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[216.160.65.90]) by smtp.gmail.com with ESMTPSA id r191sm7261663pfr.181.2020.07.24.09.38.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Jul 2020 09:38:58 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH 3/3] target/arm: Improve IMPDEF algorithm for IRG Date: Fri, 24 Jul 2020 09:38:53 -0700 Message-Id: <20200724163853.504655-4-richard.henderson@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200724163853.504655-1-richard.henderson@linaro.org> References: <20200724163853.504655-1-richard.henderson@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::442; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x442.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. 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: , Cc: peter.maydell@linaro.org, vincenzo.frascino@arm.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" When GCR_EL1.RRND==1, 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 --- 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 5ea57d487a..104752041f 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" 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, uint64_t HELPER(irg)(CPUARMState *env, uint64_t rn, uint64_t rm) { - int rtag; - - /* - * Our IMPDEF choice for GCR_EL1.RRND==1 is to behave as if - * GCR_EL1.RRND==0, always producing deterministic results. - */ uint16_t exclude = extract32(rm | env->cp15.gcr_el1, 0, 16); + int rrnd = extract32(env->cp15.gcr_el1, 16, 1); int start = extract32(env->cp15.rgsr_el1, 0, 4); int seed = extract32(env->cp15.rgsr_el1, 8, 16); - int offset, i; + int offset, i, rtag; + + /* + * Our IMPDEF choice for GCR_EL1.RRND==1 is to continue to use the + * deterministic algorithm. Except that with RRND==1 the kernel is + * not required to have set RGSR_EL1.SEED != 0, which is required for + * the deterministic algorithm to function. So we force a non-zero + * SEED for that case. + */ + if (unlikely(seed == 0) && rrnd) { + do { + Error *err = 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 seed. + */ + qemu_log_mask(LOG_UNIMP, "IRG: Crypto failure: %s\n", + error_get_pretty(err)); + error_free(err); + two = 1; + } + seed = two; + } while (seed == 0); + } /* RandomTag */ for (i = offset = 0; i < 4; ++i) { -- 2.25.1