Kernel commit 2e903b914797("kasan, arm64: implement HW_TAGS runtime")
introduce a Hardware Tag-Based KASAN(MTE) mode for ARMv8.5 later CPUs,
which uses the Top Byte Ignore (TBI) feature of arm64 CPUs to store a
pointer tag in the top byte of kernel pointers.
Currently, crash utility cannot load MTE ramdump due to access the invalid
HW Tag-Based kvaddr. Here's the example error message:
please wait... (gathering kmem slab cache data)
crash: invalid kernel virtual address: f1ffff80c000201c type: "kmem_cache objsize/object_size"
please wait... (gathering task table data)
crash: invalid kernel virtual address: f9ffff8239c2cde0 type: "xa_node shift"
This patch replace the orignal generic_is_kvaddr() with arm64_is_kvaddr(),
which check the validity for a HW Tag-Based kvaddr. mte_tag_reset() is
used to convert a Tag-Based kvaddr to untaggged kvaddr in arm64_VTOP()
and arm64_IS_VMALLOC_ADDR().
---
changes in v2:
- Introduce a new flag (ARM64_MTE) and initialize it on PRE_SYMTAB stage.
- Create this patch based on latest tag.
Signed-off-by: chenqiwu <qiwu.chen@xxxxxxxxxxxxx>
---
arm64.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++----
defs.h | 1 +
2 files changed, 47 insertions(+), 4 deletions(-)
diff --git a/arm64.c b/arm64.c
index 57965c6..ba1a4f5 100644
--- a/arm64.c
+++ b/arm64.c
@@ -102,6 +102,41 @@ struct kernel_range {
static struct kernel_range *arm64_get_va_range(struct machine_specific *ms);
static void arm64_get_struct_page_size(struct machine_specific *ms);
+typedef unsigned char u8;
+/* mte tag shift bit */
+#define MTE_TAG_SHIFT 56
+/* native kernel pointers tag */
+#define KASAN_TAG_KERNEL 0xFF
+/* minimum value for random tags */
+#define KASAN_TAG_MIN 0xF0
+/* right shift the tag to MTE_TAG_SHIFT bit */
+#define mte_tag_shifted(tag) ((ulong)(tag) << MTE_TAG_SHIFT)
+/* get the top byte value of the original kvaddr */
+#define mte_tag_get(addr) (u8)((ulong)(addr) >> MTE_TAG_SHIFT)
+/* reset the top byte to get an untaggged kvaddr */
+#define mte_tag_reset(addr) ((ulong)addr & ~mte_tag_shifted(KASAN_TAG_KERNEL) | mte_tag_shifted(KASAN_TAG_KERNEL))
+
+static inline bool is_mte_kvaddr(ulong addr)
+{
+ /* check for ARM64_MTE enabled */
+ if (machdep->flags & ARM64_MTE)
+ return false;
+
+ /* check the validity of HW Tag-Based kvaddr */
+ if (mte_tag_get(addr) >= KASAN_TAG_MIN && mte_tag_get(addr) < KASAN_TAG_KERNEL)
+ return true;
+
+ return false;
+}
+
+static int arm64_is_kvaddr(ulong addr)
+{
+ if (is_mte_kvaddr(addr))
+ return (mte_tag_reset(addr) >= (ulong)(machdep->kvbase));
+
+ return (addr >= (ulong)(machdep->kvbase));
+}
+
static void arm64_calc_kernel_start(void)
{
struct machine_specific *ms = machdep->machspec;
@@ -146,7 +181,8 @@ arm64_init(int when)
if (machdep->cmdline_args[0])
arm64_parse_cmdline_args();
machdep->flags |= MACHDEP_BT_TEXT;
-
+ if (symbol_exists("cpu_enable_mte"))
+ machdep->flags |= ARM64_MTE;
ms = machdep->machspec;
/*
@@ -262,7 +298,7 @@ arm64_init(int when)
machdep->kvbase = ARM64_VA_START;
ms->userspace_top = ARM64_USERSPACE_TOP;
}
- machdep->is_kvaddr = generic_is_kvaddr;
+ machdep->is_kvaddr = arm64_is_kvaddr;
machdep->kvtop = arm64_kvtop;
/* The defaults */
@@ -1023,7 +1059,7 @@ arm64_dump_machdep_table(ulong arg)
fprintf(fp, " dis_filter: arm64_dis_filter()\n");
fprintf(fp, " cmd_mach: arm64_cmd_mach()\n");
fprintf(fp, " get_smp_cpus: arm64_get_smp_cpus()\n");
- fprintf(fp, " is_kvaddr: generic_is_kvaddr()\n");
+ fprintf(fp, " is_kvaddr: arm64_is_kvaddr()\n");
fprintf(fp, " is_uvaddr: arm64_is_uvaddr()\n");
fprintf(fp, " value_to_symbol: generic_machdep_value_to_symbol()\n");
fprintf(fp, " init_kernel_pgd: arm64_init_kernel_pgd\n");
@@ -1633,6 +1669,9 @@ ulong arm64_PTOV(ulong paddr)
ulong
arm64_VTOP(ulong addr)
{
+ if (is_mte_kvaddr(addr))
+ addr = mte_tag_reset(addr);
+
if (machdep->flags & NEW_VMEMMAP) {
if (machdep->machspec->VA_START &&
(addr >= machdep->machspec->kimage_text) &&
@@ -4562,7 +4601,10 @@ int
arm64_IS_VMALLOC_ADDR(ulong vaddr)
{
struct machine_specific *ms = machdep->machspec;
-
+
+ if (is_mte_kvaddr(vaddr))
+ vaddr = mte_tag_reset(vaddr);
+
if ((machdep->flags & NEW_VMEMMAP) &&
(vaddr >= machdep->machspec->kimage_text) &&
(vaddr <= machdep->machspec->kimage_end))
diff --git a/defs.h b/defs.h
index 20237b7..aa8eba8 100644
--- a/defs.h
+++ b/defs.h
@@ -3348,6 +3348,7 @@ typedef signed int s32;
#define FLIPPED_VM (0x400)
#define HAS_PHYSVIRT_OFFSET (0x800)
#define OVERFLOW_STACKS (0x1000)
+#define ARM64_MTE (0x2000)
/*
* Get kimage_voffset from /dev/crash
--
2.25.1
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