xref: /qemu/common-user/host/mips/safe-syscall.inc.S (revision d7478d4229f0a2b2817a55487e6b17081099fae4)
14542adefSRichard Henderson/*
24542adefSRichard Henderson * safe-syscall.inc.S : host-specific assembly fragment
34542adefSRichard Henderson * to handle signals occurring at the same time as system calls.
4bbf15aafSRichard Henderson * This is intended to be included by common-user/safe-syscall.S
54542adefSRichard Henderson *
64542adefSRichard Henderson * Written by Richard Henderson <richard.henderson@linaro.org>
74542adefSRichard Henderson * Copyright (C) 2021 Linaro, Inc.
84542adefSRichard Henderson *
94542adefSRichard Henderson * This work is licensed under the terms of the GNU GPL, version 2 or later.
104542adefSRichard Henderson * See the COPYING file in the top-level directory.
114542adefSRichard Henderson */
124542adefSRichard Henderson
134542adefSRichard Henderson#include "sys/regdef.h"
144542adefSRichard Henderson#include "sys/asm.h"
154542adefSRichard Henderson
164542adefSRichard Henderson        .text
174542adefSRichard Henderson        .set    nomips16
184542adefSRichard Henderson        .set    reorder
194542adefSRichard Henderson
204542adefSRichard Henderson        .global safe_syscall_start
214542adefSRichard Henderson        .global safe_syscall_end
224542adefSRichard Henderson        .type   safe_syscall_start, @function
234542adefSRichard Henderson        .type   safe_syscall_end, @function
244542adefSRichard Henderson
254542adefSRichard Henderson        /*
264542adefSRichard Henderson         * This is the entry point for making a system call. The calling
274542adefSRichard Henderson         * convention here is that of a C varargs function with the
284542adefSRichard Henderson         * first argument an 'int *' to the signal_pending flag, the
294542adefSRichard Henderson         * second one the system call number (as a 'long'), and all further
304542adefSRichard Henderson         * arguments being syscall arguments (also 'long').
314542adefSRichard Henderson         */
324542adefSRichard Henderson
334542adefSRichard Henderson#if _MIPS_SIM == _ABIO32
344542adefSRichard Henderson/* 8 * 4 = 32 for outgoing parameters; 1 * 4 for s0 save; 1 * 4 for align. */
354542adefSRichard Henderson#define FRAME    40
364542adefSRichard Henderson#define OFS_S0   32
374542adefSRichard Henderson#else
384542adefSRichard Henderson/* 1 * 8 for s0 save; 1 * 8 for align. */
394542adefSRichard Henderson#define FRAME    16
404542adefSRichard Henderson#define OFS_S0   0
414542adefSRichard Henderson#endif
424542adefSRichard Henderson
434542adefSRichard Henderson
444542adefSRichard HendersonNESTED(safe_syscall_base, FRAME, ra)
454542adefSRichard Henderson        .cfi_startproc
464542adefSRichard Henderson        PTR_ADDIU sp, sp, -FRAME
474542adefSRichard Henderson        .cfi_adjust_cfa_offset FRAME
484542adefSRichard Henderson        REG_S   s0, OFS_S0(sp)
494542adefSRichard Henderson        .cfi_rel_offset s0, OFS_S0
504542adefSRichard Henderson#if _MIPS_SIM == _ABIO32
514542adefSRichard Henderson        /*
524542adefSRichard Henderson         * The syscall calling convention is nearly the same as C:
534542adefSRichard Henderson         * we enter with a0 == &signal_pending
544542adefSRichard Henderson         *               a1 == syscall number
554542adefSRichard Henderson         *               a2, a3, stack == syscall arguments
564542adefSRichard Henderson         *               and return the result in a0
574542adefSRichard Henderson         * and the syscall instruction needs
584542adefSRichard Henderson         *               v0 == syscall number
594542adefSRichard Henderson         *               a0 ... a3, stack == syscall arguments
604542adefSRichard Henderson         *               and returns the result in v0
614542adefSRichard Henderson         * Shuffle everything around appropriately.
624542adefSRichard Henderson         */
634542adefSRichard Henderson        move    s0, a0          /* signal_pending pointer */
644542adefSRichard Henderson        move    v0, a1          /* syscall number */
654542adefSRichard Henderson        move    a0, a2          /* syscall arguments */
664542adefSRichard Henderson        move    a1, a3
674542adefSRichard Henderson        lw      a2, FRAME+16(sp)
684542adefSRichard Henderson        lw      a3, FRAME+20(sp)
694542adefSRichard Henderson        lw      t4, FRAME+24(sp)
704542adefSRichard Henderson        lw      t5, FRAME+28(sp)
714542adefSRichard Henderson        lw      t6, FRAME+32(sp)
724542adefSRichard Henderson        lw      t7, FRAME+40(sp)
734542adefSRichard Henderson        sw      t4, 16(sp)
744542adefSRichard Henderson        sw      t5, 20(sp)
754542adefSRichard Henderson        sw      t6, 24(sp)
764542adefSRichard Henderson        sw      t7, 28(sp)
774542adefSRichard Henderson#else
784542adefSRichard Henderson        /*
794542adefSRichard Henderson         * The syscall calling convention is nearly the same as C:
804542adefSRichard Henderson         * we enter with a0 == &signal_pending
814542adefSRichard Henderson         *               a1 == syscall number
824542adefSRichard Henderson         *               a2 ... a7 == syscall arguments
834542adefSRichard Henderson         *               and return the result in a0
844542adefSRichard Henderson         * and the syscall instruction needs
854542adefSRichard Henderson         *               v0 == syscall number
864542adefSRichard Henderson         *               a0 ... a5 == syscall arguments
874542adefSRichard Henderson         *               and returns the result in v0
884542adefSRichard Henderson         * Shuffle everything around appropriately.
894542adefSRichard Henderson         */
904542adefSRichard Henderson        move    s0, a0          /* signal_pending pointer */
914542adefSRichard Henderson        move    v0, a1          /* syscall number */
924542adefSRichard Henderson        move    a0, a2          /* syscall arguments */
934542adefSRichard Henderson        move    a1, a3
944542adefSRichard Henderson        move    a2, a4
954542adefSRichard Henderson        move    a3, a5
964542adefSRichard Henderson        move    a4, a6
974542adefSRichard Henderson        move    a5, a7
984542adefSRichard Henderson#endif
994542adefSRichard Henderson
1004542adefSRichard Henderson        /*
1014542adefSRichard Henderson         * This next sequence of code works in conjunction with the
1024542adefSRichard Henderson         * rewind_if_safe_syscall_function(). If a signal is taken
1034542adefSRichard Henderson         * and the interrupted PC is anywhere between 'safe_syscall_start'
1044542adefSRichard Henderson         * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
1054542adefSRichard Henderson         * The code sequence must therefore be able to cope with this, and
1064542adefSRichard Henderson         * the syscall instruction must be the final one in the sequence.
1074542adefSRichard Henderson         */
1084542adefSRichard Hendersonsafe_syscall_start:
1094542adefSRichard Henderson        /* If signal_pending is non-zero, don't do the call */
1104542adefSRichard Henderson        lw      t1, 0(s0)
1114542adefSRichard Henderson        bnez    t1, 2f
1124542adefSRichard Henderson        syscall
1134542adefSRichard Hendersonsafe_syscall_end:
1144542adefSRichard Henderson
1154542adefSRichard Henderson        /* code path for having successfully executed the syscall */
1164542adefSRichard Henderson        REG_L   s0, OFS_S0(sp)
1174542adefSRichard Henderson        PTR_ADDIU sp, sp, FRAME
1184542adefSRichard Henderson        .cfi_remember_state
1194542adefSRichard Henderson        .cfi_adjust_cfa_offset -FRAME
1204542adefSRichard Henderson        .cfi_restore s0
1214542adefSRichard Henderson        bnez    a3, 1f
1224542adefSRichard Henderson        jr      ra
1234542adefSRichard Henderson        .cfi_restore_state
1244542adefSRichard Henderson
1254542adefSRichard Henderson        /* code path when we didn't execute the syscall */
1264542adefSRichard Henderson2:      REG_L   s0, OFS_S0(sp)
1274542adefSRichard Henderson        PTR_ADDIU sp, sp, FRAME
1284542adefSRichard Henderson        .cfi_adjust_cfa_offset -FRAME
1294542adefSRichard Henderson        .cfi_restore s0
130af254a27SRichard Henderson        li      v0, QEMU_ERESTARTSYS
1314542adefSRichard Henderson
1324542adefSRichard Henderson        /* code path setting errno */
1334542adefSRichard Henderson        /*
1344542adefSRichard Henderson         * We didn't setup GP on entry, optimistic of the syscall success.
1354542adefSRichard Henderson         * We must do so now to load the address of the helper, as required
1364542adefSRichard Henderson         * by the ABI, into t9.
1374542adefSRichard Henderson         *
1384542adefSRichard Henderson         * Note that SETUP_GPX and SETUP_GPX64 are themselves conditional,
1394542adefSRichard Henderson         * so we can simply let the one that's not empty succeed.
1404542adefSRichard Henderson         */
1414542adefSRichard Henderson1:      USE_ALT_CP(t0)
1424542adefSRichard Henderson        SETUP_GPX(t1)
1434542adefSRichard Henderson        SETUP_GPX64(t0, t1)
144*d7478d42SRichard Henderson        move    a0, v0
1454542adefSRichard Henderson        PTR_LA  t9, safe_syscall_set_errno_tail
1464542adefSRichard Henderson        jr      t9
1474542adefSRichard Henderson
1484542adefSRichard Henderson        .cfi_endproc
1494542adefSRichard HendersonEND(safe_syscall_base)
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