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  • Kees Cook's avatar
    security: Implement Clang's stack initialization · 709a972e
    Kees Cook authored
    CONFIG_INIT_STACK_ALL turns on stack initialization based on
    -ftrivial-auto-var-init in Clang builds, which has greater coverage
    than CONFIG_GCC_PLUGINS_STRUCTLEAK_BYREF_ALL.
    
    -ftrivial-auto-var-init Clang option provides trivial initializers for
    uninitialized local variables, variable fields and padding.
    
    It has three possible values:
      pattern - uninitialized locals are filled with a fixed pattern
        (mostly 0xAA on 64-bit platforms, see https://reviews.llvm.org/D54604
    
    
        for more details, but 0x000000AA for 32-bit pointers) likely to cause
        crashes when uninitialized value is used;
      zero (it's still debated whether this flag makes it to the official
        Clang release) - uninitialized locals are filled with zeroes;
      uninitialized (default) - uninitialized locals are left intact.
    
    This patch uses only the "pattern" mode when CONFIG_INIT_STACK_ALL is
    enabled.
    
    Developers have the possibility to opt-out of this feature on a
    per-variable basis by using __attribute__((uninitialized)), but such
    use should be well justified in comments.
    
    Co-developed-by: default avatarAlexander Potapenko <glider@google.com>
    Signed-off-by: default avatarAlexander Potapenko <glider@google.com>
    Signed-off-by: default avatarKees Cook <keescook@chromium.org>
    Tested-by: default avatarAlexander Potapenko <glider@google.com>
    Acked-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
    709a972e