[PATCH -next v5 8/8] arm64: add cow to machine check safe

Tong Tiangen
2022-05-28T06:32:37Z

In the cow(copy on write) processing, the data of the user process is
copied, when hardware memory error is encountered during copy, only the
relevant processes are affected, so killing the user process and isolate
the user page with hardware memory errors is a more reasonable choice than
kernel panic.

Add new helper copy_page_mc() which provide a page copy implementation with
machine check safe. At present, only used in cow. In future, we can expand
more scenes. As long as the consequences of page copy failure are not
fatal(eg: only affect user process), we can use this helper.

The copy_page_mc() in copy_page_mc.S is largely borrows from copy_page()
in copy_page.S and the main difference is copy_page_mc() add extable entry
to every load/store insn to support machine check safe. largely to keep the
patch simple. If needed those optimizations can be folded in.

Add new extable type EX_TYPE_COPY_PAGE_MC which used in copy_page_mc().

Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
---
arch/arm64/include/asm/asm-extable.h | 10 ++++
arch/arm64/include/asm/mte.h | 4 ++
arch/arm64/include/asm/page.h | 10 ++++
arch/arm64/lib/Makefile | 2 +
arch/arm64/lib/copy_page_mc.S | 82 ++++++++++++++++++++++++++++
arch/arm64/lib/mte.S | 19 +++++++
arch/arm64/mm/copypage.c | 41 +++++++++++---
arch/arm64/mm/extable.c | 9 +++
include/linux/highmem.h | 8 +++
mm/memory.c | 2 +-
10 files changed, 179 insertions(+), 8 deletions(-)
create mode 100644 arch/arm64/lib/copy_page_mc.S

diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
index 1f2974467273..6f626388c176 100644
--- a/arch/arm64/include/asm/asm-extable.h
+++ b/arch/arm64/include/asm/asm-extable.h
@@ -7,6 +7,7 @@
#define EX_TYPE_UACCESS_ERR_ZERO 2
#define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 3
#define EX_TYPE_KACCESS_ERR_ZERO 4
+#define EX_TYPE_COPY_PAGE_MC 5

#ifdef __ASSEMBLY__

@@ -27,6 +28,11 @@
.macro _asm_extable_uaccess, insn, fixup
__ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_UACCESS_ERR_ZERO, ~0)
.endm
+
+ .macro _asm_extable_copy_page_mc, insn, fixup
+ __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_COPY_PAGE_MC, 0)
+ .endm
+
/*
* Create an exception table entry for `insn` if `fixup` is provided. Otherwise
* do nothing.
@@ -37,6 +43,10 @@
.endif
.endm

+#define CPY_MC(l, x...) \
+9999: x; \
+ _asm_extable_copy_page_mc 9999b, l
+
#else /* __ASSEMBLY__ */

#include <linux/bits.h>
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index aa523591a44e..b8129f64cfea 100644
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -40,6 +40,7 @@ void mte_free_tag_storage(char *storage);
void mte_zero_clear_page_tags(void *addr);
void mte_sync_tags(pte_t old_pte, pte_t pte);
void mte_copy_page_tags(void *kto, const void *kfrom);
+void mte_copy_page_tags_mc(void *kto, const void *kfrom);
void mte_thread_init_user(void);
void mte_thread_switch(struct task_struct *next);
void mte_suspend_enter(void);
@@ -63,6 +64,9 @@ static inline void mte_sync_tags(pte_t old_pte, pte_t pte)
static inline void mte_copy_page_tags(void *kto, const void *kfrom)
{
}
+static inline void mte_copy_page_tags_mc(void *kto, const void *kfrom)
+{
+}
static inline void mte_thread_init_user(void)
{
}
diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
index 993a27ea6f54..832571a7dddb 100644
--- a/arch/arm64/include/asm/page.h
+++ b/arch/arm64/include/asm/page.h
@@ -29,6 +29,16 @@ void copy_user_highpage(struct page *to, struct page *from,
void copy_highpage(struct page *to, struct page *from);
#define __HAVE_ARCH_COPY_HIGHPAGE

+#ifdef CONFIG_ARCH_HAS_COPY_MC
+extern void copy_page_mc(void *to, const void *from);
+void copy_highpage_mc(struct page *to, struct page *from);
+#define __HAVE_ARCH_COPY_HIGHPAGE_MC
+
+void copy_user_highpage_mc(struct page *to, struct page *from,
+ unsigned long vaddr, struct vm_area_struct *vma);
+#define __HAVE_ARCH_COPY_USER_HIGHPAGE_MC
+#endif
+
struct page *alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
unsigned long vaddr);
#define __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index 29490be2546b..0d9f292ef68a 100644
--- a/arch/arm64/lib/Makefile
+++ b/arch/arm64/lib/Makefile
@@ -15,6 +15,8 @@ endif

lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o

+lib-$(CONFIG_ARCH_HAS_COPY_MC) += copy_page_mc.o
+
obj-$(CONFIG_CRC32) += crc32.o

obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
diff --git a/arch/arm64/lib/copy_page_mc.S b/arch/arm64/lib/copy_page_mc.S
new file mode 100644
index 000000000000..65fcad1dd7c8
--- /dev/null
+++ b/arch/arm64/lib/copy_page_mc.S
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ */
+
+#include <linux/linkage.h>
+#include <linux/const.h>
+#include <asm/assembler.h>
+#include <asm/page.h>
+#include <asm/cpufeature.h>
+#include <asm/alternative.h>
+#include <asm/asm-extable.h>
+
+/*
+ * Copy a page from src to dest (both are page aligned) with machine check
+ *
+ * Parameters:
+ * x0 - dest
+ * x1 - src
+ */
+SYM_FUNC_START(__pi_copy_page_mc)
+alternative_if ARM64_HAS_NO_HW_PREFETCH
+ // Prefetch three cache lines ahead.
+ prfm pldl1strm, [x1, #128]
+ prfm pldl1strm, [x1, #256]
+ prfm pldl1strm, [x1, #384]
+alternative_else_nop_endif
+
+CPY_MC(9998f, ldp x2, x3, [x1])
+CPY_MC(9998f, ldp x4, x5, [x1, #16])
+CPY_MC(9998f, ldp x6, x7, [x1, #32])
+CPY_MC(9998f, ldp x8, x9, [x1, #48])
+CPY_MC(9998f, ldp x10, x11, [x1, #64])
+CPY_MC(9998f, ldp x12, x13, [x1, #80])
+CPY_MC(9998f, ldp x14, x15, [x1, #96])
+CPY_MC(9998f, ldp x16, x17, [x1, #112])
+
+ add x0, x0, #256
+ add x1, x1, #128
+1:
+ tst x0, #(PAGE_SIZE - 1)
+
+alternative_if ARM64_HAS_NO_HW_PREFETCH
+ prfm pldl1strm, [x1, #384]
+alternative_else_nop_endif
+
+CPY_MC(9998f, stnp x2, x3, [x0, #-256])
+CPY_MC(9998f, ldp x2, x3, [x1])
+CPY_MC(9998f, stnp x4, x5, [x0, #16 - 256])
+CPY_MC(9998f, ldp x4, x5, [x1, #16])
+CPY_MC(9998f, stnp x6, x7, [x0, #32 - 256])
+CPY_MC(9998f, ldp x6, x7, [x1, #32])
+CPY_MC(9998f, stnp x8, x9, [x0, #48 - 256])
+CPY_MC(9998f, ldp x8, x9, [x1, #48])
+CPY_MC(9998f, stnp x10, x11, [x0, #64 - 256])
+CPY_MC(9998f, ldp x10, x11, [x1, #64])
+CPY_MC(9998f, stnp x12, x13, [x0, #80 - 256])
+CPY_MC(9998f, ldp x12, x13, [x1, #80])
+CPY_MC(9998f, stnp x14, x15, [x0, #96 - 256])
+CPY_MC(9998f, ldp x14, x15, [x1, #96])
+CPY_MC(9998f, stnp x16, x17, [x0, #112 - 256])
+CPY_MC(9998f, ldp x16, x17, [x1, #112])
+
+ add x0, x0, #128
+ add x1, x1, #128
+
+ b.ne 1b
+
+CPY_MC(9998f, stnp x2, x3, [x0, #-256])
+CPY_MC(9998f, stnp x4, x5, [x0, #16 - 256])
+CPY_MC(9998f, stnp x6, x7, [x0, #32 - 256])
+CPY_MC(9998f, stnp x8, x9, [x0, #48 - 256])
+CPY_MC(9998f, stnp x10, x11, [x0, #64 - 256])
+CPY_MC(9998f, stnp x12, x13, [x0, #80 - 256])
+CPY_MC(9998f, stnp x14, x15, [x0, #96 - 256])
+CPY_MC(9998f, stnp x16, x17, [x0, #112 - 256])
+
+9998: ret
+
+SYM_FUNC_END(__pi_copy_page_mc)
+SYM_FUNC_ALIAS(copy_page_mc, __pi_copy_page_mc)
+EXPORT_SYMBOL(copy_page_mc)
diff --git a/arch/arm64/lib/mte.S b/arch/arm64/lib/mte.S
index eeb9e45bcce8..cf728a9f39b5 100644
--- a/arch/arm64/lib/mte.S
+++ b/arch/arm64/lib/mte.S
@@ -80,6 +80,25 @@ SYM_FUNC_START(mte_copy_page_tags)
ret
SYM_FUNC_END(mte_copy_page_tags)

+/*
+ * Copy the tags from the source page to the destination one wiht machine check safe
+ * x0 - address of the destination page
+ * x1 - address of the source page
+ */
+SYM_FUNC_START(mte_copy_page_tags_mc)
+ mov x2, x0
+ mov x3, x1
+ multitag_transfer_size x5, x6
+1:
+CPY_MC(2f, ldgm x4, [x3])
+ stgm x4, [x2]
+ add x2, x2, x5
+ add x3, x3, x5
+ tst x2, #(PAGE_SIZE - 1)
+ b.ne 1b
+2: ret
+SYM_FUNC_END(mte_copy_page_tags_mc)
+
/*
* Read tags from a user buffer (one tag per byte) and set the corresponding
* tags at the given kernel address. Used by PTRACE_POKEMTETAGS.
diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c
index 0dea80bf6de4..d68c5fc753a2 100644
--- a/arch/arm64/mm/copypage.c
+++ b/arch/arm64/mm/copypage.c
@@ -14,13 +14,8 @@
#include <asm/cpufeature.h>
#include <asm/mte.h>

-void copy_highpage(struct page *to, struct page *from)
+static void do_mte(struct page *to, struct page *from, void *kto, void *kfrom, bool mc)
{
- void *kto = page_address(to);
- void *kfrom = page_address(from);
-
- copy_page(kto, kfrom);
-
if (system_supports_mte() && test_bit(PG_mte_tagged, &from->flags)) {
set_bit(PG_mte_tagged, &to->flags);
page_kasan_tag_reset(to);
@@ -32,9 +27,21 @@ void copy_highpage(struct page *to, struct page *from)
* the new page->flags are visible before the tags were updated.
*/
smp_wmb();
- mte_copy_page_tags(kto, kfrom);
+ if (mc)
+ mte_copy_page_tags_mc(kto, kfrom);
+ else
+ mte_copy_page_tags(kto, kfrom);
}
}
+
+void copy_highpage(struct page *to, struct page *from)
+{
+ void *kto = page_address(to);
+ void *kfrom = page_address(from);
+
+ copy_page(kto, kfrom);
+ do_mte(to, from, kto, kfrom, false);
+}
EXPORT_SYMBOL(copy_highpage);

void copy_user_highpage(struct page *to, struct page *from,
@@ -44,3 +51,23 @@ void copy_user_highpage(struct page *to, struct page *from,
flush_dcache_page(to);
}
EXPORT_SYMBOL_GPL(copy_user_highpage);
+
+#ifdef CONFIG_ARCH_HAS_COPY_MC
+void copy_highpage_mc(struct page *to, struct page *from)
+{
+ void *kto = page_address(to);
+ void *kfrom = page_address(from);
+
+ copy_page_mc(kto, kfrom);
+ do_mte(to, from, kto, kfrom, true);
+}
+EXPORT_SYMBOL(copy_highpage_mc);
+
+void copy_user_highpage_mc(struct page *to, struct page *from,
+ unsigned long vaddr, struct vm_area_struct *vma)
+{
+ copy_highpage_mc(to, from);
+ flush_dcache_page(to);
+}
+EXPORT_SYMBOL_GPL(copy_user_highpage_mc);
+#endif
diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
index 8ca8d9639f9f..c96274a4db40 100644
--- a/arch/arm64/mm/extable.c
+++ b/arch/arm64/mm/extable.c
@@ -17,6 +17,13 @@ get_ex_fixup(const struct exception_table_entry *ex)
return ((unsigned long)&ex->fixup + ex->fixup);
}

+static bool ex_handler_fixup(const struct exception_table_entry *ex,
+ struct pt_regs *regs)
+{
+ regs->pc = get_ex_fixup(ex);
+ return true;
+}
+
static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
struct pt_regs *regs)
{
@@ -89,6 +96,8 @@ bool fixup_exception_mc(struct pt_regs *regs)
switch (ex->type) {
case EX_TYPE_UACCESS_ERR_ZERO:
return ex_handler_uaccess_err_zero(ex, regs);
+ case EX_TYPE_COPY_PAGE_MC:
+ return ex_handler_fixup(ex, regs);
}

return false;
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 3af34de54330..6c19e6bc0746 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -308,6 +308,10 @@ static inline void copy_user_highpage(struct page *to, struct page *from,

#endif

+#ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE_MC
+#define copy_user_highpage_mc copy_user_highpage
+#endif
+
#ifndef __HAVE_ARCH_COPY_HIGHPAGE

static inline void copy_highpage(struct page *to, struct page *from)
@@ -323,6 +327,10 @@ static inline void copy_highpage(struct page *to, struct page *from)

#endif

+#ifndef __HAVE_ARCH_COPY_HIGHPAGE_MC
+#define cop_highpage_mc copy_highpage
+#endif
+
static inline void memcpy_page(struct page *dst_page, size_t dst_off,
struct page *src_page, size_t src_off,
size_t len)
diff --git a/mm/memory.c b/mm/memory.c
index 21dadf03f089..06408451ed38 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2845,7 +2845,7 @@ static inline bool __wp_page_copy_user(struct page *dst, struct page *src,
unsigned long addr = vmf->address;

if (likely(src)) {
- copy_user_highpage(dst, src, addr, vma);
+ copy_user_highpage_mc(dst, src, addr, vma);
return true;
}

--
2.25.1