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620c41147d
commit fe8c8a126806fea4465c43d62a1f9d273a572bf5 upstream. [Only use the compiler.h portion of this patch, to get the OPTIMIZER_HIDE_VAR() macro, which we need for other -stable patches - gregkh] Disabling compiler optimizations can be fragile, since a new optimization could be added to -O0 or -Os that breaks the assumptions the code is making. Instead of disabling compiler optimizations, use a dummy inline assembly (based on RELOC_HIDE) to block the problematic kinds of optimization, while still allowing other optimizations to be applied to the code. The dummy inline assembly is added after every OR, and has the accumulator variable as its input and output. The compiler is forced to assume that the dummy inline assembly could both depend on the accumulator variable and change the accumulator variable, so it is forced to compute the value correctly before the inline assembly, and cannot assume anything about its value after the inline assembly. This change should be enough to make crypto_memneq work correctly (with data-independent timing) even if it is inlined at its call sites. That can be done later in a followup patch. Compile-tested on x86_64. Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.eti.br> Acked-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
43 lines
1.1 KiB
C
43 lines
1.1 KiB
C
#ifndef __LINUX_COMPILER_H
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#error "Please don't include <linux/compiler-intel.h> directly, include <linux/compiler.h> instead."
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#endif
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#ifdef __ECC
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/* Some compiler specific definitions are overwritten here
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* for Intel ECC compiler
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*/
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#include <asm/intrinsics.h>
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/* Intel ECC compiler doesn't support gcc specific asm stmts.
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* It uses intrinsics to do the equivalent things.
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*/
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#undef barrier
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#undef RELOC_HIDE
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#undef OPTIMIZER_HIDE_VAR
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#define barrier() __memory_barrier()
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#define RELOC_HIDE(ptr, off) \
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({ unsigned long __ptr; \
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__ptr = (unsigned long) (ptr); \
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(typeof(ptr)) (__ptr + (off)); })
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/* This should act as an optimization barrier on var.
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* Given that this compiler does not have inline assembly, a compiler barrier
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* is the best we can do.
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*/
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#define OPTIMIZER_HIDE_VAR(var) barrier()
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/* Intel ECC compiler doesn't support __builtin_types_compatible_p() */
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#define __must_be_array(a) 0
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#endif
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#ifndef __HAVE_BUILTIN_BSWAP16__
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/* icc has this, but it's called _bswap16 */
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#define __HAVE_BUILTIN_BSWAP16__
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#define __builtin_bswap16 _bswap16
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#endif
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