Kernel commit 11167161e553d("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(). Signed-off-by: chenqiwu <qiwu.chen(a)transsion.com&gt; --- arm64.c | 48 +++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 45 insertions(+), 3 deletions(-) diff --git a/arm64.c b/arm64.c index 2b6b0e5..18d1627 100644 --- a/arm64.c +++ b/arm64.c @@ -101,6 +101,42 @@ 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 mte enabled */ + if (!symbol_exists("cpu_enable_mte")) + return false; + + /* check for 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) +{ + /* Check for the untaggged kvaddr for HW tag-based KASAN mode */ + 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; @@ -268,7 +304,7 @@ 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"); @@ -1642,6 +1678,9 @@ 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) && @@ -4571,7 +4610,10 @@ 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)) -- 2.25.1