Sean Christopherson 64639d1118 Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug ... commit 1aa0e8b144 upstream. Add a config option to guard (future) usage of asm_volatile_goto() that includes "tied outputs", i.e. "+" constraints that specify both an input and output parameter. clang-13 has a bug[1] that causes compilation of such inline asm to fail, and KVM wants to use a "+m" constraint to implement a uaccess form of CMPXCHG[2]. E.g. the test code fails with <stdin>:1:29: error: invalid operand in inline asm: '.long (${1:l}) - .' int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; } ^ <stdin>:1:29: error: unknown token in expression <inline asm>:1:9: note: instantiated into assembly here .long () - . ^ 2 errors generated. on clang-13, but passes on gcc (with appropriate asm goto support). The bug is fixed in clang-14, but won't be backported to clang-13 as the changes are too invasive/risky. gcc also had a similar bug[3], fixed in gcc-11, where gcc failed to account for its behavior of assigning two numbers to tied outputs (one for input, one for output) when evaluating symbolic references. [1] https://github.com/ClangBuiltLinux/linux/issues/1512 [2] https://lore.kernel.org/all/YfMruK8%2F1izZ2VHS@google.com [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98096 Suggested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20220202004945.2540433-2-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-06-09 10:23:26 +02:00
..
calibrate.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
do_mounts_initrd.c	Merge branch 'hch.init_path' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2020-08-07 09:40:34 -07:00
do_mounts_rd.c	init: add an init_unlink helper	2020-07-31 08:17:52 +02:00
do_mounts.c	init: don't panic if mount_nodev_root failed	2021-09-19 22:24:52 -04:00
do_mounts.h	init: add an init_mknod helper	2020-07-31 08:17:54 +02:00
init_task.c	sched: Introduce task_struct::user_cpus_ptr to track requested affinity	2021-08-20 12:33:00 +02:00
initramfs.c	init: move usermodehelper_enable() to populate_rootfs()	2021-09-08 11:50:27 -07:00
Kconfig	Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug	2022-06-09 10:23:26 +02:00
main.c	random: handle latent entropy and command line from random_init()	2022-05-30 09:29:16 +02:00
Makefile	init: use $(call cmd,) for generating include/generated/compile.h	2021-05-27 04:01:50 +09:00
noinitramfs.c	init: move usermodehelper_enable() to populate_rootfs()	2021-09-08 11:50:27 -07:00
version.c	kbuild: add an elfnote for whether vmlinux is built with lto	2021-04-25 05:25:42 +09:00