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- /* Copyright (C) 2014 Stony Brook University
- This file is part of Graphene Library OS.
- Graphene Library OS is free software: you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public License
- as published by the Free Software Foundation, either version 3 of the
- License, or (at your option) any later version.
- Graphene Library OS is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
- /*
- * db_signal.c
- *
- * This file contains APIs to set up handlers of exceptions issued by the
- * host, and the methods to pass the exceptions to the upcalls.
- */
- #include "pal_defs.h"
- #include "pal_linux_defs.h"
- #include "pal.h"
- #include "pal_internal.h"
- #include "pal_linux.h"
- #include "pal_debug.h"
- #include "pal_error.h"
- #include "pal_security.h"
- #include "api.h"
- #include <atomic.h>
- #include <sigset.h>
- #include <linux/signal.h>
- #include <ucontext.h>
- #include <asm/errno.h>
- #if !defined(__i386__)
- /* In x86_64 kernels, sigaction is required to have a user-defined
- * restorer. Also, they not yet support SA_INFO. The reference:
- * http://lxr.linux.no/linux+v2.6.35/arch/x86/kernel/signal.c#L448
- *
- * / * x86-64 should always use SA_RESTORER. * /
- * if (ka->sa.sa_flags & SA_RESTORER) {
- * put_user_ex(ka->sa.sa_restorer, &frame->pretcode);
- * } else {
- * / * could use a vstub here * /
- * err |= -EFAULT;
- * }
- */
- #ifndef SA_RESTORER
- #define SA_RESTORER 0x04000000
- #endif
- #define DEFINE_RESTORE_RT(syscall) DEFINE_RESTORE_RT2(syscall)
- #define DEFINE_RESTORE_RT2(syscall) \
- __asm__ ( \
- " nop\n" \
- ".align 16\n" \
- ".LSTART_restore_rt:\n" \
- " .type __restore_rt,@function\n" \
- "__restore_rt:\n" \
- " movq $" #syscall ", %rax\n" \
- " syscall\n");
- DEFINE_RESTORE_RT(__NR_rt_sigreturn)
- /* Workaround for an old GAS (2.27) bug that incorrectly
- * omits relocations when referencing this symbol */
- __attribute__((visibility("hidden"))) void __restore_rt(void);
- #endif
- static const int async_signals[] =
- {
- SIGTERM,
- SIGINT,
- SIGCONT,
- };
- static const int nasync_signals = ARRAY_SIZE(async_signals);
- int set_sighandler (int * sigs, int nsig, void * handler)
- {
- struct sigaction action;
- if (handler) {
- action.sa_handler = (void (*)(int)) handler;
- action.sa_flags = SA_SIGINFO;
- #if !defined(__i386__)
- action.sa_flags |= SA_RESTORER;
- action.sa_restorer = __restore_rt;
- #endif
- } else {
- action.sa_flags = 0x0u;
- action.sa_handler = SIG_IGN;
- }
- #ifdef DEBUG
- if (!linux_state.in_gdb)
- #endif
- action.sa_flags |= SA_NOCLDWAIT;
- __sigemptyset((__sigset_t *) &action.sa_mask);
- __sigaddset((__sigset_t *) &action.sa_mask, SIGCONT);
- for (int i = 0 ; i < nsig ; i++) {
- #if defined(__i386__)
- int ret = INLINE_SYSCALL(sigaction, 3, sigs[i], &action, NULL)
- #else
- int ret = INLINE_SYSCALL(rt_sigaction, 4, sigs[i], &action, NULL,
- sizeof(sigset_t));
- #endif
- if (IS_ERR(ret))
- return -PAL_ERROR_DENIED;
- }
- int ret = 0;
- __sigset_t mask;
- __sigemptyset(&mask);
- for (int i = 0 ; i < nsig ; i++)
- __sigaddset(&mask, sigs[i]);
- #if defined(__i386__)
- ret = INLINE_SYSCALL(sigprocmask, 3, SIG_UNBLOCK, &mask, NULL)
- #else
- ret = INLINE_SYSCALL(rt_sigprocmask, 4, SIG_UNBLOCK, &mask, NULL,
- sizeof(sigset_t));
- #endif
- if (IS_ERR(ret))
- return unix_to_pal_error(ERRNO(ret));
- return 0;
- }
- int block_signals (bool block, const int * sigs, int nsig)
- {
- int how = block? SIG_BLOCK: SIG_UNBLOCK;
- int ret = 0;
- __sigset_t mask;
- __sigemptyset(&mask);
- for (int i = 0 ; i < nsig ; i++)
- __sigaddset(&mask, sigs[i]);
- #if defined(__i386__)
- ret = INLINE_SYSCALL(sigprocmask, 3, how, &mask, NULL)
- #else
- ret = INLINE_SYSCALL(rt_sigprocmask, 4, how, &mask, NULL,
- sizeof(sigset_t));
- #endif
- if (IS_ERR(ret))
- return unix_to_pal_error(ERRNO(ret));
- return 0;
- }
- int block_async_signals (bool block)
- {
- return block_signals(block, async_signals, nasync_signals);
- }
- static int get_event_num (int signum)
- {
- switch(signum) {
- case SIGFPE: return PAL_EVENT_ARITHMETIC_ERROR;
- case SIGSEGV: case SIGBUS: return PAL_EVENT_MEMFAULT;
- case SIGILL: case SIGSYS: return PAL_EVENT_ILLEGAL;
- case SIGTERM: return PAL_EVENT_QUIT;
- case SIGINT: return PAL_EVENT_SUSPEND;
- case SIGCONT: return PAL_EVENT_RESUME;
- default: return -1;
- }
- }
- static void _DkGenericEventTrigger(PAL_EVENT_HANDLER upcall,
- PAL_NUM arg, ucontext_t* uc) {
- if (!uc) {
- (*upcall)(NULL, arg, NULL);
- return;
- }
- PAL_CONTEXT context;
- memcpy(&context, uc->uc_mcontext.gregs, sizeof(context));
- context.fpregs = (PAL_XREGS_STATE*)uc->uc_mcontext.fpregs;
- (*upcall)(NULL, arg, &context);
- /* copy the context back to ucontext */
- memcpy(uc->uc_mcontext.gregs, &context, sizeof(context));
- uc->uc_mcontext.fpregs = (struct _libc_fpstate*)context.fpregs;
- }
- static bool _DkGenericSignalHandle (int event_num, siginfo_t * info,
- ucontext_t * uc)
- {
- PAL_EVENT_HANDLER upcall = _DkGetExceptionHandler(event_num);
- if (upcall) {
- PAL_NUM arg = 0;
- if (event_num == PAL_EVENT_ARITHMETIC_ERROR ||
- event_num == PAL_EVENT_MEMFAULT ||
- event_num == PAL_EVENT_ILLEGAL)
- arg = (PAL_NUM) (info ? info->si_addr : 0);
- _DkGenericEventTrigger(upcall, arg, uc);
- return true;
- }
- return false;
- }
- static void _DkGenericSighandler (int signum, siginfo_t * info,
- struct ucontext * uc)
- {
- int event_num = get_event_num(signum);
- if (event_num == -1)
- return;
- uintptr_t rip = uc->uc_mcontext.gregs[REG_RIP];
- if (ADDR_IN_PAL(rip)) {
- // We expect none of the memory faults, illegal instructions, or arithmetic exceptions
- // will happen in PAL. If these exceptions happen in PAL, exit the thread with loud warning.
- int pid = INLINE_SYSCALL(getpid, 0);
- int tid = INLINE_SYSCALL(gettid, 0);
- const char * name = "exception";
- switch(event_num) {
- case PAL_EVENT_ARITHMETIC_ERROR: name = "arithmetic exception"; break;
- case PAL_EVENT_MEMFAULT: name = "memory fault"; break;
- case PAL_EVENT_ILLEGAL: name = "illegal instruction"; break;
- }
- printf("*** An unexpected %s occurred inside PAL. Exiting the thread. "
- "(PID = %d, TID = %d, RIP = +0x%08lx) ***\n",
- name, pid, tid, rip - (uintptr_t) TEXT_START);
- #ifdef DEBUG
- // Hang for debugging
- while (true) {
- struct timespec sleeptime;
- sleeptime.tv_sec = 36000;
- sleeptime.tv_nsec = 0;
- INLINE_SYSCALL(nanosleep, 2, &sleeptime, NULL);
- }
- #endif
- _DkThreadExit(/*clear_child_tid=*/NULL);
- return;
- }
- _DkGenericSignalHandle(event_num, info, uc);
- }
- static void _DkTerminateSighandler (int signum, siginfo_t * info,
- struct ucontext * uc)
- {
- __UNUSED(info);
- int event_num = get_event_num(signum);
- if (event_num == -1)
- return;
- uintptr_t rip = uc->uc_mcontext.gregs[REG_RIP];
- // If the signal arrives in the middle of a PAL call, add the event
- // to pending in the current TCB.
- if (ADDR_IN_PAL(rip)) {
- PAL_TCB_LINUX * tcb = get_tcb_linux();
- assert(tcb);
- if (!tcb->pending_event) {
- // Use the preserved pending event slot
- tcb->pending_event = event_num;
- } else {
- // If there is already a pending event, add the new event to the queue.
- // (a relatively rare case.)
- struct event_queue * ev = malloc(sizeof(*ev));
- if (!ev)
- return;
- INIT_LIST_HEAD(ev, list);
- ev->event_num = event_num;
- LISTP_ADD_TAIL(ev, &tcb->pending_queue, list);
- }
- return;
- }
- // Call the event handler. If there is no handler, terminate the thread
- // unless it is a resuming event (then ignore the event).
- if (!_DkGenericSignalHandle(event_num, NULL, uc) && event_num != PAL_EVENT_RESUME)
- _DkThreadExit(/*clear_child_tid=*/NULL);
- }
- static void _DkPipeSighandler (int signum, siginfo_t * info,
- struct ucontext * uc)
- {
- __UNUSED(signum);
- __UNUSED(info);
- assert(signum == SIGPIPE);
- uintptr_t rip = uc->uc_mcontext.gregs[REG_RIP];
- __UNUSED(rip);
- assert(ADDR_IN_PAL(rip)); // This signal can only happens inside PAL
- return;
- }
- /*
- * __check_pending_event(): checks the existence of a pending event in the TCB
- * and handles the event consequently.
- */
- void __check_pending_event (void)
- {
- PAL_TCB_LINUX * tcb = get_tcb_linux();
- assert(tcb);
- if (tcb->pending_event) {
- int event = tcb->pending_event;
- tcb->pending_event = 0;
- _DkGenericSignalHandle(event, NULL, NULL);
- if (!LISTP_EMPTY(&tcb->pending_queue)) {
- // If there are more than one pending events, process them from the queue
- struct event_queue * ev, * n;
- LISTP_FOR_EACH_ENTRY_SAFE(ev, n, &tcb->pending_queue, list) {
- LISTP_DEL(ev, &tcb->pending_queue, list);
- _DkGenericSignalHandle(ev->event_num, NULL, NULL);
- free(ev);
- }
- }
- }
- }
- void _DkRaiseFailure(int error) {
- PAL_EVENT_HANDLER upcall = _DkGetExceptionHandler(PAL_EVENT_FAILURE);
- if (upcall) {
- _DkGenericEventTrigger(upcall, error, NULL);
- }
- }
- struct signal_ops {
- int signum[3];
- void (*handler) (int signum, siginfo_t * info, ucontext_t * uc);
- };
- struct signal_ops on_signals[] = {
- [PAL_EVENT_ARITHMETIC_ERROR] = { .signum = { SIGFPE, 0 },
- .handler = _DkGenericSighandler },
- [PAL_EVENT_MEMFAULT] = { .signum = { SIGSEGV, SIGBUS, 0 },
- .handler = _DkGenericSighandler },
- [PAL_EVENT_ILLEGAL] = { .signum = { SIGILL, SIGSYS, 0 },
- .handler = _DkGenericSighandler },
- [PAL_EVENT_QUIT] = { .signum = { SIGTERM, 0, 0 },
- .handler = _DkTerminateSighandler },
- [PAL_EVENT_SUSPEND] = { .signum = { SIGINT, 0 },
- .handler = _DkTerminateSighandler },
- [PAL_EVENT_RESUME] = { .signum = { SIGCONT, 0 },
- .handler = _DkTerminateSighandler },
- };
- static int _DkPersistentSighandlerSetup (int event_num)
- {
- int nsigs, * sigs = on_signals[event_num].signum;
- for (nsigs = 0 ; sigs[nsigs] ; nsigs++);
- int ret = set_sighandler(sigs, nsigs, on_signals[event_num].handler);
- if (ret < 0)
- return ret;
- return 0;
- }
- void signal_setup (void)
- {
- int ret, sig = SIGCHLD;
- #ifdef DEBUG
- if (!linux_state.in_gdb)
- #endif
- set_sighandler(&sig, 1, NULL);
- sig = SIGPIPE;
- if ((ret = set_sighandler(&sig, 1, &_DkPipeSighandler)) < 0)
- goto err;
- int events[] = {
- PAL_EVENT_ARITHMETIC_ERROR,
- PAL_EVENT_MEMFAULT,
- PAL_EVENT_ILLEGAL,
- PAL_EVENT_QUIT,
- PAL_EVENT_SUSPEND,
- PAL_EVENT_RESUME,
- };
- for (size_t e = 0; e < ARRAY_SIZE(events); e++)
- if ((ret = _DkPersistentSighandlerSetup(events[e])) < 0)
- goto err;
- return;
- err:
- INIT_FAIL(-ret, "cannot setup signal handlers");
- }
- void _DkExceptionReturn(void* event) {
- __UNUSED(event);
- }
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