4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Nick Desaulniers <ndesaulni...@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. Debugged-by: Alistair Strachan <astrac...@google.com> Debugged-by: Matthias Kaehlcke <m...@chromium.org> Suggested-by: Arnd Bergmann <a...@arndb.de> Suggested-by: H. Peter Anvin <h...@zytor.com> Suggested-by: Tom Stellar <tstel...@redhat.com> Reported-by: Sedat Dilek <sedat.di...@gmail.com> Tested-by: Sedat Dilek <sedat.di...@gmail.com> Signed-off-by: Nick Desaulniers <ndesaulni...@google.com> Acked-by: Juergen Gross <jgr...@suse.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: a...@redhat.com Cc: akata...@vmware.com Cc: a...@linux-foundation.org Cc: andrea.pa...@amarulasolutions.com Cc: ard.biesheu...@linaro.org Cc: aryabi...@virtuozzo.com Cc: astrac...@google.com Cc: boris.ostrov...@oracle.com Cc: brijesh.si...@amd.com Cc: caoj.f...@cn.fujitsu.com Cc: ge...@linux-m68k.org Cc: ghackm...@google.com Cc: gre...@linuxfoundation.org Cc: jan.kis...@siemens.com Cc: jarkko.sakki...@linux.intel.com Cc: j...@perches.com Cc: jpoim...@redhat.com Cc: keesc...@google.com Cc: kirill.shute...@linux.intel.com Cc: kstew...@linuxfoundation.org Cc: linux-efi@vger.kernel.org Cc: linux-kbu...@vger.kernel.org Cc: manojgu...@google.com Cc: mawil...@microsoft.com Cc: michal.l...@markovi.net Cc: mj...@google.com Cc: m...@chromium.org Cc: pombreda...@nexb.com Cc: rient...@google.com Cc: rost...@goodmis.org Cc: thomas.lenda...@amd.com Cc: tw...@google.com Cc: virtualizat...@lists.linux-foundation.org Cc: will.dea...@arm.com Cc: yamada.masah...@socionext.com Link: http://lkml.kernel.org/r/20180621162324.36656-4-ndesaulni...@google.com Signed-off-by: Ingo Molnar <mi...@kernel.org> Signed-off-by: Greg Kroah-Hartman <gre...@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 @@ -12,7 +12,7 @@ * 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 @@ -56,6 +56,7 @@ 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/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) -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
