From nobody Wed Dec 17 20:46:53 2025 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 2363A1FDE35 for ; Fri, 14 Mar 2025 17:32:41 +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=1741973564; cv=none; b=lVafhpUlWDjbKgG8aM/TJ0atdG7qd/5+L0mqrLYgVQINAbc+sZIz3kYDq8zqPF1zcB/HL68VVgIkLtgp+RMVjwatELtKOw5MwHd6ZvAFr0zMsSFoQcUogyt3/0VF2gaUT9hyZwgXdmX7DXVVJlNKyI8xMo6SUqnQTKBn/H95cLM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741973564; c=relaxed/simple; bh=3KV2A40aE8hziNQ20v2xlelA3ksEf/i1QIUUg5cXLdw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iBgzddzjfymNq2p9UoQ/jFVlGxaIgbkUPB0SO3oWNHjHy9PFGES94Wog778qNrB1AOzBRATHWYivAOLBqtuPb84mL/YIsUDSd8LkGhQPiXcmznblg+4ycpaBGnlIp2uQPC+enY3TjHs5P6wlBHFIxBXM+uzrLMSwjYfafWPEkSk= 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=qwvTc2uY; 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="qwvTc2uY" 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=XiU2A8Hf++dNsHgUZJbi/FS+hirzyzKI9tlEDEk267E=; b=qwvTc2uY27wXLSW8SnjfbZSPNf XAx+8qyapF9t8uM9JwqFtY4otTLYNWpp74MkZJFNsDshKBXbD4iPWBhriarGMwWdct1OTlUfFtuPy E0frzIt+40jJPGf8Ogc2tLscxKdFROaavwx5bOS5Qte33Z7bAkSzkEnJHXB/J+fWlFaaMlWhuGbOl 0bGReU5nf9pB/mgIKtpfgHAxfpZiBz/ji2hY9F8nRlcq6R3jazyZMKHOWVt41vJudQEU3Iu5jxRgm JtZCcXiUb+K/kvxk2oH2d1Zq0dkrctHQnr9KmwV7QTD1Mix3WDWvZ6WXsZ1vV0mTvl8gsaCxQ+4xT 0vht+9Uw==; 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 1tt8tb-00000002vUB-3fgc; Fri, 14 Mar 2025 17:32:32 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tt8tY-0000000CsVp-3WmP; Fri, 14 Mar 2025 17:32:28 +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 v8 2/7] x86/kexec: Debugging support: Dump registers on exception Date: Fri, 14 Mar 2025 17:27:34 +0000 Message-ID: <20250314173226.3062535-3-dwmw2@infradead.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250314173226.3062535-1-dwmw2@infradead.org> References: <20250314173226.3062535-1-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 | 121 +++++++++++++++++++++++++-- 1 file changed, 115 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocat= e_kernel_64.S index b07c55019ce5..c2f73998d1b6 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -379,6 +379,69 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) int3 SYM_CODE_END(swap_pages) =20 +/* + * 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 @@ -422,17 +485,63 @@ SYM_CODE_START_LOCAL_NOALIGN(exc_handler) VALIDATE_UNRET_END =20 pushq %rax + pushq %rbx + pushq %rcx pushq %rdx - movw $0x3f8, %dx - movb $'A', %al - outb %al, %dx - popq %rdx - popq %rax + pushq %rsi + + /* Stack frame */ +#define EXC_SS 0x58 /* Architectural... */ +#define EXC_RSP 0x50 +#define EXC_EFLAGS 0x48 +#define EXC_CS 0x40 +#define EXC_RIP 0x38 +#define EXC_ERRORCODE 0x30 /* Either architectural or zero pushed by handl= er */ +#define EXC_EXCEPTION 0x28 /* Pushed by handler entry point */ +#define EXC_RAX 0x20 /* Pushed just above in exc_handler */ +#define EXC_RBX 0x18 +#define EXC_RCX 0x10 +#define EXC_RDX 0x08 +#define EXC_RSI 0x00 + + /* Set up %rdx/%rsi for debug output */ + pr_setup + + /* rip and exception info */ + print_reg 'E', 'x', 'c', ':', EXC_EXCEPTION(%rsp) + print_reg 'E', 'r', 'r', ':', EXC_ERRORCODE(%rsp) + print_reg 'r', 'i', 'p', ':', EXC_RIP(%rsp) + print_reg 'r', 's', 'p', ':', EXC_RSP(%rsp) + + /* We spilled these to the stack */ + print_reg 'r', 'a', 'x', ':', EXC_RAX(%rsp) + print_reg 'r', 'b', 'x', ':', EXC_RBX(%rsp) + print_reg 'r', 'c', 'x', ':', EXC_RCX(%rsp) + print_reg 'r', 'd', 'x', ':', EXC_RDX(%rsp) + print_reg 'r', 's', 'i', ':', EXC_RSI(%rsp) + + /* Other registers untouched */ + 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 =20 /* Only return from int3 */ - cmpq $3, (%rsp) + cmpq $3, EXC_EXCEPTION(%rsp) jne .Ldie =20 + popq %rsi + popq %rdx + popq %rcx + popq %rbx + popq %rax + addq $16, %rsp iretq =20 --=20 2.48.1