Messages in this thread Patch in this message | | | Subject | Re: [PATCH] LoongArch: Add kernel address sanitizer support | From | Youling Tang <> | Date | Fri, 31 Mar 2023 16:07:53 +0800 |
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Hi, Qing
On 03/28/2023 07:17 PM, Qing Zhang wrote: > 1/8 of kernel addresses reserved for shadow memory. But for LoongArch, > There are a lot of holes between different segments and valid address > space(256T available) is insufficient to map all these segments to kasan > shadow memory with the common formula provided by kasan core, saying > addr >> KASAN_SHADOW_SCALE_SHIFT) + KASAN_SHADOW_OFFSET > > So Loongarch has a ARCH specific mapping formula,different segments > are mapped individually, and only limited length of space of that > specific segment is mapped to shadow. > > At early boot stage the whole shadow region populated with just > one physical page (kasan_early_shadow_page). Later, this page is > reused as readonly zero shadow for some memory that Kasan currently > don't track. > After mapping the physical memory, pages for shadow memory are > allocated and mapped. > > Functions like memset/memmove/memcpy do a lot of memory accesses. > If bad pointer passed to one of these function it is important > to catch this. Compiler's instrumentation cannot do this since > these functions are written in assembly. > KASan replaces memory functions with manually instrumented variants. > Original functions declared as weak symbols so strong definitions > in mm/kasan/kasan.c could replace them. Original functions have aliases > with '__' prefix in name, so we could call non-instrumented variant > if needed. > > Signed-off-by: Qing Zhang <zhangqing@loongson.cn> > --- > Documentation/dev-tools/kasan.rst | 4 +- > .../features/debug/KASAN/arch-support.txt | 2 +- > arch/loongarch/Kconfig | 7 + > arch/loongarch/include/asm/kasan.h | 120 +++++++++ > arch/loongarch/include/asm/pgtable.h | 7 + > arch/loongarch/include/asm/setup.h | 2 +- > arch/loongarch/include/asm/string.h | 20 ++ > arch/loongarch/kernel/Makefile | 3 + > arch/loongarch/kernel/head.S | 14 +- > arch/loongarch/kernel/relocate.c | 8 +- > arch/loongarch/kernel/setup.c | 4 + > arch/loongarch/lib/memcpy.S | 4 +- > arch/loongarch/lib/memmove.S | 13 +- > arch/loongarch/lib/memset.S | 4 +- > arch/loongarch/mm/Makefile | 2 + > arch/loongarch/mm/kasan_init.c | 255 ++++++++++++++++++ > arch/loongarch/vdso/Makefile | 4 + > include/linux/kasan.h | 2 + > mm/kasan/generic.c | 5 + > mm/kasan/init.c | 10 +- > mm/kasan/kasan.h | 6 + > 21 files changed, 470 insertions(+), 26 deletions(-) > create mode 100644 arch/loongarch/include/asm/kasan.h > create mode 100644 arch/loongarch/mm/kasan_init.c > > diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst > index e66916a483cd..ee91f2872767 100644 > --- a/Documentation/dev-tools/kasan.rst > +++ b/Documentation/dev-tools/kasan.rst > @@ -41,8 +41,8 @@ Support > Architectures > ~~~~~~~~~~~~~ > > -Generic KASAN is supported on x86_64, arm, arm64, powerpc, riscv, s390, and > -xtensa, and the tag-based KASAN modes are supported only on arm64. > +Generic KASAN is supported on x86_64, arm, arm64, powerpc, riscv, s390, xtensa, > +and loongarch, and the tag-based KASAN modes are supported only on arm64.
Maybe you need to update `Documentation/translations/zh_CN/dev-tools /kasan.rst` synchronously.
> > Compilers > ~~~~~~~~~ > diff --git a/Documentation/features/debug/KASAN/arch-support.txt b/Documentation/features/debug/KASAN/arch-support.txt > index bf0124fae643..c4581c2edb28 100644 > --- a/Documentation/features/debug/KASAN/arch-support.txt > +++ b/Documentation/features/debug/KASAN/arch-support.txt > @@ -13,7 +13,7 @@ > | csky: | TODO | > | hexagon: | TODO | > | ia64: | TODO | > - | loongarch: | TODO | > + | loongarch: | ok | > | m68k: | TODO | > | microblaze: | TODO | > | mips: | TODO | > diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig > index 72dd00f48b8c..61f883c51045 100644 > --- a/arch/loongarch/Kconfig > +++ b/arch/loongarch/Kconfig > @@ -7,6 +7,7 @@ config LOONGARCH > select ACPI_MCFG if ACPI > select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI > select ARCH_BINFMT_ELF_STATE > + select ARCH_DISABLE_KASAN_INLINE > select ARCH_ENABLE_MEMORY_HOTPLUG > select ARCH_ENABLE_MEMORY_HOTREMOVE > select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI > @@ -83,6 +84,7 @@ config LOONGARCH > select HAVE_ARCH_AUDITSYSCALL > select HAVE_ARCH_MMAP_RND_BITS if MMU > select HAVE_ARCH_SECCOMP_FILTER > + select HAVE_ARCH_KASAN if 64BIT > select HAVE_ARCH_TRACEHOOK > select HAVE_ARCH_TRANSPARENT_HUGEPAGE > select HAVE_ASM_MODVERSIONS > @@ -626,6 +628,11 @@ config ARCH_MMAP_RND_BITS_MIN > config ARCH_MMAP_RND_BITS_MAX > default 18 > > +config KASAN_SHADOW_OFFSET > + hex > + default 0x0 > + depends on KASAN > + > menu "Power management options" > > config ARCH_SUSPEND_POSSIBLE > diff --git a/arch/loongarch/include/asm/kasan.h b/arch/loongarch/include/asm/kasan.h > new file mode 100644 > index 000000000000..582bcded311e > --- /dev/null > +++ b/arch/loongarch/include/asm/kasan.h > @@ -0,0 +1,120 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ASM_KASAN_H > +#define __ASM_KASAN_H > + > +#ifndef __ASSEMBLY__ > + > +#include <linux/linkage.h> > +#include <linux/mmzone.h> > +#include <asm/addrspace.h> > +#include <asm/io.h> > +#include <asm/pgtable.h> > + > +#define __HAVE_ARCH_SHADOW_MAP > + > +#define KASAN_SHADOW_SCALE_SHIFT 3 > +#define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) > + > +#define XRANGE_SHIFT (48) > + > +/* Valid address length */ > +#define XRANGE_SHADOW_SHIFT (PGDIR_SHIFT + PAGE_SHIFT - 3) > +/* Used for taking out the valid address */ > +#define XRANGE_SHADOW_MASK GENMASK_ULL(XRANGE_SHADOW_SHIFT - 1, 0) > +/* One segment whole address space size */ > +#define XRANGE_SIZE (XRANGE_SHADOW_MASK + 1) > + > +/* 64-bit segment value. */ > +#define XKPRANGE_UC_SEG (0x8000) > +#define XKPRANGE_CC_SEG (0x9000) > +#define XKVRANGE_VC_SEG (0xffff) > + > +/* Cached */ > +#define XKPRANGE_CC_START CACHE_BASE > +#define XKPRANGE_CC_SIZE XRANGE_SIZE > +#define XKPRANGE_CC_KASAN_OFFSET (0) > +#define XKPRANGE_CC_SHADOW_SIZE (XKPRANGE_CC_SIZE >> KASAN_SHADOW_SCALE_SHIFT) > +#define XKPRANGE_CC_SHADOW_END (XKPRANGE_CC_KASAN_OFFSET + XKPRANGE_CC_SHADOW_SIZE) > + > +/* UnCached */ > +#define XKPRANGE_UC_START UNCACHE_BASE > +#define XKPRANGE_UC_SIZE XRANGE_SIZE > +#define XKPRANGE_UC_KASAN_OFFSET XKPRANGE_CC_SHADOW_END > +#define XKPRANGE_UC_SHADOW_SIZE (XKPRANGE_UC_SIZE >> KASAN_SHADOW_SCALE_SHIFT) > +#define XKPRANGE_UC_SHADOW_END (XKPRANGE_UC_KASAN_OFFSET + XKPRANGE_UC_SHADOW_SIZE) > + > +/* VMALLOC (Cached or UnCached) */ > +#define XKVRANGE_VC_START MODULES_VADDR > +#define XKVRANGE_VC_SIZE round_up(VMEMMAP_END - MODULES_VADDR + 1, PGDIR_SIZE) > +#define XKVRANGE_VC_KASAN_OFFSET XKPRANGE_UC_SHADOW_END > +#define XKVRANGE_VC_SHADOW_SIZE (XKVRANGE_VC_SIZE >> KASAN_SHADOW_SCALE_SHIFT) > +#define XKVRANGE_VC_SHADOW_END (XKVRANGE_VC_KASAN_OFFSET + XKVRANGE_VC_SHADOW_SIZE) > + > +/* Kasan shadow memory start right after vmalloc. */ > +#define KASAN_SHADOW_START round_up(VMEMMAP_END, PGDIR_SIZE) > +#define KASAN_SHADOW_SIZE (XKVRANGE_VC_SHADOW_END - XKPRANGE_CC_KASAN_OFFSET) > +#define KASAN_SHADOW_END round_up(KASAN_SHADOW_START + KASAN_SHADOW_SIZE, PGDIR_SIZE) > + > +#define XKPRANGE_CC_SHADOW_OFFSET (KASAN_SHADOW_START + XKPRANGE_CC_KASAN_OFFSET) > +#define XKPRANGE_UC_SHADOW_OFFSET (KASAN_SHADOW_START + XKPRANGE_UC_KASAN_OFFSET) > +#define XKVRANGE_VC_SHADOW_OFFSET (KASAN_SHADOW_START + XKVRANGE_VC_KASAN_OFFSET) > + > +extern bool kasan_early_stage; > +extern unsigned char kasan_early_shadow_page[PAGE_SIZE]; > + > +static inline void *kasan_mem_to_shadow(const void *addr) > +{ > + if (kasan_early_stage) { > + return (void *)(kasan_early_shadow_page); > + } else { > + unsigned long maddr = (unsigned long)addr; > + unsigned long xrange = (maddr >> XRANGE_SHIFT) & 0xffff; > + unsigned long offset = 0; > + > + maddr &= XRANGE_SHADOW_MASK; > + switch (xrange) { > + case XKPRANGE_CC_SEG: > + offset = XKPRANGE_CC_SHADOW_OFFSET; > + break; > + case XKPRANGE_UC_SEG: > + offset = XKPRANGE_UC_SHADOW_OFFSET; > + break; > + case XKVRANGE_VC_SEG: > + offset = XKVRANGE_VC_SHADOW_OFFSET; > + break; > + default: > + WARN_ON(1); > + return NULL;
When the "earlycon=uart,mmio,0x1fe001e0,115200n8" cmdline parameter is added under CONFIG_KASAN, the kernel will not start normally and stay at the following position: ... [ 0.000000] On node 0, zone DMA32: 4 pages in unavailable ranges [ 0.000000] On node 0, zone Normal: 8 pages in unavailable ranges [ 0.000000] On node 0, zone Normal: 8 pages in unavailable ranges [ 0.000000] On node 0, zone Normal: 160 pages in unavailable ranges [ 0.000000] On node 0, zone Normal: 256 pages in unavailable ranges
The reason is that when accessing the serial port address `0x1fe001e0`, kasan will add relevant checks, such as inserting `__asan_load1()`, and will eventually enter the `default` branch in kasan_mem_to_shadow(), causing the kernel to fail to start.
Add the following modification to avoid inserting the kasan check in 8250_early.o, and it will be able to start successfully.
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile index 4fc2fc1f41b6..3c17d0e72c83 100644 --- a/drivers/tty/serial/8250/Makefile +++ b/drivers/tty/serial/8250/Makefile @@ -3,6 +3,8 @@ # Makefile for the 8250 serial device drivers. #
+KASAN_SANITIZE_8250_early.o := n + obj-$(CONFIG_SERIAL_8250) += 8250.o 8250_base.o 8250-y := 8250_core.o 8250-$(CONFIG_ALPHA_GENERIC) += 8250_alpha.o Thanks, Youling
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