From: Josh Poimboeuf <jpoimboe@redhat.com>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Alexander Potapenko <glider@google.com>,
Dmitriy Vyukov <dvyukov@google.com>,
Matthias Kaehlcke <mka@chromium.org>,
Arnd Bergmann <arnd@arndb.de>,
Peter Zijlstra <peterz@infradead.org>
Subject: [RFC PATCH 0/4] x86/asm: Add ASM_CALL() macro for inline asms with call instructions
Date: Thu, 31 Aug 2017 09:11:16 -0500 [thread overview]
Message-ID: <cover.1504186968.git.jpoimboe@redhat.com> (raw)
Making this RFC because I'm not sure if there's a better solution (like
maybe trying to convince the clang folks to support the undocumented GCC
syntax for this). Opinions and better ideas welcome.
For inline asm statements which have a "call" instruction, we have to
set the stack pointer as a constraint to convince GCC to ensure the
frame pointer is set up first:
register void *__sp asm(_ASM_SP);
asm("call foo" : "+r" (__sp))
Clang doesn't have a known way to do the same thing. Doing the sp
constraint thing causes it to corrupt the stack pointer.
Patch 4/4 adds a wrapper around such inline asm statements.
Before:
register void *__sp asm(_ASM_SP);
asm("call foo" : outputs, "+r" (__sp) : inputs : clobbers);
After:
ASM_CALL("call foo", outputs, inputs, clobbers);
A limitation of the wrapper is that it doesn't support positional
operand names ("%0") and constraints ("0" (foo)).
The benefits of the wrapper are:
- Allows clang-built kernels to boot.
- Removes the stack pointer constraint with CONFIG_FRAME_POINTER=n
(which may soon become the default).
- Will make it easy to handle if we ever get a documented way to do
this.
NOTE: Patch 4/4 triggers a bug in the sparse preprocessor which causes
the kbuild robot to complain. I've reported the bug to the sparse
mailing list.
Josh Poimboeuf (4):
x86/paravirt: Fix output constraint macro names
x86/asm: Convert some inline asm positional operands to named operands
x86/asm: Make alternative macro interfaces more clear and consistent
x86/asm: Use ASM_CALL() macro for inline asm statements with call
instructions
arch/x86/include/asm/alternative.h | 72 ++++-------
arch/x86/include/asm/apic.h | 7 +-
arch/x86/include/asm/arch_hweight.h | 14 +-
arch/x86/include/asm/atomic64_32.h | 101 +++++++++------
arch/x86/include/asm/cmpxchg_32.h | 20 +--
arch/x86/include/asm/mshyperv.h | 51 ++++----
arch/x86/include/asm/page_64.h | 6 +-
arch/x86/include/asm/paravirt_types.h | 86 ++++++-------
arch/x86/include/asm/percpu.h | 13 +-
arch/x86/include/asm/preempt.h | 15 +--
arch/x86/include/asm/processor.h | 41 +++---
arch/x86/include/asm/rwsem.h | 155 ++++++++++++-----------
arch/x86/include/asm/special_insns.h | 7 +-
arch/x86/include/asm/uaccess.h | 24 ++--
arch/x86/include/asm/uaccess_64.h | 16 +--
arch/x86/include/asm/xen/hypercall.h | 59 +++++----
arch/x86/kvm/emulate.c | 9 +-
arch/x86/kvm/vmx.c | 17 +--
arch/x86/mm/fault.c | 13 +-
include/linux/compiler-clang.h | 2 +
include/linux/compiler-gcc.h | 19 +++
include/linux/compiler.h | 34 +++++
tools/objtool/Documentation/stack-validation.txt | 19 +--
23 files changed, 427 insertions(+), 373 deletions(-)
--
2.13.5
next reply other threads:[~2017-08-31 14:13 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-31 14:11 Josh Poimboeuf [this message]
2017-08-31 14:11 ` [RFC PATCH 1/4] x86/paravirt: Fix output constraint macro names Josh Poimboeuf
2017-08-31 14:11 ` [RFC PATCH 2/4] x86/asm: Convert some inline asm positional operands to named operands Josh Poimboeuf
2017-08-31 14:11 ` [RFC PATCH 3/4] x86/asm: Make alternative macro interfaces more clear and consistent Josh Poimboeuf
2017-08-31 16:11 ` Linus Torvalds
2017-08-31 17:25 ` Josh Poimboeuf
2017-08-31 17:31 ` Josh Poimboeuf
2017-09-02 10:32 ` Ingo Molnar
2017-09-14 14:48 ` Josh Poimboeuf
2017-09-14 17:16 ` Linus Torvalds
2017-09-14 17:26 ` Josh Poimboeuf
2017-09-14 17:33 ` Josh Poimboeuf
2017-09-14 18:28 ` Linus Torvalds
2017-09-14 18:45 ` Josh Poimboeuf
2017-09-15 16:10 ` Josh Poimboeuf
2017-09-15 16:53 ` Andrey Ryabinin
2017-09-15 17:20 ` Josh Poimboeuf
2017-09-15 18:01 ` Linus Torvalds
2017-09-15 23:29 ` Josh Poimboeuf
2017-09-16 22:22 ` Andrey Ryabinin
2017-09-18 17:40 ` Josh Poimboeuf
2017-09-19 16:02 ` Josh Poimboeuf
2017-08-31 14:11 ` [RFC PATCH 4/4] x86/asm: Use ASM_CALL() macro for inline asm statements with call instructions Josh Poimboeuf
2017-08-31 14:50 ` Peter Zijlstra
2017-08-31 15:21 ` Josh Poimboeuf
2017-08-31 15:36 ` Dmitry Vyukov
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