From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id YFktAEH13WHsWAAAWB0awg (envelope-from ) for ; Tue, 11 Jan 2022 16:23:13 -0500 Received: by simark.ca (Postfix, from userid 112) id E5A771F34E; Tue, 11 Jan 2022 16:23:12 -0500 (EST) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on simark.ca X-Spam-Level: X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RDNS_DYNAMIC,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (ip-8-43-85-97.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id 78F5E1F0E7 for ; Tue, 11 Jan 2022 16:23:11 -0500 (EST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 1C312393A415 for ; Tue, 11 Jan 2022 21:23:11 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 1C312393A415 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1641936191; bh=IKoEB5o4cqmX4AxNeC1OTfjhvlE7zrBOA3qiJdyqw6M=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=RTjkeDgh2h0YEyB+RhVPoooSYttY7luHzPMPOZzhDC70j7RaHKNrMFB6e+RfiNaMh 18J6fs3kQ3EQOjd9fypLdNyx4qI7n2lmVLApSiHv8Bor8IFxzjEqCZxKTv5fV6XYHv luY69X7kpg3Fu6Bv4rlLKkfK7URlcy4ye3DKk1/A= Received: from mail-vk1-xa36.google.com (mail-vk1-xa36.google.com [IPv6:2607:f8b0:4864:20::a36]) by sourceware.org (Postfix) with ESMTPS id 9AABB393A412 for ; Tue, 11 Jan 2022 21:22:28 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 9AABB393A412 Received: by mail-vk1-xa36.google.com with SMTP id e123so373404vkb.8 for ; Tue, 11 Jan 2022 13:22:28 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=IKoEB5o4cqmX4AxNeC1OTfjhvlE7zrBOA3qiJdyqw6M=; b=bPy6UGts/+ujQDXpbYuNPGNlbB2r7A3aR2cdDGvS/hglVojKiCGokH5PgX3LOipEK/ lnMDMU9LTJVeVvio4ua5dsBnWFQbTnXJTngtgFm5BbmuHUm/Qf6qt/lVAbWyYTwRjaoO kFgDNwhMt6diHcdh9xBdwEqzmCq0uGTPeOMTD/rzXPdvpqxbW+KAT9qt7RdIYXACnHuh BI/ANg/2bGptwHiseqn0B3C2CYx4+btFsKU4uvxEEZ5YUwqg82HT8f6sXebl1uVVup+T DuwtY5oJKqHbIr4/TL48mZdtV6Xtxc+ZON2mUl87QjRYGDR5cO5scFtixUa+ngGjbZcS VJlg== X-Gm-Message-State: AOAM53325Ntmhbm9QvVk4x28MCcjhkWcWvplj1ndA3WuPdUeTGCRmqdK JDX8oYC6X1oFOEfyRFYUAWtqGQrf82Ljxg== X-Google-Smtp-Source: ABdhPJzsIAEi2/R2gDsR8B0ZEuFFnC1omaj0YAAlyAfZfOWID9JJpSqFAmQEgojD9wOwOvrYerVIlg== X-Received: by 2002:a05:6122:8ca:: with SMTP id 10mr3473034vkg.11.1641936148135; Tue, 11 Jan 2022 13:22:28 -0800 (PST) Received: from localhost.localdomain ([2804:7f0:4841:563b:7d4b:2a3c:90db:b35f]) by smtp.gmail.com with ESMTPSA id l62sm271008vke.51.2022.01.11.13.22.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Jan 2022 13:22:27 -0800 (PST) To: gdb-patches@sourceware.org, alan.hayward@arm.com, aburgess@redhat.com Subject: [PATCH] [AArch64] Properly extract the reference to a return value from x8 Date: Tue, 11 Jan 2022 18:22:19 -0300 Message-Id: <20220111212219.4018309-1-luis.machado@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220104172254.3665546-1-luis.machado@linaro.org> References: <20220104172254.3665546-1-luis.machado@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Luis Machado via Gdb-patches Reply-To: Luis Machado Errors-To: gdb-patches-bounces+public-inbox=simark.ca@sourceware.org Sender: "Gdb-patches" When running gdb.cp/non-trivial-retval.exp, the following shows up for AArch64-Linux: Breakpoint 3, f1 (i1=23, i2=100) at src/gdb/testsuite/gdb.cp/non-trivial-retval.cc:35 35 A a; (gdb) finish Run till exit from #0 f1 (i1=23, i2=100) at src/gdb/testsuite/gdb.cp/non-trivial-retval.cc:35 main () at /src/gdb/testsuite/gdb.cp/non-trivial-retval.cc:163 163 B b = f2 (i1, i2); Value returned is $6 = {a = -11952} (gdb) The return value should be {a = 123} instead. This happens because the AArch64 backend doesn't extract the return value from the correct location. GDB should fetch a pointer to the memory location from X8. With the patch, gdb.cp/non-trivial-retval.exp has full passes on AArch64-Linux Ubuntu 20.04/18.04. The problem only shows up with the "finish" command. The "call" command works correctly and displays the correct return value. This is also related to PR gdb/28681 (https://sourceware.org/bugzilla/show_bug.cgi?id=28681). --- gdb/aarch64-tdep.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c index 63d626f90ac..0efb3834584 100644 --- a/gdb/aarch64-tdep.c +++ b/gdb/aarch64-tdep.c @@ -2362,7 +2362,8 @@ aarch64_return_in_memory (struct gdbarch *gdbarch, struct type *type) return 0; } - if (TYPE_LENGTH (type) > 16) + if (TYPE_LENGTH (type) > 16 + || !language_pass_by_reference (type).trivially_copyable) { /* PCS B.6 Aggregates larger than 16 bytes are passed by invisible reference. */ @@ -2474,8 +2475,24 @@ aarch64_return_value (struct gdbarch *gdbarch, struct value *func_value, { if (aarch64_return_in_memory (gdbarch, valtype)) { + /* From the AAPCS64's Result Return section: + + "Otherwise, the caller shall reserve a block of memory of + sufficient size and alignment to hold the result. The address + of the memory block shall be passed as an additional argument to + the function in x8. */ + aarch64_debug_printf ("return value in memory"); - return RETURN_VALUE_STRUCT_CONVENTION; + + if (readbuf) + { + CORE_ADDR addr; + + regcache->cooked_read (AARCH64_STRUCT_RETURN_REGNUM, &addr); + read_memory (addr, readbuf, TYPE_LENGTH (valtype)); + } + + return RETURN_VALUE_ABI_RETURNS_ADDRESS; } } -- 2.25.1