@@ -48,7 +48,8 @@ Complete virtual memory map with 4-level page tables
ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole
ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base)
ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole
- ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory
+ ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory (generic mode)
+ fffff80000000000 | -8 TB | fffffc0000000000 | 4 TB | KASAN shadow memory (software tag-based mode)
__________________|____________|__________________|_________|____________________________________________________________
|
| Identical layout to the 56-bit one from here on:
@@ -107,7 +108,8 @@ Complete virtual memory map with 5-level page tables
ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused hole
ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base)
ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole
- ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory
+ ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory (generic mode)
+ ffe8000000000000 | -6 PB | fff0000000000000 | 2 PB | KASAN shadow memory (software tag-based mode)
__________________|____________|__________________|_________|____________________________________________________________
|
| Identical layout to the 47-bit one from here on:
@@ -392,8 +392,7 @@ config AUDIT_ARCH
config KASAN_SHADOW_OFFSET
hex
- depends on KASAN
- default 0xdffffc0000000000
+ default 0xdffffc0000000000 if KASAN_GENERIC
config HAVE_INTEL_TXT
def_bool y
@@ -5,7 +5,7 @@
#include <linux/const.h>
#include <linux/kasan-tags.h>
#include <linux/types.h>
-#define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
+
#define KASAN_SHADOW_SCALE_SHIFT 3
/*
@@ -14,6 +14,8 @@
* for kernel really starts from compiler's shadow offset +
* 'kernel address space start' >> KASAN_SHADOW_SCALE_SHIFT
*/
+#ifdef CONFIG_KASAN_GENERIC
+#define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
#define KASAN_SHADOW_START (KASAN_SHADOW_OFFSET + \
((-1UL << __VIRTUAL_MASK_SHIFT) >> \
KASAN_SHADOW_SCALE_SHIFT))
@@ -24,12 +26,22 @@
#define KASAN_SHADOW_END (KASAN_SHADOW_START + \
(1ULL << (__VIRTUAL_MASK_SHIFT - \
KASAN_SHADOW_SCALE_SHIFT)))
+#endif
+
#ifndef __ASSEMBLY__
+#include <asm/runtime-const.h>
#include <linux/bitops.h>
#include <linux/bitfield.h>
#include <linux/bits.h>
+#ifdef CONFIG_KASAN_SW_TAGS
+extern unsigned long KASAN_SHADOW_END_RC;
+#define KASAN_SHADOW_END runtime_const_ptr(KASAN_SHADOW_END_RC)
+#define KASAN_SHADOW_OFFSET KASAN_SHADOW_END
+#define KASAN_SHADOW_START (KASAN_SHADOW_END - ((UL(1)) << (__VIRTUAL_MASK_SHIFT - KASAN_SHADOW_SCALE_SHIFT)))
+#endif
+
#define arch_kasan_set_tag(addr, tag) __tag_set(addr, tag)
#define arch_kasan_reset_tag(addr) __tag_reset(addr)
#define arch_kasan_get_tag(addr) __tag_get(addr)
@@ -359,6 +359,7 @@ SECTIONS
RUNTIME_CONST_VARIABLES
RUNTIME_CONST(ptr, USER_PTR_MAX)
+ RUNTIME_CONST(ptr, KASAN_SHADOW_END_RC)
. = ALIGN(PAGE_SIZE);
@@ -358,6 +358,9 @@ void __init kasan_init(void)
int i;
memcpy(early_top_pgt, init_top_pgt, sizeof(early_top_pgt));
+ unsigned long KASAN_SHADOW_END_RC = pgtable_l5_enabled() ? 0xfff0000000000000 : 0xfffffc0000000000;
+
+ runtime_const_init(ptr, KASAN_SHADOW_END_RC);
/*
* We use the same shadow offset for 4- and 5-level paging to
@@ -372,7 +375,7 @@ void __init kasan_init(void)
* bunch of things like kernel code, modules, EFI mapping, etc.
* We need to take extra steps to not overwrite them.
*/
- if (pgtable_l5_enabled()) {
+ if (pgtable_l5_enabled() && !IS_ENABLED(CONFIG_KASAN_SW_TAGS)) {
void *ptr;
ptr = (void *)pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_END));
On x86, generic KASAN is setup in a way that needs a single KASAN_SHADOW_OFFSET value for both 4 and 5 level paging. It's required to facilitate boot time switching and it's a compiler ABI so it can't be changed during runtime. Software tag-based mode doesn't tie shadow start and end to any linear addresses as part of the compiler ABI so it can be changed during runtime. This notion, for KASAN purposes, allows to optimize out macros such us pgtable_l5_enabled() which would otherwise be used in every single KASAN related function. Use runtime_const infrastructure with pgtable_l5_enabled() to initialize the end address of KASAN's shadow address space. It's a good choice since in software tag based mode KASAN_SHADOW_OFFSET and KASAN_SHADOW_END refer to the same value and the offset in kasan_mem_to_shadow() is a signed negative value. Setup KASAN_SHADOW_END values so that they're aligned to 4TB in 4-level paging mode and to 2PB in 5-level paging mode. Also update x86 memory map documentation. Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> --- Documentation/arch/x86/x86_64/mm.rst | 6 ++++-- arch/x86/Kconfig | 3 +-- arch/x86/include/asm/kasan.h | 14 +++++++++++++- arch/x86/kernel/vmlinux.lds.S | 1 + arch/x86/mm/kasan_init_64.c | 5 ++++- 5 files changed, 23 insertions(+), 6 deletions(-)