From nobody Mon Feb 9 17:58:39 2026 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4127C1D63FD for ; Wed, 15 Jan 2025 19:14:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736968486; cv=none; b=npd1KGEZJhR90QBVlB64llTwKFMlwnjoJsD/SCVLbVttS0wip7VO/r33w438aj+sdQIV5obF/tPxysZFBfkLaqZFtZDVBcPtQoC6BGLGJAR+18NRKTy5Vevgxa3icts5tN7+WH977wyRjojNEdaouaMy4vJvZ0xejCjUsKM/Xjs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736968486; c=relaxed/simple; bh=Oi6SW6jVaOG+3GRiLQLmC0w3ufiMhi/qukAnrc5l5Xg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SEzitCswCx9DYMbjlmTn0eWp/UgqRlOSW8ZVLFUXFawXKxsMCSETyj1eUSFejVuZ75E50QdKG0ZUJJ9zUboH5NsII7RXtF94tH8+TFEX1/4UcReQtZkvTYTAIyy3ow+1Ci6DOtKwiiDWqTTrEsTK2FhWILqFqon1K+pu7pM5B8E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=nrdkr+Tq; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="nrdkr+Tq" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=O03Tc2q45eY1dgZWv0tL053b8rPNbzwQjWQWfzAB6PA=; b=nrdkr+Tq+pjs/xef8ARok0TTNm us2M71UipT8QCVTEp7EN9WdiMQM0yDRMtFg5mMMyuB5o5BNv+MDzvUkANFWVhxJ5oNa0LFpLp/twd /ju1xD3XH4F6np2GQLlxTGitTWFFSnLdZ6AuINFAf868vd17O6X8kMjWIdBSXZhX2wjMOyf3zpPnT r+Vx2J33WYVC8hNMd+MtwarJlDm0KglMWUBQFYA2yQeMG0+nKjkYl9k6r/MbCt4PMsXeeXvpPVpBY +Da+mpBnugY67vcoG2mBNtJJdYkmLA3OqGOWk2m/IcF+pJxm1cwux9MnHFNAfEiBYk/EPYQNfKbeI 8svrmF8A==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tY8qS-0000000AvMd-034B; Wed, 15 Jan 2025 19:14:29 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tY8qO-00000002Uw4-46fA; Wed, 15 Jan 2025 19:14:25 +0000 From: David Woodhouse To: kexec@lists.infradead.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , David Woodhouse , "Kirill A . Shutemov" , Kai Huang , Nikolay Borisov , linux-kernel@vger.kernel.org, Simon Horman , Dave Young , Peter Zijlstra , jpoimboe@kernel.org, bsz@amazon.de Subject: [PATCH v6 4/7] x86/kexec: Debugging support: Dump registers on exception Date: Wed, 15 Jan 2025 19:09:33 +0000 Message-ID: <20250115191423.587774-5-dwmw2@infradead.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250115191423.587774-1-dwmw2@infradead.org> References: <20250115191423.587774-1-dwmw2@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html Content-Type: text/plain; charset="utf-8" From: David Woodhouse The actual serial output function is a no-op for now. Signed-off-by: David Woodhouse --- arch/x86/kernel/relocate_kernel_64.S | 106 +++++++++++++++++++++++++-- 1 file changed, 98 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocat= e_kernel_64.S index f5b134a81827..020f0f6e3e2e 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -119,11 +119,6 @@ SYM_CODE_START_NOALIGN(relocate_kernel) jmp *%rsi SYM_CODE_END(relocate_kernel) =20 -#ifdef DEBUG - UNWIND_HINT_UNDEFINED - .balign 0x100 /* relocate_kernel will be overwritten with an IDT */ -#endif - SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) UNWIND_HINT_END_OF_STACK /* @@ -389,6 +384,69 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) SYM_CODE_END(swap_pages) =20 #ifdef CONFIG_KEXEC_DEBUG +/* + * Generic 'print character' routine (as yet unimplemented) + * - %al: Character to be printed (may clobber %rax) + * - %rdx: MMIO address or port. + */ +SYM_CODE_START_LOCAL_NOALIGN(pr_char) + UNWIND_HINT_FUNC + ANNOTATE_NOENDBR + ANNOTATE_UNRET_SAFE + ret +SYM_CODE_END(pr_char) + +/* + * Load pr_char function pointer into %rsi and load %rdx with whatever + * that function wants to see there (typically port/MMIO address). + */ +.macro pr_setup + /* No output; pr_char just returns */ + leaq pr_char(%rip), %rsi +.endm + +/* Print the nybble in %bl, clobber %rax */ +SYM_CODE_START_LOCAL_NOALIGN(pr_nybble) + UNWIND_HINT_FUNC + movb %bl, %al + nop + andb $0x0f, %al + addb $0x30, %al + cmpb $0x3a, %al + jb 1f + addb $('a' - '0' - 10), %al + ANNOTATE_RETPOLINE_SAFE +1: jmp *%rsi +SYM_CODE_END(pr_nybble) + +SYM_CODE_START_LOCAL_NOALIGN(pr_qword) + UNWIND_HINT_FUNC + movq $16, %rcx +1: rolq $4, %rbx + call pr_nybble + loop 1b + movb $'\n', %al + ANNOTATE_RETPOLINE_SAFE + jmp *%rsi +SYM_CODE_END(pr_qword) + +.macro print_reg a, b, c, d, r + movb $\a, %al + ANNOTATE_RETPOLINE_SAFE + call *%rsi + movb $\b, %al + ANNOTATE_RETPOLINE_SAFE + call *%rsi + movb $\c, %al + ANNOTATE_RETPOLINE_SAFE + call *%rsi + movb $\d, %al + ANNOTATE_RETPOLINE_SAFE + call *%rsi + movq \r, %rbx + call pr_qword +.endm + SYM_CODE_START_NOALIGN(kexec_debug_exc_vectors) /* Each of these is 6 bytes. */ .macro vec_err exc @@ -429,11 +487,43 @@ SYM_CODE_END(kexec_debug_exc_vectors) =20 SYM_CODE_START_LOCAL_NOALIGN(exc_handler) pushq %rax + pushq %rbx + pushq %rcx pushq %rdx - movw $0x3f8, %dx - movb $'A', %al - outb %al, %dx + pushq %rsi + + /* Set up %rdx/%rsi for debug output */ + pr_setup + + /* rip and exception info */ + print_reg 'E', 'x', 'c', ':', 0x28(%rsp) + print_reg 'E', 'r', 'r', ':', 0x30(%rsp) + print_reg 'r', 'i', 'p', ':', 0x38(%rsp) + print_reg 'r', 's', 'p', ':', 0x50(%rsp) + + /* We spilled these to the stack */ + print_reg 'r', 'a', 'x', ':', 0x20(%rsp) + print_reg 'r', 'b', 'x', ':', 0x18(%rsp) + print_reg 'r', 'c', 'x', ':', 0x10(%rsp) + print_reg 'r', 'd', 'x', ':', 0x08(%rsp) + + /* Other registers */ + print_reg 'r', 's', 'i', ':', (%rsp) + print_reg 'r', 'd', 'i', ':', %rdi + print_reg 'r', '8', ' ', ':', %r8 + print_reg 'r', '9', ' ', ':', %r9 + print_reg 'r', '1', '0', ':', %r10 + print_reg 'r', '1', '1', ':', %r11 + print_reg 'r', '1', '2', ':', %r12 + print_reg 'r', '1', '3', ':', %r13 + print_reg 'r', '1', '4', ':', %r14 + print_reg 'r', '1', '5', ':', %r15 + print_reg 'c', 'r', '2', ':', %cr2 + + popq %rsi popq %rdx + popq %rcx + popq %rbx popq %rax =20 /* Only return from int3 */ --=20 2.47.0