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From: Joerg Roedel <jroedel@suse.de>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] x86/boot/64: Explicitly map boot_params and command line
Date: Thu, 8 Oct 2020 11:48:36 +0200	[thread overview]
Message-ID: <20201008094836.GH3209@suse.de> (raw)
In-Reply-To: <20201007195351.776555-5-nivedita@alum.mit.edu>

On Wed, Oct 07, 2020 at 03:53:50PM -0400, Arvind Sankar wrote:
> This is fragile, as boot_params and the command line mappings are
> required for the main kernel. If EARLY_PRINTK and RANDOMIZE_BASE are
> disabled, a QEMU/OVMF boot never accesses the command line in the
> decompressor stub, and so it never gets mapped. The main kernel accesses
> it from the identity mapping if AMD_MEM_ENCRYPT is enabled, and will
> crash.

Looked again, and I think that is wrong for boot_params, which are
touched unconditionally at the beginning of extract_kernel().

For the cmdline you are right, but one of CONFIG_ACPI,
CONFIG_RANDOMIZE_BASE, CONFIG_X86_5LEVEL or CONFIG_EARLY_PRINTK is
sufficient to have it touched during this boot stage.

Regards,

	Joerg


  parent reply	other threads:[~2020-10-08  9:48 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-07 19:53 [PATCH 0/5] Couple of bugfixes to sev-es series Arvind Sankar
2020-10-07 19:53 ` [PATCH 1/5] x86/boot: Initialize boot_params in startup code Arvind Sankar
2020-10-08  9:04   ` Joerg Roedel
2020-10-08 13:44     ` Arvind Sankar
2020-10-07 19:53 ` [PATCH 2/5] x86/boot: Move get_cmd_line_ptr() and COMMAND_LINE_SIZE into misc.h Arvind Sankar
2020-10-08  9:11   ` Joerg Roedel
2020-10-08  9:30   ` Borislav Petkov
2020-10-08 13:47     ` Arvind Sankar
2020-10-08 15:10       ` Borislav Petkov
2020-10-08 15:30         ` Arvind Sankar
2020-10-08 16:16           ` Borislav Petkov
2020-10-07 19:53 ` [PATCH 3/5] x86/boot/64: Change add_identity_map() to take size for ease of use Arvind Sankar
2020-10-08  9:14   ` Joerg Roedel
2020-10-08 13:49     ` Arvind Sankar
2020-10-07 19:53 ` [PATCH 4/5] x86/boot/64: Explicitly map boot_params and command line Arvind Sankar
2020-10-08  9:17   ` Joerg Roedel
2020-10-08  9:48   ` Joerg Roedel [this message]
2020-10-08 13:57     ` Arvind Sankar
2020-10-07 19:53 ` [PATCH 5/5] x86/head/64: Disable stack protection for head$(BITS).o Arvind Sankar
2020-10-08  8:42   ` Joerg Roedel
2020-10-08 14:52     ` Arvind Sankar

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