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authorDan Williams <dan.j.williams@intel.com>2018-05-03 17:06:26 -0700
committerIngo Molnar <mingo@kernel.org>2018-05-15 08:32:42 +0200
commit12c89130a56ae8e8d85db753d70333c4ee0ea835 (patch)
treeb3ec091a965a9a0674c005e6d5b0df429c5c70a3
parent60622d68227d6d71fdfba5fb39f7f3d44cdd8815 (diff)
x86/asm/memcpy_mcsafe: Add write-protection-fault handling
In preparation for using memcpy_mcsafe() to handle user copies it needs to be to handle write-protection faults while writing user pages. Add MMU-fault handlers alongside the machine-check exception handlers. Note that the machine check fault exception handling makes assumptions about source buffer alignment and poison alignment. In the write fault case, given the destination buffer is arbitrarily aligned, it needs a separate / additional fault handling approach. The mcsafe_handle_tail() helper is reused. The @limit argument is set to @len since there is no safety concern about retriggering an MMU fault, and this simplifies the assembly. Co-developed-by: Tony Luck <tony.luck@intel.com> Reported-by: Mika Penttilä <mika.penttila@nextfour.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Cc: hch@lst.de Cc: linux-fsdevel@vger.kernel.org Cc: linux-nvdimm@lists.01.org Link: http://lkml.kernel.org/r/152539238635.31796.14056325365122961778.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/include/asm/uaccess_64.h3
-rw-r--r--arch/x86/lib/memcpy_64.S14
-rw-r--r--arch/x86/lib/usercopy_64.c21
3 files changed, 38 insertions, 0 deletions
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 62546b3a398e..c63efc07891f 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -194,4 +194,7 @@ __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
unsigned long
copy_user_handle_tail(char *to, char *from, unsigned len);
+unsigned long
+mcsafe_handle_tail(char *to, char *from, unsigned len);
+
#endif /* _ASM_X86_UACCESS_64_H */
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index f01a88391c98..c3b527a9f95d 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -265,9 +265,23 @@ EXPORT_SYMBOL_GPL(__memcpy_mcsafe)
mov %ecx, %eax
ret
+ /*
+ * For write fault handling, given the destination is unaligned,
+ * we handle faults on multi-byte writes with a byte-by-byte
+ * copy up to the write-protected page.
+ */
+.E_write_words:
+ shll $3, %ecx
+ addl %edx, %ecx
+ movl %ecx, %edx
+ jmp mcsafe_handle_tail
+
.previous
_ASM_EXTABLE_FAULT(.L_read_leading_bytes, .E_leading_bytes)
_ASM_EXTABLE_FAULT(.L_read_words, .E_read_words)
_ASM_EXTABLE_FAULT(.L_read_trailing_bytes, .E_trailing_bytes)
+ _ASM_EXTABLE(.L_write_leading_bytes, .E_leading_bytes)
+ _ASM_EXTABLE(.L_write_words, .E_write_words)
+ _ASM_EXTABLE(.L_write_trailing_bytes, .E_trailing_bytes)
#endif
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index 75d3776123cc..7ebc9901dd05 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -75,6 +75,27 @@ copy_user_handle_tail(char *to, char *from, unsigned len)
return len;
}
+/*
+ * Similar to copy_user_handle_tail, probe for the write fault point,
+ * but reuse __memcpy_mcsafe in case a new read error is encountered.
+ * clac() is handled in _copy_to_iter_mcsafe().
+ */
+__visible unsigned long
+mcsafe_handle_tail(char *to, char *from, unsigned len)
+{
+ for (; len; --len, to++, from++) {
+ /*
+ * Call the assembly routine back directly since
+ * memcpy_mcsafe() may silently fallback to memcpy.
+ */
+ unsigned long rem = __memcpy_mcsafe(to, from, 1);
+
+ if (rem)
+ break;
+ }
+ return len;
+}
+
#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
/**
* clean_cache_range - write back a cache range with CLWB