Commit cbf8b5a2 authored Mar 14, 2016 by Tony Luck Committed by Ingo Molnar Mar 16, 2016

x86/mm, x86/mce: Fix return type/value for memcpy_mcsafe()



Returning a 'bool' was very unpopular. Doubly so because the
code was just wrong (returning zero for true, one for false;
great for shell programming, not so good for C).

Change return type to "int". Keep zero as the success indicator
because it matches other similar code and people may be more
comfortable writing:

	if (memcpy_mcsafe(to, from, count)) {
		printk("Sad panda, copy failed\n");
		...
	}

Make the failure return value -EFAULT for now.

Reported by: Mika Penttilä <mika.penttila@nextfour.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: mika.penttila@nextfour.com
Fixes: 92b0729c ("x86/mm, x86/mce: Add memcpy_mcsafe()")
Link: http://lkml.kernel.org/r/695f14233fa7a54fcac4406c706d7fec228e3f4c.1457993040.git.tony.luck@intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent ba4e06d6

arch/x86/include/asm/string_64.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -87,9 +87,9 @@ int strcmp(const char cs, const char ct);
		*
		* Low level memory copy function that catches machine checks
		*
		* Return true for success, false for fail
		* Return 0 for success, -EFAULT for fail
		*/
		bool memcpy_mcsafe(void dst, const void src, size_t cnt);
		int memcpy_mcsafe(void dst, const void src, size_t cnt);

		#endif /* __KERNEL__ */

arch/x86/lib/memcpy_64.S

+4 −3

Original line number	Diff line number	Diff line
		/* Copyright 2002 Andi Kleen */

		#include <linux/linkage.h>
		#include <asm/errno.h>
		#include <asm/cpufeatures.h>
		#include <asm/alternative-asm.h>

		@@ -268,16 +269,16 @@ ENTRY(memcpy_mcsafe)
		decl %ecx
		jnz .L_copy_trailing_bytes

		/* Copy successful. Return true */
		/* Copy successful. Return zero */
		.L_done_memcpy_trap:
		xorq %rax, %rax
		ret
		ENDPROC(memcpy_mcsafe)

		.section .fixup, "ax"
		/* Return false for any failure */
		/* Return -EFAULT for any failure */
		.L_memcpy_mcsafe_fail:
		mov $1, %rax
		mov $-EFAULT, %rax
		ret

		.previous

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