From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f48.google.com (mail-wm1-f48.google.com [209.85.128.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 50E5B3B19CE for ; Mon, 30 Mar 2026 08:59:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774861189; cv=none; b=HkzJO0n43m40SqqCLVq+ocZ9wX9SqPfAej2sbyRfpGEnNOCwijc+GbmqenxUo5ORKeXt39taAKUQAW6MoIWl9J3we89CfsssLHN4IFmNgKnhSL6jtsUbLVhVSjJWwihUvI4Pf2PdFNiFie2FqsR6j1Ulo3IF1utMRAtk1FrUiww= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774861189; c=relaxed/simple; bh=66bp/k9GY+4ptWbVrKMVvreo6EEmCiXuznFokbYrln8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=fYNGvxja0zc9RLM5pEQfgFnJoLhFOR4AhgMonleCmIV6x4T5vTJV+neafYXTmeUKfQJ05DP65lGdk8izZBvolmx4HPa3eyoV2Pk+dM1g2Chjx3y4o3bE14gHXiKFuP07ZLvtCOkNvN3uv+R+WXd/ytOKuipZVuPeLk87W/j1w1c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=I6QOuht+; arc=none smtp.client-ip=209.85.128.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="I6QOuht+" Received: by mail-wm1-f48.google.com with SMTP id 5b1f17b1804b1-486fd3a577eso37161255e9.1 for ; Mon, 30 Mar 2026 01:59:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1774861187; x=1775465987; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=mTLmdpRtf95czTiZ7AUfHq4PIURTTcyT5Fzc9qMK0ZQ=; b=I6QOuht+WgA7jVxRvUuorjpdojAqsjaBG2GQDp0NV4bN36U2VssshkjsrFsLW9YUFa mZxObSWPevaGZwj+Fsmqybm56621VN1NgGM8yt6ubNnYPATao92rS4P70qXsJCkSmZPx OksSlkJJ5N/8IdTVrF25J8DK/S9xkq768kWsx+bYOjggQYDAQ1wBKNAl75uSgGRyBylE tEA0QSxbNIgjfZDwne67jFOfmvU+VkHN9ma9vLfmwFVGz0ApuBEZiOoiH64hosLxSpAI UAfaWLil6tXkCFQq1vSgPcFzwMY2ljFQq5qsNdiFbElgUiPyRXpo+cRi9gwGs5AJxsJ7 eXuQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774861187; x=1775465987; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=mTLmdpRtf95czTiZ7AUfHq4PIURTTcyT5Fzc9qMK0ZQ=; b=YPKKlyKps6r9lN+9kE1TpFUZibSa64ZpxiXsQldpUCkmoIeZDcymJJWdlKnUbb5pYZ 2OErtpfsl4VdZvgk5PgHcQCFjpyBWRxBQmqZ1kEj76RHqW1MRXLgXumQOcQc+qV3638l S/idrUlWecC3aj4Zpwkf53puhVhcmFwBUrOQ31W01KSuqGli2V20aQgX7RoODg9TK4nL V8xFmqnB3e7NXwGfREFNTtZ9c9k791o1StNjQ7J69rvyazO7nWSCiPbNVMK7X38dHZEC dis24ir3DeHdBg743QRBklZ9piVpmPO5EdtVqenLFlOzwGgtPsPMpr9ylU8R9OWY1hT9 3f7w== X-Forwarded-Encrypted: i=1; AJvYcCUuzKbUljlB80QeqzVL8yL+JGch9EDAbhDz8swC6YxjVLHg4CR0wLJjW//+PXUXby7roU8tsIlqw3w8zV8=@vger.kernel.org X-Gm-Message-State: AOJu0YyLZXEDp8i8KAmeCmvT0Sv2XaeMDZzKVEsSAVQoWwomnf8Cj4L9 Y+gv4jgWZ7Oez4gbeJ2Fk9+xlo3CpOcKNOBPlo8h+Tr1QQdk0K5twlYy X-Gm-Gg: ATEYQzz+zWxmLuOH7t5qSjO67R5yP0cHSVY4UXo6+uJ8OH/7b/wc1kHUp6D6QHM+vTG T88Cko1tnAkIeV952O378w0J+NyG0cBo2VNwcbGFOnYvW9nejpQlg2au8ahTw25rau5ul67GiUF MJBrF24+5visagtmF8bCvj+eWyIQ/JqlbIjUdKhHZGM565ytmv7Mx720NNWTH7Z/UfLKQPG6v2u ns7dBxNPFeztsviNyMTHUvLODuMZ8YcsfmoNPKOJA1zi0wB6Xl1bi6Sll3v9lI/OsNd22l2xu/S 0yUGL4ybBxiENw9MGfNmUV/w1sA0enEv7AXnAjzrc7aLelq7lpOwe8S+8ZFe0h4H1PUNUTF21U+ UP2Y6EGf6L343vNlQwyTLk62CHgCHTThVyKGCwpRkp1ZSeUFPQDIPOD79t/5HHycKXNIXosKlto qdxB8pGcrAG5Bpuj5Iz+7urL7QHrf/P57tZG3RV6NgEgR5AXkoobXqwZJzMatBfAba1corR0alN hV9fPzuu7Vr87TeARa+1Fxn2YTMup5T2Y4kR1jpGwe2 X-Received: by 2002:a05:600c:4744:b0:486:af22:4a2a with SMTP id 5b1f17b1804b1-48727d5a2e4mr189509265e9.7.1774861186429; Mon, 30 Mar 2026 01:59:46 -0700 (PDT) Received: from fedora ([193.77.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4873881c195sm44111025e9.9.2026.03.30.01.59.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 01:59:45 -0700 (PDT) From: Uros Bizjak To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Subject: [PATCH -tip 1/4] x86/elf: Use savesegment() for segment register reads in ELF core dump Date: Mon, 30 Mar 2026 10:59:20 +0200 Message-ID: <20260330085938.67985-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ELF_CORE_COPY_REGS() currently reads %ds, %es, %fs, and %gs using inline assembly and manual zero-extension. This results in redundant instructions like `mov %eax,%eax`. Replace the inline assembly with the `savesegment()` helper, which automatically zero-extends the value to the full register width, eliminating unnecessary instructions. For example, the %ds load sequence changes from: d03: 8c d8 mov %ds,%eax d05: 89 c0 mov %eax,%eax d07: 48 89 84 24 38 01 00 mov %rax,0x138(%rsp) d0e: 00 to: ce8: 8c d8 mov %ds,%eax cea: 48 89 84 24 38 01 00 mov %rax,0x138(%rsp) cf1: 00 thus eliminating the unnecessary zero-extending `mov %eax,%eax`. No functional change intended. Signed-off-by: Uros Bizjak Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" --- arch/x86/include/asm/elf.h | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 2ba5f166e58f..c7f98977663c 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -187,7 +187,6 @@ void set_personality_ia32(bool); #define ELF_CORE_COPY_REGS(pr_reg, regs) \ do { \ - unsigned v; \ (pr_reg)[0] = (regs)->r15; \ (pr_reg)[1] = (regs)->r14; \ (pr_reg)[2] = (regs)->r13; \ @@ -211,10 +210,10 @@ do { \ (pr_reg)[20] = (regs)->ss; \ (pr_reg)[21] = x86_fsbase_read_cpu(); \ (pr_reg)[22] = x86_gsbase_read_cpu_inactive(); \ - asm("movl %%ds,%0" : "=r" (v)); (pr_reg)[23] = v; \ - asm("movl %%es,%0" : "=r" (v)); (pr_reg)[24] = v; \ - asm("movl %%fs,%0" : "=r" (v)); (pr_reg)[25] = v; \ - asm("movl %%gs,%0" : "=r" (v)); (pr_reg)[26] = v; \ + savesegment(ds, (pr_reg)[23]); \ + savesegment(es, (pr_reg)[24]); \ + savesegment(fs, (pr_reg)[25]); \ + savesegment(gs, (pr_reg)[26]); \ } while (0); /* I'm not sure if we can use '-' here */ -- 2.53.0