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-rw-r--r--arch/s390/Kconfig13
-rw-r--r--arch/s390/boot/startup.c58
-rw-r--r--arch/s390/boot/vmem.c14
-rw-r--r--arch/s390/boot/vmlinux.lds.S7
-rw-r--r--arch/s390/include/asm/page.h3
-rw-r--r--arch/s390/kernel/setup.c19
-rw-r--r--arch/s390/kernel/vmlinux.lds.S2
-rw-r--r--arch/s390/tools/relocs.c2
8 files changed, 85 insertions, 33 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index a822f952f64a..c60e699e99f5 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -604,6 +604,19 @@ config RANDOMIZE_BASE
as a security feature that deters exploit attempts relying on
knowledge of the location of kernel internals.
+config RANDOMIZE_IDENTITY_BASE
+ bool "Randomize the address of the identity mapping base"
+ depends on RANDOMIZE_BASE
+ default DEBUG_VM
+ help
+ The identity mapping base address is pinned to zero by default.
+ Allow randomization of that base to expose otherwise missed
+ notion of physical and virtual addresses of data structures.
+ That does not have any impact on the base address at which the
+ kernel image is loaded.
+
+ If unsure, say N
+
config KERNEL_IMAGE_BASE
hex "Kernel image base address"
range 0x100000 0x1FFFFFE0000000 if !KASAN
diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index ce232552bc1c..c73b5118ad42 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -162,7 +162,7 @@ static void kaslr_adjust_relocs(unsigned long min_addr, unsigned long max_addr,
loc = (long)*reloc + phys_offset;
if (loc < min_addr || loc > max_addr)
error("64-bit relocation outside of kernel!\n");
- *(u64 *)loc += offset - __START_KERNEL;
+ *(u64 *)loc += offset;
}
}
@@ -177,7 +177,7 @@ static void kaslr_adjust_got(unsigned long offset)
*/
for (entry = (u64 *)vmlinux.got_start; entry < (u64 *)vmlinux.got_end; entry++) {
if (*entry)
- *entry += offset - __START_KERNEL;
+ *entry += offset;
}
}
@@ -252,7 +252,7 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
vmemmap_size = SECTION_ALIGN_UP(pages) * sizeof(struct page);
/* choose kernel address space layout: 4 or 3 levels. */
- BUILD_BUG_ON(!IS_ALIGNED(__START_KERNEL, THREAD_SIZE));
+ BUILD_BUG_ON(!IS_ALIGNED(TEXT_OFFSET, THREAD_SIZE));
BUILD_BUG_ON(!IS_ALIGNED(__NO_KASLR_START_KERNEL, THREAD_SIZE));
BUILD_BUG_ON(__NO_KASLR_END_KERNEL > _REGION1_SIZE);
vsize = get_vmem_size(ident_map_size, vmemmap_size, vmalloc_size, _REGION3_SIZE);
@@ -341,7 +341,8 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
BUILD_BUG_ON(MAX_DCSS_ADDR > (1UL << MAX_PHYSMEM_BITS));
max_mappable = max(ident_map_size, MAX_DCSS_ADDR);
max_mappable = min(max_mappable, vmemmap_start);
- __identity_base = round_down(vmemmap_start - max_mappable, rte_size);
+ if (IS_ENABLED(CONFIG_RANDOMIZE_IDENTITY_BASE))
+ __identity_base = round_down(vmemmap_start - max_mappable, rte_size);
return asce_limit;
}
@@ -388,31 +389,25 @@ static void kaslr_adjust_vmlinux_info(long offset)
#endif
}
-static void fixup_vmlinux_info(void)
-{
- vmlinux.entry -= __START_KERNEL;
- kaslr_adjust_vmlinux_info(-__START_KERNEL);
-}
-
void startup_kernel(void)
{
- unsigned long kernel_size = vmlinux.image_size + vmlinux.bss_size;
- unsigned long nokaslr_offset_phys, kaslr_large_page_offset;
- unsigned long amode31_lma = 0;
+ unsigned long vmlinux_size = vmlinux.image_size + vmlinux.bss_size;
+ unsigned long nokaslr_text_lma, text_lma = 0, amode31_lma = 0;
+ unsigned long kernel_size = TEXT_OFFSET + vmlinux_size;
+ unsigned long kaslr_large_page_offset;
unsigned long max_physmem_end;
unsigned long asce_limit;
unsigned long safe_addr;
psw_t psw;
- fixup_vmlinux_info();
setup_lpp();
/*
* Non-randomized kernel physical start address must be _SEGMENT_SIZE
* aligned (see blow).
*/
- nokaslr_offset_phys = ALIGN(mem_safe_offset(), _SEGMENT_SIZE);
- safe_addr = PAGE_ALIGN(nokaslr_offset_phys + kernel_size);
+ nokaslr_text_lma = ALIGN(mem_safe_offset(), _SEGMENT_SIZE);
+ safe_addr = PAGE_ALIGN(nokaslr_text_lma + vmlinux_size);
/*
* Reserve decompressor memory together with decompression heap,
@@ -456,16 +451,27 @@ void startup_kernel(void)
*/
kaslr_large_page_offset = __kaslr_offset & ~_SEGMENT_MASK;
if (kaslr_enabled()) {
- unsigned long end = ident_map_size - kaslr_large_page_offset;
+ unsigned long size = vmlinux_size + kaslr_large_page_offset;
- __kaslr_offset_phys = randomize_within_range(kernel_size, _SEGMENT_SIZE, 0, end);
+ text_lma = randomize_within_range(size, _SEGMENT_SIZE, TEXT_OFFSET, ident_map_size);
}
- if (!__kaslr_offset_phys)
- __kaslr_offset_phys = nokaslr_offset_phys;
- __kaslr_offset_phys |= kaslr_large_page_offset;
+ if (!text_lma)
+ text_lma = nokaslr_text_lma;
+ text_lma |= kaslr_large_page_offset;
+
+ /*
+ * [__kaslr_offset_phys..__kaslr_offset_phys + TEXT_OFFSET] region is
+ * never accessed via the kernel image mapping as per the linker script:
+ *
+ * . = TEXT_OFFSET;
+ *
+ * Therefore, this region could be used for something else and does
+ * not need to be reserved. See how it is skipped in setup_vmem().
+ */
+ __kaslr_offset_phys = text_lma - TEXT_OFFSET;
kaslr_adjust_vmlinux_info(__kaslr_offset_phys);
- physmem_reserve(RR_VMLINUX, __kaslr_offset_phys, kernel_size);
- deploy_kernel((void *)__kaslr_offset_phys);
+ physmem_reserve(RR_VMLINUX, text_lma, vmlinux_size);
+ deploy_kernel((void *)text_lma);
/* vmlinux decompression is done, shrink reserved low memory */
physmem_reserve(RR_DECOMPRESSOR, 0, (unsigned long)_decompressor_end);
@@ -488,7 +494,7 @@ void startup_kernel(void)
amode31_lma = randomize_within_range(vmlinux.amode31_size, PAGE_SIZE, amode31_min, SZ_2G);
}
if (!amode31_lma)
- amode31_lma = __kaslr_offset_phys - vmlinux.amode31_size;
+ amode31_lma = text_lma - vmlinux.amode31_size;
physmem_reserve(RR_AMODE31, amode31_lma, vmlinux.amode31_size);
/*
@@ -504,8 +510,8 @@ void startup_kernel(void)
* - copy_bootdata() must follow setup_vmem() to propagate changes
* to bootdata made by setup_vmem()
*/
- clear_bss_section(__kaslr_offset_phys);
- kaslr_adjust_relocs(__kaslr_offset_phys, __kaslr_offset_phys + vmlinux.image_size,
+ clear_bss_section(text_lma);
+ kaslr_adjust_relocs(text_lma, text_lma + vmlinux.image_size,
__kaslr_offset, __kaslr_offset_phys);
kaslr_adjust_got(__kaslr_offset);
setup_vmem(__kaslr_offset, __kaslr_offset + kernel_size, asce_limit);
diff --git a/arch/s390/boot/vmem.c b/arch/s390/boot/vmem.c
index 2847cc059ab7..145035f84a0e 100644
--- a/arch/s390/boot/vmem.c
+++ b/arch/s390/boot/vmem.c
@@ -90,7 +90,7 @@ static void kasan_populate_shadow(unsigned long kernel_start, unsigned long kern
}
memgap_start = end;
}
- kasan_populate(kernel_start, kernel_end, POPULATE_KASAN_MAP_SHADOW);
+ kasan_populate(kernel_start + TEXT_OFFSET, kernel_end, POPULATE_KASAN_MAP_SHADOW);
kasan_populate(0, (unsigned long)__identity_va(0), POPULATE_KASAN_ZERO_SHADOW);
kasan_populate(AMODE31_START, AMODE31_END, POPULATE_KASAN_ZERO_SHADOW);
if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
@@ -475,7 +475,17 @@ void setup_vmem(unsigned long kernel_start, unsigned long kernel_end, unsigned l
(unsigned long)__identity_va(end),
POPULATE_IDENTITY);
}
- pgtable_populate(kernel_start, kernel_end, POPULATE_KERNEL);
+
+ /*
+ * [kernel_start..kernel_start + TEXT_OFFSET] region is never
+ * accessed as per the linker script:
+ *
+ * . = TEXT_OFFSET;
+ *
+ * Therefore, skip mapping TEXT_OFFSET bytes to prevent access to
+ * [__kaslr_offset_phys..__kaslr_offset_phys + TEXT_OFFSET] region.
+ */
+ pgtable_populate(kernel_start + TEXT_OFFSET, kernel_end, POPULATE_KERNEL);
pgtable_populate(AMODE31_START, AMODE31_END, POPULATE_DIRECT);
pgtable_populate(__abs_lowcore, __abs_lowcore + sizeof(struct lowcore),
POPULATE_ABS_LOWCORE);
diff --git a/arch/s390/boot/vmlinux.lds.S b/arch/s390/boot/vmlinux.lds.S
index a750711d44c8..66670212a361 100644
--- a/arch/s390/boot/vmlinux.lds.S
+++ b/arch/s390/boot/vmlinux.lds.S
@@ -109,7 +109,12 @@ SECTIONS
#ifdef CONFIG_KERNEL_UNCOMPRESSED
. = ALIGN(PAGE_SIZE);
. += AMODE31_SIZE; /* .amode31 section */
- . = ALIGN(1 << 20); /* _SEGMENT_SIZE */
+
+ /*
+ * Make sure the location counter is not less than TEXT_OFFSET.
+ * _SEGMENT_SIZE is not available, use ALIGN(1 << 20) instead.
+ */
+ . = MAX(TEXT_OFFSET, ALIGN(1 << 20));
#else
. = ALIGN(8);
#endif
diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 06416b3f94f5..16e4caa931f1 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -279,8 +279,9 @@ static inline unsigned long virt_to_pfn(const void *kaddr)
#define AMODE31_SIZE (3 * PAGE_SIZE)
#define KERNEL_IMAGE_SIZE (512 * 1024 * 1024)
-#define __START_KERNEL 0x100000
#define __NO_KASLR_START_KERNEL CONFIG_KERNEL_IMAGE_BASE
#define __NO_KASLR_END_KERNEL (__NO_KASLR_START_KERNEL + KERNEL_IMAGE_SIZE)
+#define TEXT_OFFSET 0x100000
+
#endif /* _S390_PAGE_H */
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 4ec99f73fa27..a3fea683b227 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -734,7 +734,23 @@ static void __init memblock_add_physmem_info(void)
}
/*
- * Reserve memory used for lowcore/command line/kernel image.
+ * Reserve memory used for lowcore.
+ */
+static void __init reserve_lowcore(void)
+{
+ void *lowcore_start = get_lowcore();
+ void *lowcore_end = lowcore_start + sizeof(struct lowcore);
+ void *start, *end;
+
+ if ((void *)__identity_base < lowcore_end) {
+ start = max(lowcore_start, (void *)__identity_base);
+ end = min(lowcore_end, (void *)(__identity_base + ident_map_size));
+ memblock_reserve(__pa(start), __pa(end));
+ }
+}
+
+/*
+ * Reserve memory used for absolute lowcore/command line/kernel image.
*/
static void __init reserve_kernel(void)
{
@@ -918,6 +934,7 @@ void __init setup_arch(char **cmdline_p)
/* Do some memory reservations *before* memory is added to memblock */
reserve_pgtables();
+ reserve_lowcore();
reserve_kernel();
reserve_initrd();
reserve_certificate_list();
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index e67cd409b858..ae5d0a9d6911 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -39,7 +39,7 @@ PHDRS {
SECTIONS
{
- . = __START_KERNEL;
+ . = TEXT_OFFSET;
.text : {
_stext = .; /* Start of text section */
_text = .; /* Text and read-only data */
diff --git a/arch/s390/tools/relocs.c b/arch/s390/tools/relocs.c
index a74dbd5c9896..30a732c808f3 100644
--- a/arch/s390/tools/relocs.c
+++ b/arch/s390/tools/relocs.c
@@ -280,7 +280,7 @@ static int do_reloc(struct section *sec, Elf_Rel *rel)
case R_390_GOTOFF64:
break;
case R_390_64:
- add_reloc(&relocs64, offset - ehdr.e_entry);
+ add_reloc(&relocs64, offset);
break;
default:
die("Unsupported relocation type: %d\n", r_type);
generated by cgit v1.2.3-58-ga151 (git 2.39.0) at 2024-11-27 03:10:53 +0000