All of lore.kernel.org
 help / color / mirror / Atom feed
From: Arvind Sankar <nivedita@alum.mit.edu>
To: x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	clang-built-linux@googlegroups.com
Cc: Tom Lendacky <thomas.lendacky@amd.com>, linux-kernel@vger.kernel.org
Subject: [PATCH] x86/cmdline: Disable jump tables for cmdline.c
Date: Wed,  2 Sep 2020 22:30:56 -0400	[thread overview]
Message-ID: <20200903023056.3914690-1-nivedita@alum.mit.edu> (raw)

When CONFIG_RETPOLINE is disabled, Clang uses a jump table for the
switch statement in cmdline_find_option (jump tables are disabled when
CONFIG_RETPOLINE is enabled). This function is called very early in boot
from sme_enable() if CONFIG_AMD_MEM_ENCRYPT is enabled. At this time,
the kernel is still executing out of the identity mapping, but the jump
table will contain virtual addresses.

Fix this by disabling jump tables for cmdline.c when AMD_MEM_ENCRYPT is
enabled.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
 arch/x86/lib/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index d46fff11f06f..aa067859a70b 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -24,7 +24,7 @@ ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_cmdline.o = -pg
 endif
 
-CFLAGS_cmdline.o := -fno-stack-protector
+CFLAGS_cmdline.o := -fno-stack-protector -fno-jump-tables
 endif
 
 inat_tables_script = $(srctree)/arch/x86/tools/gen-insn-attr-x86.awk
-- 
2.26.2


             reply	other threads:[~2020-09-03  2:31 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-03  2:30 Arvind Sankar [this message]
2020-09-03  9:00 ` [tip: x86/urgent] x86/cmdline: Disable jump tables for cmdline.c tip-bot2 for Arvind Sankar
2020-12-21 19:14 ` [PATCH] " Nick Desaulniers
2020-12-21 21:23   ` Arvind Sankar
2020-12-21 21:40     ` Nick Desaulniers

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200903023056.3914690-1-nivedita@alum.mit.edu \
    --to=nivedita@alum.mit.edu \
    --cc=bp@alien8.de \
    --cc=clang-built-linux@googlegroups.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=tglx@linutronix.de \
    --cc=thomas.lendacky@amd.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.