• Gustavo A. R. Silva's avatar
    drm/[radeon|amdgpu]: Replace one-element array and use struct_size() helper · 4541ea81
    Gustavo A. R. Silva authored
    The current codebase makes use of one-element arrays in the following
    form:
    
    struct something {
        int length;
        u8 data[1];
    };
    
    struct something *instance;
    
    instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
    instance->length = size;
    memcpy(instance->data, source, size);
    
    but the preferred mechanism to declare variable-length types such as
    these ones is a flexible array member[1][2], introduced in C99:
    
    struct foo {
            int stuff;
            struct boo array[];
    };
    
    By making use of the mechanism above, we will get a compiler warning
    in case the flexible array does not occur last in the structure, which
    will help us prevent some kind of undefined behavior bugs from being
    inadvertently introduced[3] to the codebase from now on. So, replace
    the one-element array with a flexible-array member.
    
    Also, make use of the new struct_size() helper to properly calculate the
    size of struct SISLANDS_SMC_SWSTATE.
    
    This issue was found with the help of Coccinelle and, audited and fixed
    _manually_.
    
    [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
    [2] https://github.com/KSPP/linux/issues/21
    [3] commit 76497732 ("cxgb3/l2t: Fix undefined behaviour")
    Signed-off-by: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
    Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
    4541ea81
si_dpm.c 229 KB