/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright 2023 Oxide Computer Company
 */

        .file   "getcontext.s"

#include <sys/asm_linkage.h>

        ANSI_PRAGMA_WEAK(getcontext,function)
        ANSI_PRAGMA_WEAK(swapcontext,function)

#include "SYS.h"
#include <assym.h>

/*
 * getcontext() and swapcontext() are written in assembler since it has to
 * capture the correct machine state of the caller, including
 * the registers: %edi, %esi and %ebx.
 *
 * As swapcontext() is actually equivalent to getcontext() + setcontext(),
 * swapcontext() shares the most code with getcontext().
 */


#define GETCONTEXT_IMPL(func)                                           \
        movl    4(%esp), %eax;          /* %eax <-- first arg: ucp */   \
        pushl   %eax;                   /* push ucp for system call */  \
        call    func;                   /* call syscall */              \
        addl    $4, %esp;               /* pop arg */                   \
        andl    %eax, %eax;             /* if (err_ret_from_syscall) */ \
        je      1f;                                                     \
        ret;                            /*      then return */          \
1:                                                                      \
        movl    4(%esp), %eax;          /* recompute first arg */       \
        /*                                                              \
         * fix up %esp and %eip                                         \
         */                                                             \
        leal    UC_MCONTEXT_GREGS (%eax), %edx;                         \
                                /* %edx <-- &ucp->uc_mcontext.gregs */  \
        movl    0(%esp), %eax;  /* read return PC from stack */         \
        movl    %eax, EIP_OFF (%edx);                                   \
                                /* store ret PC in EIP of env var */    \
        leal    4(%esp), %eax;  /* get caller's sp at time of call */   \
        movl    %eax, UESP_OFF (%edx);                                  \
                                /* store the sp into UESP of env var */ \
        xorl    %eax, %eax;     /* return 0 */                          \
        movl    %eax, EAX_OFF (%edx);                                   \
                                /* getcontext returns 0 after a setcontext */

/*
 * int getcontext(ucontext_t *ucp)
 */
        ENTRY(getcontext)
        GETCONTEXT_IMPL(__getcontext)
        ret
        SET_SIZE(getcontext)


/*
 * int swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
 */
        ENTRY(swapcontext)
        GETCONTEXT_IMPL(__getcontext)
        /* call setcontext */
        movl    8(%esp), %eax           /* %eax <-- second arg: ucp */
        pushl   %eax                    /* push ucp for setcontext */
        call    setcontext
        addl    $4, %esp                /* pop arg: just in case */
        ret
        SET_SIZE(swapcontext)

/*
 * int getcontext_extd(ucontext_t *ucp, uint32_t flags)
 */
        ENTRY(getcontext_extd)
        movl    8(%esp), %eax
        cmpl    $0, %eax                /* if (flags != 0) */
        jne     2f
        GETCONTEXT_IMPL(__getcontext_extd)
        ret
2:
        movl    $EINVAL, %eax           /* errno = EINVAL; */
        jmp     __cerror                /* return (-1) */
        SET_SIZE(getcontext_extd)


/*
 * int swapcontext_extd(ucontext_t *oucp, const ucontext_t *ucp)
 */
        ENTRY(swapcontext_extd)
        movl    8(%esp), %eax
        cmpl    $0, %eax                /* if (flags != 0) */
        jne     2f
        GETCONTEXT_IMPL(__getcontext_extd)
        /* call setcontext */
        movl    12(%esp), %eax          /* %eax <-- second arg: ucp */
        pushl   %eax                    /* push ucp for setcontext */
        call    setcontext
        addl    $4, %esp                /* pop arg: just in case */
        ret
2:
        movl    $EINVAL, %eax           /* errno = EINVAL; */
        jmp     __cerror                /* return (-1) */
        SET_SIZE(swapcontext_extd)