Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 asm changes from Ingo Molnar:
 "The main change in this cycle is another step in the big x86 system
  call interface rework by Andy Lutomirski, which moves most of the low
  level x86 entry code from assembly to C, for all syscall entries
  except native 64-bit system calls:

    arch/x86/entry/entry_32.S        | 182 ++++------
    arch/x86/entry/entry_64_compat.S | 547 ++++++++-----------------------
    194 insertions(+), 535 deletions(-)

  ... our hope is that the final remaining step (converting native
  64-bit system calls) will be less painful as all the previous steps,
  given that most of the legacies and quirks are concentrated around
  native 32-bit and compat environments"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (47 commits)
  x86/entry/32: Fix FS and GS restore in opportunistic SYSEXIT
  x86/entry/32: Fix entry_INT80_32() to expect interrupts to be on
  um/x86: Fix build after x86 syscall changes
  x86/asm: Remove the xyz_cfi macros from dwarf2.h
  selftests/x86: Style fixes for the 'unwind_vdso' test
  x86/entry/64/compat: Document sysenter_fix_flags's reason for existence
  x86/entry: Split and inline syscall_return_slowpath()
  x86/entry: Split and inline prepare_exit_to_usermode()
  x86/entry: Use pt_regs_to_thread_info() in syscall entry tracing
  x86/entry: Hide two syscall entry assertions behind CONFIG_DEBUG_ENTRY
  x86/entry: Micro-optimize compat fast syscall arg fetch
  x86/entry: Force inlining of 32-bit syscall code
  x86/entry: Make irqs_disabled checks in exit code depend on lockdep
  x86/entry: Remove unnecessary IRQ twiddling in fast 32-bit syscalls
  x86/asm: Remove thread_info.sysenter_return
  x86/entry/32: Re-implement SYSENTER using the new C path
  x86/entry/32: Switch INT80 to the new C syscall path
  x86/entry/32: Open-code return tracking from fork and kthreads
  x86/entry/compat: Implement opportunistic SYSRETL for compat syscalls
  x86/vdso/compat: Wire up SYSENTER and SYSCSALL for compat userspace
  ...

1 files changed, 55 insertions, 0 deletions

diff --git a/tools/testing/selftests/x86/thunks_32.S b/tools/testing/selftests/x86/thunks_32.S
new file mode 100644
index 000000000000..29b644bb9f2f
--- /dev/null
+++ b/tools/testing/selftests/x86/thunks_32.S
@@ -0,0 +1,55 @@
+/*
+ * thunks_32.S - assembly helpers for mixed-bitness code
+ * Copyright (c) 2015 Denys Vlasenko
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * These are little helpers that make it easier to switch bitness on
+ * the fly.
+ */
+
+	.text
+	.code32
+
+	.global call64_from_32
+	.type call32_from_64, @function
+
+	// 4(%esp): function to call
+call64_from_32:
+	// Fetch function address
+	mov	4(%esp), %eax
+
+	// Save registers which are callee-clobbered by 64-bit ABI
+	push	%ecx
+	push	%edx
+	push	%esi
+	push	%edi
+
+	// Switch to long mode
+	jmp	$0x33,$1f
+1:	.code64
+
+	// Call the function
+	call	*%rax
+
+	// Switch to compatibility mode
+	push	$0x23  /* USER32_CS */
+	.code32; push $1f; .code64 /* hack: can't have X86_64_32S relocation in 32-bit ELF */
+	lretq
+1:	.code32
+
+	pop	%edi
+	pop	%esi
+	pop	%edx
+	pop	%ecx
+
+	ret
+
+.size call64_from_32, .-call64_from_32