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* missing/explicit_bzero.c: add ruby_explicit_bzero_hook_unused

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for preventing optimization. Inspired from OpenBSD.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52839 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
kosaki 2015-12-01 21:52:02 +00:00
parent 8ea5564183
commit 48de9684b9
3 changed files with 60 additions and 27 deletions
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78
missing/explicit_bzero.c
View file

@ -5,11 +5,14 @@
#include <windows.h>
#endif
/*
*BSD have explicit_bzero().
Windows, OS-X have memset_s().
Linux has none. *Sigh*
*/
/* Similar to bzero(), but have a guarantee not to be eliminated from compiler
optimization. */
/* OS support note:
* BSD have explicit_bzero().
* Windows, OS-X have memset_s().
* Linux has none. *Sigh*
*/
/*
* Following URL explain why memset_s is added to the standard.
@ -21,35 +24,56 @@
#endif
#ifndef HAVE_EXPLICIT_BZERO
/* Similar to bzero(), but have a guarantee not to be eliminated from compiler
optimization. */
#ifdef HAVE_MEMSET_S
void
explicit_bzero(void *b, size_t len)
{
memset_s(b, len, 0, len);
}
#elif defined SecureZeroMemory
void
explicit_bzero(void *b, size_t len)
{
SecureZeroMemory(b, len);
}
#elif defined HAVE_FUNC_WEAK
/* A weak function never be optimization away. Even if nobody use it. */
WEAK(void ruby_explicit_bzero_hook_unused(void *buf, size_t len));
void
ruby_explicit_bzero_hook_unused(void *buf, size_t len)
{
}
void
explicit_bzero(void *b, size_t len)
{
memset(b, len);
ruby_explicit_bzero_hook_unused(b, len);
}
#else /* Your OS have no capability. Sigh. */
#ifndef HAVE_MEMSET_S
FUNC_UNOPTIMIZED(void explicit_bzero(void *b, size_t len));
#endif
#undef explicit_bzero
void
explicit_bzero(void *b, size_t len)
{
#ifdef HAVE_MEMSET_S
memset_s(b, len, 0, len);
#elif defined SecureZeroMemory
SecureZeroMemory(b, len);
#else
{
/*
* TODO: volatile is not enough if compiler have a LTO (link time
* optimization)
*/
volatile char* p = (volatile char*)b;
/*
* volatile is not enough if compiler have a LTO (link time
* optimization). At least, the standard provide no guarantee.
* However, gcc and major other compiler never optimization a volatile
* variable away. So, using volatile is practically ok.
*/
volatile char* p = (volatile char*)b;
while(len) {
*p = 0;
p++;
len--;
}
while(len) {
*p = 0;
p++;
len--;
}
#endif
}
#endif
#endif
#endif /* HAVE_EXPLICIT_BZERO */