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 8C36B2222758A for ; Sun, 7 Jan 2018 09:26:00 -0800 (PST) Received: by mail-wr0-x241.google.com with SMTP id o15so8572810wrf.12 for ; Sun, 07 Jan 2018 09:31:09 -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=nr7qJEbpSHS+J58/Lm6mc5FWiQ2G47m8GKX3onxqNMY=; b=BUU/BNSnSUBsLuo4IEO1fQ+2QS/k9iSxA6qQ0gOoT02kh3LxVmLroReSOo0W+G4V3/ cFBySJgAJxPDIsL7LXHvIw29a1FqNoFLf8EQbUz7rH2I7o8HDMAfQ5+Cdcqk1AaKJSvl ZYLodkJhgdRmKMl5cRMZ+VM1/B8JqjsS9AC34Ww99LA2X8RuGkpXZ7uyEkjgHBYSOxT4 1dEwJP1RtUPZNIaXsZyOOfrbG0qVPilMwyiezfbvlTRjRHze6OPTQMRwX1fqWmfT0OGk 1XmyujX+hoT2zxP8CBKmkQAYsuDk46SRMbZpMDFg2aRpRZ/OYVtEswtvVKAILru7nPMi zZjQ== 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=nr7qJEbpSHS+J58/Lm6mc5FWiQ2G47m8GKX3onxqNMY=; b=L7+yJtzZlZT9MD2VruO5nvNCkXZduAzYX9q08CtIaMmNHH/OlqOzNbjyntan6cXzGo euWmbmkeaRF0buukY6a3rT0E7hKDhEPDgqTI4H2dtzAEh7pt8JQrYYjOZETudi1nBgwv +UCGVSk6gHWVr+Sir5MEvHIqNS2RPBkm4aOKDrxtJGZYzP57v0lS0UUMyA5uXfLog6BQ eoJ1T1Jb7aDMFR7E1PhuEZGzj9hh3tv4Ex4UDJyAYM1Gz8qrvcUiDGJb8DNFfwHazkNR 8QNQQBDFXV4UxjDV5MkX+dW3Hen8LsoV9FLIe+GX0SAJo2D2fvxYb9/r4lpVCUPHswvy dH/w== X-Gm-Message-State: AKGB3mLtZrd/9WMQXg+OyZ9yXf2E9LrRvulTrxqjY57dKKvgFm4lCikv 9/zFfLeTdJxF3xeXLqPLXZm0zsJC X-Google-Smtp-Source: ACJfBovaVhDwy6o7fBtKgIClaghm9Ittxb1jgop+Aco+v5ftl+hHxgo0ZIbHtv23k87JOOSUh8umRg== X-Received: by 10.223.177.143 with SMTP id q15mr7081559wra.228.1515346265971; Sun, 07 Jan 2018 09:31:05 -0800 (PST) Received: from localhost.localdomain ([2a02:908:5a9:8400:5ec8:3210:9b68:c91c]) by smtp.gmail.com with ESMTPSA id 127sm12092315wmk.14.2018.01.07.09.31.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 07 Jan 2018 09:31:05 -0800 (PST) From: M1cha To: edk2-devel@lists.01.org Cc: Ard Biesheuvel , Michael D Kinney , Liming Gao Date: Sun, 7 Jan 2018 18:31:03 +0100 Message-Id: <20180107173103.29032-1-sigmaepsilon92@gmail.com> X-Mailer: git-send-email 2.15.1 Subject: [PATCH v3 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: Sun, 07 Jan 2018 17:26:01 -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 05eb4e33a086..39573db0c8da 100644 --- a/MdePkg/Include/Library/BaseLib.h +++ b/MdePkg/Include/Library/BaseLib.h @@ -4903,6 +4903,7 @@ MemoryFence ( @retval 0 Indicates a return from SetJump(). **/ +RETURNS_TWICE UINTN EFIAPI SetJump ( diff --git a/MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c b/MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c index 4c0dba55d52f..683527a36fda 100644 --- a/MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c +++ b/MdePkg/Library/BaseLib/Ebc/SetJumpLongJump.c @@ -32,6 +32,7 @@ @retval 0 Indicates a return from SetJump(). **/ +RETURNS_TWICE UINTN EFIAPI SetJump ( diff --git a/MdePkg/Library/BaseLib/Ia32/SetJump.c b/MdePkg/Library/BaseLib/Ia32/SetJump.c index 304f3839b108..652d45d53ba7 100644 --- a/MdePkg/Library/BaseLib/Ia32/SetJump.c +++ b/MdePkg/Library/BaseLib/Ia32/SetJump.c @@ -49,6 +49,7 @@ InternalAssertJumpBuffer ( **/ _declspec (naked) +RETURNS_TWICE UINTN EFIAPI SetJump ( -- 2.15.1