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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=kikYfFSTfca/HkjJiT4VwZFMKgohIqKorfyIql1wDNc=; b=ctCRG5kS6VXS89jAf2mCvaCQtJauSEZzOuQAGjEFVFITsDSA2jQeVtyC2JogNIsSqK FSRgfuNps0HlDWguU95YhqwxBoaH1M9ikasQKgixQWpZomEdplsTSSF3Fy+hUBQMFY6C lcC17OmvyhINRtPmLYjM9Xra8uxcWVmthHTfrWltF9VHbnCrA7CO2Aap7xyKGRME8trF 8w50j20TtnldzlTDzfOFihX3Ef+WN7VvagP+uFmvXicsTzSj8kTCT3BIUU55ae5opBy5 lW1mFI8qkGA0PrxAKYOrdNDcLtsHXqWLK9NgCSGPo7gGF2ZkTr12t2dgzvXejExUveG/ OwCw== X-Gm-Message-State: AGi0PuZ1JNakQAu7qL8TWBbVb09rBljpXXfPwjOtZ9lRRbXbU28gb13W HKl2FxKiOnVNNRGK6PWUgCxbcpiUPpBKhgMRSqc= X-Google-Smtp-Source: APiQypIgO4clcO6Z7kvhUaBuvYACtL+F9hDoKmeBmaTp5Edf0BzJT+qKnh+MwC69KhaGLcQ8wc5C0JEBbMo44i2AOQM= X-Received: by 2002:a25:ddc3:: with SMTP id u186mr36888616ybg.383.1588003232559; Mon, 27 Apr 2020 09:00:32 -0700 (PDT) Date: Mon, 27 Apr 2020 09:00:09 -0700 In-Reply-To: <20200427160018.243569-1-samitolvanen@google.com> Message-Id: <20200427160018.243569-4-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200427160018.243569-1-samitolvanen@google.com> X-Mailer: git-send-email 2.26.2.303.gf8c07b1a785-goog Subject: [PATCH v13 03/12] scs: add support for stack usage debugging From: Sami Tolvanen To: Will Deacon , Catalin Marinas , James Morse , Steven Rostedt , Ard Biesheuvel , Mark Rutland , Masahiro Yamada , Michal Marek , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200427_090035_447626_626F78CA X-CRM114-Status: GOOD ( 10.60 ) X-Spam-Score: -7.7 (-------) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (-7.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:b49 listed in] [list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.0 DKIMWL_WL_MED DKIMwl.org - Medium sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , Jann Horn , Marc Zyngier , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , Masami Hiramatsu , Sami Tolvanen , clang-built-linux@googlegroups.com, Laura Abbott , Dave Martin , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Implements CONFIG_DEBUG_STACK_USAGE for shadow stacks. When enabled, also prints out the highest shadow stack usage per process. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Acked-by: Will Deacon --- kernel/scs.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/kernel/scs.c b/kernel/scs.c index 8769016c714c..2a96573f2b1b 100644 --- a/kernel/scs.c +++ b/kernel/scs.c @@ -68,6 +68,43 @@ int scs_prepare(struct task_struct *tsk, int node) return 0; } +#ifdef CONFIG_DEBUG_STACK_USAGE +static unsigned long __scs_used(struct task_struct *tsk) +{ + unsigned long *p = task_scs(tsk); + unsigned long *end = __scs_magic(p); + unsigned long s = (unsigned long)p; + + while (p < end && READ_ONCE_NOCHECK(*p)) + p++; + + return (unsigned long)p - s; +} + +static void scs_check_usage(struct task_struct *tsk) +{ + static unsigned long highest; + unsigned long used = __scs_used(tsk); + unsigned long prev; + unsigned long curr = highest; + + while (used > curr) { + prev = cmpxchg_relaxed(&highest, curr, used); + + if (prev == curr) { + pr_info("%s (%d): highest shadow stack usage: " + "%lu bytes\n", + tsk->comm, task_pid_nr(tsk), used); + break; + } + + curr = prev; + } +} +#else +static inline void scs_check_usage(struct task_struct *tsk) {} +#endif + void scs_release(struct task_struct *tsk) { void *s; @@ -77,6 +114,7 @@ void scs_release(struct task_struct *tsk) return; WARN_ON(scs_corrupted(tsk)); + scs_check_usage(tsk); scs_account(tsk, -1); scs_free(s);