[PATCH v7 3/3] x86, mce: Add __mcsafe_copy()
From: Tony Luck
Date: Mon Jan 04 2016 - 19:13:48 EST
Make use of the EXTABLE_FAULT exception table entries. This routine
returns a structure to indicate the result of the copy:
struct mcsafe_ret {
u64 trapnr;
u64 remain;
};
If the copy is successful, then both 'trapnr' and 'remain' are zero.
If we faulted during the copy, then 'trapnr' will say which type
of trap (X86_TRAP_PF or X86_TRAP_MC) and 'remain' says how many
bytes were not copied.
Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
arch/x86/Kconfig | 10 +++
arch/x86/include/asm/string_64.h | 10 +++
arch/x86/kernel/x8664_ksyms_64.c | 4 ++
arch/x86/lib/memcpy_64.S | 136 +++++++++++++++++++++++++++++++++++++++
4 files changed, 160 insertions(+)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 96d058a87100..42d26b4d1ec4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1001,6 +1001,16 @@ config X86_MCE_INJECT
If you don't know what a machine check is and you don't do kernel
QA it is safe to say n.
+config MCE_KERNEL_RECOVERY
+ bool "Recovery from machine checks in special kernel memory copy functions"
+ default n
+ depends on X86_MCE && X86_64
+ ---help---
+ This option provides a new memory copy function mcsafe_memcpy()
+ that is annotated to allow the machine check handler to return
+ to an alternate code path to return an error to the caller instead
+ of crashing the system. Say yes if you have a driver that uses this.
+
config X86_THERMAL_VECTOR
def_bool y
depends on X86_MCE_INTEL
diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h
index ff8b9a17dc4b..16a8f0e56e4a 100644
--- a/arch/x86/include/asm/string_64.h
+++ b/arch/x86/include/asm/string_64.h
@@ -78,6 +78,16 @@ int strcmp(const char *cs, const char *ct);
#define memset(s, c, n) __memset(s, c, n)
#endif
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+struct mcsafe_ret {
+ u64 trapnr;
+ u64 remain;
+};
+
+struct mcsafe_ret __mcsafe_copy(void *dst, const void __user *src, size_t cnt);
+extern void __mcsafe_copy_end(void);
+#endif
+
#endif /* __KERNEL__ */
#endif /* _ASM_X86_STRING_64_H */
diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c
index a0695be19864..3d42d0ef3333 100644
--- a/arch/x86/kernel/x8664_ksyms_64.c
+++ b/arch/x86/kernel/x8664_ksyms_64.c
@@ -37,6 +37,10 @@ EXPORT_SYMBOL(__copy_user_nocache);
EXPORT_SYMBOL(_copy_from_user);
EXPORT_SYMBOL(_copy_to_user);
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+EXPORT_SYMBOL(__mcsafe_copy);
+#endif
+
EXPORT_SYMBOL(copy_page);
EXPORT_SYMBOL(clear_page);
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 16698bba87de..e5b1acad8b1e 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -177,3 +177,139 @@ ENTRY(memcpy_orig)
.Lend:
retq
ENDPROC(memcpy_orig)
+
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+/*
+ * __mcsafe_copy - memory copy with machine check exception handling
+ * Note that we only catch machine checks when reading the source addresses.
+ * Writes to target are posted and don't generate machine checks.
+ */
+ENTRY(__mcsafe_copy)
+ cmpl $8,%edx
+ jb 20f /* less then 8 bytes, go to byte copy loop */
+
+ /* check for bad alignment of source */
+ movl %esi,%ecx
+ andl $7,%ecx
+ jz 102f /* already aligned */
+ subl $8,%ecx
+ negl %ecx
+ subl %ecx,%edx
+0: movb (%rsi),%al
+ movb %al,(%rdi)
+ incq %rsi
+ incq %rdi
+ decl %ecx
+ jnz 0b
+102:
+ movl %edx,%ecx
+ andl $63,%edx
+ shrl $6,%ecx
+ jz 17f
+1: movq (%rsi),%r8
+2: movq 1*8(%rsi),%r9
+3: movq 2*8(%rsi),%r10
+4: movq 3*8(%rsi),%r11
+ mov %r8,(%rdi)
+ mov %r9,1*8(%rdi)
+ mov %r10,2*8(%rdi)
+ mov %r11,3*8(%rdi)
+9: movq 4*8(%rsi),%r8
+10: movq 5*8(%rsi),%r9
+11: movq 6*8(%rsi),%r10
+12: movq 7*8(%rsi),%r11
+ mov %r8,4*8(%rdi)
+ mov %r9,5*8(%rdi)
+ mov %r10,6*8(%rdi)
+ mov %r11,7*8(%rdi)
+ leaq 64(%rsi),%rsi
+ leaq 64(%rdi),%rdi
+ decl %ecx
+ jnz 1b
+17: movl %edx,%ecx
+ andl $7,%edx
+ shrl $3,%ecx
+ jz 20f
+18: movq (%rsi),%r8
+ mov %r8,(%rdi)
+ leaq 8(%rsi),%rsi
+ leaq 8(%rdi),%rdi
+ decl %ecx
+ jnz 18b
+20: andl %edx,%edx
+ jz 23f
+ movl %edx,%ecx
+21: movb (%rsi),%al
+ movb %al,(%rdi)
+ incq %rsi
+ incq %rdi
+ decl %ecx
+ jnz 21b
+23: xorq %rax, %rax
+ xorq %rdx, %rdx
+ sfence
+ /* copy successful. return 0 */
+ ret
+
+ .section .fixup,"ax"
+ /* fixups for machine check */
+30:
+ add %ecx,%edx
+ jmp 100f
+31:
+ shl $6,%ecx
+ add %ecx,%edx
+ jmp 100f
+32:
+ shl $6,%ecx
+ lea -8(%ecx,%edx),%edx
+ jmp 100f
+33:
+ shl $6,%ecx
+ lea -16(%ecx,%edx),%edx
+ jmp 100f
+34:
+ shl $6,%ecx
+ lea -24(%ecx,%edx),%edx
+ jmp 100f
+35:
+ shl $6,%ecx
+ lea -32(%ecx,%edx),%edx
+ jmp 100f
+36:
+ shl $6,%ecx
+ lea -40(%ecx,%edx),%edx
+ jmp 100f
+37:
+ shl $6,%ecx
+ lea -48(%ecx,%edx),%edx
+ jmp 100f
+38:
+ shl $6,%ecx
+ lea -56(%ecx,%edx),%edx
+ jmp 100f
+39:
+ lea (%rdx,%rcx,8),%rdx
+ jmp 100f
+40:
+ mov %ecx,%edx
+100:
+ sfence
+
+ /* %rax set the fault number in fixup_exception() */
+ ret
+ .previous
+
+ _ASM_EXTABLE_FAULT(0b,30b)
+ _ASM_EXTABLE_FAULT(1b,31b)
+ _ASM_EXTABLE_FAULT(2b,32b)
+ _ASM_EXTABLE_FAULT(3b,33b)
+ _ASM_EXTABLE_FAULT(4b,34b)
+ _ASM_EXTABLE_FAULT(9b,35b)
+ _ASM_EXTABLE_FAULT(10b,36b)
+ _ASM_EXTABLE_FAULT(11b,37b)
+ _ASM_EXTABLE_FAULT(12b,38b)
+ _ASM_EXTABLE_FAULT(18b,39b)
+ _ASM_EXTABLE_FAULT(21b,40b)
+ENDPROC(__mcsafe_copy)
+#endif
--
2.1.4
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