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48de9684b9
for preventing optimization. Inspired from OpenBSD. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52839 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
79 lines
1.6 KiB
C
79 lines
1.6 KiB
C
#include "ruby/missing.h"
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#include <string.h>
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#ifdef _WIN32
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#include <windows.h>
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#endif
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/* Similar to bzero(), but have a guarantee not to be eliminated from compiler
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optimization. */
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/* OS support note:
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* BSD have explicit_bzero().
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* Windows, OS-X have memset_s().
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* Linux has none. *Sigh*
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*/
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/*
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* Following URL explain why memset_s is added to the standard.
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* http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1381.pdf
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*/
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#ifndef FUNC_UNOPTIMIZED
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# define FUNC_UNOPTIMIZED(x) x
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#endif
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#ifndef HAVE_EXPLICIT_BZERO
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#ifdef HAVE_MEMSET_S
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void
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explicit_bzero(void *b, size_t len)
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{
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memset_s(b, len, 0, len);
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}
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#elif defined SecureZeroMemory
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void
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explicit_bzero(void *b, size_t len)
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{
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SecureZeroMemory(b, len);
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}
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#elif defined HAVE_FUNC_WEAK
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/* A weak function never be optimization away. Even if nobody use it. */
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WEAK(void ruby_explicit_bzero_hook_unused(void *buf, size_t len));
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void
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ruby_explicit_bzero_hook_unused(void *buf, size_t len)
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{
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}
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void
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explicit_bzero(void *b, size_t len)
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{
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memset(b, len);
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ruby_explicit_bzero_hook_unused(b, len);
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}
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#else /* Your OS have no capability. Sigh. */
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FUNC_UNOPTIMIZED(void explicit_bzero(void *b, size_t len));
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#undef explicit_bzero
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void
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explicit_bzero(void *b, size_t len)
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{
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/*
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* volatile is not enough if compiler have a LTO (link time
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* optimization). At least, the standard provide no guarantee.
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* However, gcc and major other compiler never optimization a volatile
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* variable away. So, using volatile is practically ok.
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*/
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volatile char* p = (volatile char*)b;
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while(len) {
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*p = 0;
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p++;
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len--;
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}
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}
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#endif
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#endif /* HAVE_EXPLICIT_BZERO */
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