[mirror_qemu.git] / linux-user / host / mips / safe-syscall.inc.S

/*
 * safe-syscall.inc.S : host-specific assembly fragment
 * to handle signals occurring at the same time as system calls.
 * This is intended to be included by linux-user/safe-syscall.S
 *
 * Written by Richard Henderson <richard.henderson@linaro.org>
 * Copyright (C) 2021 Linaro, Inc.
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 */

#include "sys/regdef.h"
#include "sys/asm.h"

        .text
        .set    nomips16
        .set    reorder

        .global safe_syscall_start
        .global safe_syscall_end
        .type   safe_syscall_start, @function
        .type   safe_syscall_end, @function

        /*
         * This is the entry point for making a system call. The calling
         * convention here is that of a C varargs function with the
         * first argument an 'int *' to the signal_pending flag, the
         * second one the system call number (as a 'long'), and all further
         * arguments being syscall arguments (also 'long').
         */

#if _MIPS_SIM == _ABIO32
/* 8 * 4 = 32 for outgoing parameters; 1 * 4 for s0 save; 1 * 4 for align. */
#define FRAME    40
#define OFS_S0   32
#else
/* 1 * 8 for s0 save; 1 * 8 for align. */
#define FRAME    16
#define OFS_S0   0
#endif


NESTED(safe_syscall_base, FRAME, ra)
        .cfi_startproc
        PTR_ADDIU sp, sp, -FRAME
        .cfi_adjust_cfa_offset FRAME
        REG_S   s0, OFS_S0(sp)
        .cfi_rel_offset s0, OFS_S0
#if _MIPS_SIM == _ABIO32
        /*
         * The syscall calling convention is nearly the same as C:
         * we enter with a0 == &signal_pending
         *               a1 == syscall number
         *               a2, a3, stack == syscall arguments
         *               and return the result in a0
         * and the syscall instruction needs
         *               v0 == syscall number
         *               a0 ... a3, stack == syscall arguments
         *               and returns the result in v0
         * Shuffle everything around appropriately.
         */
        move    s0, a0          /* signal_pending pointer */
        move    v0, a1          /* syscall number */
        move    a0, a2          /* syscall arguments */
        move    a1, a3
        lw      a2, FRAME+16(sp)
        lw      a3, FRAME+20(sp)
        lw      t4, FRAME+24(sp)
        lw      t5, FRAME+28(sp)
        lw      t6, FRAME+32(sp)
        lw      t7, FRAME+40(sp)
        sw      t4, 16(sp)
        sw      t5, 20(sp)
        sw      t6, 24(sp)
        sw      t7, 28(sp)
#else
        /*
         * The syscall calling convention is nearly the same as C:
         * we enter with a0 == &signal_pending
         *               a1 == syscall number
         *               a2 ... a7 == syscall arguments
         *               and return the result in a0
         * and the syscall instruction needs
         *               v0 == syscall number
         *               a0 ... a5 == syscall arguments
         *               and returns the result in v0
         * Shuffle everything around appropriately.
         */
        move    s0, a0          /* signal_pending pointer */
        move    v0, a1          /* syscall number */
        move    a0, a2          /* syscall arguments */
        move    a1, a3
        move    a2, a4
        move    a3, a5
        move    a4, a6
        move    a5, a7
#endif

        /*
         * This next sequence of code works in conjunction with the
         * rewind_if_safe_syscall_function(). If a signal is taken
         * and the interrupted PC is anywhere between 'safe_syscall_start'
         * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
         * The code sequence must therefore be able to cope with this, and
         * the syscall instruction must be the final one in the sequence.
         */
safe_syscall_start:
        /* If signal_pending is non-zero, don't do the call */
        lw      t1, 0(s0)
        bnez    t1, 2f
        syscall
safe_syscall_end:

        /* code path for having successfully executed the syscall */
        REG_L   s0, OFS_S0(sp)
        PTR_ADDIU sp, sp, FRAME
        .cfi_remember_state
        .cfi_adjust_cfa_offset -FRAME
        .cfi_restore s0
        bnez    a3, 1f
        jr      ra
        .cfi_restore_state

        /* code path when we didn't execute the syscall */
2:      REG_L   s0, OFS_S0(sp)
        PTR_ADDIU sp, sp, FRAME
        .cfi_adjust_cfa_offset -FRAME
        .cfi_restore s0
        li      v0, QEMU_ERESTARTSYS

        /* code path setting errno */
        /*
         * We didn't setup GP on entry, optimistic of the syscall success.
         * We must do so now to load the address of the helper, as required
         * by the ABI, into t9.
         *
         * Note that SETUP_GPX and SETUP_GPX64 are themselves conditional,
         * so we can simply let the one that's not empty succeed.
         */
1:      USE_ALT_CP(t0)
        SETUP_GPX(t1)
        SETUP_GPX64(t0, t1)
        PTR_LA  t9, safe_syscall_set_errno_tail
        jr      t9

        .cfi_endproc
END(safe_syscall_base)
Commit	Line	Data
4542adef RH	1	/*
	2	* safe-syscall.inc.S : host-specific assembly fragment
	3	* to handle signals occurring at the same time as system calls.
	4	* This is intended to be included by linux-user/safe-syscall.S
	5	*
	6	* Written by Richard Henderson <richard.henderson@linaro.org>
	7	* Copyright (C) 2021 Linaro, Inc.
	8	*
	9	* This work is licensed under the terms of the GNU GPL, version 2 or later.
	10	* See the COPYING file in the top-level directory.
	11	*/
	12
	13	#include "sys/regdef.h"
	14	#include "sys/asm.h"
	15
	16	.text
	17	.set nomips16
	18	.set reorder
	19
	20	.global safe_syscall_start
	21	.global safe_syscall_end
	22	.type safe_syscall_start, @function
	23	.type safe_syscall_end, @function
	24
	25	/*
	26	* This is the entry point for making a system call. The calling
	27	* convention here is that of a C varargs function with the
	28	* first argument an 'int *' to the signal_pending flag, the
	29	* second one the system call number (as a 'long'), and all further
	30	* arguments being syscall arguments (also 'long').
	31	*/
	32
	33	#if _MIPS_SIM == _ABIO32
	34	/* 8 * 4 = 32 for outgoing parameters; 1 * 4 for s0 save; 1 * 4 for align. */
	35	#define FRAME 40
	36	#define OFS_S0 32
	37	#else
	38	/* 1 * 8 for s0 save; 1 * 8 for align. */
	39	#define FRAME 16
	40	#define OFS_S0 0
	41	#endif
	42
	43
	44	NESTED(safe_syscall_base, FRAME, ra)
	45	.cfi_startproc
	46	PTR_ADDIU sp, sp, -FRAME
	47	.cfi_adjust_cfa_offset FRAME
	48	REG_S s0, OFS_S0(sp)
	49	.cfi_rel_offset s0, OFS_S0
	50	#if _MIPS_SIM == _ABIO32
	51	/*
	52	* The syscall calling convention is nearly the same as C:
	53	* we enter with a0 == &signal_pending
	54	* a1 == syscall number
	55	* a2, a3, stack == syscall arguments
	56	* and return the result in a0
	57	* and the syscall instruction needs
	58	* v0 == syscall number
	59	* a0 ... a3, stack == syscall arguments
	60	* and returns the result in v0
	61	* Shuffle everything around appropriately.
	62	*/
	63	move s0, a0 /* signal_pending pointer */
	64	move v0, a1 /* syscall number */
65	move a0, a2 /* syscall arguments */
66	move a1, a3
67	lw a2, FRAME+16(sp)
68	lw a3, FRAME+20(sp)
69	lw t4, FRAME+24(sp)
70	lw t5, FRAME+28(sp)
71	lw t6, FRAME+32(sp)
72	lw t7, FRAME+40(sp)
73	sw t4, 16(sp)
74	sw t5, 20(sp)
75	sw t6, 24(sp)
76	sw t7, 28(sp)
77	#else
78	/*
79	* The syscall calling convention is nearly the same as C:
80	* we enter with a0 == &signal_pending
81	* a1 == syscall number
82	* a2 ... a7 == syscall arguments
83	* and return the result in a0
84	* and the syscall instruction needs
85	* v0 == syscall number
86	* a0 ... a5 == syscall arguments
87	* and returns the result in v0
88	* Shuffle everything around appropriately.
89	*/
90	move s0, a0 /* signal_pending pointer */
91	move v0, a1 /* syscall number */
92	move a0, a2 /* syscall arguments */
93	move a1, a3
94	move a2, a4
95	move a3, a5
96	move a4, a6
97	move a5, a7
98	#endif
99
100	/*
101	* This next sequence of code works in conjunction with the
102	* rewind_if_safe_syscall_function(). If a signal is taken
103	* and the interrupted PC is anywhere between 'safe_syscall_start'
104	* and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
105	* The code sequence must therefore be able to cope with this, and
106	* the syscall instruction must be the final one in the sequence.
107	*/
108	safe_syscall_start:
109	/* If signal_pending is non-zero, don't do the call */
110	lw t1, 0(s0)
111	bnez t1, 2f
112	syscall
113	safe_syscall_end:
114
115	/* code path for having successfully executed the syscall */
116	REG_L s0, OFS_S0(sp)
117	PTR_ADDIU sp, sp, FRAME
118	.cfi_remember_state
119	.cfi_adjust_cfa_offset -FRAME
120	.cfi_restore s0
121	bnez a3, 1f
122	jr ra
123	.cfi_restore_state
124
125	/* code path when we didn't execute the syscall */
126	2: REG_L s0, OFS_S0(sp)
127	PTR_ADDIU sp, sp, FRAME
128	.cfi_adjust_cfa_offset -FRAME
129	.cfi_restore s0
af254a27	130	li v0, QEMU_ERESTARTSYS
4542adef RH	131
	132	/* code path setting errno */
	133	/*
	134	* We didn't setup GP on entry, optimistic of the syscall success.
	135	* We must do so now to load the address of the helper, as required
	136	* by the ABI, into t9.
	137	*
	138	* Note that SETUP_GPX and SETUP_GPX64 are themselves conditional,
	139	* so we can simply let the one that's not empty succeed.
	140	*/
	141	1: USE_ALT_CP(t0)
	142	SETUP_GPX(t1)
	143	SETUP_GPX64(t0, t1)
	144	PTR_LA t9, safe_syscall_set_errno_tail
	145	jr t9
	146
	147	.cfi_endproc
	148	END(safe_syscall_base)