1*4542adefSRichard Henderson/* 2*4542adefSRichard Henderson * safe-syscall.inc.S : host-specific assembly fragment 3*4542adefSRichard Henderson * to handle signals occurring at the same time as system calls. 4*4542adefSRichard Henderson * This is intended to be included by linux-user/safe-syscall.S 5*4542adefSRichard Henderson * 6*4542adefSRichard Henderson * Written by Richard Henderson <richard.henderson@linaro.org> 7*4542adefSRichard Henderson * Copyright (C) 2021 Linaro, Inc. 8*4542adefSRichard Henderson * 9*4542adefSRichard Henderson * This work is licensed under the terms of the GNU GPL, version 2 or later. 10*4542adefSRichard Henderson * See the COPYING file in the top-level directory. 11*4542adefSRichard Henderson */ 12*4542adefSRichard Henderson 13*4542adefSRichard Henderson#include "sys/regdef.h" 14*4542adefSRichard Henderson#include "sys/asm.h" 15*4542adefSRichard Henderson 16*4542adefSRichard Henderson .text 17*4542adefSRichard Henderson .set nomips16 18*4542adefSRichard Henderson .set reorder 19*4542adefSRichard Henderson 20*4542adefSRichard Henderson .global safe_syscall_start 21*4542adefSRichard Henderson .global safe_syscall_end 22*4542adefSRichard Henderson .type safe_syscall_start, @function 23*4542adefSRichard Henderson .type safe_syscall_end, @function 24*4542adefSRichard Henderson 25*4542adefSRichard Henderson /* 26*4542adefSRichard Henderson * This is the entry point for making a system call. The calling 27*4542adefSRichard Henderson * convention here is that of a C varargs function with the 28*4542adefSRichard Henderson * first argument an 'int *' to the signal_pending flag, the 29*4542adefSRichard Henderson * second one the system call number (as a 'long'), and all further 30*4542adefSRichard Henderson * arguments being syscall arguments (also 'long'). 31*4542adefSRichard Henderson */ 32*4542adefSRichard Henderson 33*4542adefSRichard Henderson#if _MIPS_SIM == _ABIO32 34*4542adefSRichard Henderson/* 8 * 4 = 32 for outgoing parameters; 1 * 4 for s0 save; 1 * 4 for align. */ 35*4542adefSRichard Henderson#define FRAME 40 36*4542adefSRichard Henderson#define OFS_S0 32 37*4542adefSRichard Henderson#else 38*4542adefSRichard Henderson/* 1 * 8 for s0 save; 1 * 8 for align. */ 39*4542adefSRichard Henderson#define FRAME 16 40*4542adefSRichard Henderson#define OFS_S0 0 41*4542adefSRichard Henderson#endif 42*4542adefSRichard Henderson 43*4542adefSRichard Henderson 44*4542adefSRichard HendersonNESTED(safe_syscall_base, FRAME, ra) 45*4542adefSRichard Henderson .cfi_startproc 46*4542adefSRichard Henderson PTR_ADDIU sp, sp, -FRAME 47*4542adefSRichard Henderson .cfi_adjust_cfa_offset FRAME 48*4542adefSRichard Henderson REG_S s0, OFS_S0(sp) 49*4542adefSRichard Henderson .cfi_rel_offset s0, OFS_S0 50*4542adefSRichard Henderson#if _MIPS_SIM == _ABIO32 51*4542adefSRichard Henderson /* 52*4542adefSRichard Henderson * The syscall calling convention is nearly the same as C: 53*4542adefSRichard Henderson * we enter with a0 == &signal_pending 54*4542adefSRichard Henderson * a1 == syscall number 55*4542adefSRichard Henderson * a2, a3, stack == syscall arguments 56*4542adefSRichard Henderson * and return the result in a0 57*4542adefSRichard Henderson * and the syscall instruction needs 58*4542adefSRichard Henderson * v0 == syscall number 59*4542adefSRichard Henderson * a0 ... a3, stack == syscall arguments 60*4542adefSRichard Henderson * and returns the result in v0 61*4542adefSRichard Henderson * Shuffle everything around appropriately. 62*4542adefSRichard Henderson */ 63*4542adefSRichard Henderson move s0, a0 /* signal_pending pointer */ 64*4542adefSRichard Henderson move v0, a1 /* syscall number */ 65*4542adefSRichard Henderson move a0, a2 /* syscall arguments */ 66*4542adefSRichard Henderson move a1, a3 67*4542adefSRichard Henderson lw a2, FRAME+16(sp) 68*4542adefSRichard Henderson lw a3, FRAME+20(sp) 69*4542adefSRichard Henderson lw t4, FRAME+24(sp) 70*4542adefSRichard Henderson lw t5, FRAME+28(sp) 71*4542adefSRichard Henderson lw t6, FRAME+32(sp) 72*4542adefSRichard Henderson lw t7, FRAME+40(sp) 73*4542adefSRichard Henderson sw t4, 16(sp) 74*4542adefSRichard Henderson sw t5, 20(sp) 75*4542adefSRichard Henderson sw t6, 24(sp) 76*4542adefSRichard Henderson sw t7, 28(sp) 77*4542adefSRichard Henderson#else 78*4542adefSRichard Henderson /* 79*4542adefSRichard Henderson * The syscall calling convention is nearly the same as C: 80*4542adefSRichard Henderson * we enter with a0 == &signal_pending 81*4542adefSRichard Henderson * a1 == syscall number 82*4542adefSRichard Henderson * a2 ... a7 == syscall arguments 83*4542adefSRichard Henderson * and return the result in a0 84*4542adefSRichard Henderson * and the syscall instruction needs 85*4542adefSRichard Henderson * v0 == syscall number 86*4542adefSRichard Henderson * a0 ... a5 == syscall arguments 87*4542adefSRichard Henderson * and returns the result in v0 88*4542adefSRichard Henderson * Shuffle everything around appropriately. 89*4542adefSRichard Henderson */ 90*4542adefSRichard Henderson move s0, a0 /* signal_pending pointer */ 91*4542adefSRichard Henderson move v0, a1 /* syscall number */ 92*4542adefSRichard Henderson move a0, a2 /* syscall arguments */ 93*4542adefSRichard Henderson move a1, a3 94*4542adefSRichard Henderson move a2, a4 95*4542adefSRichard Henderson move a3, a5 96*4542adefSRichard Henderson move a4, a6 97*4542adefSRichard Henderson move a5, a7 98*4542adefSRichard Henderson#endif 99*4542adefSRichard Henderson 100*4542adefSRichard Henderson /* 101*4542adefSRichard Henderson * This next sequence of code works in conjunction with the 102*4542adefSRichard Henderson * rewind_if_safe_syscall_function(). If a signal is taken 103*4542adefSRichard Henderson * and the interrupted PC is anywhere between 'safe_syscall_start' 104*4542adefSRichard Henderson * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. 105*4542adefSRichard Henderson * The code sequence must therefore be able to cope with this, and 106*4542adefSRichard Henderson * the syscall instruction must be the final one in the sequence. 107*4542adefSRichard Henderson */ 108*4542adefSRichard Hendersonsafe_syscall_start: 109*4542adefSRichard Henderson /* If signal_pending is non-zero, don't do the call */ 110*4542adefSRichard Henderson lw t1, 0(s0) 111*4542adefSRichard Henderson bnez t1, 2f 112*4542adefSRichard Henderson syscall 113*4542adefSRichard Hendersonsafe_syscall_end: 114*4542adefSRichard Henderson 115*4542adefSRichard Henderson /* code path for having successfully executed the syscall */ 116*4542adefSRichard Henderson REG_L s0, OFS_S0(sp) 117*4542adefSRichard Henderson PTR_ADDIU sp, sp, FRAME 118*4542adefSRichard Henderson .cfi_remember_state 119*4542adefSRichard Henderson .cfi_adjust_cfa_offset -FRAME 120*4542adefSRichard Henderson .cfi_restore s0 121*4542adefSRichard Henderson bnez a3, 1f 122*4542adefSRichard Henderson jr ra 123*4542adefSRichard Henderson .cfi_restore_state 124*4542adefSRichard Henderson 125*4542adefSRichard Henderson /* code path when we didn't execute the syscall */ 126*4542adefSRichard Henderson2: REG_L s0, OFS_S0(sp) 127*4542adefSRichard Henderson PTR_ADDIU sp, sp, FRAME 128*4542adefSRichard Henderson .cfi_adjust_cfa_offset -FRAME 129*4542adefSRichard Henderson .cfi_restore s0 130*4542adefSRichard Henderson li v0, TARGET_ERESTARTSYS 131*4542adefSRichard Henderson 132*4542adefSRichard Henderson /* code path setting errno */ 133*4542adefSRichard Henderson /* 134*4542adefSRichard Henderson * We didn't setup GP on entry, optimistic of the syscall success. 135*4542adefSRichard Henderson * We must do so now to load the address of the helper, as required 136*4542adefSRichard Henderson * by the ABI, into t9. 137*4542adefSRichard Henderson * 138*4542adefSRichard Henderson * Note that SETUP_GPX and SETUP_GPX64 are themselves conditional, 139*4542adefSRichard Henderson * so we can simply let the one that's not empty succeed. 140*4542adefSRichard Henderson */ 141*4542adefSRichard Henderson1: USE_ALT_CP(t0) 142*4542adefSRichard Henderson SETUP_GPX(t1) 143*4542adefSRichard Henderson SETUP_GPX64(t0, t1) 144*4542adefSRichard Henderson PTR_LA t9, safe_syscall_set_errno_tail 145*4542adefSRichard Henderson jr t9 146*4542adefSRichard Henderson 147*4542adefSRichard Henderson .cfi_endproc 148*4542adefSRichard HendersonEND(safe_syscall_base) 149