linux-user/riscv/signal.c

   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 "user-internals.h"
  22 #include "signal-common.h"
  23 #include "linux-user/trace.h"
  24
  25 /* Signal handler invocation must be transparent for the code being
  26    interrupted. Complete CPU (hart) state is saved on entry and restored
  27    before returning from the handler. Process sigmask is also saved to block
  28    signals while the handler is running. The handler gets its own stack,
  29    which also doubles as storage for the CPU state and sigmask.
  30
  31    The code below is qemu re-implementation of arch/riscv/kernel/signal.c */
  32
  33 struct target_sigcontext {
  34     abi_long pc;
  35     abi_long gpr[31]; /* x0 is not present, so all offsets must be -1 */
  36     uint64_t fpr[32];
  37     uint32_t fcsr;
  38 }; /* cf. riscv-linux:arch/riscv/include/uapi/asm/ptrace.h */
  39
  40 struct target_ucontext {
  41     unsigned long uc_flags;
  42     struct target_ucontext *uc_link;
  43     target_stack_t uc_stack;
  44     target_sigset_t uc_sigmask;
  45     uint8_t   __unused[1024 / 8 - sizeof(target_sigset_t)];
  46     struct target_sigcontext uc_mcontext QEMU_ALIGNED(16);
  47 };
  48
  49 struct target_rt_sigframe {
  50     uint32_t tramp[2]; /* not in kernel, which uses VDSO instead */
  51     struct target_siginfo info;
  52     struct target_ucontext uc;
  53 };
  54
  55 static abi_ulong get_sigframe(struct target_sigaction *ka,
  56                               CPURISCVState *regs, size_t framesize)
  57 {
  58     abi_ulong sp = get_sp_from_cpustate(regs);
  59
  60     /* If we are on the alternate signal stack and would overflow it, don't.
  61        Return an always-bogus address instead so we will die with SIGSEGV. */
  62     if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize))) {
  63         return -1L;
  64     }
  65
  66     /* This is the X/Open sanctioned signal stack switching.  */
  67     sp = target_sigsp(sp, ka) - framesize;
  68
  69     /* XXX: kernel aligns with 0xf ? */
  70     sp &= ~3UL; /* align sp on 4-byte boundary */
  71
  72     return sp;
  73 }
  74
  75 static void setup_sigcontext(struct target_sigcontext *sc, CPURISCVState *env)
  76 {
  77     int i;
  78
  79     __put_user(env->pc, &sc->pc);
  80
  81     for (i = 1; i < 32; i++) {
  82         __put_user(env->gpr[i], &sc->gpr[i - 1]);
  83     }
  84     for (i = 0; i < 32; i++) {
  85         __put_user(env->fpr[i], &sc->fpr[i]);
  86     }
  87
  88     uint32_t fcsr = riscv_csr_read(env, CSR_FCSR);
  89     __put_user(fcsr, &sc->fcsr);
  90 }
  91
  92 static void setup_ucontext(struct target_ucontext *uc,
  93                            CPURISCVState *env, target_sigset_t *set)
  94 {
  95     __put_user(0,    &(uc->uc_flags));
  96     __put_user(0,    &(uc->uc_link));
  97
  98     target_save_altstack(&uc->uc_stack, env);
  99
 100     int i;
 101     for (i = 0; i < TARGET_NSIG_WORDS; i++) {
 102         __put_user(set->sig[i], &(uc->uc_sigmask.sig[i]));
 103     }
 104
 105     setup_sigcontext(&uc->uc_mcontext, env);
 106 }
 107
 108 static inline void install_sigtramp(uint32_t *tramp)
 109 {
 110     __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
 111     __put_user(0x00000073, tramp + 1);  /* ecall */
 112 }
 113
 114 void setup_rt_frame(int sig, struct target_sigaction *ka,
 115                     target_siginfo_t *info,
 116                     target_sigset_t *set, CPURISCVState *env)
 117 {
 118     abi_ulong frame_addr;
 119     struct target_rt_sigframe *frame;
 120
 121     frame_addr = get_sigframe(ka, env, sizeof(*frame));
 122     trace_user_setup_rt_frame(env, frame_addr);
 123
 124     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
 125         goto badframe;
 126     }
 127
 128     setup_ucontext(&frame->uc, env, set);
 129     tswap_siginfo(&frame->info, info);
 130     install_sigtramp(frame->tramp);
 131
 132     env->pc = ka->_sa_handler;
 133     env->gpr[xSP] = frame_addr;
 134     env->gpr[xA0] = sig;
 135     env->gpr[xA1] = frame_addr + offsetof(struct target_rt_sigframe, info);
 136     env->gpr[xA2] = frame_addr + offsetof(struct target_rt_sigframe, uc);
 137     env->gpr[xRA] = frame_addr + offsetof(struct target_rt_sigframe, tramp);
 138
 139     return;
 140
 141 badframe:
 142     unlock_user_struct(frame, frame_addr, 1);
 143     if (sig == TARGET_SIGSEGV) {
 144         ka->_sa_handler = TARGET_SIG_DFL;
 145     }
 146     force_sig(TARGET_SIGSEGV);
 147 }
 148
 149 static void restore_sigcontext(CPURISCVState *env, struct target_sigcontext *sc)
 150 {
 151     int i;
 152
 153     __get_user(env->pc, &sc->pc);
 154
 155     for (i = 1; i < 32; ++i) {
 156         __get_user(env->gpr[i], &sc->gpr[i - 1]);
 157     }
 158     for (i = 0; i < 32; ++i) {
 159         __get_user(env->fpr[i], &sc->fpr[i]);
 160     }
 161
 162     uint32_t fcsr;
 163     __get_user(fcsr, &sc->fcsr);
 164     riscv_csr_write(env, CSR_FCSR, fcsr);
 165 }
 166
 167 static void restore_ucontext(CPURISCVState *env, struct target_ucontext *uc)
 168 {
 169     sigset_t blocked;
 170     target_sigset_t target_set;
 171     int i;
 172
 173     target_sigemptyset(&target_set);
 174     for (i = 0; i < TARGET_NSIG_WORDS; i++) {
 175         __get_user(target_set.sig[i], &(uc->uc_sigmask.sig[i]));
 176     }
 177
 178     target_to_host_sigset_internal(&blocked, &target_set);
 179     set_sigmask(&blocked);
 180
 181     restore_sigcontext(env, &uc->uc_mcontext);
 182 }
 183
 184 long do_rt_sigreturn(CPURISCVState *env)
 185 {
 186     struct target_rt_sigframe *frame;
 187     abi_ulong frame_addr;
 188
 189     frame_addr = env->gpr[xSP];
 190     trace_user_do_sigreturn(env, frame_addr);
 191     if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
 192         goto badframe;
 193     }
 194
 195     restore_ucontext(env, &frame->uc);
 196     target_restore_altstack(&frame->uc.uc_stack, env);
 197
 198     unlock_user_struct(frame, frame_addr, 0);
 199     return -TARGET_QEMU_ESIGRETURN;
 200
 201 badframe:
 202     unlock_user_struct(frame, frame_addr, 0);
 203     force_sig(TARGET_SIGSEGV);
 204     return 0;
 205 }