x86/asm/entry/64/compat: Rename ia32entry.S -> entry_64_compat.S

So we now have the following system entry code related
files, which define the following system call instruction
and other entry paths:

   entry_32.S            # 32-bit binaries on 32-bit kernels
   entry_64.S            # 64-bit binaries on 64-bit kernels
   entry_64_compat.S	 # 32-bit binaries on 64-bit kernels

Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 547 insertions, 0 deletions

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
new file mode 100644
index 000000000000..9558dacf32b9
--- /dev/null
+++ b/arch/x86/entry/entry_64_compat.S
@@ -0,0 +1,547 @@
+/*
+ * Compatibility mode system call entry point for x86-64.
+ *
+ * Copyright 2000-2002 Andi Kleen, SuSE Labs.
+ */
+#include "calling.h"
+#include <asm/asm-offsets.h>
+#include <asm/current.h>
+#include <asm/errno.h>
+#include <asm/ia32_unistd.h>
+#include <asm/thread_info.h>
+#include <asm/segment.h>
+#include <asm/irqflags.h>
+#include <asm/asm.h>
+#include <asm/smap.h>
+#include <linux/linkage.h>
+#include <linux/err.h>
+
+/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
+#include <linux/elf-em.h>
+#define AUDIT_ARCH_I386		(EM_386|__AUDIT_ARCH_LE)
+#define __AUDIT_ARCH_LE		0x40000000
+
+#ifndef CONFIG_AUDITSYSCALL
+# define sysexit_audit		ia32_ret_from_sys_call
+# define sysretl_audit		ia32_ret_from_sys_call
+#endif
+
+	.section .entry.text, "ax"
+
+#ifdef CONFIG_PARAVIRT
+ENTRY(native_usergs_sysret32)
+	swapgs
+	sysretl
+ENDPROC(native_usergs_sysret32)
+#endif
+
+/*
+ * 32-bit SYSENTER instruction entry.
+ *
+ * SYSENTER loads ss, rsp, cs, and rip from previously programmed MSRs.
+ * IF and VM in rflags are cleared (IOW: interrupts are off).
+ * SYSENTER does not save anything on the stack,
+ * and does not save old rip (!!!) and rflags.
+ *
+ * Arguments:
+ * eax  system call number
+ * ebx  arg1
+ * ecx  arg2
+ * edx  arg3
+ * esi  arg4
+ * edi  arg5
+ * ebp  user stack
+ * 0(%ebp) arg6
+ *
+ * This is purely a fast path. For anything complicated we use the int 0x80
+ * path below. We set up a complete hardware stack frame to share code
+ * with the int 0x80 path.
+ */
+ENTRY(ia32_sysenter_target)
+	/*
+	 * Interrupts are off on entry.
+	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
+	 * it is too small to ever cause noticeable irq latency.
+	 */
+	SWAPGS_UNSAFE_STACK
+	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+	ENABLE_INTERRUPTS(CLBR_NONE)
+
+	/* Zero-extending 32-bit regs, do not remove */
+	movl	%ebp, %ebp
+	movl	%eax, %eax
+
+	movl	ASM_THREAD_INFO(TI_sysenter_return, %rsp, 0), %r10d
+
+	/* Construct struct pt_regs on stack */
+	pushq	$__USER32_DS		/* pt_regs->ss */
+	pushq	%rbp			/* pt_regs->sp */
+	pushfq				/* pt_regs->flags */
+	pushq	$__USER32_CS		/* pt_regs->cs */
+	pushq	%r10			/* pt_regs->ip = thread_info->sysenter_return */
+	pushq	%rax			/* pt_regs->orig_ax */
+	pushq	%rdi			/* pt_regs->di */
+	pushq	%rsi			/* pt_regs->si */
+	pushq	%rdx			/* pt_regs->dx */
+	pushq	%rcx			/* pt_regs->cx */
+	pushq	$-ENOSYS		/* pt_regs->ax */
+	cld
+	sub	$(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */
+
+	/*
+	 * no need to do an access_ok check here because rbp has been
+	 * 32-bit zero extended
+	 */
+	ASM_STAC
+1:	movl	(%rbp), %ebp
+	_ASM_EXTABLE(1b, ia32_badarg)
+	ASM_CLAC
+
+	/*
+	 * Sysenter doesn't filter flags, so we need to clear NT
+	 * ourselves.  To save a few cycles, we can check whether
+	 * NT was set instead of doing an unconditional popfq.
+	 */
+	testl	$X86_EFLAGS_NT, EFLAGS(%rsp)
+	jnz	sysenter_fix_flags
+sysenter_flags_fixed:
+
+	orl     $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
+	testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz	sysenter_tracesys
+
+sysenter_do_call:
+	/* 32-bit syscall -> 64-bit C ABI argument conversion */
+	movl	%edi, %r8d		/* arg5 */
+	movl	%ebp, %r9d		/* arg6 */
+	xchg	%ecx, %esi		/* rsi:arg2, rcx:arg4 */
+	movl	%ebx, %edi		/* arg1 */
+	movl	%edx, %edx		/* arg3 (zero extension) */
+sysenter_dispatch:
+	cmpq	$(IA32_NR_syscalls-1), %rax
+	ja	1f
+	call	*ia32_sys_call_table(, %rax, 8)
+	movq	%rax, RAX(%rsp)
+1:
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	testl	$_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz	sysexit_audit
+sysexit_from_sys_call:
+	/*
+	 * NB: SYSEXIT is not obviously safe for 64-bit kernels -- an
+	 * NMI between STI and SYSEXIT has poorly specified behavior,
+	 * and and NMI followed by an IRQ with usergs is fatal.  So
+	 * we just pretend we're using SYSEXIT but we really use
+	 * SYSRETL instead.
+	 *
+	 * This code path is still called 'sysexit' because it pairs
+	 * with 'sysenter' and it uses the SYSENTER calling convention.
+	 */
+	andl    $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
+	movl	RIP(%rsp), %ecx		/* User %eip */
+	RESTORE_RSI_RDI
+	xorl	%edx, %edx		/* Do not leak kernel information */
+	xorq	%r8, %r8
+	xorq	%r9, %r9
+	xorq	%r10, %r10
+	movl	EFLAGS(%rsp), %r11d	/* User eflags */
+	TRACE_IRQS_ON
+
+	/*
+	 * SYSRETL works even on Intel CPUs.  Use it in preference to SYSEXIT,
+	 * since it avoids a dicey window with interrupts enabled.
+	 */
+	movl	RSP(%rsp), %esp
+
+	/*
+	 * USERGS_SYSRET32 does:
+	 *  gsbase = user's gs base
+	 *  eip = ecx
+	 *  rflags = r11
+	 *  cs = __USER32_CS
+	 *  ss = __USER_DS
+	 *
+	 * The prologue set RIP(%rsp) to VDSO32_SYSENTER_RETURN, which does:
+	 *
+	 *  pop %ebp
+	 *  pop %edx
+	 *  pop %ecx
+	 *
+	 * Therefore, we invoke SYSRETL with EDX and R8-R10 zeroed to
+	 * avoid info leaks.  R11 ends up with VDSO32_SYSENTER_RETURN's
+	 * address (already known to user code), and R12-R15 are
+	 * callee-saved and therefore don't contain any interesting
+	 * kernel data.
+	 */
+	USERGS_SYSRET32
+
+#ifdef CONFIG_AUDITSYSCALL
+	.macro auditsys_entry_common
+	movl	%esi, %r8d		/* 5th arg: 4th syscall arg */
+	movl	%ecx, %r9d		/* swap with edx */
+	movl	%edx, %ecx		/* 4th arg: 3rd syscall arg */
+	movl	%r9d, %edx		/* 3rd arg: 2nd syscall arg */
+	movl	%ebx, %esi		/* 2nd arg: 1st syscall arg */
+	movl	%eax, %edi		/* 1st arg: syscall number */
+	call	__audit_syscall_entry
+	movl	ORIG_RAX(%rsp), %eax	/* reload syscall number */
+	movl	%ebx, %edi		/* reload 1st syscall arg */
+	movl	RCX(%rsp), %esi		/* reload 2nd syscall arg */
+	movl	RDX(%rsp), %edx		/* reload 3rd syscall arg */
+	movl	RSI(%rsp), %ecx		/* reload 4th syscall arg */
+	movl	RDI(%rsp), %r8d		/* reload 5th syscall arg */
+	.endm
+
+	.macro auditsys_exit exit
+	testl	$(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz	ia32_ret_from_sys_call
+	TRACE_IRQS_ON
+	ENABLE_INTERRUPTS(CLBR_NONE)
+	movl	%eax, %esi		/* second arg, syscall return value */
+	cmpl	$-MAX_ERRNO, %eax	/* is it an error ? */
+	jbe	1f
+	movslq	%eax, %rsi		/* if error sign extend to 64 bits */
+1:	setbe	%al			/* 1 if error, 0 if not */
+	movzbl	%al, %edi		/* zero-extend that into %edi */
+	call	__audit_syscall_exit
+	movq	RAX(%rsp), %rax		/* reload syscall return value */
+	movl	$(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %edi
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	testl	%edi, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jz	\exit
+	xorl	%eax, %eax		/* Do not leak kernel information */
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%rax, R9(%rsp)
+	movq	%rax, R8(%rsp)
+	jmp	int_with_check
+	.endm
+
+sysenter_auditsys:
+	auditsys_entry_common
+	movl	%ebp, %r9d		/* reload 6th syscall arg */
+	jmp	sysenter_dispatch
+
+sysexit_audit:
+	auditsys_exit sysexit_from_sys_call
+#endif
+
+sysenter_fix_flags:
+	pushq $(X86_EFLAGS_IF|X86_EFLAGS_FIXED)
+	popfq
+	jmp	sysenter_flags_fixed
+
+sysenter_tracesys:
+#ifdef CONFIG_AUDITSYSCALL
+	testl	$(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jz	sysenter_auditsys
+#endif
+	SAVE_EXTRA_REGS
+	xorl	%eax, %eax		/* Do not leak kernel information */
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%rax, R9(%rsp)
+	movq	%rax, R8(%rsp)
+	movq	%rsp, %rdi		/* &pt_regs -> arg1 */
+	call	syscall_trace_enter
+
+	/* Reload arg registers from stack. (see sysenter_tracesys) */
+	movl	RCX(%rsp), %ecx
+	movl	RDX(%rsp), %edx
+	movl	RSI(%rsp), %esi
+	movl	RDI(%rsp), %edi
+	movl	%eax, %eax		/* zero extension */
+
+	RESTORE_EXTRA_REGS
+	jmp	sysenter_do_call
+ENDPROC(ia32_sysenter_target)
+
+/*
+ * 32-bit SYSCALL instruction entry.
+ *
+ * 32-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,
+ * then loads new ss, cs, and rip from previously programmed MSRs.
+ * rflags gets masked by a value from another MSR (so CLD and CLAC
+ * are not needed). SYSCALL does not save anything on the stack
+ * and does not change rsp.
+ *
+ * Note: rflags saving+masking-with-MSR happens only in Long mode
+ * (in legacy 32-bit mode, IF, RF and VM bits are cleared and that's it).
+ * Don't get confused: rflags saving+masking depends on Long Mode Active bit
+ * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes
+ * or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
+ *
+ * Arguments:
+ * eax  system call number
+ * ecx  return address
+ * ebx  arg1
+ * ebp  arg2	(note: not saved in the stack frame, should not be touched)
+ * edx  arg3
+ * esi  arg4
+ * edi  arg5
+ * esp  user stack
+ * 0(%esp) arg6
+ *
+ * This is purely a fast path. For anything complicated we use the int 0x80
+ * path below. We set up a complete hardware stack frame to share code
+ * with the int 0x80 path.
+ */
+ENTRY(ia32_cstar_target)
+	/*
+	 * Interrupts are off on entry.
+	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
+	 * it is too small to ever cause noticeable irq latency.
+	 */
+	SWAPGS_UNSAFE_STACK
+	movl	%esp, %r8d
+	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+	ENABLE_INTERRUPTS(CLBR_NONE)
+
+	/* Zero-extending 32-bit regs, do not remove */
+	movl	%eax, %eax
+
+	/* Construct struct pt_regs on stack */
+	pushq	$__USER32_DS		/* pt_regs->ss */
+	pushq	%r8			/* pt_regs->sp */
+	pushq	%r11			/* pt_regs->flags */
+	pushq	$__USER32_CS		/* pt_regs->cs */
+	pushq	%rcx			/* pt_regs->ip */
+	pushq	%rax			/* pt_regs->orig_ax */
+	pushq	%rdi			/* pt_regs->di */
+	pushq	%rsi			/* pt_regs->si */
+	pushq	%rdx			/* pt_regs->dx */
+	pushq	%rbp			/* pt_regs->cx */
+	movl	%ebp, %ecx
+	pushq	$-ENOSYS		/* pt_regs->ax */
+	sub	$(10*8), %rsp		/* pt_regs->r8-11, bp, bx, r12-15 not saved */
+
+	/*
+	 * No need to do an access_ok check here because r8 has been
+	 * 32-bit zero extended:
+	 */
+	ASM_STAC
+1:	movl	(%r8), %ebp
+	_ASM_EXTABLE(1b, ia32_badarg)
+	ASM_CLAC
+	orl     $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
+	testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz   cstar_tracesys
+
+cstar_do_call:
+	/* 32-bit syscall -> 64-bit C ABI argument conversion */
+	movl	%edi, %r8d		/* arg5 */
+	movl	%ebp, %r9d		/* arg6 */
+	xchg	%ecx, %esi		/* rsi:arg2, rcx:arg4 */
+	movl	%ebx, %edi		/* arg1 */
+	movl	%edx, %edx		/* arg3 (zero extension) */
+
+cstar_dispatch:
+	cmpq	$(IA32_NR_syscalls-1), %rax
+	ja	1f
+
+	call	*ia32_sys_call_table(, %rax, 8)
+	movq	%rax, RAX(%rsp)
+1:
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	testl	$_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz	sysretl_audit
+
+sysretl_from_sys_call:
+	andl	$~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
+	movl	RCX(%rsp), %ebp
+	RESTORE_RSI_RDI_RDX
+	movl	RIP(%rsp), %ecx
+	movl	EFLAGS(%rsp), %r11d
+	xorq	%r10, %r10
+	xorq	%r9, %r9
+	xorq	%r8, %r8
+	TRACE_IRQS_ON
+	movl	RSP(%rsp), %esp
+	/*
+	 * 64-bit->32-bit SYSRET restores eip from ecx,
+	 * eflags from r11 (but RF and VM bits are forced to 0),
+	 * cs and ss are loaded from MSRs.
+	 * (Note: 32-bit->32-bit SYSRET is different: since r11
+	 * does not exist, it merely sets eflags.IF=1).
+	 *
+	 * NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss
+	 * descriptor is not reinitialized.  This means that we must
+	 * avoid SYSRET with SS == NULL, which could happen if we schedule,
+	 * exit the kernel, and re-enter using an interrupt vector.  (All
+	 * interrupt entries on x86_64 set SS to NULL.)  We prevent that
+	 * from happening by reloading SS in __switch_to.
+	 */
+	USERGS_SYSRET32
+
+#ifdef CONFIG_AUDITSYSCALL
+cstar_auditsys:
+	auditsys_entry_common
+	movl	%ebp, %r9d		/* reload 6th syscall arg */
+	jmp	cstar_dispatch
+
+sysretl_audit:
+	auditsys_exit sysretl_from_sys_call
+#endif
+
+cstar_tracesys:
+#ifdef CONFIG_AUDITSYSCALL
+	testl	$(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jz	cstar_auditsys
+#endif
+	SAVE_EXTRA_REGS
+	xorl	%eax, %eax		/* Do not leak kernel information */
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%rax, R9(%rsp)
+	movq	%rax, R8(%rsp)
+	movq	%rsp, %rdi		/* &pt_regs -> arg1 */
+	call	syscall_trace_enter
+
+	/* Reload arg registers from stack. (see sysenter_tracesys) */
+	movl	RCX(%rsp), %ecx
+	movl	RDX(%rsp), %edx
+	movl	RSI(%rsp), %esi
+	movl	RDI(%rsp), %edi
+	movl	%eax, %eax		/* zero extension */
+
+	RESTORE_EXTRA_REGS
+	jmp	cstar_do_call
+END(ia32_cstar_target)
+
+ia32_badarg:
+	ASM_CLAC
+	movq	$-EFAULT, %rax
+	jmp	ia32_sysret
+
+ia32_ret_from_sys_call:
+	xorl	%eax, %eax		/* Do not leak kernel information */
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%rax, R9(%rsp)
+	movq	%rax, R8(%rsp)
+	jmp	int_ret_from_sys_call
+
+/*
+ * Emulated IA32 system calls via int 0x80.
+ *
+ * Arguments:
+ * eax  system call number
+ * ebx  arg1
+ * ecx  arg2
+ * edx  arg3
+ * esi  arg4
+ * edi  arg5
+ * ebp  arg6	(note: not saved in the stack frame, should not be touched)
+ *
+ * Notes:
+ * Uses the same stack frame as the x86-64 version.
+ * All registers except eax must be saved (but ptrace may violate that).
+ * Arguments are zero extended. For system calls that want sign extension and
+ * take long arguments a wrapper is needed. Most calls can just be called
+ * directly.
+ * Assumes it is only called from user space and entered with interrupts off.
+ */
+
+ENTRY(ia32_syscall)
+	/*
+	 * Interrupts are off on entry.
+	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
+	 * it is too small to ever cause noticeable irq latency.
+	 */
+	PARAVIRT_ADJUST_EXCEPTION_FRAME
+	SWAPGS
+	ENABLE_INTERRUPTS(CLBR_NONE)
+
+	/* Zero-extending 32-bit regs, do not remove */
+	movl	%eax, %eax
+
+	/* Construct struct pt_regs on stack (iret frame is already on stack) */
+	pushq	%rax			/* pt_regs->orig_ax */
+	pushq	%rdi			/* pt_regs->di */
+	pushq	%rsi			/* pt_regs->si */
+	pushq	%rdx			/* pt_regs->dx */
+	pushq	%rcx			/* pt_regs->cx */
+	pushq	$-ENOSYS		/* pt_regs->ax */
+	pushq	$0			/* pt_regs->r8 */
+	pushq	$0			/* pt_regs->r9 */
+	pushq	$0			/* pt_regs->r10 */
+	pushq	$0			/* pt_regs->r11 */
+	cld
+	sub	$(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */
+
+	orl	$TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
+	testl	$_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz	ia32_tracesys
+
+ia32_do_call:
+	/* 32-bit syscall -> 64-bit C ABI argument conversion */
+	movl	%edi, %r8d		/* arg5 */
+	movl	%ebp, %r9d		/* arg6 */
+	xchg	%ecx, %esi		/* rsi:arg2, rcx:arg4 */
+	movl	%ebx, %edi		/* arg1 */
+	movl	%edx, %edx		/* arg3 (zero extension) */
+	cmpq	$(IA32_NR_syscalls-1), %rax
+	ja	1f
+
+	call	*ia32_sys_call_table(, %rax, 8) /* RIP relative */
+
+ia32_sysret:
+	movq	%rax, RAX(%rsp)
+1:
+	jmp	int_ret_from_sys_call
+
+ia32_tracesys:
+	SAVE_EXTRA_REGS
+	movq	%rsp, %rdi			/* &pt_regs -> arg1 */
+	call	syscall_trace_enter
+	/*
+	 * Reload arg registers from stack in case ptrace changed them.
+	 * Don't reload %eax because syscall_trace_enter() returned
+	 * the %rax value we should see.  But do truncate it to 32 bits.
+	 * If it's -1 to make us punt the syscall, then (u32)-1 is still
+	 * an appropriately invalid value.
+	 */
+	movl	RCX(%rsp), %ecx
+	movl	RDX(%rsp), %edx
+	movl	RSI(%rsp), %esi
+	movl	RDI(%rsp), %edi
+	movl	%eax, %eax		/* zero extension */
+	RESTORE_EXTRA_REGS
+	jmp	ia32_do_call
+END(ia32_syscall)
+
+	.macro PTREGSCALL label, func
+	ALIGN
+GLOBAL(\label)
+	leaq	\func(%rip), %rax
+	jmp	ia32_ptregs_common
+	.endm
+
+	PTREGSCALL stub32_rt_sigreturn,	sys32_rt_sigreturn
+	PTREGSCALL stub32_sigreturn,	sys32_sigreturn
+	PTREGSCALL stub32_fork,		sys_fork
+	PTREGSCALL stub32_vfork,	sys_vfork
+
+	ALIGN
+GLOBAL(stub32_clone)
+	leaq	sys_clone(%rip), %rax
+	/*
+	 * The 32-bit clone ABI is: clone(..., int tls_val, int *child_tidptr).
+	 * The 64-bit clone ABI is: clone(..., int *child_tidptr, int tls_val).
+	 *
+	 * The native 64-bit kernel's sys_clone() implements the latter,
+	 * so we need to swap arguments here before calling it:
+	 */
+	xchg	%r8, %rcx
+	jmp	ia32_ptregs_common
+
+	ALIGN
+ia32_ptregs_common:
+	SAVE_EXTRA_REGS 8
+	call	*%rax
+	RESTORE_EXTRA_REGS 8
+	ret
+END(ia32_ptregs_common)