From: "H. Peter Anvin" <hpa@zytor.com>
To: David Laight <david.laight.linux@gmail.com>
Cc: Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Uros Bizjak <ubizjak@gmail.com>, Petr Mladek <pmladek@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <kees@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Nathan Chancellor <nathan@kernel.org>,
Kiryl Shutsemau <kas@kernel.org>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev,
x86@kernel.org
Subject: Re: [PATCH v1 02/14] x86/realmode: make %gs == 0 an invariant
Date: Tue, 20 Jan 2026 14:51:50 -0800 [thread overview]
Message-ID: <dec1687a-a70d-48cb-806b-0320de7f96f1@zytor.com> (raw)
In-Reply-To: <20260120224014.29e7f326@pumpkin>
On 2026-01-20 14:40, David Laight wrote:
>
> Would it be better to wrap that as (say) read_abs_32() since the
> objective is to read an absolute address (using the relevant zero segment
> register) rather than to read though either fs or gs.
>
> Is this code all running in 32bit linear mode with non-zero cs/ss/ds
> segment registers and 'suitable' entries in the GDT?
> That mode makes my brain hurt :-)
> Or is there a fudge to get 16bit asm from the C.
>
The code is running in 16-bit real mode, compiled using -m16.
-hpa
next prev parent reply other threads:[~2026-01-20 22:52 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260119192923.651588-1-hpa@zytor.com>
2026-01-20 19:53 ` [PATCH v1 00/14] x86 boot code cleanups, batch 1 H. Peter Anvin
2026-01-20 19:53 ` [PATCH v1 01/14] x86/realmode: remove I/O port paravirtualization H. Peter Anvin
2026-01-20 21:47 ` David Laight
2026-01-21 12:27 ` Kiryl Shutsemau
2026-01-28 17:01 ` Borislav Petkov
2026-01-20 19:53 ` [PATCH v1 02/14] x86/realmode: make %gs == 0 an invariant H. Peter Anvin
2026-01-20 22:40 ` David Laight
2026-01-20 22:51 ` H. Peter Anvin [this message]
2026-01-21 0:47 ` H. Peter Anvin
2026-01-21 10:03 ` Uros Bizjak
2026-01-20 19:53 ` [PATCH v1 03/14] x86/boot: use <linux/compiler.h> H. Peter Anvin
2026-01-21 10:04 ` Uros Bizjak
2026-01-20 19:53 ` [PATCH v1 04/14] x86/boot: modernize the segment structure for the header and setup H. Peter Anvin
2026-01-20 19:53 ` [PATCH v1 05/14] x86/boot: call puts() from within die() H. Peter Anvin
2026-01-21 10:07 ` Uros Bizjak
2026-01-20 19:53 ` [PATCH v1 06/14] x86/boot: add comment barriers for the different headers H. Peter Anvin
2026-01-20 19:53 ` [PATCH v1 07/14] x86/boot: factor out the 16-bit startup code from header.S H. Peter Anvin
2026-01-21 10:08 ` Uros Bizjak
2026-01-20 19:54 ` [PATCH v1 08/14] x86: make CONFIG_EFI_STUB unconditional H. Peter Anvin
2026-01-20 19:54 ` [PATCH v1 09/14] x86/boot: make the relocatable kernel unconditional H. Peter Anvin
2026-01-20 19:54 ` [PATCH v1 10/14] x86/boot: explicitly put the old command line pointer in header.S H. Peter Anvin
2026-01-20 19:54 ` [PATCH v1 11/14] x86/boot: use __seg_fs and __seg_gs in the real-mode boot code H. Peter Anvin
2026-01-21 8:56 ` Uros Bizjak
2026-01-21 9:40 ` Uros Bizjak
2026-01-21 15:13 ` H. Peter Anvin
2026-01-21 16:03 ` Uros Bizjak
2026-01-22 18:57 ` [PATCH v1 08/14] x86: make CONFIG_EFI_STUB unconditional Simon Glass
2026-01-23 0:11 ` H. Peter Anvin
2026-01-26 21:19 ` Simon Glass
2026-01-26 22:20 ` H. Peter Anvin
2026-01-27 1:44 ` Simon Glass
2026-01-27 2:39 ` H. Peter Anvin
2026-01-27 2:54 ` H. Peter Anvin
2026-01-27 3:14 ` Simon Glass
2026-01-27 3:21 ` H. Peter Anvin
2026-01-29 22:13 ` Simon Glass
2026-01-29 22:22 ` H. Peter Anvin
2026-01-21 16:07 ` [PATCH v1 11/14] x86/boot: use __seg_fs and __seg_gs in the real-mode boot code Uros Bizjak
2026-01-20 19:54 ` [PATCH v1 12/14] x86/boot: tweak a20.c for better code generation H. Peter Anvin
2026-01-21 10:10 ` Uros Bizjak
2026-01-21 11:49 ` David Laight
2026-01-24 3:00 ` Maciej W. Rozycki
2026-01-24 4:24 ` H. Peter Anvin
2026-01-24 23:07 ` David Laight
2026-01-24 23:16 ` H. Peter Anvin
2026-01-24 23:40 ` H. Peter Anvin
2026-01-20 19:54 ` [PATCH v1 13/14] x86/boot: simplify x86/boot/cmdline.c by using __seg_fs H. Peter Anvin
2026-01-21 10:11 ` Uros Bizjak
2026-01-20 19:54 ` [PATCH v1 14/14] compiler-gcc: Remove obsolete RELOC_HIDE() macro H. Peter Anvin
2026-01-21 10:18 ` [PATCH v1 00/14] x86 boot code cleanups, batch 1 Uros Bizjak
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