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 "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     struct target_sigcontext uc_mcontext;
  44     target_sigset_t uc_sigmask;
  45 };
  46
  47 struct target_rt_sigframe {
  48     uint32_t tramp[2]; /* not in kernel, which uses VDSO instead */
  49     struct target_siginfo info;
  50     struct target_ucontext uc;
  51 };
  52
  53 static abi_ulong get_sigframe(struct target_sigaction *ka,
  54                               CPURISCVState *regs, size_t framesize)
  55 {
  56     abi_ulong sp = get_sp_from_cpustate(regs);
  57
  58     /* If we are on the alternate signal stack and would overflow it, don't.
  59        Return an always-bogus address instead so we will die with SIGSEGV. */
  60     if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize))) {
  61         return -1L;
  62     }
  63
  64     /* This is the X/Open sanctioned signal stack switching.  */
  65     sp = target_sigsp(sp, ka) - framesize;
  66
  67     /* XXX: kernel aligns with 0xf ? */
  68     sp &= ~3UL; /* align sp on 4-byte boundary */
  69
  70     return sp;
  71 }
  72
  73 static void setup_sigcontext(struct target_sigcontext *sc, CPURISCVState *env)
  74 {
  75     int i;
  76
  77     __put_user(env->pc, &sc->pc);
  78
  79     for (i = 1; i < 32; i++) {
  80         __put_user(env->gpr[i], &sc->gpr[i - 1]);
  81     }
  82     for (i = 0; i < 32; i++) {
  83         __put_user(env->fpr[i], &sc->fpr[i]);
  84     }
  85
  86     uint32_t fcsr = riscv_csr_read(env, CSR_FCSR);
  87     __put_user(fcsr, &sc->fcsr);
  88 }
  89
  90 static void setup_ucontext(struct target_ucontext *uc,
  91                            CPURISCVState *env, target_sigset_t *set)
  92 {
  93     __put_user(0,    &(uc->uc_flags));
  94     __put_user(0,    &(uc->uc_link));
  95
  96     target_save_altstack(&uc->uc_stack, env);
  97
  98     int i;
  99     for (i = 0; i < TARGET_NSIG_WORDS; i++) {
 100         __put_user(set->sig[i], &(uc->uc_sigmask.sig[i]));
 101     }
 102
 103     setup_sigcontext(&uc->uc_mcontext, env);
 104 }
 105
 106 static inline void install_sigtramp(uint32_t *tramp)
 107 {
 108     __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
 109     __put_user(0x00000073, tramp + 1);  /* ecall */
 110 }
 111
 112 void setup_rt_frame(int sig, struct target_sigaction *ka,
 113                     target_siginfo_t *info,
 114                     target_sigset_t *set, CPURISCVState *env)
 115 {
 116     abi_ulong frame_addr;
 117     struct target_rt_sigframe *frame;
 118
 119     frame_addr = get_sigframe(ka, env, sizeof(*frame));
 120     trace_user_setup_rt_frame(env, frame_addr);
 121
 122     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
 123         goto badframe;
 124     }
 125
 126     setup_ucontext(&frame->uc, env, set);
 127     tswap_siginfo(&frame->info, info);
 128     install_sigtramp(frame->tramp);
 129
 130     env->pc = ka->_sa_handler;
 131     env->gpr[xSP] = frame_addr;
 132     env->gpr[xA0] = sig;
 133     env->gpr[xA1] = frame_addr + offsetof(struct target_rt_sigframe, info);
 134     env->gpr[xA2] = frame_addr + offsetof(struct target_rt_sigframe, uc);
 135     env->gpr[xRA] = frame_addr + offsetof(struct target_rt_sigframe, tramp);
 136
 137     return;
 138
 139 badframe:
 140     unlock_user_struct(frame, frame_addr, 1);
 141     if (sig == TARGET_SIGSEGV) {
 142         ka->_sa_handler = TARGET_SIG_DFL;
 143     }
 144     force_sig(TARGET_SIGSEGV);
 145 }
 146
 147 static void restore_sigcontext(CPURISCVState *env, struct target_sigcontext *sc)
 148 {
 149     int i;
 150
 151     __get_user(env->pc, &sc->pc);
 152
 153     for (i = 1; i < 32; ++i) {
 154         __get_user(env->gpr[i], &sc->gpr[i - 1]);
 155     }
 156     for (i = 0; i < 32; ++i) {
 157         __get_user(env->fpr[i], &sc->fpr[i]);
 158     }
 159
 160     uint32_t fcsr;
 161     __get_user(fcsr, &sc->fcsr);
 162     riscv_csr_write(env, CSR_FCSR, fcsr);
 163 }
 164
 165 static void restore_ucontext(CPURISCVState *env, struct target_ucontext *uc)
 166 {
 167     sigset_t blocked;
 168     target_sigset_t target_set;
 169     int i;
 170
 171     target_sigemptyset(&target_set);
 172     for (i = 0; i < TARGET_NSIG_WORDS; i++) {
 173         __get_user(target_set.sig[i], &(uc->uc_sigmask.sig[i]));
 174     }
 175
 176     target_to_host_sigset_internal(&blocked, &target_set);
 177     set_sigmask(&blocked);
 178
 179     restore_sigcontext(env, &uc->uc_mcontext);
 180 }
 181
 182 long do_rt_sigreturn(CPURISCVState *env)
 183 {
 184     struct target_rt_sigframe *frame;
 185     abi_ulong frame_addr;
 186
 187     frame_addr = env->gpr[xSP];
 188     trace_user_do_sigreturn(env, frame_addr);
 189     if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
 190         goto badframe;
 191     }
 192
 193     restore_ucontext(env, &frame->uc);
 194
 195     if (do_sigaltstack(frame_addr + offsetof(struct target_rt_sigframe,
 196             uc.uc_stack), 0, get_sp_from_cpustate(env)) == -EFAULT) {
 197         goto badframe;
 198     }
 199
 200     unlock_user_struct(frame, frame_addr, 0);
 201     return -TARGET_QEMU_ESIGRETURN;
 202
 203 badframe:
 204     unlock_user_struct(frame, frame_addr, 0);
 205     force_sig(TARGET_SIGSEGV);
 206     return 0;
 207 }