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That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @linaro.org) Content-Type: text/plain; charset="utf-8" From: Richard Henderson When GCR_EL1.RRND=3D=3D1, the choosing of the random value is IMPDEF, and the kernel is not expected to have set RGSR_EL1. Force a non-zero value into SEED, so that we do not continually return the same tag. Reported-by: Vincenzo Frascino Signed-off-by: Richard Henderson Message-id: 20200724163853.504655-4-richard.henderson@linaro.org Reviewed-by: Peter Maydell Signed-off-by: Peter Maydell --- target/arm/mte_helper.c | 37 ++++++++++++++++++++++++++++++------- 1 file changed, 30 insertions(+), 7 deletions(-) diff --git a/target/arm/mte_helper.c b/target/arm/mte_helper.c index 5ea57d487a4..104752041f7 100644 --- a/target/arm/mte_helper.c +++ b/target/arm/mte_helper.c @@ -24,6 +24,8 @@ #include "exec/ram_addr.h" #include "exec/cpu_ldst.h" #include "exec/helper-proto.h" +#include "qapi/error.h" +#include "qemu/guest-random.h" =20 =20 static int choose_nonexcluded_tag(int tag, int offset, uint16_t exclude) @@ -211,16 +213,37 @@ static uint8_t *allocation_tag_mem(CPUARMState *env, = int ptr_mmu_idx, =20 uint64_t HELPER(irg)(CPUARMState *env, uint64_t rn, uint64_t rm) { - int rtag; - - /* - * Our IMPDEF choice for GCR_EL1.RRND=3D=3D1 is to behave as if - * GCR_EL1.RRND=3D=3D0, always producing deterministic results. - */ uint16_t exclude =3D extract32(rm | env->cp15.gcr_el1, 0, 16); + int rrnd =3D extract32(env->cp15.gcr_el1, 16, 1); int start =3D extract32(env->cp15.rgsr_el1, 0, 4); int seed =3D extract32(env->cp15.rgsr_el1, 8, 16); - int offset, i; + int offset, i, rtag; + + /* + * Our IMPDEF choice for GCR_EL1.RRND=3D=3D1 is to continue to use the + * deterministic algorithm. Except that with RRND=3D=3D1 the kernel is + * not required to have set RGSR_EL1.SEED !=3D 0, which is required for + * the deterministic algorithm to function. So we force a non-zero + * SEED for that case. + */ + if (unlikely(seed =3D=3D 0) && rrnd) { + do { + Error *err =3D NULL; + uint16_t two; + + if (qemu_guest_getrandom(&two, sizeof(two), &err) < 0) { + /* + * Failed, for unknown reasons in the crypto subsystem. + * Best we can do is log the reason and use a constant see= d. + */ + qemu_log_mask(LOG_UNIMP, "IRG: Crypto failure: %s\n", + error_get_pretty(err)); + error_free(err); + two =3D 1; + } + seed =3D two; + } while (seed =3D=3D 0); + } =20 /* RandomTag */ for (i =3D offset =3D 0; i < 4; ++i) { --=20 2.20.1