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cmake: Check for HAVE_GCC_VOLATILE_MEMORY_PROTECTION.

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This ensures that the memset call is not optimized out by the compiler
(works works with gcc and clang).
This commit is contained in:
Andreas Schneider
2013-07-22 10:18:33 +02:00
parent 5145daba69
commit 1829e9981b
3 changed files with 49 additions and 2 deletions
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37
include/libssh/priv.h
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@@ -137,6 +137,17 @@ int gettimeofday(struct timeval *__p, void *__t);
# define LIBSSH_THREAD
#endif
/*
* This makes sure that the compiler doesn't optimize out the code
*
* Use it in a macro where the provided variable is 'x'.
*/
#if defined(HAVE_GCC_VOLATILE_MEMORY_PROTECTION)
# define LIBSSH_MEM_PROTECTION __asm__ volatile("" : : "r"(&(x)) : "memory")
#else
# define LIBSSH_MEM_PROTECTION
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
@@ -226,11 +237,33 @@ int match_hostname(const char *host, const char *pattern, unsigned int len);
/** Get the size of an array */
#define ARRAY_SIZE(a) (sizeof(a)/sizeof(a[0]))
/*
* See http://llvm.org/bugs/show_bug.cgi?id=15495
*/
#if defined(HAVE_GCC_VOLATILE_MEMORY_PROTECTION)
/** Overwrite a string with '\0' */
#define BURN_STRING(x) do { if ((x) != NULL) memset((x), '\0', strlen((x))); __asm__ volatile ("" : : : "memory"); } while(0)
# define BURN_STRING(x) do { \
if ((x) != NULL) \
memset((x), '\0', strlen((x))); __asm__ volatile("" : : "r"(&(x)) : "memory"); \
} while(0)
/** Overwrite the buffer with '\0' */
#define BURN_BUFFER(x, size) do { if ((x) != NULL) memset((x), '\0', (size))); __asm__ volatile ("") : : : "memory"; } while(0)
# define BURN_BUFFER(x, size) do { \
if ((x) != NULL) \
memset((x), '\0', (size))); __asm__ volatile("" : : "r"(&(x)) : "memory"); \
} while(0)
#else /* HAVE_GCC_VOLATILE_MEMORY_PROTECTION */
/** Overwrite a string with '\0' */
# define BURN_STRING(x) do { \
if ((x) != NULL) memset((x), '\0', strlen((x))); \
} while(0)
/** Overwrite the buffer with '\0' */
# define BURN_BUFFER(x, size) do { \
if ((x) != NULL) \
memset((x), '\0', (size))); __asm__ volatile("" : : "r"(&(x)) : "memory"); \
} while(0)
#endif /* HAVE_GCC_VOLATILE_MEMORY_PROTECTION */
/**
* This is a hack to fix warnings. The idea is to use this everywhere that we