2 ms·

That's the section that made me post this snippet; crazy isn't it?!

• jareklupinski 3y ago
  can't edit original post, but i just realized after lining up the monospace how #define AUTH_SUCCESS 0x52a2925 /* 0101001010100010100100100101 */ #define AUTH_FAILURE 0xad5d6da /* 1010110101011101011011011010 */ #define AUTH_INTR 0x69d61fc8 /* 1101001110101100001111111001000 */ #define AUTH_ERROR 0x1629e037 /* 0010110001010011110000000110111 */ #define AUTH_NONINTERACTIVE 0x1fc8d3ac /* 11111110010001101001110101100 */ AUTH_FAILURE is still just !AUTH_SUCCESS (and almost a palindrome)
  • kelnos 3y ago
    It sorta is, but isn't actually, sadly. I mean, if they were 28-bit values, they'd be binary complements, but they're actually 32-bit values, so they're really: #define AUTH_SUCCESS 0x052a2925 /* 00000101001010100010100100100101 */ #define AUTH_FAILURE 0x0ad5d6da /* 00001010110101011101011011011010 */ Doing a '!' operation in C on one of them won't yield the other value unless you also zero out the top 4 bits. Close enough, though... I still enjoy the symmetry as you did. Anyway, I'm curious why three of the values they chose have all zeroes for the top 4 bits. I wonder if there's a security-related reason for that.
  • zaroth 3y ago
    I think the theory is that means the most number of bits need to be flipped. Because rowhammer is attacking the physical memory structure, it can’t function at the level that knows what AUTH_SUCCESS is. This attack just targets raw bits, so we need to protect these crucial state variables from bit-flips.