From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 6BD03433B5 for ; Tue, 5 Nov 2024 22:28:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730845703; cv=none; b=ToZ5l0PWUiK0IhGw5Aym3m33hHSfbULmjcQW2ZAXJzdrLpKVnt7s60zEwKoFkMVYD54JYVmSGyadYsI73VZjE626hFsN0uPiJD6IEqMtoVY7F4LOSfGe3CfVV0Pkimz3JuePwxzBoEEDt9DpjpF92i0oZM8YpMwqbDeg8J0AgKs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730845703; c=relaxed/simple; bh=5l1GZ3eq9pJoL4+XRdcVTCjlrO2K599BLtz8uf88Nao=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=QOTG6Fum/FcrxJWyS94JoqY9zV0ySKHvikizx4hCo1zTS7azM/axhZ74FxQqav+seTQlQojDjB/7YWPUzwJduYqCi419WAUsJp3FzSvBeoRd1SbE3/7Ld8enWpSJXVoqR7iUZdHEWcCaY/QXRdhlILyPMeha8ExvUmAfhcG4SE0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=HChlsozM; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="HChlsozM" Received: from [172.27.3.244] ([76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 4A5MRoc9414997 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Tue, 5 Nov 2024 14:27:51 -0800 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 4A5MRoc9414997 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2024101701; t=1730845672; bh=IH13q9iPFTI89hpznrhXCva+vUvCu42Sl1a7/K/TTAk=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=HChlsozMrvOP1l8+5N9GO+W6JSJdNeClPzJnm1LHT4mpzRjbJt6m+DX2/lbDkKj5O sfiVcmysHFrEviRMc3GiEc9G/EiSBAEQuX1O++erTD1TXGLg6qO8s1/v+akVn5GAP6 SjNoo8kO+dyftE5HjXDQxDpxaYk8wZEWOc/vV6yW2G4k1SeL0EHMnykUwLGh47zP3Q kLSYp/IibDRH/NV3bdn9Bfd+SIXBLtd59ZMT4HBg7cl5ICIKEbK50oAofCcQYc/7L9 UDlSexWhd34TGSkLbuTdkd8qtI+Ky97BZulRmd7T1ZJrV2YYb1xlxoMIyDh6mAlFEP 4HbSo1YRdV73w== Message-ID: <88c01eea-9d0f-4cac-914b-50993cbbb3ce@zytor.com> Date: Tue, 5 Nov 2024 14:27:50 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 6/7] x86/kexec: Debugging support: Dump registers on exception From: "H. Peter Anvin" To: "Woodhouse, David" , "peterz@infradead.org" , "kexec@lists.infradead.org" , "jpoimboe@kernel.org" Cc: "horms@kernel.org" , "x86@kernel.org" , "bp@alien8.de" , "mingo@redhat.com" , "tglx@linutronix.de" , "kai.huang@intel.com" , "linux-kernel@vger.kernel.org" , "kirill.shutemov@linux.intel.com" , "nik.borisov@suse.com" , "dave.hansen@linux.intel.com" References: <20241103054019.3795299-1-dwmw2@infradead.org> <20241103054019.3795299-7-dwmw2@infradead.org> <230aacb0ca0d57581f9350f96390933646f203e4.camel@amazon.co.uk> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/5/24 13:58, H. Peter Anvin wrote: > > Then you can just do the obvious (have your assembly stub point %rdi to > the base of the register dump; set the frame order to whatever you'd > like, except rip/err/exc, or reverse the order if you prefer by changing > the loop): > > static inline __noreturn void die(void) > { >     while (1) >         asm volatile("hlt"); > } > > void dump_register_frame(const unsigned long frame[]) > { >     static const char regnames[][5] = { >         "rax:", "rcx:", "rdx:", "rbx:", >         "rsp:", "rbp:", "rsi:", "rdi:", >         "r8: ", "r9: ", "r10:", "r11:", >         "r12:", "r13:", "r14:", "r15:", >         "cr2:", "Exc:", "Err:", "rip:" >     }; > >     for (size_t i = 0; i < ARRAY_SIZE(regnames); i++) { >         __putstr(regnames[i]); >         __puthex(frame[i]); >         __putstr("\n"); >     } > >     /* Only return from int3 */ >     if (frame[17] != 3) >         die(); > } > I don't know if it is necessary, but you can do something like this to make absolutely sure you don't end up with non-relative symbol references: static inline __constfunc void * sym_addr(const void *sym) { void *addr; asm("lea %c1(%%rip),%0" : "=r" (addr) : "i" (sym)); return addr; }