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bsd-user/signal.c: Implement host_signal_handler

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Implement host_signal_handler to handle signals generated by the host
and to do safe system calls.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Kyle Evans <kevans@freebsd.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Warner Losh 2022-01-08 17:57:34 -07:00
parent aae57ac37a
commit e625c7ef5c
1 changed files with 105 additions and 0 deletions
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105
bsd-user/signal.c
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@ -223,6 +223,111 @@ void force_sig_fault(int sig, int code, abi_ulong addr)
static void host_signal_handler(int host_sig, siginfo_t *info, void *puc)
{
CPUArchState *env = thread_cpu->env_ptr;
CPUState *cpu = env_cpu(env);
TaskState *ts = cpu->opaque;
target_siginfo_t tinfo;
ucontext_t *uc = puc;
struct emulated_sigtable *k;
int guest_sig;
uintptr_t pc = 0;
bool sync_sig = false;
/*
* Non-spoofed SIGSEGV and SIGBUS are synchronous, and need special
* handling wrt signal blocking and unwinding.
*/
if ((host_sig == SIGSEGV || host_sig == SIGBUS) && info->si_code > 0) {
MMUAccessType access_type;
uintptr_t host_addr;
abi_ptr guest_addr;
bool is_write;
host_addr = (uintptr_t)info->si_addr;
/*
* Convert forcefully to guest address space: addresses outside
* reserved_va are still valid to report via SEGV_MAPERR.
*/
guest_addr = h2g_nocheck(host_addr);
pc = host_signal_pc(uc);
is_write = host_signal_write(info, uc);
access_type = adjust_signal_pc(&pc, is_write);
if (host_sig == SIGSEGV) {
bool maperr = true;
if (info->si_code == SEGV_ACCERR && h2g_valid(host_addr)) {
/* If this was a write to a TB protected page, restart. */
if (is_write &&
handle_sigsegv_accerr_write(cpu, &uc->uc_sigmask,
pc, guest_addr)) {
return;
}
/*
* With reserved_va, the whole address space is PROT_NONE,
* which means that we may get ACCERR when we want MAPERR.
*/
if (page_get_flags(guest_addr) & PAGE_VALID) {
maperr = false;
} else {
info->si_code = SEGV_MAPERR;
}
}
sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);
cpu_loop_exit_sigsegv(cpu, guest_addr, access_type, maperr, pc);
} else {
sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);
if (info->si_code == BUS_ADRALN) {
cpu_loop_exit_sigbus(cpu, guest_addr, access_type, pc);
}
}
sync_sig = true;
}
/* Get the target signal number. */
guest_sig = host_to_target_signal(host_sig);
if (guest_sig < 1 || guest_sig > TARGET_NSIG) {
return;
}
trace_user_host_signal(cpu, host_sig, guest_sig);
host_to_target_siginfo_noswap(&tinfo, info);
k = &ts->sigtab[guest_sig - 1];
k->info = tinfo;
k->pending = guest_sig;
ts->signal_pending = 1;
/*
* For synchronous signals, unwind the cpu state to the faulting
* insn and then exit back to the main loop so that the signal
* is delivered immediately.
*/
if (sync_sig) {
cpu->exception_index = EXCP_INTERRUPT;
cpu_loop_exit_restore(cpu, pc);
}
rewind_if_in_safe_syscall(puc);
/*
* Block host signals until target signal handler entered. We
* can't block SIGSEGV or SIGBUS while we're executing guest
* code in case the guest code provokes one in the window between
* now and it getting out to the main loop. Signals will be
* unblocked again in process_pending_signals().
*/
sigfillset(&uc->uc_sigmask);
sigdelset(&uc->uc_sigmask, SIGSEGV);
sigdelset(&uc->uc_sigmask, SIGBUS);
/* Interrupt the virtual CPU as soon as possible. */
cpu_exit(thread_cpu);
}
void signal_init(void)