From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=2a00:1450:400c:c0c::241; helo=mail-wr0-x241.google.com; envelope-from=sigmaepsilon92@gmail.com; receiver=edk2-devel@lists.01.org Received: from mail-wr0-x241.google.com (mail-wr0-x241.google.com [IPv6:2a00:1450:400c:c0c::241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id E8DC5222CB30D for ; Thu, 21 Dec 2017 23:18:53 -0800 (PST) Received: by mail-wr0-x241.google.com with SMTP id l19so14750210wrc.2 for ; Thu, 21 Dec 2017 23:23:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=o8zmwRxmYxX2wPq6wz4QvVcma8nuExuhc9+Am0QhdTE=; b=qm/0gGbNredN0xy7E4Q3jAPq6eB23CaLCNOEW49J25aADgI+VSufn+w2XrvSn6ZkE7 Gxlh7R5v+jEhnK9YyI/i+tskHjJXm4aVwyx6knnH170Ds0zeHCB6CKMLhKDqRcMmTxbN wermOpnwM1E/HAHSY4HoLjkUsXOEekmqCf5zQnHBgzbJI8biY/sQWLwyLd1e+1Qt7h9K W270FvIaqVGHhT9z5SCFxQP5LGtN9YJcgh/WRQP8u4JxBC65EX4bk3Ai6YaUFSVy3c++ 6V+mctUC3XC9BtToKiXm9MReSqdW2Z++LIzz6cN9I2lDkWRyZTuTGi33TcdrQuFVk8+j Y5nw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=o8zmwRxmYxX2wPq6wz4QvVcma8nuExuhc9+Am0QhdTE=; b=sax5HkzxM+3yFAgC7ZEtYv9pnfPk8pPkEjgpcnI01SQY7GEMJtW7NZS3aqpKl8DZMg jw/dThaSlGsz/nvpkFhRRUFiohqmGOdyBbcSMrCHQtmvy65lgHWwjqGmr+Bth4mZxOhn 3LreXC0d6lDLjnoIrmMpKsZsVvmbKSSiTGmncb1NX1bQxlhxUUkbR5dOzLE2hgwKzsn8 TUfTB1i69SnbbzmY0ZJGzni04dILhYMQRO65Dhv4eaE+dLgiDQv5W+m+RwNtJMbqV2g2 D2GyjR+wdlz7yeCOVkExvybc7Z+7Ml5RMxc4plZyWc/6Bj1n5o8fMK00+mSjT3/7L0jP mjYQ== X-Gm-Message-State: AKGB3mKhftptBxpsTbjgXV9MAwwhlCI21cMH2GB9e5okJVaWL5mFzDuH lKv8aqxuXcqNmC6ssk+NLqlNPmC1 X-Google-Smtp-Source: ACJfBotmzb4JxhnfuR+00MPZZCoDdyQ+AFmdZnqRZbW9D32I6/G1LtfA0KM1Wk5NsilucUlAe3o5VA== X-Received: by 10.223.136.243 with SMTP id g48mr5980366wrg.247.1513927422065; Thu, 21 Dec 2017 23:23:42 -0800 (PST) Received: from localhost.localdomain ([2a02:908:5a9:8400:5ec8:3210:9b68:c91c]) by smtp.gmail.com with ESMTPSA id m68sm16070965wmi.28.2017.12.21.23.23.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Dec 2017 23:23:41 -0800 (PST) From: M1cha To: edk2-devel@lists.01.org Cc: Ard Biesheuvel , Michael D Kinney , Liming Gao Date: Fri, 22 Dec 2017 08:23:35 +0100 Message-Id: <20171222072336.23504-3-sigmaepsilon92@gmail.com> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171222072336.23504-1-sigmaepsilon92@gmail.com> References: <20171222072336.23504-1-sigmaepsilon92@gmail.com> Subject: [PATCH 2/3] MdePkg/BaseLib: add attribute 'RETURNS_TWICE' to SetJump X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 22 Dec 2017 07:18:54 -0000 When compiling with any ARM toolchain and Os, registers can get trashed when returning for the second time from SetJump because GCC only handles this correctly when using standard names like 'setjmp' or 'getcontext'. When different names are used you have to use the attribute 'returns_twice' to tell gcc to be extra careful. example: extern int FN_NAME(void*); void jmp_buf_set(void *jmpb, void (*f)(void)) { if (!FN_NAME(jmpb)) f(); } this code produces this wrong code with Os: 00000000 : 0: e92d4010 push {r4, lr} 4: e1a04001 mov r4, r1 8: ebfffffe bl 0 c: e3500000 cmp r0, #0 10: 01a03004 moveq r3, r4 14: 08bd4010 popeq {r4, lr} 18: 012fff13 bxeq r3 1c: e8bd4010 pop {r4, lr} 20: e12fff1e bx lr The generated code pushes backups of r4 and lr to the stack and then saves all registers using nonstandard_setjmp. Then it pops the stack and jumps to the function in r3 which is the main problem because now the function can overwrite our register backups on the stack. When we return a second time from the call to nonstandard_setjmp, the stack pointer has it's original(pushed) position and when the code pops r4 and lr from the stack the values are not guaranteed to be the same. When using a standard name like setjmp or getcontext or adding '__attribute__((returns_twice))' to nonstandard_setjmp's declaration the code looks different: 00000000 : 0: e92d4007 push {r0, r1, r2, lr} 4: e58d1004 str r1, [sp, #4] 8: ebfffffe bl 0 c: e3500000 cmp r0, #0 10: 059d3004 ldreq r3, [sp, #4] 14: 01a0e00f moveq lr, pc 18: 012fff13 bxeq r3 1c: e28dd00c add sp, sp, #12 20: e49de004 pop {lr} ; (ldr lr, [sp], #4) 24: e12fff1e bx lr Here the problem is being solved by restoring r3 from the stack without popping it. Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Michael Zimmermann --- MdePkg/Include/Library/BaseLib.h | 1 + 1 file changed, 1 insertion(+) diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h index 2b98af4cd17e..10976032adaa 100644 --- a/MdePkg/Include/Library/BaseLib.h +++ b/MdePkg/Include/Library/BaseLib.h @@ -4905,6 +4905,7 @@ MemoryFence ( **/ UINTN EFIAPI +RETURNS_TWICE SetJump ( OUT BASE_LIBRARY_JUMP_BUFFER *JumpBuffer ); -- 2.15.1