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[2620:137:e000::1:20]) by mx.google.com with ESMTP id s32-20020a63ff60000000b004607161e35dsi11077610pgk.830.2022.11.15.01.02.09; Tue, 15 Nov 2022 01:02:30 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@rivosinc-com.20210112.gappssmtp.com header.s=20210112 header.b=efIjWq1q; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236873AbiKOItj (ORCPT + 99 others); Tue, 15 Nov 2022 03:49:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56294 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232870AbiKOIth (ORCPT ); Tue, 15 Nov 2022 03:49:37 -0500 Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [IPv6:2607:f8b0:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D83EF5B6 for ; Tue, 15 Nov 2022 00:49:36 -0800 (PST) Received: by mail-pl1-x62e.google.com with SMTP id l2so12523078pld.13 for ; Tue, 15 Nov 2022 00:49:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=qDByETx1OVv/ToHgra70XmddV8aLSLYjbfOVuUtVUdA=; b=efIjWq1qpJbOkdAufChryyAS7BGpLb40UjUYYHCrOH4VmIF8UEsFamcHZpm9b3MCkr DBZDZyhpN8hrX8GXGIB/XTfbR6aH/zjQmgZC4WThNXjwv4E0yex2T4OEXFSHUp4ipSbu VuTbNYcPj25M2JP4LXssjHphTCgprCHIN1ExEqqZe3qyobBmMuXP7RfaDni79DQXL1+x UmSAnk7Twr34PFKD8egLFLJXYM8t09IhWUlIkwdXV9UenflcdzkhVZfNFtq9jc7R6ZiY UwIluASviXxgVcKTlZlF9BC+h6EyRkcPRFuNzhWTM2XR3TqfUrinh/8c0asCRaqTH6VM g+gw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qDByETx1OVv/ToHgra70XmddV8aLSLYjbfOVuUtVUdA=; b=Hi+bqz9RFW5KJNq9o9Xdelqdj1TrllCzdUWUpTwIWSvQ8hgpiuVdHAdAiE5XcWywji a773OU+xvPsNPliJfjNg51KaUcPL4oNDFjefIcVbuDEXMrn1usC4ScYSNid8NHUOc1/8 Q6Jqzu56r0dUyYyDII2FPuo6lRalNtFHvnkjDzrs7vGZ3wdhvvrY+5f5pmAYOrYajVni fsz4Byfq7C4suNybA+pRzRBf59qT1Kg7iylqidaWcPzjDvmUtf+WsHH8eX6uICyZRJxZ OFd7NkBoM03/W8FttQs4pIf1CzUSE9B48a8wdAirDvVXT0Bnk0sbE/HoCr885lU3oDA+ u8Eg== X-Gm-Message-State: ANoB5pnHmLpKvWvqJrkIzo/4ILchzXZ0jud0b1G4c223lVnhWQyTFae6 +MTwoo4iXr4JEX4qrr2EY8q0Eg== X-Received: by 2002:a17:90a:aa12:b0:218:4859:287c with SMTP id k18-20020a17090aaa1200b002184859287cmr1134445pjq.204.1668502176038; Tue, 15 Nov 2022 00:49:36 -0800 (PST) Received: from debug.ba.rivosinc.com ([66.220.2.162]) by smtp.gmail.com with ESMTPSA id w37-20020a631625000000b00464858cf6b0sm7224125pgl.54.2022.11.15.00.49.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Nov 2022 00:49:35 -0800 (PST) From: Deepak Gupta To: debug@rivosinc.com Cc: aou@eecs.berkeley.edu, jan.kiszka@siemens.com, kbingham@kernel.org, linux-kernel@vger.kernel.org, palmer@dabbelt.com, paul.walmsley@sifive.com Subject: [PATCH v3] scripts/gdb: add lx_current support for riscv Date: Tue, 15 Nov 2022 00:49:23 -0800 Message-Id: <20221115084923.1822572-1-debug@rivosinc.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20221115012917.1781185-1-debug@rivosinc.com> References: <20221115012917.1781185-1-debug@rivosinc.com> MIME-Version: 1.0 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1749523804126868167?= X-GMAIL-MSGID: =?utf-8?q?1749552149976796958?= csr_sscratch CSR holds current task_struct address when hart is in user space. Trap handler on entry spills csr_sscratch into "tp" (x2) register and zeroes out csr_sscratch CSR. Trap handler on exit reloads "tp" with expected user mode value and place current task_struct address again in csr_scratch CSR. This patch assumes "tp" is pointing to task_struct. If value in csr_scratch is numerically greater than "tp" then it assumes csr_scratch is correct address of current task_struct. This logic holds when - hart is in user space, "tp" will be less than csr_scratch. - hart is in kernel space but not in trap handler, "tp" will be more than csr_scratch (csr_scratch being equal to 0). - hart is executing trap handler - "tp" is still pointing to user mode but csr_scratch contains ptr to task_struct. Thus numerically higher. - "tp" is pointing to task_struct but csr_scratch now contains either 0 or numerically smaller value (transiently holds user mode tp) Patch also adds new cached type "ulong" in scripts/gdb/linux/utils.py Signed-off-by: Deepak Gupta --- scripts/gdb/linux/cpus.py | 15 +++++++++++++++ scripts/gdb/linux/utils.py | 5 +++++ 2 files changed, 20 insertions(+) diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py index 15fc4626d236..ca5215a660c7 100644 --- a/scripts/gdb/linux/cpus.py +++ b/scripts/gdb/linux/cpus.py @@ -173,6 +173,21 @@ def get_current_task(cpu): else: raise gdb.GdbError("Sorry, obtaining the current task is not allowed " "while running in userspace(EL0)") + elif utils.is_target_arch("riscv"): + current_tp = gdb.parse_and_eval("$tp") + scratch_reg = gdb.parse_and_eval("$sscratch") + + # by default tp points to current task + current_task = current_tp.cast(task_ptr_type) + + # scratch register is set 0 in trap handler after entering kernel. + # When hart is in user mode, scratch register is pointing to task_struct. + # and tp is used by user mode. So when scratch register holds larger value + # (negative address as ulong is larger value) than tp, then use scratch register. + if (scratch_reg.cast(utils.get_ulong_type()) > current_tp.cast(utils.get_ulong_type())): + current_task = scratch_reg.cast(task_ptr_type) + + return current_task.dereference() else: raise gdb.GdbError("Sorry, obtaining the current task is not yet " "supported with this arch") diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py index 1553f68716cc..ddaf3089170d 100644 --- a/scripts/gdb/linux/utils.py +++ b/scripts/gdb/linux/utils.py @@ -35,12 +35,17 @@ class CachedType: long_type = CachedType("long") +ulong_type = CachedType("ulong") atomic_long_type = CachedType("atomic_long_t") def get_long_type(): global long_type return long_type.get_type() +def get_ulong_type(): + global ulong_type + return ulong_type.get_type() + def offset_of(typeobj, field): element = gdb.Value(0).cast(typeobj) return int(str(element[field].address).split()[0], 16)