From nobody Thu May 15 10:51:59 2025 Delivered-To: importer2@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer2=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1699539108016482.3068331884899; Thu, 9 Nov 2023 06:11:48 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r15eY-0002G1-Jh; Thu, 09 Nov 2023 09:05:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r15ce-000569-Gf; Thu, 09 Nov 2023 09:03:11 -0500 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r15cO-0006sU-ST; Thu, 09 Nov 2023 09:03:04 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id ED86131BDB; Thu, 9 Nov 2023 16:59:56 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id 028E434514; Thu, 9 Nov 2023 16:59:49 +0300 (MSK) Received: (nullmailer pid 1462890 invoked by uid 1000); Thu, 09 Nov 2023 13:59:47 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Mikulas Patocka , Yoshinori Sato , Richard Henderson , Michael Tokarev Subject: [Stable-7.2.7 37/62] linux-user/sh4: Fix crashes on signal delivery Date: Thu, 9 Nov 2023 16:59:05 +0300 Message-Id: <20231109135933.1462615-37-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer2=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer2=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer2=patchew.org@nongnu.org X-ZM-MESSAGEID: 1699539109726100003 Content-Type: text/plain; charset="utf-8" From: Mikulas Patocka sh4 uses gUSA (general UserSpace Atomicity) to provide atomicity on CPUs that don't have atomic instructions. A gUSA region that adds 1 to an atomic variable stored in @R2 looks like this: 4004b6: 03 c7 mova 4004c4 ,r0 4004b8: f3 61 mov r15,r1 4004ba: 09 00 nop 4004bc: fa ef mov #-6,r15 4004be: 22 63 mov.l @r2,r3 4004c0: 01 73 add #1,r3 4004c2: 32 22 mov.l r3,@r2 4004c4: 13 6f mov r1,r15 R0 contains a pointer to the end of the gUSA region R1 contains the saved stack pointer R15 contains negative length of the gUSA region When this region is interrupted by a signal, the kernel detects if R15 >=3D -128U. If yes, the kernel rolls back PC to the beginning of the region and restores SP by copying R1 to R15. The problem happens if we are interrupted by a signal at address 4004c4. R15 still holds the value -6, but the atomic value was already written by an instruction at address 4004c2. In this situation we can't undo the gUSA. The function unwind_gusa does nothing, the signal handler attempts to push a signal frame to the address -6 and crashes. This patch fixes it, so that if we are interrupted at the last instruction in a gUSA region, we copy R1 to R15 to restore the correct stack pointer and avoid crashing. There's another bug: if we are interrupted in a delay slot, we save the address of the instruction in the delay slot. We must save the address of the previous instruction. Cc: qemu-stable@nongnu.org Signed-off-by: Mikulas Patocka Reviewed-by: Yoshinori Sato Message-Id: Reviewed-by: Richard Henderson Signed-off-by: Richard Henderson (cherry picked from commit 3b894b699c9a9c064466e128c18be80a3f2113bc) Signed-off-by: Michael Tokarev diff --git a/linux-user/sh4/signal.c b/linux-user/sh4/signal.c index c4ba962708..c16c2c2d57 100644 --- a/linux-user/sh4/signal.c +++ b/linux-user/sh4/signal.c @@ -104,6 +104,14 @@ static void unwind_gusa(CPUSH4State *regs) =20 /* Reset the SP to the saved version in R1. */ regs->gregs[15] =3D regs->gregs[1]; + } else if (regs->gregs[15] >=3D -128u && regs->pc =3D=3D regs->gregs[0= ]) { + /* If we are on the last instruction of a gUSA region, we must res= et + the SP, otherwise we would be pushing the signal context to + invalid memory. */ + regs->gregs[15] =3D regs->gregs[1]; + } else if (regs->flags & TB_FLAG_DELAY_SLOT) { + /* If we are in a delay slot, push the previous instruction. */ + regs->pc -=3D 2; } } =20 --=20 2.39.2