_amode31(unsigned long safe_addr)
 
 void startup_kernel(void)
 {
+	unsigned long max_physmem_end;
 	unsigned long random_lma;
 	unsigned long safe_addr;
 	unsigned long asce_limit;
@@ -294,12 +296,13 @@ void startup_kernel(void)
 	safe_addr = reserve_amode31(safe_addr);
 	safe_addr = read_ipl_report(safe_addr);
 	uv_query_info();
-	rescue_initrd(safe_addr);
+	safe_addr = rescue_initrd(safe_addr);
 	sclp_early_read_info();
 	setup_boot_command_line();
 	parse_boot_command_line();
 	sanitize_prot_virt_host();
-	setup_ident_map_size(detect_memory());
+	max_physmem_end = detect_memory(&safe_addr);
+	setup_ident_map_size(max_physmem_end);
 	setup_vmalloc_size();
 	asce_limit = setup_kernel_memory_layout();