On Mon, Jan 29, 2024 at 09:46:52PM +0800, Tong Tiangen wrote:
> The copy_mc_to_kernel() helper is memory copy implementation that handles
> source exceptions. It can be used in memory copy scenarios that tolerate
> hardware memory errors(e.g: pmem_read/dax_copy_to_iter).
>
> Currnently, only x86 and ppc suuport this helper, after arm64 support
> machine check safe framework, we introduce copy_mc_to_kernel()
> implementation.
>
> Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/string.h | 5 +
> arch/arm64/include/asm/uaccess.h | 21 +++
> arch/arm64/lib/Makefile | 2 +-
> arch/arm64/lib/memcpy_mc.S | 257 +++++++++++++++++++++++++++++++
> mm/kasan/shadow.c | 12 ++
> 5 files changed, 296 insertions(+), 1 deletion(-)
> create mode 100644 arch/arm64/lib/memcpy_mc.S
Looking at the diffstat and code, this duplicates arch/arm64/lib/memcpy.S with
a few annotations. Duplicating that code is not maintainable, and so we cannot
take this as-is.
If you want a version that can handle faults that *must* be written such that
the code is shared with the regular memcpy. That could be done by using macros
to instantiate two copies (one with fault handling, the other without).
It would also be very helpful to see *any* indication that this has been
tested, which is sorely lacking in the series as-is.
Mark.
> diff --git a/arch/arm64/include/asm/string.h b/arch/arm64/include/asm/string.h
> index 3a3264ff47b9..995b63c26e99 100644
> --- a/arch/arm64/include/asm/string.h
> +++ b/arch/arm64/include/asm/string.h
> @@ -35,6 +35,10 @@ extern void *memchr(const void *, int, __kernel_size_t);
> extern void *memcpy(void *, const void *, __kernel_size_t);
> extern void *__memcpy(void *, const void *, __kernel_size_t);
>
> +#define __HAVE_ARCH_MEMCPY_MC
> +extern int memcpy_mcs(void *, const void *, __kernel_size_t);
> +extern int __memcpy_mcs(void *, const void *, __kernel_size_t);
> +
> #define __HAVE_ARCH_MEMMOVE
> extern void *memmove(void *, const void *, __kernel_size_t);
> extern void *__memmove(void *, const void *, __kernel_size_t);
> @@ -57,6 +61,7 @@ void memcpy_flushcache(void *dst, const void *src, size_t cnt);
> */
>
> #define memcpy(dst, src, len) __memcpy(dst, src, len)
> +#define memcpy_mcs(dst, src, len) __memcpy_mcs(dst, src, len)
> #define memmove(dst, src, len) __memmove(dst, src, len)
> #define memset(s, c, n) __memset(s, c, n)
>
> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
> index 14be5000c5a0..61e28ef2112a 100644
> --- a/arch/arm64/include/asm/uaccess.h
> +++ b/arch/arm64/include/asm/uaccess.h
> @@ -425,4 +425,25 @@ static inline size_t probe_subpage_writeable(const char __user *uaddr,
>
> #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
>
> +#ifdef CONFIG_ARCH_HAS_COPY_MC
> +/**
> + * copy_mc_to_kernel - memory copy that handles source exceptions
> + *
> + * @dst: destination address
> + * @src: source address
> + * @len: number of bytes to copy
> + *
> + * Return 0 for success, or #size if there was an exception.
> + */
> +static inline unsigned long __must_check
> +copy_mc_to_kernel(void *to, const void *from, unsigned long size)
> +{
> + int ret;
> +
> + ret = memcpy_mcs(to, from, size);
> + return (ret == -EFAULT) ? size : 0;
> +}
> +#define copy_mc_to_kernel copy_mc_to_kernel
> +#endif
> +
> #endif /* __ASM_UACCESS_H */
> diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
> index a2fd865b816d..899d6ae9698c 100644
> --- a/arch/arm64/lib/Makefile
> +++ b/arch/arm64/lib/Makefile
> @@ -3,7 +3,7 @@ lib-y := clear_user.o delay.o copy_from_user.o \
> copy_to_user.o copy_page.o \
> clear_page.o csum.o insn.o memchr.o memcpy.o \
> memset.o memcmp.o strcmp.o strncmp.o strlen.o \
> - strnlen.o strchr.o strrchr.o tishift.o
> + strnlen.o strchr.o strrchr.o tishift.o memcpy_mc.o
>
> ifeq ($(CONFIG_KERNEL_MODE_NEON), y)
> obj-$(CONFIG_XOR_BLOCKS) += xor-neon.o
> diff --git a/arch/arm64/lib/memcpy_mc.S b/arch/arm64/lib/memcpy_mc.S
> new file mode 100644
> index 000000000000..7076b500d154
> --- /dev/null
> +++ b/arch/arm64/lib/memcpy_mc.S
> @@ -0,0 +1,257 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2012-2021, Arm Limited.
> + *
> + * Adapted from the original at:
> + * https://github.com/ARM-software/optimized-routines/blob/afd6244a1f8d9229/string/aarch64/memcpy.S
> + */
> +
> +#include <linux/linkage.h>
> +#include <asm/assembler.h>
> +
> +/* Assumptions:
> + *
> + * ARMv8-a, AArch64, unaligned accesses.
> + *
> + */
> +
> +#define L(label) .L ## label
> +
> +#define dstin x0
> +#define src x1
> +#define count x2
> +#define dst x3
> +#define srcend x4
> +#define dstend x5
> +#define A_l x6
> +#define A_lw w6
> +#define A_h x7
> +#define B_l x8
> +#define B_lw w8
> +#define B_h x9
> +#define C_l x10
> +#define C_lw w10
> +#define C_h x11
> +#define D_l x12
> +#define D_h x13
> +#define E_l x14
> +#define E_h x15
> +#define F_l x16
> +#define F_h x17
> +#define G_l count
> +#define G_h dst
> +#define H_l src
> +#define H_h srcend
> +#define tmp1 x14
> +
> +/* This implementation handles overlaps and supports both memcpy and memmove
> + from a single entry point. It uses unaligned accesses and branchless
> + sequences to keep the code small, simple and improve performance.
> +
> + Copies are split into 3 main cases: small copies of up to 32 bytes, medium
> + copies of up to 128 bytes, and large copies. The overhead of the overlap
> + check is negligible since it is only required for large copies.
> +
> + Large copies use a software pipelined loop processing 64 bytes per iteration.
> + The destination pointer is 16-byte aligned to minimize unaligned accesses.
> + The loop tail is handled by always copying 64 bytes from the end.
> +*/
> +
> +SYM_FUNC_START(__pi_memcpy_mcs)
> + add srcend, src, count
> + add dstend, dstin, count
> + cmp count, 128
> + b.hi L(copy_long)
> + cmp count, 32
> + b.hi L(copy32_128)
> +
> + /* Small copies: 0..32 bytes. */
> + cmp count, 16
> + b.lo L(copy16)
> + CPY_MC(9998f, ldp A_l, A_h, [src])
> + CPY_MC(9998f, ldp D_l, D_h, [srcend, -16])
> + CPY_MC(9998f, stp A_l, A_h, [dstin])
> + CPY_MC(9998f, stp D_l, D_h, [dstend, -16])
> + mov x0, #0
> + ret
> +
> + /* Copy 8-15 bytes. */
> +L(copy16):
> + tbz count, 3, L(copy8)
> + CPY_MC(9998f, ldr A_l, [src])
> + CPY_MC(9998f, ldr A_h, [srcend, -8])
> + CPY_MC(9998f, str A_l, [dstin])
> + CPY_MC(9998f, str A_h, [dstend, -8])
> + mov x0, #0
> + ret
> +
> + .p2align 3
> + /* Copy 4-7 bytes. */
> +L(copy8):
> + tbz count, 2, L(copy4)
> + CPY_MC(9998f, ldr A_lw, [src])
> + CPY_MC(9998f, ldr B_lw, [srcend, -4])
> + CPY_MC(9998f, str A_lw, [dstin])
> + CPY_MC(9998f, str B_lw, [dstend, -4])
> + mov x0, #0
> + ret
> +
> + /* Copy 0..3 bytes using a branchless sequence. */
> +L(copy4):
> + cbz count, L(copy0)
> + lsr tmp1, count, 1
> + CPY_MC(9998f, ldrb A_lw, [src])
> + CPY_MC(9998f, ldrb C_lw, [srcend, -1])
> + CPY_MC(9998f, ldrb B_lw, [src, tmp1])
> + CPY_MC(9998f, strb A_lw, [dstin])
> + CPY_MC(9998f, strb B_lw, [dstin, tmp1])
> + CPY_MC(9998f, strb C_lw, [dstend, -1])
> +L(copy0):
> + mov x0, #0
> + ret
> +
> + .p2align 4
> + /* Medium copies: 33..128 bytes. */
> +L(copy32_128):
> + CPY_MC(9998f, ldp A_l, A_h, [src])
> + CPY_MC(9998f, ldp B_l, B_h, [src, 16])
> + CPY_MC(9998f, ldp C_l, C_h, [srcend, -32])
> + CPY_MC(9998f, ldp D_l, D_h, [srcend, -16])
> + cmp count, 64
> + b.hi L(copy128)
> + CPY_MC(9998f, stp A_l, A_h, [dstin])
> + CPY_MC(9998f, stp B_l, B_h, [dstin, 16])
> + CPY_MC(9998f, stp C_l, C_h, [dstend, -32])
> + CPY_MC(9998f, stp D_l, D_h, [dstend, -16])
> + mov x0, #0
> + ret
> +
> + .p2align 4
> + /* Copy 65..128 bytes. */
> +L(copy128):
> + CPY_MC(9998f, ldp E_l, E_h, [src, 32])
> + CPY_MC(9998f, ldp F_l, F_h, [src, 48])
> + cmp count, 96
> + b.ls L(copy96)
> + CPY_MC(9998f, ldp G_l, G_h, [srcend, -64])
> + CPY_MC(9998f, ldp H_l, H_h, [srcend, -48])
> + CPY_MC(9998f, stp G_l, G_h, [dstend, -64])
> + CPY_MC(9998f, stp H_l, H_h, [dstend, -48])
> +L(copy96):
> + CPY_MC(9998f, stp A_l, A_h, [dstin])
> + CPY_MC(9998f, stp B_l, B_h, [dstin, 16])
> + CPY_MC(9998f, stp E_l, E_h, [dstin, 32])
> + CPY_MC(9998f, stp F_l, F_h, [dstin, 48])
> + CPY_MC(9998f, stp C_l, C_h, [dstend, -32])
> + CPY_MC(9998f, stp D_l, D_h, [dstend, -16])
> + mov x0, #0
> + ret
> +
> + .p2align 4
> + /* Copy more than 128 bytes. */
> +L(copy_long):
> + /* Use backwards copy if there is an overlap. */
> + sub tmp1, dstin, src
> + cbz tmp1, L(copy0)
> + cmp tmp1, count
> + b.lo L(copy_long_backwards)
> +
> + /* Copy 16 bytes and then align dst to 16-byte alignment. */
> +
> + CPY_MC(9998f, ldp D_l, D_h, [src])
> + and tmp1, dstin, 15
> + bic dst, dstin, 15
> + sub src, src, tmp1
> + add count, count, tmp1 /* Count is now 16 too large. */
> + CPY_MC(9998f, ldp A_l, A_h, [src, 16])
> + CPY_MC(9998f, stp D_l, D_h, [dstin])
> + CPY_MC(9998f, ldp B_l, B_h, [src, 32])
> + CPY_MC(9998f, ldp C_l, C_h, [src, 48])
> + CPY_MC(9998f, ldp D_l, D_h, [src, 64]!)
> + subs count, count, 128 + 16 /* Test and readjust count. */
> + b.ls L(copy64_from_end)
> +
> +L(loop64):
> + CPY_MC(9998f, stp A_l, A_h, [dst, 16])
> + CPY_MC(9998f, ldp A_l, A_h, [src, 16])
> + CPY_MC(9998f, stp B_l, B_h, [dst, 32])
> + CPY_MC(9998f, ldp B_l, B_h, [src, 32])
> + CPY_MC(9998f, stp C_l, C_h, [dst, 48])
> + CPY_MC(9998f, ldp C_l, C_h, [src, 48])
> + CPY_MC(9998f, stp D_l, D_h, [dst, 64]!)
> + CPY_MC(9998f, ldp D_l, D_h, [src, 64]!)
> + subs count, count, 64
> + b.hi L(loop64)
> +
> + /* Write the last iteration and copy 64 bytes from the end. */
> +L(copy64_from_end):
> + CPY_MC(9998f, ldp E_l, E_h, [srcend, -64])
> + CPY_MC(9998f, stp A_l, A_h, [dst, 16])
> + CPY_MC(9998f, ldp A_l, A_h, [srcend, -48])
> + CPY_MC(9998f, stp B_l, B_h, [dst, 32])
> + CPY_MC(9998f, ldp B_l, B_h, [srcend, -32])
> + CPY_MC(9998f, stp C_l, C_h, [dst, 48])
> + CPY_MC(9998f, ldp C_l, C_h, [srcend, -16])
> + CPY_MC(9998f, stp D_l, D_h, [dst, 64])
> + CPY_MC(9998f, stp E_l, E_h, [dstend, -64])
> + CPY_MC(9998f, stp A_l, A_h, [dstend, -48])
> + CPY_MC(9998f, stp B_l, B_h, [dstend, -32])
> + CPY_MC(9998f, stp C_l, C_h, [dstend, -16])
> + mov x0, #0
> + ret
> +
> + .p2align 4
> +
> + /* Large backwards copy for overlapping copies.
> + Copy 16 bytes and then align dst to 16-byte alignment. */
> +L(copy_long_backwards):
> + CPY_MC(9998f, ldp D_l, D_h, [srcend, -16])
> + and tmp1, dstend, 15
> + sub srcend, srcend, tmp1
> + sub count, count, tmp1
> + CPY_MC(9998f, ldp A_l, A_h, [srcend, -16])
> + CPY_MC(9998f, stp D_l, D_h, [dstend, -16])
> + CPY_MC(9998f, ldp B_l, B_h, [srcend, -32])
> + CPY_MC(9998f, ldp C_l, C_h, [srcend, -48])
> + CPY_MC(9998f, ldp D_l, D_h, [srcend, -64]!)
> + sub dstend, dstend, tmp1
> + subs count, count, 128
> + b.ls L(copy64_from_start)
> +
> +L(loop64_backwards):
> + CPY_MC(9998f, stp A_l, A_h, [dstend, -16])
> + CPY_MC(9998f, ldp A_l, A_h, [srcend, -16])
> + CPY_MC(9998f, stp B_l, B_h, [dstend, -32])
> + CPY_MC(9998f, ldp B_l, B_h, [srcend, -32])
> + CPY_MC(9998f, stp C_l, C_h, [dstend, -48])
> + CPY_MC(9998f, ldp C_l, C_h, [srcend, -48])
> + CPY_MC(9998f, stp D_l, D_h, [dstend, -64]!)
> + CPY_MC(9998f, ldp D_l, D_h, [srcend, -64]!)
> + subs count, count, 64
> + b.hi L(loop64_backwards)
> +
> + /* Write the last iteration and copy 64 bytes from the start. */
> +L(copy64_from_start):
> + CPY_MC(9998f, ldp G_l, G_h, [src, 48])
> + CPY_MC(9998f, stp A_l, A_h, [dstend, -16])
> + CPY_MC(9998f, ldp A_l, A_h, [src, 32])
> + CPY_MC(9998f, stp B_l, B_h, [dstend, -32])
> + CPY_MC(9998f, ldp B_l, B_h, [src, 16])
> + CPY_MC(9998f, stp C_l, C_h, [dstend, -48])
> + CPY_MC(9998f, ldp C_l, C_h, [src])
> + CPY_MC(9998f, stp D_l, D_h, [dstend, -64])
> + CPY_MC(9998f, stp G_l, G_h, [dstin, 48])
> + CPY_MC(9998f, stp A_l, A_h, [dstin, 32])
> + CPY_MC(9998f, stp B_l, B_h, [dstin, 16])
> + CPY_MC(9998f, stp C_l, C_h, [dstin])
> + mov x0, #0
> + ret
> +
> +9998: mov x0, #-EFAULT
> + ret
> +SYM_FUNC_END(__pi_memcpy_mcs)
> +
> +SYM_FUNC_ALIAS(__memcpy_mcs, __pi_memcpy_mcs)
> +EXPORT_SYMBOL(__memcpy_mcs)
> +SYM_FUNC_ALIAS_WEAK(memcpy_mcs, __memcpy_mcs)
> +EXPORT_SYMBOL(memcpy_mcs)
> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
> index 9ef84f31833f..e6519fd329b2 100644
> --- a/mm/kasan/shadow.c
> +++ b/mm/kasan/shadow.c
> @@ -79,6 +79,18 @@ void *memcpy(void *dest, const void *src, size_t len)
> }
> #endif
>
> +#ifdef __HAVE_ARCH_MEMCPY_MC
> +#undef memcpy_mcs
> +int memcpy_mcs(void *dest, const void *src, size_t len)
> +{
> + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
> + !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
> + return (unsigned long)len;
> +
> + return __memcpy_mcs(dest, src, len);
> +}
> +#endif
> +
> void *__asan_memset(void *addr, int c, ssize_t len)
> {
> if (!kasan_check_range(addr, len, true, _RET_IP_))
> --
> 2.25.1
>
