android_kernel_asus_sm8350/init
Sean Christopherson 6462323626 Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug
commit 1aa0e8b144b6474c4914439d232d15bfe883636b 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>
2022-06-14 18:11:47 +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 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-01-05 13:25:58 -08:00
do_mounts_md.c init/: remove ineffective sparse disabling 2018-08-22 10:52:49 -07:00
do_mounts_rd.c init/: remove ineffective sparse disabling 2018-08-22 10:52:49 -07:00
do_mounts.c vfs: Convert ramfs, shmem, tmpfs, devtmpfs, rootfs to use the new mount API 2019-09-12 21:05:34 -04:00
do_mounts.h fs: add do_mknodat() helper and ksys_mknod() wrapper; remove in-kernel calls to syscall 2018-04-02 20:15:56 +02:00
init_task.c fgraph: Initialize tracing_graph_pause at task creation 2021-02-10 09:25:29 +01:00
initramfs.c initramfs: fix clang build failure 2020-12-30 11:51:30 +01:00
Kconfig Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug 2022-06-14 18:11:47 +02:00
main.c init/main.c: return 1 from handled __setup() functions 2022-04-15 14:18:35 +02:00
Makefile Kbuild: Handle PREEMPT_RT for version string and magic 2019-08-14 01:10:42 +09:00
noinitramfs.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 167 2019-05-30 11:26:39 -07:00
version.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00