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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//
// System calls and other sys.stuff for 386, Linux
//
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
// Most linux systems use glibc's dynamic linker, which puts the
// __kernel_vsyscall vdso helper at 0x10(GS) for easy access from position
// independent code and setldt in runtime does the same in the statically
// linked case. However, systems that use alternative libc such as Android's
// bionic and musl, do not save the helper anywhere, and so the only way to
// invoke a syscall from position independent code is boring old int $0x80
// (which is also what syscall wrappers in bionic/musl use).
//
// The benchmarks also showed that using int $0x80 is as fast as calling
// *%gs:0x10 except on AMD Opteron. See https://golang.org/cl/19833
// for the benchmark program and raw data.
//#define INVOKE_SYSCALL CALL 0x10(GS) // non-portable
#define INVOKE_SYSCALL INT $0x80
#define SYS_exit 1
#define SYS_read 3
#define SYS_write 4
#define SYS_open 5
#define SYS_close 6
#define SYS_getpid 20
#define SYS_access 33
#define SYS_kill 37
#define SYS_brk 45
#define SYS_munmap 91
#define SYS_socketcall 102
#define SYS_setittimer 104
#define SYS_clone 120
#define SYS_sched_yield 158
#define SYS_nanosleep 162
#define SYS_rt_sigreturn 173
#define SYS_rt_sigaction 174
#define SYS_rt_sigprocmask 175
#define SYS_sigaltstack 186
#define SYS_mmap2 192
#define SYS_mincore 218
#define SYS_madvise 219
#define SYS_gettid 224
#define SYS_futex 240
#define SYS_sched_getaffinity 242
#define SYS_set_thread_area 243
#define SYS_exit_group 252
#define SYS_timer_create 259
#define SYS_timer_settime 260
#define SYS_timer_delete 263
#define SYS_clock_gettime 265
#define SYS_tgkill 270
#define SYS_pipe2 331
TEXT runtime·exit(SB),NOSPLIT,$0
MOVL $SYS_exit_group, AX
MOVL code+0(FP), BX
INVOKE_SYSCALL
INT $3 // not reached
RET
TEXT exit1<>(SB),NOSPLIT,$0
MOVL $SYS_exit, AX
MOVL code+0(FP), BX
INVOKE_SYSCALL
INT $3 // not reached
RET
// func exitThread(wait *atomic.Uint32)
TEXT runtime·exitThread(SB),NOSPLIT,$0-4
MOVL wait+0(FP), AX
// We're done using the stack.
MOVL $0, (AX)
MOVL $1, AX // exit (just this thread)
MOVL $0, BX // exit code
INT $0x80 // no stack; must not use CALL
// We may not even have a stack any more.
INT $3
JMP 0(PC)
TEXT runtime·open(SB),NOSPLIT,$0
MOVL $SYS_open, AX
MOVL name+0(FP), BX
MOVL mode+4(FP), CX
MOVL perm+8(FP), DX
INVOKE_SYSCALL
CMPL AX, $0xfffff001
JLS 2(PC)
MOVL $-1, AX
MOVL AX, ret+12(FP)
RET
TEXT runtime·closefd(SB),NOSPLIT,$0
MOVL $SYS_close, AX
MOVL fd+0(FP), BX
INVOKE_SYSCALL
CMPL AX, $0xfffff001
JLS 2(PC)
MOVL $-1, AX
MOVL AX, ret+4(FP)
RET
TEXT runtime·write1(SB),NOSPLIT,$0
MOVL $SYS_write, AX
MOVL fd+0(FP), BX
MOVL p+4(FP), CX
MOVL n+8(FP), DX
INVOKE_SYSCALL
MOVL AX, ret+12(FP)
RET
TEXT runtime·read(SB),NOSPLIT,$0
MOVL $SYS_read, AX
MOVL fd+0(FP), BX
MOVL p+4(FP), CX
MOVL n+8(FP), DX
INVOKE_SYSCALL
MOVL AX, ret+12(FP)
RET
// func pipe2(flags int32) (r, w int32, errno int32)
TEXT runtime·pipe2(SB),NOSPLIT,$0-16
MOVL $SYS_pipe2, AX
LEAL r+4(FP), BX
MOVL flags+0(FP), CX
INVOKE_SYSCALL
MOVL AX, errno+12(FP)
RET
TEXT runtime·usleep(SB),NOSPLIT,$8
MOVL $0, DX
MOVL usec+0(FP), AX
MOVL $1000000, CX
DIVL CX
MOVL AX, 0(SP)
MOVL $1000, AX // usec to nsec
MULL DX
MOVL AX, 4(SP)
// nanosleep(&ts, 0)
MOVL $SYS_nanosleep, AX
LEAL 0(SP), BX
MOVL $0, CX
INVOKE_SYSCALL
RET
TEXT runtime·gettid(SB),NOSPLIT,$0-4
MOVL $SYS_gettid, AX
INVOKE_SYSCALL
MOVL AX, ret+0(FP)
RET
TEXT runtime·raise(SB),NOSPLIT,$12
MOVL $SYS_getpid, AX
INVOKE_SYSCALL
MOVL AX, BX // arg 1 pid
MOVL $SYS_gettid, AX
INVOKE_SYSCALL
MOVL AX, CX // arg 2 tid
MOVL sig+0(FP), DX // arg 3 signal
MOVL $SYS_tgkill, AX
INVOKE_SYSCALL
RET
TEXT runtime·raiseproc(SB),NOSPLIT,$12
MOVL $SYS_getpid, AX
INVOKE_SYSCALL
MOVL AX, BX // arg 1 pid
MOVL sig+0(FP), CX // arg 2 signal
MOVL $SYS_kill, AX
INVOKE_SYSCALL
RET
TEXT ·getpid(SB),NOSPLIT,$0-4
MOVL $SYS_getpid, AX
INVOKE_SYSCALL
MOVL AX, ret+0(FP)
RET
TEXT ·tgkill(SB),NOSPLIT,$0
MOVL $SYS_tgkill, AX
MOVL tgid+0(FP), BX
MOVL tid+4(FP), CX
MOVL sig+8(FP), DX
INVOKE_SYSCALL
RET
TEXT runtime·setitimer(SB),NOSPLIT,$0-12
MOVL $SYS_setittimer, AX
MOVL mode+0(FP), BX
MOVL new+4(FP), CX
MOVL old+8(FP), DX
INVOKE_SYSCALL
RET
TEXT runtime·timer_create(SB),NOSPLIT,$0-16
MOVL $SYS_timer_create, AX
MOVL clockid+0(FP), BX
MOVL sevp+4(FP), CX
MOVL timerid+8(FP), DX
INVOKE_SYSCALL
MOVL AX, ret+12(FP)
RET
TEXT runtime·timer_settime(SB),NOSPLIT,$0-20
MOVL $SYS_timer_settime, AX
MOVL timerid+0(FP), BX
MOVL flags+4(FP), CX
MOVL new+8(FP), DX
MOVL old+12(FP), SI
INVOKE_SYSCALL
MOVL AX, ret+16(FP)
RET
TEXT runtime·timer_delete(SB),NOSPLIT,$0-8
MOVL $SYS_timer_delete, AX
MOVL timerid+0(FP), BX
INVOKE_SYSCALL
MOVL AX, ret+4(FP)
RET
TEXT runtime·mincore(SB),NOSPLIT,$0-16
MOVL $SYS_mincore, AX
MOVL addr+0(FP), BX
MOVL n+4(FP), CX
MOVL dst+8(FP), DX
INVOKE_SYSCALL
MOVL AX, ret+12(FP)
RET
// func walltime() (sec int64, nsec int32)
TEXT runtime·walltime(SB), NOSPLIT, $8-12
// We don't know how much stack space the VDSO code will need,
// so switch to g0.
MOVL SP, BP // Save old SP; BP unchanged by C code.
get_tls(CX)
MOVL g(CX), AX
MOVL g_m(AX), SI // SI unchanged by C code.
// Set vdsoPC and vdsoSP for SIGPROF traceback.
// Save the old values on stack and restore them on exit,
// so this function is reentrant.
MOVL m_vdsoPC(SI), CX
MOVL m_vdsoSP(SI), DX
MOVL CX, 0(SP)
MOVL DX, 4(SP)
LEAL sec+0(FP), DX
MOVL -4(DX), CX
MOVL CX, m_vdsoPC(SI)
MOVL DX, m_vdsoSP(SI)
CMPL AX, m_curg(SI) // Only switch if on curg.
JNE noswitch
MOVL m_g0(SI), DX
MOVL (g_sched+gobuf_sp)(DX), SP // Set SP to g0 stack
noswitch:
SUBL $16, SP // Space for results
ANDL $~15, SP // Align for C code
// Stack layout, depending on call path:
// x(SP) vDSO INVOKE_SYSCALL
// 12 ts.tv_nsec ts.tv_nsec
// 8 ts.tv_sec ts.tv_sec
// 4 &ts -
// 0 CLOCK_<id> -
MOVL runtime·vdsoClockgettimeSym(SB), AX
CMPL AX, $0
JEQ fallback
LEAL 8(SP), BX // &ts (struct timespec)
MOVL BX, 4(SP)
MOVL $0, 0(SP) // CLOCK_REALTIME
CALL AX
JMP finish
fallback:
MOVL $SYS_clock_gettime, AX
MOVL $0, BX // CLOCK_REALTIME
LEAL 8(SP), CX
INVOKE_SYSCALL
finish:
MOVL 8(SP), AX // sec
MOVL 12(SP), BX // nsec
MOVL BP, SP // Restore real SP
// Restore vdsoPC, vdsoSP
// We don't worry about being signaled between the two stores.
// If we are not in a signal handler, we'll restore vdsoSP to 0,
// and no one will care about vdsoPC. If we are in a signal handler,
// we cannot receive another signal.
MOVL 4(SP), CX
MOVL CX, m_vdsoSP(SI)
MOVL 0(SP), CX
MOVL CX, m_vdsoPC(SI)
// sec is in AX, nsec in BX
MOVL AX, sec_lo+0(FP)
MOVL $0, sec_hi+4(FP)
MOVL BX, nsec+8(FP)
RET
// int64 nanotime(void) so really
// void nanotime(int64 *nsec)
TEXT runtime·nanotime1(SB), NOSPLIT, $8-8
// Switch to g0 stack. See comment above in runtime·walltime.
MOVL SP, BP // Save old SP; BP unchanged by C code.
get_tls(CX)
MOVL g(CX), AX
MOVL g_m(AX), SI // SI unchanged by C code.
// Set vdsoPC and vdsoSP for SIGPROF traceback.
// Save the old values on stack and restore them on exit,
// so this function is reentrant.
MOVL m_vdsoPC(SI), CX
MOVL m_vdsoSP(SI), DX
MOVL CX, 0(SP)
MOVL DX, 4(SP)
LEAL ret+0(FP), DX
MOVL -4(DX), CX
MOVL CX, m_vdsoPC(SI)
MOVL DX, m_vdsoSP(SI)
CMPL AX, m_curg(SI) // Only switch if on curg.
JNE noswitch
MOVL m_g0(SI), DX
MOVL (g_sched+gobuf_sp)(DX), SP // Set SP to g0 stack
noswitch:
SUBL $16, SP // Space for results
ANDL $~15, SP // Align for C code
MOVL runtime·vdsoClockgettimeSym(SB), AX
CMPL AX, $0
JEQ fallback
LEAL 8(SP), BX // &ts (struct timespec)
MOVL BX, 4(SP)
MOVL $1, 0(SP) // CLOCK_MONOTONIC
CALL AX
JMP finish
fallback:
MOVL $SYS_clock_gettime, AX
MOVL $1, BX // CLOCK_MONOTONIC
LEAL 8(SP), CX
INVOKE_SYSCALL
finish:
MOVL 8(SP), AX // sec
MOVL 12(SP), BX // nsec
MOVL BP, SP // Restore real SP
// Restore vdsoPC, vdsoSP
// We don't worry about being signaled between the two stores.
// If we are not in a signal handler, we'll restore vdsoSP to 0,
// and no one will care about vdsoPC. If we are in a signal handler,
// we cannot receive another signal.
MOVL 4(SP), CX
MOVL CX, m_vdsoSP(SI)
MOVL 0(SP), CX
MOVL CX, m_vdsoPC(SI)
// sec is in AX, nsec in BX
// convert to DX:AX nsec
MOVL $1000000000, CX
MULL CX
ADDL BX, AX
ADCL $0, DX
MOVL AX, ret_lo+0(FP)
MOVL DX, ret_hi+4(FP)
RET
TEXT runtime·rtsigprocmask(SB),NOSPLIT,$0
MOVL $SYS_rt_sigprocmask, AX
MOVL how+0(FP), BX
MOVL new+4(FP), CX
MOVL old+8(FP), DX
MOVL size+12(FP), SI
INVOKE_SYSCALL
CMPL AX, $0xfffff001
JLS 2(PC)
INT $3
RET
TEXT runtime·rt_sigaction(SB),NOSPLIT,$0
MOVL $SYS_rt_sigaction, AX
MOVL sig+0(FP), BX
MOVL new+4(FP), CX
MOVL old+8(FP), DX
MOVL size+12(FP), SI
INVOKE_SYSCALL
MOVL AX, ret+16(FP)
RET
TEXT runtime·sigfwd(SB),NOSPLIT,$12-16
MOVL fn+0(FP), AX
MOVL sig+4(FP), BX
MOVL info+8(FP), CX
MOVL ctx+12(FP), DX
MOVL SP, SI
SUBL $32, SP
ANDL $-15, SP // align stack: handler might be a C function
MOVL BX, 0(SP)
MOVL CX, 4(SP)
MOVL DX, 8(SP)
MOVL SI, 12(SP) // save SI: handler might be a Go function
CALL AX
MOVL 12(SP), AX
MOVL AX, SP
RET
// Called using C ABI.
TEXT runtime·sigtramp(SB),NOSPLIT|TOPFRAME,$28
// Save callee-saved C registers, since the caller may be a C signal handler.
MOVL BX, bx-4(SP)
MOVL BP, bp-8(SP)
MOVL SI, si-12(SP)
MOVL DI, di-16(SP)
// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
// modify them.
MOVL (28+4)(SP), BX
MOVL BX, 0(SP)
MOVL (28+8)(SP), BX
MOVL BX, 4(SP)
MOVL (28+12)(SP), BX
MOVL BX, 8(SP)
CALL runtime·sigtrampgo(SB)
MOVL di-16(SP), DI
MOVL si-12(SP), SI
MOVL bp-8(SP), BP
MOVL bx-4(SP), BX
RET
TEXT runtime·cgoSigtramp(SB),NOSPLIT,$0
JMP runtime·sigtramp(SB)
TEXT runtime·sigreturn(SB),NOSPLIT,$0
MOVL $SYS_rt_sigreturn, AX
// Sigreturn expects same SP as signal handler,
// so cannot CALL 0x10(GS) here.
INT $0x80
INT $3 // not reached
RET
TEXT runtime·mmap(SB),NOSPLIT,$0
MOVL $SYS_mmap2, AX
MOVL addr+0(FP), BX
MOVL n+4(FP), CX
MOVL prot+8(FP), DX
MOVL flags+12(FP), SI
MOVL fd+16(FP), DI
MOVL off+20(FP), BP
SHRL $12, BP
INVOKE_SYSCALL
CMPL AX, $0xfffff001
JLS ok
NOTL AX
INCL AX
MOVL $0, p+24(FP)
MOVL AX, err+28(FP)
RET
ok:
MOVL AX, p+24(FP)
MOVL $0, err+28(FP)
RET
TEXT runtime·munmap(SB),NOSPLIT,$0
MOVL $SYS_munmap, AX
MOVL addr+0(FP), BX
MOVL n+4(FP), CX
INVOKE_SYSCALL
CMPL AX, $0xfffff001
JLS 2(PC)
INT $3
RET
TEXT runtime·madvise(SB),NOSPLIT,$0
MOVL $SYS_madvise, AX
MOVL addr+0(FP), BX
MOVL n+4(FP), CX
MOVL flags+8(FP), DX
INVOKE_SYSCALL
MOVL AX, ret+12(FP)
RET
// int32 futex(int32 *uaddr, int32 op, int32 val,
// struct timespec *timeout, int32 *uaddr2, int32 val2);
TEXT runtime·futex(SB),NOSPLIT,$0
MOVL $SYS_futex, AX
MOVL addr+0(FP), BX
MOVL op+4(FP), CX
MOVL val+8(FP), DX
MOVL ts+12(FP), SI
MOVL addr2+16(FP), DI
MOVL val3+20(FP), BP
INVOKE_SYSCALL
MOVL AX, ret+24(FP)
RET
// int32 clone(int32 flags, void *stack, M *mp, G *gp, void (*fn)(void));
TEXT runtime·clone(SB),NOSPLIT,$0
MOVL $SYS_clone, AX
MOVL flags+0(FP), BX
MOVL stk+4(FP), CX
MOVL $0, DX // parent tid ptr
MOVL $0, DI // child tid ptr
// Copy mp, gp, fn off parent stack for use by child.
SUBL $16, CX
MOVL mp+8(FP), SI
MOVL SI, 0(CX)
MOVL gp+12(FP), SI
MOVL SI, 4(CX)
MOVL fn+16(FP), SI
MOVL SI, 8(CX)
MOVL $1234, 12(CX)
// cannot use CALL 0x10(GS) here, because the stack changes during the
// system call (after CALL 0x10(GS), the child is still using the
// parent's stack when executing its RET instruction).
INT $0x80
// In parent, return.
CMPL AX, $0
JEQ 3(PC)
MOVL AX, ret+20(FP)
RET
// Paranoia: check that SP is as we expect.
NOP SP // tell vet SP changed - stop checking offsets
MOVL 12(SP), BP
CMPL BP, $1234
JEQ 2(PC)
INT $3
// Initialize AX to Linux tid
MOVL $SYS_gettid, AX
INVOKE_SYSCALL
MOVL 0(SP), BX // m
MOVL 4(SP), DX // g
MOVL 8(SP), SI // fn
CMPL BX, $0
JEQ nog
CMPL DX, $0
JEQ nog
MOVL AX, m_procid(BX) // save tid as m->procid
// set up ldt 7+id to point at m->tls.
LEAL m_tls(BX), BP
MOVL m_id(BX), DI
ADDL $7, DI // m0 is LDT#7. count up.
// setldt(tls#, &tls, sizeof tls)
PUSHAL // save registers
PUSHL $32 // sizeof tls
PUSHL BP // &tls
PUSHL DI // tls #
CALL runtime·setldt(SB)
POPL AX
POPL AX
POPL AX
POPAL
// Now segment is established. Initialize m, g.
get_tls(AX)
MOVL DX, g(AX)
MOVL BX, g_m(DX)
CALL runtime·stackcheck(SB) // smashes AX, CX
MOVL 0(DX), DX // paranoia; check they are not nil
MOVL 0(BX), BX
// more paranoia; check that stack splitting code works
PUSHAL
CALL runtime·emptyfunc(SB)
POPAL
nog:
CALL SI // fn()
CALL exit1<>(SB)
MOVL $0x1234, 0x1005
TEXT runtime·sigaltstack(SB),NOSPLIT,$-8
MOVL $SYS_sigaltstack, AX
MOVL new+0(FP), BX
MOVL old+4(FP), CX
INVOKE_SYSCALL
CMPL AX, $0xfffff001
JLS 2(PC)
INT $3
RET
// <asm-i386/ldt.h>
// struct user_desc {
// unsigned int entry_number;
// unsigned long base_addr;
// unsigned int limit;
// unsigned int seg_32bit:1;
// unsigned int contents:2;
// unsigned int read_exec_only:1;
// unsigned int limit_in_pages:1;
// unsigned int seg_not_present:1;
// unsigned int useable:1;
// };
#define SEG_32BIT 0x01
// contents are the 2 bits 0x02 and 0x04.
#define CONTENTS_DATA 0x00
#define CONTENTS_STACK 0x02
#define CONTENTS_CODE 0x04
#define READ_EXEC_ONLY 0x08
#define LIMIT_IN_PAGES 0x10
#define SEG_NOT_PRESENT 0x20
#define USEABLE 0x40
// `-1` means the kernel will pick a TLS entry on the first setldt call,
// which happens during runtime init, and that we'll store back the saved
// entry and reuse that on subsequent calls when creating new threads.
DATA runtime·tls_entry_number+0(SB)/4, $-1
GLOBL runtime·tls_entry_number(SB), NOPTR, $4
// setldt(int entry, int address, int limit)
// We use set_thread_area, which mucks with the GDT, instead of modify_ldt,
// which would modify the LDT, but is disabled on some kernels.
// The name, setldt, is a misnomer, although we leave this name as it is for
// the compatibility with other platforms.
TEXT runtime·setldt(SB),NOSPLIT,$32
MOVL base+4(FP), DX
#ifdef GOOS_android
// Android stores the TLS offset in runtime·tls_g.
SUBL runtime·tls_g(SB), DX
MOVL DX, 0(DX)
#else
/*
* When linking against the system libraries,
* we use its pthread_create and let it set up %gs
* for us. When we do that, the private storage
* we get is not at 0(GS), but -4(GS).
* To insulate the rest of the tool chain from this
* ugliness, 8l rewrites 0(TLS) into -4(GS) for us.
* To accommodate that rewrite, we translate
* the address here and bump the limit to 0xffffffff (no limit)
* so that -4(GS) maps to 0(address).
* Also, the final 0(GS) (current 4(DX)) has to point
* to itself, to mimic ELF.
*/
ADDL $0x4, DX // address
MOVL DX, 0(DX)
#endif
// get entry number
MOVL runtime·tls_entry_number(SB), CX
// set up user_desc
LEAL 16(SP), AX // struct user_desc
MOVL CX, 0(AX) // unsigned int entry_number
MOVL DX, 4(AX) // unsigned long base_addr
MOVL $0xfffff, 8(AX) // unsigned int limit
MOVL $(SEG_32BIT|LIMIT_IN_PAGES|USEABLE|CONTENTS_DATA), 12(AX) // flag bits
// call set_thread_area
MOVL AX, BX // user_desc
MOVL $SYS_set_thread_area, AX
// We can't call this via 0x10(GS) because this is called from setldt0 to set that up.
INT $0x80
// breakpoint on error
CMPL AX, $0xfffff001
JLS 2(PC)
INT $3
// read allocated entry number back out of user_desc
LEAL 16(SP), AX // get our user_desc back
MOVL 0(AX), AX
// store entry number if the kernel allocated it
CMPL CX, $-1
JNE 2(PC)
MOVL AX, runtime·tls_entry_number(SB)
// compute segment selector - (entry*8+3)
SHLL $3, AX
ADDL $3, AX
MOVW AX, GS
RET
TEXT runtime·osyield(SB),NOSPLIT,$0
MOVL $SYS_sched_yield, AX
INVOKE_SYSCALL
RET
TEXT runtime·sched_getaffinity(SB),NOSPLIT,$0
MOVL $SYS_sched_getaffinity, AX
MOVL pid+0(FP), BX
MOVL len+4(FP), CX
MOVL buf+8(FP), DX
INVOKE_SYSCALL
MOVL AX, ret+12(FP)
RET
// int access(const char *name, int mode)
TEXT runtime·access(SB),NOSPLIT,$0
MOVL $SYS_access, AX
MOVL name+0(FP), BX
MOVL mode+4(FP), CX
INVOKE_SYSCALL
MOVL AX, ret+8(FP)
RET
// int connect(int fd, const struct sockaddr *addr, socklen_t addrlen)
TEXT runtime·connect(SB),NOSPLIT,$0-16
// connect is implemented as socketcall(NR_socket, 3, *(rest of args))
// stack already should have fd, addr, addrlen.
MOVL $SYS_socketcall, AX
MOVL $3, BX // connect
LEAL fd+0(FP), CX
INVOKE_SYSCALL
MOVL AX, ret+12(FP)
RET
// int socket(int domain, int type, int protocol)
TEXT runtime·socket(SB),NOSPLIT,$0-16
// socket is implemented as socketcall(NR_socket, 1, *(rest of args))
// stack already should have domain, type, protocol.
MOVL $SYS_socketcall, AX
MOVL $1, BX // socket
LEAL domain+0(FP), CX
INVOKE_SYSCALL
MOVL AX, ret+12(FP)
RET
// func sbrk0() uintptr
TEXT runtime·sbrk0(SB),NOSPLIT,$0-4
// Implemented as brk(NULL).
MOVL $SYS_brk, AX
MOVL $0, BX // NULL
INVOKE_SYSCALL
MOVL AX, ret+0(FP)
RET