1 /* 2 * Emulation of Linux signals 3 * 4 * Copyright (c) 2003 Fabrice Bellard 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or 9 * (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, see <http://www.gnu.org/licenses/>. 18 */ 19 #include "qemu/osdep.h" 20 #include "qemu.h" 21 #include "signal-common.h" 22 #include "linux-user/trace.h" 23 24 /* Signal handler invocation must be transparent for the code being 25 interrupted. Complete CPU (hart) state is saved on entry and restored 26 before returning from the handler. Process sigmask is also saved to block 27 signals while the handler is running. The handler gets its own stack, 28 which also doubles as storage for the CPU state and sigmask. 29 30 The code below is qemu re-implementation of arch/riscv/kernel/signal.c */ 31 32 struct target_sigcontext { 33 abi_long pc; 34 abi_long gpr[31]; /* x0 is not present, so all offsets must be -1 */ 35 uint64_t fpr[32]; 36 uint32_t fcsr; 37 }; /* cf. riscv-linux:arch/riscv/include/uapi/asm/ptrace.h */ 38 39 struct target_ucontext { 40 unsigned long uc_flags; 41 struct target_ucontext *uc_link; 42 target_stack_t uc_stack; 43 target_sigset_t uc_sigmask; 44 uint8_t __unused[1024 / 8 - sizeof(target_sigset_t)]; 45 struct target_sigcontext uc_mcontext QEMU_ALIGNED(16); 46 }; 47 48 struct target_rt_sigframe { 49 uint32_t tramp[2]; /* not in kernel, which uses VDSO instead */ 50 struct target_siginfo info; 51 struct target_ucontext uc; 52 }; 53 54 static abi_ulong get_sigframe(struct target_sigaction *ka, 55 CPURISCVState *regs, size_t framesize) 56 { 57 abi_ulong sp = get_sp_from_cpustate(regs); 58 59 /* If we are on the alternate signal stack and would overflow it, don't. 60 Return an always-bogus address instead so we will die with SIGSEGV. */ 61 if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize))) { 62 return -1L; 63 } 64 65 /* This is the X/Open sanctioned signal stack switching. */ 66 sp = target_sigsp(sp, ka) - framesize; 67 68 /* XXX: kernel aligns with 0xf ? */ 69 sp &= ~3UL; /* align sp on 4-byte boundary */ 70 71 return sp; 72 } 73 74 static void setup_sigcontext(struct target_sigcontext *sc, CPURISCVState *env) 75 { 76 int i; 77 78 __put_user(env->pc, &sc->pc); 79 80 for (i = 1; i < 32; i++) { 81 __put_user(env->gpr[i], &sc->gpr[i - 1]); 82 } 83 for (i = 0; i < 32; i++) { 84 __put_user(env->fpr[i], &sc->fpr[i]); 85 } 86 87 uint32_t fcsr = riscv_csr_read(env, CSR_FCSR); 88 __put_user(fcsr, &sc->fcsr); 89 } 90 91 static void setup_ucontext(struct target_ucontext *uc, 92 CPURISCVState *env, target_sigset_t *set) 93 { 94 __put_user(0, &(uc->uc_flags)); 95 __put_user(0, &(uc->uc_link)); 96 97 target_save_altstack(&uc->uc_stack, env); 98 99 int i; 100 for (i = 0; i < TARGET_NSIG_WORDS; i++) { 101 __put_user(set->sig[i], &(uc->uc_sigmask.sig[i])); 102 } 103 104 setup_sigcontext(&uc->uc_mcontext, env); 105 } 106 107 static inline void install_sigtramp(uint32_t *tramp) 108 { 109 __put_user(0x08b00893, tramp + 0); /* li a7, 139 = __NR_rt_sigreturn */ 110 __put_user(0x00000073, tramp + 1); /* ecall */ 111 } 112 113 void setup_rt_frame(int sig, struct target_sigaction *ka, 114 target_siginfo_t *info, 115 target_sigset_t *set, CPURISCVState *env) 116 { 117 abi_ulong frame_addr; 118 struct target_rt_sigframe *frame; 119 120 frame_addr = get_sigframe(ka, env, sizeof(*frame)); 121 trace_user_setup_rt_frame(env, frame_addr); 122 123 if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) { 124 goto badframe; 125 } 126 127 setup_ucontext(&frame->uc, env, set); 128 tswap_siginfo(&frame->info, info); 129 install_sigtramp(frame->tramp); 130 131 env->pc = ka->_sa_handler; 132 env->gpr[xSP] = frame_addr; 133 env->gpr[xA0] = sig; 134 env->gpr[xA1] = frame_addr + offsetof(struct target_rt_sigframe, info); 135 env->gpr[xA2] = frame_addr + offsetof(struct target_rt_sigframe, uc); 136 env->gpr[xRA] = frame_addr + offsetof(struct target_rt_sigframe, tramp); 137 138 return; 139 140 badframe: 141 unlock_user_struct(frame, frame_addr, 1); 142 if (sig == TARGET_SIGSEGV) { 143 ka->_sa_handler = TARGET_SIG_DFL; 144 } 145 force_sig(TARGET_SIGSEGV); 146 } 147 148 static void restore_sigcontext(CPURISCVState *env, struct target_sigcontext *sc) 149 { 150 int i; 151 152 __get_user(env->pc, &sc->pc); 153 154 for (i = 1; i < 32; ++i) { 155 __get_user(env->gpr[i], &sc->gpr[i - 1]); 156 } 157 for (i = 0; i < 32; ++i) { 158 __get_user(env->fpr[i], &sc->fpr[i]); 159 } 160 161 uint32_t fcsr; 162 __get_user(fcsr, &sc->fcsr); 163 riscv_csr_write(env, CSR_FCSR, fcsr); 164 } 165 166 static void restore_ucontext(CPURISCVState *env, struct target_ucontext *uc) 167 { 168 sigset_t blocked; 169 target_sigset_t target_set; 170 int i; 171 172 target_sigemptyset(&target_set); 173 for (i = 0; i < TARGET_NSIG_WORDS; i++) { 174 __get_user(target_set.sig[i], &(uc->uc_sigmask.sig[i])); 175 } 176 177 target_to_host_sigset_internal(&blocked, &target_set); 178 set_sigmask(&blocked); 179 180 restore_sigcontext(env, &uc->uc_mcontext); 181 } 182 183 long do_rt_sigreturn(CPURISCVState *env) 184 { 185 struct target_rt_sigframe *frame; 186 abi_ulong frame_addr; 187 188 frame_addr = env->gpr[xSP]; 189 trace_user_do_sigreturn(env, frame_addr); 190 if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) { 191 goto badframe; 192 } 193 194 restore_ucontext(env, &frame->uc); 195 target_restore_altstack(&frame->uc.uc_stack, env); 196 197 unlock_user_struct(frame, frame_addr, 0); 198 return -TARGET_QEMU_ESIGRETURN; 199 200 badframe: 201 unlock_user_struct(frame, frame_addr, 0); 202 force_sig(TARGET_SIGSEGV); 203 return 0; 204 } 205