On 15/01/18 10:14, Jan Beulich wrote: >>>> On 12.01.18 at 19:00, <andrew.coop...@citrix.com> wrote: >> --- a/xen/arch/x86/Rules.mk >> +++ b/xen/arch/x86/Rules.mk >> @@ -30,3 +30,10 @@ CFLAGS += -fno-asynchronous-unwind-tables >> ifneq ($(call cc-option,$(CC),-fvisibility=hidden,n),n) >> CFLAGS += -DGCC_HAS_VISIBILITY_ATTRIBUTE >> endif >> + >> +# Compile with thunk-extern, indirect-branch-register if avaiable. >> +ifneq ($(call cc-option,$(CC),-mindirect-branch-register,n),n) >> +CFLAGS += -mindirect-branch=thunk-extern -mindirect-branch-register >> +CFLAGS += -DCONFIG_INDIRECT_THUNK >> +export CONFIG_INDIRECT_THUNK=y >> +endif > Still not a proper config option?
No, for backportability. I'm preparing a post-SP2 series with some cleanup for staging. > >> --- /dev/null >> +++ b/xen/arch/x86/indirect-thunk.S >> @@ -0,0 +1,38 @@ >> +/* >> + * Implement __x86_indirect_thunk_* symbols for use with compatbile >> compilers >> + * and the -mindirect-branch=thunk-extern -mindirect-branch-register >> options. >> + * >> + * Copyright (c) 2017-2018 Citrix Systems Ltd. >> + * >> + * This source code is licensed under the GNU General Public License, >> + * Version 2. See the file COPYING for more details. >> + */ >> + .file __FILE__ >> + >> +#include <asm/asm_defns.h> >> + >> +.macro IND_THUNK_RETPOLINE reg:req >> + call 2f >> +1: >> + lfence >> + jmp 1b >> +2: > As noted in a couple of other places, I'd prefer if numeric labels > weren't used in macros (and especially new ones), in favor of > .L ones utilizing \@. For macros in header files, I can see this rational. However, this is a local macro which only gets expanded in this file, and isn't likely to move elsewhere. I don't see the value in reducing the readability. > >> + mov %\reg, (%rsp) >> + ret >> +.endm >> + >> +/* >> + * Build the __x86_indirect_thunk_* symbols. Currently implement the >> + * retpoline thunk only. >> + */ >> +.macro GEN_INDIRECT_THUNK reg:req >> + .section .text.__x86_indirect_thunk_\reg, "ax", @progbits >> + >> +ENTRY(__x86_indirect_thunk_\reg) >> + IND_THUNK_RETPOLINE \reg >> +.endm > Still unnecessary leading underscores in the section name? Having the section names different to the symbols in them is far worse than using double underscores. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
