gregkh at linuxfoundation.org
2018-Jul-23 07:58 UTC
Patch "x86/paravirt: Make native_save_fl() extern inline" has been added to the 4.4-stable tree
This is a note to let you know that I've just added the patch titled
x86/paravirt: Make native_save_fl() extern inline
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-paravirt-make-native_save_fl-extern-inline.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.
>From d0a8d9378d16eb3c69bd8e6d23779fbdbee3a8c7 Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers at google.com>
Date: Thu, 21 Jun 2018 09:23:24 -0700
Subject: x86/paravirt: Make native_save_fl() extern inline
From: Nick Desaulniers <ndesaulniers at google.com>
commit d0a8d9378d16eb3c69bd8e6d23779fbdbee3a8c7 upstream.
native_save_fl() is marked static inline, but by using it as
a function pointer in arch/x86/kernel/paravirt.c, it MUST be outlined.
paravirt's use of native_save_fl() also requires that no GPRs other than
%rax are clobbered.
Compilers have different heuristics which they use to emit stack guard
code, the emittance of which can break paravirt's callee saved assumption
by clobbering %rcx.
Marking a function definition extern inline means that if this version
cannot be inlined, then the out-of-line version will be preferred. By
having the out-of-line version be implemented in assembly, it cannot be
instrumented with a stack protector, which might violate custom calling
conventions that code like paravirt rely on.
The semantics of extern inline has changed since gnu89. This means that
folks using GCC versions >= 5.1 may see symbol redefinition errors at
link time for subdirs that override KBUILD_CFLAGS (making the C standard
used implicit) regardless of this patch. This has been cleaned up
earlier in the patch set, but is left as a note in the commit message
for future travelers.
Reports:
https://lkml.org/lkml/2018/5/7/534
https://github.com/ClangBuiltLinux/linux/issues/16
Discussion:
https://bugs.llvm.org/show_bug.cgi?id=37512
https://lkml.org/lkml/2018/5/24/1371
Thanks to the many folks that participated in the discussion.
[Backport for 4.4. 4.4 is missing commit 784d5699eddc "x86: move exports to
actual definitions" which doesn't apply cleanly, and not really worth
backporting IMO. It's simpler to change this patch from upstream:
+ #include <asm-generic/export.h>
rather than
+ #include <asm/export.h>]
Debugged-by: Alistair Strachan <astrachan at google.com>
Debugged-by: Matthias Kaehlcke <mka at chromium.org>
Suggested-by: Arnd Bergmann <arnd at arndb.de>
Suggested-by: H. Peter Anvin <hpa at zytor.com>
Suggested-by: Tom Stellar <tstellar at redhat.com>
Reported-by: Sedat Dilek <sedat.dilek at gmail.com>
Tested-by: Sedat Dilek <sedat.dilek at gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers at google.com>
Acked-by: Juergen Gross <jgross at suse.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: acme at redhat.com
Cc: akataria at vmware.com
Cc: akpm at linux-foundation.org
Cc: andrea.parri at amarulasolutions.com
Cc: ard.biesheuvel at linaro.org
Cc: aryabinin at virtuozzo.com
Cc: astrachan at google.com
Cc: boris.ostrovsky at oracle.com
Cc: brijesh.singh at amd.com
Cc: caoj.fnst at cn.fujitsu.com
Cc: geert at linux-m68k.org
Cc: ghackmann at google.com
Cc: gregkh at linuxfoundation.org
Cc: jan.kiszka at siemens.com
Cc: jarkko.sakkinen at linux.intel.com
Cc: joe at perches.com
Cc: jpoimboe at redhat.com
Cc: keescook at google.com
Cc: kirill.shutemov at linux.intel.com
Cc: kstewart at linuxfoundation.org
Cc: linux-efi at vger.kernel.org
Cc: linux-kbuild at vger.kernel.org
Cc: manojgupta at google.com
Cc: mawilcox at microsoft.com
Cc: michal.lkml at markovi.net
Cc: mjg59 at google.com
Cc: mka at chromium.org
Cc: pombredanne at nexb.com
Cc: rientjes at google.com
Cc: rostedt at goodmis.org
Cc: thomas.lendacky at amd.com
Cc: tweek at google.com
Cc: virtualization at lists.linux-foundation.org
Cc: will.deacon at arm.com
Cc: yamada.masahiro at socionext.com
Link: http://lkml.kernel.org/r/20180621162324.36656-4-ndesaulniers at google.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
arch/x86/include/asm/irqflags.h | 2 +-
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/irqflags.S | 26 ++++++++++++++++++++++++++
3 files changed, 28 insertions(+), 1 deletion(-)
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -8,7 +8,7 @@
* Interrupt control:
*/
-static inline unsigned long native_save_fl(void)
+extern inline unsigned long native_save_fl(void)
{
unsigned long flags;
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -41,6 +41,7 @@ obj-y += alternative.o i8253.o pci-nom
obj-y += tsc.o tsc_msr.o io_delay.o rtc.o
obj-y += pci-iommu_table.o
obj-y += resource.o
+obj-y += irqflags.o
obj-y += process.o
obj-y += fpu/
--- /dev/null
+++ b/arch/x86/kernel/irqflags.S
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <asm/asm.h>
+#include <asm-generic/export.h>
+#include <linux/linkage.h>
+
+/*
+ * unsigned long native_save_fl(void)
+ */
+ENTRY(native_save_fl)
+ pushf
+ pop %_ASM_AX
+ ret
+ENDPROC(native_save_fl)
+EXPORT_SYMBOL(native_save_fl)
+
+/*
+ * void native_restore_fl(unsigned long flags)
+ * %eax/%rdi: flags
+ */
+ENTRY(native_restore_fl)
+ push %_ASM_ARG1
+ popf
+ ret
+ENDPROC(native_restore_fl)
+EXPORT_SYMBOL(native_restore_fl)
Patches currently in stable-queue which might be from ndesaulniers at google.com
are
queue-4.4/x86-paravirt-make-native_save_fl-extern-inline.patch