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    SubjectRe: [PATCH v2] x86, random: Fix get_random_bytes() warning in x86 start_kernel
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    On 2/1/19 10:02 PM, Theodore Y. Ts'o wrote:
    > On Fri, Feb 01, 2019 at 01:08:31PM -0500, Prarit Bhargava wrote:
    >> After 43838a23a05f ("random: fix crng_ready() test") early boot calls to
    >> get_random_bytes() will warn on x86 because the crng is not initialized.
    >> For example,
    >>
    >> random: get_random_bytes called from start_kernel+0x8e/0x587 with crng_init=0
    >>
    >> x86 only uses get_random_bytes() for better randomization of the stack
    >> canary value so the warning is of no consequence.
    >>
    >> Test if the crng is initialized before calling get_random_bytes(). If it
    >> is not available then attempt to read from the hardware random generator,
    >> before finally using the TSC.
    >
    > If you want to trust the CPU's hardware number generator, there is a
    > way to do this already. Simply enable CONFIG_RANDOM_TRUST_CPU, or set
    > the boot command line option "random.trust_cpu=on".
    >
    Ted, the bug I'm trying to fix is the warning:

    random: get_random_bytes called from start_kernel+0x8e/0x587 with crng_init=0

    during early boot. Even with the kernel parameter the warning appears.


    > Also, relying on the TSC for entropy is not something we should be
    > recommending.

    The current code uses the TSC. It is not something new I'm introducing.

    P.

    >
    > So, NAK.
    >
    > - Ted
    >

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