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 0F1C5222F4E02 for ; Fri, 22 Dec 2017 11:09:29 -0800 (PST) Received: by mail-wr0-x241.google.com with SMTP id l19so16337052wrc.2 for ; Fri, 22 Dec 2017 11:14:20 -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; bh=pPoKMO69XZ9v4uSs3alpNSQJWgEM3nggdmDF9Wvb2NQ=; b=tMUQdSceSlykueaKaYfuh8WOCnqzbYHq4fTYd6vpcqsyQEXlGE8plE3CkyLCrKgHMS kKFpWgwCUfeNvY2FoqwZwnahPXsJKmSk9BCGhT7Cx4DGg6xJF6DsT4PzsAXl8ii8lgCv u1Qnhd7UuBUWBBIFAVrKIafbeqv6uI4XCU3zmcRJL2vUDxzMsyP1PHSAt8D4SNwSipor GsWVoPtfnI9V6fHz3E33DOifdSywxAlJbT5KGiwvON6V0zwztEwONULEuDo+CbRmJYmq lwC3UnIYFb8hDd3+aeVFo8eyKyMOQ1EKNuOEyG2q8nMJJ2f84M+QM23bE7NWJGXg+Fd5 ICUA== 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; bh=pPoKMO69XZ9v4uSs3alpNSQJWgEM3nggdmDF9Wvb2NQ=; b=M49HyObtHb6TBkjBWLLe2ypj9P0sLlLSzwWRXbSFENcwwDQaUYHv0bDdeAg/Rgb4Ly yDNPJNYq0QQ+iwjt0z9nW0D99muJtQKepopclNI/oQPc9xB7Xskp95vVU4bqChOoJkFN NkCMMeY6spy0SUIhXQKIoYW+5n0+TSytVLNd7afhU66yGrgFm5HiECUzZClupJ4atZMf frT9D7H4xDE+IS8IKY5FR+3Env68cL4vkMkWMIZxDc7VnUIsA28C7xhFN+Q5ievXJXIm I3G5hgshXjQ/ewh9hECB7jy3ekKRiOOs4pnP1JZd585IkpRc+VP/QjBaekDvG1oevbHn is7w== X-Gm-Message-State: AKGB3mIuYjgmgXO2ULwlEH7+D09dVyViA8xIy0Ql5qws6fZSBu/BlL6j epVj9g1KLjLUL1wXtcHT1+JgzS9Y X-Google-Smtp-Source: ACJfBovLThQCNbpjqZmabzmezA5ffGOiT+2yBTJSOUubO9V4pSm11vzszdLqMKXQOoEz1KGfFaSvQw== X-Received: by 10.223.128.9 with SMTP id 9mr8832545wrk.70.1513970058185; Fri, 22 Dec 2017 11:14:18 -0800 (PST) Received: from localhost.localdomain ([2a02:908:5a9:8400:5ec8:3210:9b68:c91c]) by smtp.gmail.com with ESMTPSA id t10sm27622204wra.16.2017.12.22.11.14.17 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Dec 2017 11:14:17 -0800 (PST) From: M1cha To: edk2-devel@lists.01.org Cc: Ard Biesheuvel , Michael D Kinney , Liming Gao Date: Fri, 22 Dec 2017 20:14:15 +0100 Message-Id: <20171222191416.5105-1-sigmaepsilon92@gmail.com> X-Mailer: git-send-email 2.15.1 Subject: [PATCH v2 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 19:09:30 -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 + MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c | 1 + MdePkg/Library/BaseLib/Ia32/SetJump.c | 1 + 3 files changed, 3 insertions(+) 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 ); diff --git a/MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c b/MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c index 4c0dba55d52f..e309e8b57d7a 100644 --- a/MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c +++ b/MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c @@ -34,6 +34,7 @@ **/ UINTN EFIAPI +RETURNS_TWICE SetJump ( OUT BASE_LIBRARY_JUMP_BUFFER *JumpBuffer ) diff --git a/MdePkg/Library/BaseLib/Ia32/SetJump.c b/MdePkg/Library/BaseLib/Ia32/SetJump.c index 304f3839b108..40fd16bae8fd 100644 --- a/MdePkg/Library/BaseLib/Ia32/SetJump.c +++ b/MdePkg/Library/BaseLib/Ia32/SetJump.c @@ -51,6 +51,7 @@ InternalAssertJumpBuffer ( _declspec (naked) UINTN EFIAPI +RETURNS_TWICE SetJump ( OUT BASE_LIBRARY_JUMP_BUFFER *JumpBuffer ) -- 2.15.1