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Message-Id: <ce84932301823b991b9b439a4715be93f1912c05.1451002295.git.tony.luck@intel.com> Date: Tue, 15 Dec 2015 17:30:49 -0800 From: Tony Luck <tony.luck@...el.com> To: Ingo Molnar <mingo@...nel.org> Cc: Borislav Petkov <bp@...en8.de>, Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Dan Williams <dan.j.williams@...el.com>, <elliott@....com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-nvdimm@...1.01.org, x86@...nel.org Subject: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from machine checks Using __copy_user_nocache() as inspiration create a memory copy routine for use by kernel code with annotations to allow for recovery from machine checks. Notes: 1) We align the source address rather than the destination. This means we never have to deal with a memory read that spans two cache lines ... so we can provide a precise indication of where the error occurred without having to re-execute at a byte-by-byte level to find the exact spot like the original did. 2) We 'or' BIT(63) into the return if the copy failed because of a machine check. If we failed during a copy from user space because the user provided a bad address, then we just return then number of bytes not copied like other copy_from_user functions. 3) This code doesn't play any cache games. Future functions can use non-temporal loads/stores to meet needs of different callers. 4) Provide helpful macros to decode the return value. Signed-off-by: Tony Luck <tony.luck@...el.com> --- Boris: This version has all the return options coded. return 0; /* SUCCESS */ return remain_bytes | (1ul << 63); /* failed because of machine check */ return remain_bytes; /* failed because of invalid source address */ arch/x86/include/asm/string_64.h | 8 ++ arch/x86/kernel/x8664_ksyms_64.c | 4 + arch/x86/lib/memcpy_64.S | 202 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 214 insertions(+) diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index ff8b9a17dc4b..4359ebb86b86 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -78,6 +78,14 @@ int strcmp(const char *cs, const char *ct); #define memset(s, c, n) __memset(s, c, n) #endif +#ifdef CONFIG_MCE_KERNEL_RECOVERY +u64 __mcsafe_copy(void *dst, const void __user *src, unsigned size); + +#define COPY_MCHECK_ERRBIT BIT(63) +#define COPY_HAD_MCHECK(ret) ((ret) & COPY_MCHECK_ERRBIT) +#define COPY_MCHECK_REMAIN(ret) ((ret) & ~COPY_MCHECK_ERRBIT) +#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..23aac781ce59 100644 --- a/arch/x86/lib/memcpy_64.S +++ b/arch/x86/lib/memcpy_64.S @@ -177,3 +177,205 @@ 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: xorl %eax,%eax + sfence + /* copy successful. return 0 */ + ret + + .section .fixup,"ax" + /* fixups for machine check */ +30: + addl %ecx,%edx + jmp 100f +31: + shll $6,%ecx + addl %ecx,%edx + jmp 100f +32: + shll $6,%ecx + leal -8(%ecx,%edx),%edx + jmp 100f +33: + shll $6,%ecx + leal -16(%ecx,%edx),%edx + jmp 100f +34: + shll $6,%ecx + leal -24(%ecx,%edx),%edx + jmp 100f +35: + shll $6,%ecx + leal -32(%ecx,%edx),%edx + jmp 100f +36: + shll $6,%ecx + leal -40(%ecx,%edx),%edx + jmp 100f +37: + shll $6,%ecx + leal -48(%ecx,%edx),%edx + jmp 100f +38: + shll $6,%ecx + leal -56(%ecx,%edx),%edx + jmp 100f +39: + lea (%rdx,%rcx,8),%rdx + jmp 100f +40: + mov %ecx,%edx +100: + sfence + /* + * copy failed because of machine check on source address + * return value is number of bytes NOT copied plus we set + * bit 63 to distinguish this from the page fault case below. + */ + mov %edx,%eax + bts $63,%rax + ret + + /* fixups for page fault */ +130: + addl %ecx,%edx + jmp 200f +131: + shll $6,%ecx + addl %ecx,%edx + jmp 200f +132: + shll $6,%ecx + leal -8(%ecx,%edx),%edx + jmp 200f +133: + shll $6,%ecx + leal -16(%ecx,%edx),%edx + jmp 200f +134: + shll $6,%ecx + leal -24(%ecx,%edx),%edx + jmp 200f +135: + shll $6,%ecx + leal -32(%ecx,%edx),%edx + jmp 200f +136: + shll $6,%ecx + leal -40(%ecx,%edx),%edx + jmp 200f +137: + shll $6,%ecx + leal -48(%ecx,%edx),%edx + jmp 200f +138: + shll $6,%ecx + leal -56(%ecx,%edx),%edx + jmp 200f +139: + lea (%rdx,%rcx,8),%rdx + jmp 200f +140: + mov %ecx,%edx +200: + sfence + /* + * copy failed because of page fault on source address + * return value is number of bytes NOT copied. + */ + mov %edx,%eax + ret + .previous + + _ASM_EXTABLE(0b,130b) + _ASM_EXTABLE(1b,131b) + _ASM_EXTABLE(2b,132b) + _ASM_EXTABLE(3b,133b) + _ASM_EXTABLE(4b,134b) + _ASM_EXTABLE(9b,135b) + _ASM_EXTABLE(10b,136b) + _ASM_EXTABLE(11b,137b) + _ASM_EXTABLE(12b,138b) + _ASM_EXTABLE(18b,139b) + _ASM_EXTABLE(21b,140b) + + _ASM_MCEXTABLE(0b,30b) + _ASM_MCEXTABLE(1b,31b) + _ASM_MCEXTABLE(2b,32b) + _ASM_MCEXTABLE(3b,33b) + _ASM_MCEXTABLE(4b,34b) + _ASM_MCEXTABLE(9b,35b) + _ASM_MCEXTABLE(10b,36b) + _ASM_MCEXTABLE(11b,37b) + _ASM_MCEXTABLE(12b,38b) + _ASM_MCEXTABLE(18b,39b) + _ASM_MCEXTABLE(21b,40b) +ENDPROC(__mcsafe_copy) +#endif -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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