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From: "H. Peter Anvin" <hpa@zytor.com>
To: "Woodhouse, David" <dwmw@amazon.co.uk>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"jpoimboe@kernel.org" <jpoimboe@kernel.org>
Cc: "horms@kernel.org" <horms@kernel.org>,
	"x86@kernel.org" <x86@kernel.org>, "bp@alien8.de" <bp@alien8.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"kai.huang@intel.com" <kai.huang@intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kirill.shutemov@linux.intel.com"
	<kirill.shutemov@linux.intel.com>,
	"nik.borisov@suse.com" <nik.borisov@suse.com>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
Subject: Re: [RFC PATCH 6/7] x86/kexec: Debugging support: Dump registers on exception
Date: Tue, 5 Nov 2024 14:57:28 -0800	[thread overview]
Message-ID: <3a91abd7-5edd-4f4e-bb15-fb9c91f64cc9@zytor.com> (raw)
In-Reply-To: <88c01eea-9d0f-4cac-914b-50993cbbb3ce@zytor.com>

On 11/5/24 14:27, H. Peter Anvin wrote:
> 
> 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;
> }
> 

Compiling with "-fpic -fvisibility=hidden -mcmodel=medium" can also be 
used to suppress non-relative references. If you have external symbol 
references they at least *should* be emitted as GOTPCRELX relocations 
which the linker should relax to relative references; however, I would 
think that you really don't want any of those :)

	-hpa


  reply	other threads:[~2024-11-05 22:57 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-11-03  5:35 [RFC PATCH 0/7] x86/kexec: Add exception handling for relocate_kernel David Woodhouse
2024-11-03  5:35 ` [RFC PATCH 1/7] x86/kexec: Clean up and document register use in relocate_kernel_64.S David Woodhouse
2024-11-05 10:00   ` Huang, Kai
2024-11-05 20:17     ` David Woodhouse
2024-11-03  5:35 ` [RFC PATCH 2/7] x86/kexec: Use named labels in swap_pages " David Woodhouse
2024-11-05 10:01   ` Huang, Kai
2024-11-03  5:35 ` [RFC PATCH 3/7] x86/kexec: Only swap pages for preserve_context mode David Woodhouse
2024-11-03  5:35 ` [RFC PATCH 4/7] x86/kexec: Debugging support: load a GDT David Woodhouse
2024-11-03  5:35 ` [RFC PATCH 5/7] x86/kexec: Debugging support: Load an IDT and basic exception entry points David Woodhouse
2024-11-03  5:35 ` [RFC PATCH 6/7] x86/kexec: Debugging support: Dump registers on exception David Woodhouse
2024-11-05 20:38   ` Woodhouse, David
2024-11-05 20:50     ` H. Peter Anvin
2024-11-05 21:29       ` David Woodhouse
2024-11-05 22:08         ` H. Peter Anvin
2024-11-05 21:37     ` H. Peter Anvin
2024-11-05 21:58       ` H. Peter Anvin
2024-11-05 22:27         ` H. Peter Anvin
2024-11-05 22:57           ` H. Peter Anvin [this message]
2024-11-14  7:40         ` Andy Shevchenko
2024-11-06  2:43       ` David Woodhouse
2024-11-06  2:47         ` H. Peter Anvin
2024-11-06  3:07           ` David Woodhouse
2024-11-08  5:21           ` David Woodhouse
2024-11-08  5:22             ` [RFC PATCH 1/2] x86/kexec: Use linker script for relocate_kernel page layout David Woodhouse
2024-11-08  5:22               ` [RFC PATCH 2/2] x86/kexec: Add data section to relocate_kernel David Woodhouse
2024-11-08  5:35                 ` David Woodhouse
2024-11-08 11:26                 ` H. Peter Anvin
2024-11-08 12:29                   ` David Woodhouse
2024-11-12  8:44                   ` David Woodhouse
2024-11-12 10:14                     ` Peter Zijlstra
2024-11-12 10:45                       ` David Woodhouse
2024-11-14  1:46                         ` jpoimboe
2024-11-03  5:35 ` [RFC PATCH 7/7] [DO NOT MERGE] x86/kexec: enable DEBUG David Woodhouse

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