On Fri, 14 Dec 2018 at 05:24, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> This is not really functional yet, because the crypto is not yet
> implemented. This, however follows the AddPAC pseudo function.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> target/arm/helper-a64.c | 40 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/target/arm/helper-a64.c b/target/arm/helper-a64.c
> index 87cff7d96a..19486b9677 100644
> --- a/target/arm/helper-a64.c
> +++ b/target/arm/helper-a64.c
> @@ -1066,7 +1066,45 @@ static uint64_t pauth_computepac(uint64_t data, uint64_t modifier,
> static uint64_t pauth_addpac(CPUARMState *env, uint64_t ptr, uint64_t modifier,
> ARMPACKey *key, bool data)
> {
> - g_assert_not_reached(); /* FIXME */
> + ARMMMUIdx mmu_idx = arm_stage1_mmu_idx(env);
> + ARMVAParameters param = aa64_va_parameters(env, ptr, mmu_idx, data);
> + uint64_t pac, ext_ptr, ext, test;
> + int bot_bit, top_bit;
> +
> + /* If tagged pointers are in use, use ptr<55>, otherwise ptr<63>. */
> + if (param.tbi) {
> + ext = sextract64(ptr, 55, 1);
> + } else {
> + ext = sextract64(ptr, 63, 1);
> + }
> +
> + /* Build a pointer with known good extension bits. */
> + top_bit = 64 - 8 * param.tbi;
> + bot_bit = 64 - param.tsz;
> + ext_ptr = deposit64(ptr, bot_bit, top_bit - bot_bit, ext);
> +
> + pac = pauth_computepac(ext_ptr, modifier, *key);
> +
> + /* Check if the ptr has good extension bits and corrupt the
> + * pointer authentication code if not.
> + */
Newer checkpatch will grumble about this style of block
comment, by the way.
> + test = sextract64(ptr, bot_bit, top_bit - bot_bit);
> + if (test != 0 && test != -1) {
> + pac ^= 1ull << (top_bit - 1);
MAKE_64BIT_MASK(top_bit - 1, 1) might be more consistent with
the code below ?
> + }
> +
> + /* Preserve the determination between upper and lower at bit 55,
> + * and insert pointer authentication code.
> + */
> + if (param.tbi) {
> + ptr &= ~MAKE_64BIT_MASK(bot_bit, 55 - bot_bit + 1);
> + pac &= MAKE_64BIT_MASK(bot_bit, 54 - bot_bit + 1);
> + } else {
> + ptr &= MAKE_64BIT_MASK(0, bot_bit);
> + pac &= ~(MAKE_64BIT_MASK(55, 1) | MAKE_64BIT_MASK(0, bot_bit));
> + }
> + ext &= MAKE_64BIT_MASK(55, 1);
I found this a bit confusing to disentangle and compare with
the pseudocode: the difference between the tbi and
not-tbi cases is only "what are bits 63:56 in the result",
but the implementation of how we put together bits 55:0 is
different in the two code paths here.
> + return pac | ext | ptr;
> }
>
> static uint64_t pauth_original_ptr(uint64_t ptr, ARMVAParameters param)
> --
> 2.17.2
Anyway, the implementation is correct, so:
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
thanks
-- PMM