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signal信号的处理过程
mips架构下signal信号的处理。信号是linux下非常重要的部分，把这几天看的整理一下。
执行kill -l列出所有的信号
HUP INT QUIT ILL TRAP ABRT BUS FPE KILL
USR1 SEGV USR2 PIPE ALRM TERM STKFLT CHLD CONT
STOP TSTP TTIN TTOU URG XCPU XFSZ VTALRM PROF
WINCH POLL PWR SYS
HUP是1， 依次往下排。
信号相关的过程有三部分：
- 信号处理handler的注册
- 信号的发送
- 信号的处理
除了某些信号不能在用户层被捕获，不能注册handler函数之外，所有信号都有这三个过程。
task_struct 中signal相关的结构
int exit_state;
int exit_code, exit_signal;
int pdeath_signal; /* The signal sent when the parent dies */
unsigned int jobctl; /* JOBCTL_*, siglock protected */
/* signal handlers */
struct signal_struct *signal;
struct sighand_struct *sighand;
sigset_t blocked, real_blocked;
sigset_t saved_sigmask; /* restored if set_restore_sigmask() was used */
struct sigpending pending;// task_struct 中sigqueue的链表头
struct signal_struct {
atomic_t sigcnt;
atomic_t live;
int nr_threads;
wait_queue_head_t wait_chldexit; /* for wait4() */
/* current thread group signal load-balancing target: */
struct task_struct *curr_target;
/* shared signal handling: */
struct sigpending shared_pending;
/* thread group exit support */
int group_exit_code;
/* overloaded:
* - notify group_exit_task when ->count is equal to notify_count
* - everyone except group_exit_task is stopped during signal delivery
* of fatal signals, group_exit_task processes the signal.
*/
int notify_count;
struct task_struct *group_exit_task;
/* thread group stop support, overloads group_exit_code too */
int group_stop_count;
unsigned int flags; /* see SIGNAL_* flags below */
/*
* PR_SET_CHILD_SUBREAPER marks a process, like a service
* manager, to re-parent orphan (double-forking) child processes
* to this process instead of 'init'. The service manager is
* able to receive SIGCHLD signals and is able to investigate
* the process until it calls wait(). All children of this
* process will inherit a flag if they should look for a
* child_subreaper process at exit.
*/
unsigned int is_child_subreaper:1;
unsigned int has_child_subreaper:1;
/* POSIX.1b Interval Timers */
int posix_timer_id;
struct list_head posix_timers;
/* ITIMER_REAL timer for the process */
struct hrtimer real_timer;
struct pid *leader_pid;
ktime_t it_real_incr;
/*
* ITIMER_PROF and ITIMER_VIRTUAL timers for the process, we use
* CPUCLOCK_PROF and CPUCLOCK_VIRT for indexing array as these
* values are defined to 0 and 1 respectively
*/
struct cpu_itimer it[2];
/*
* Thread group totals for process CPU timers.
* See thread_group_cputimer(), et al, for details.
*/
struct thread_group_cputimer cputimer;
/* Earliest-expiration cache. */
struct task_cputime cputime_expires;
struct list_head cpu_timers[3];
struct pid *tty_old_pgrp;
/* boolean value for session group leader */
int leader;
struct tty_struct *tty; /* NULL if no tty */
#ifdef CONFIG_SCHED_AUTOGROUP
struct autogroup *autogroup;
#endif
/*
* Cumulative resource counters for dead threads in the group,
* and for reaped dead child processes forked by this group.
* Live threads maintain their own counters and add to these
* in __exit_signal, except for the group leader.
*/
cputime_t utime, stime, cutime, cstime;
cputime_t gtime;
cputime_t cgtime;
#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
struct cputime prev_cputime;
#endif
unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
unsigned long inblock, oublock, cinblock, coublock;
unsigned long maxrss, cmaxrss;
struct task_io_accounting ioac;
/*
* Cumulative ns of schedule CPU time fo dead threads in the
* group, not including a zombie group leader, (This only differs
* from jiffies_to_ns(utime + stime) if sched_clock uses something
* other than jiffies.)
*/
unsigned long long sum_sched_runtime;
/*
* We don't bother to synchronize most readers of this at all,
* because there is no reader checking a limit that actually needs
* to get both rlim_cur and rlim_max atomically, and either one
* alone is a single word that can safely be read normally.
* getrlimit/setrlimit use task_lock(current->group_leader) to
* protect this instead of the siglock, because they really
* have no need to disable irqs.
*/
struct rlimit rlim[RLIM_NLIMITS];
#ifdef CONFIG_BSD_PROCESS_ACCT
struct pacct_struct pacct; /* per-process accounting information */
#endif
#ifdef CONFIG_TASKSTATS
struct taskstats *stats;
#endif
#ifdef CONFIG_AUDIT
unsigned audit_tty;
unsigned audit_tty_log_passwd;
struct tty_audit_buf *tty_audit_buf;
#endif
#ifdef CONFIG_CGROUPS
/*
* group_rwsem prevents new tasks from entering the threadgroup and
* member tasks from exiting,a more specifically, setting of
* PF_EXITING. fork and exit paths are protected with this rwsem
* using threadgroup_change_begin/end(). Users which require
* threadgroup to remain stable should use threadgroup_[un]lock()
* which also takes care of exec path. Currently, cgroup is the
* only user.
*/
struct rw_semaphore group_rwsem;
#endif
oom_flags_t oom_flags;
short oom_score_adj; /* OOM kill score adjustment */
short oom_score_adj_min; /* OOM kill score adjustment min value.
* Only settable by CAP_SYS_RESOURCE. */
struct mutex cred_guard_mutex; /* guard against foreign influences on
* credential calculations
* (notably. ptrace) */
};
struct sighand_struct {
atomic_t count;
struct k_sigaction action[_NSIG]; // 信号的handler函数
spinlock_t siglock;
wait_queue_head_t signalfd_wqh;
};
struct sigpending {
struct list_head list; //链表头
sigset_t signal; //收到信号的位图
};
struct sigqueue {
struct list_head list;
int flags;
siginfo_t info;
struct user_struct *user;
};
typedef struct siginfo { //接收到信号的相关信息
int si_signo;
int si_code;
int si_errno;
int __pad0[SI_MAX_SIZE / sizeof(int) - SI_PAD_SIZE - 3];
union {
int _pad[SI_PAD_SIZE];
/* kill() */
struct {
pid_t _pid; /* sender's pid */
__ARCH_SI_UID_T _uid; /* sender's uid */
} _kill;
/* POSIX.1b timers */
struct {
timer_t _tid; /* timer id */
int _overrun; /* overrun count */
char _pad[sizeof( __ARCH_SI_UID_T) - sizeof(int)];
sigval_t _sigval; /* same as below */
int _sys_private; /* not to be passed to user */
} _timer;
/* POSIX.1b signals */
struct {
pid_t _pid; /* sender's pid */
__ARCH_SI_UID_T _uid; /* sender's uid */
sigval_t _sigval;
} _rt;
/* SIGCHLD */
struct {
pid_t _pid; /* which child */
__ARCH_SI_UID_T _uid; /* sender's uid */
int _status; /* exit code */
clock_t _utime;
clock_t _stime;
} _sigchld;
/* IRIX SIGCHLD */
struct {
pid_t _pid; /* which child */
clock_t _utime;
int _status; /* exit code */
clock_t _stime;
} _irix_sigchld;
/* SIGILL, SIGFPE, SIGSEGV, SIGBUS */
struct {
void __user *_addr; /* faulting insn/memory ref. */
#ifdef __ARCH_SI_TRAPNO
int _trapno; /* TRAP # which caused the signal */
#endif
short _addr_lsb;
} _sigfault;
/* SIGPOLL, SIGXFSZ (To do ...) */
struct {
__ARCH_SI_BAND_T _band; /* POLL_IN, POLL_OUT, POLL_MSG */
int _fd;
} _sigpoll;
} _sifields;
} siginfo_t;
信号处理handler的注册
用户层注册信号处理handler的函数是signal
#include <signal.h>
typedef void (*sighandler_t)(int);
sighandler_t signal(int signum, sighandler_t handler);
内核中的定义在/kernel/signal.c 中。
/*
* For backwards compatibility. Functionality superseded by sigaction.
*/
SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
{
struct k_sigaction new_sa, old_sa;
int ret;
new_sa.sa.sa_handler = handler;
new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
sigemptyset(&new_sa.sa.sa_mask);
ret = do_sigaction(sig, &new_sa, &old_sa);
return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
}
#endif /* __ARCH_WANT_SYS_SIGNAL */
struct k_sigaction {
struct sigaction sa;
#ifdef __ARCH_HAS_KA_RESTORER
__sigrestore_t ka_restorer;
#endif
};
struct sigaction {
unsigned int sa_flags;
__sighandler_t sa_handler;
sigset_t sa_mask; /* mask last for extensibility */
};
do_sigaction函数中，sig_kernel_only表示只能由内核处理的信号，不能被用户捕获，即注册用户的信号处理函数， SIGKILL，SIGSTOP就是只能由内核处理的信号。
SIGKILL是9号signal， 就是经常用的kill -9 操作，发送到进程的信号。
#define sig_kernel_only(sig) \
(((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_ONLY_MASK))
#define SIG_KERNEL_ONLY_MASK (\
rt_sigmask(SIGKILL) | rt_sigmask(SIGSTOP))
int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
{
struct task_struct *t = current;
struct k_sigaction *k;
sigset_t mask;
if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
return -EINVAL;
k = &t->sighand->action[sig-1];
spin_lock_irq(¤t->sighand->siglock);
if (oact)
*oact = *k;
if (act) {
sigdelsetmask(&act->sa.sa_mask,
sigmask(SIGKILL) | sigmask(SIGSTOP));
*k = *act;
/*
* POSIX 3.3.1.3:
* "Setting a signal action to SIG_IGN for a signal that is
* pending shall cause the pending signal to be discarded,
* whether or not it is blocked."
*
* "Setting a signal action to SIG_DFL for a signal that is
* pending and whose default action is to ignore the signal
* (for example, SIGCHLD), shall cause the pending signal to
* be discarded, whether or not it is blocked"
*/
if (sig_handler_ignored(sig_handler(t, sig), sig)) {
sigemptyset(&mask);
sigaddset(&mask, sig);
rm_from_queue_full(&mask, &t->signal->shared_pending);
do {
rm_from_queue_full(&mask, &t->pending);
t = next_thread(t);
} while (t != current);
}
}
spin_unlock_irq(¤t->sighand->siglock);
return 0;
}
若不是内核处理的信号和被忽略的信号，就会将注册的handler替换默认的action。信号handler的注册工作完成。
向进程发送信号
/**
* sys_kill - send a signal to a process
* @pid: the PID of the process
* @sig: signal to be sent
*/
SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
{
struct siginfo info;
info.si_signo = sig;
info.si_errno = 0;
info.si_code = SI_USER;
info.si_pid = task_tgid_vnr(current);
info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
return kill_something_info(sig, &info, pid);
}
/*
* kill_something_info() interprets pid in interesting ways just like kill(2).
*
* POSIX specifies that kill(-1,sig) is unspecified, but what we have
* is probably wrong. Should make it like BSD or SYSV.
*/
static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
{
int ret;
if (pid > 0) {
rcu_read_lock();
ret = kill_pid_info(sig, info, find_vpid(pid));
rcu_read_unlock();
return ret;
}
read_lock(&tasklist_lock);
if (pid != -1) {
ret = __kill_pgrp_info(sig, info,
pid ? find_vpid(-pid) : task_pgrp(current));
} else {
int retval = 0, count = 0;
struct task_struct * p;
for_each_process(p) {
if (task_pid_vnr(p) > 1 &&
!same_thread_group(p, current)) {
int err = group_send_sig_info(sig, info, p);
++count;
if (err != -EPERM)
retval = err;
}
}
ret = count ? retval : -ESRCH;
}
read_unlock(&tasklist_lock);
return ret;
}
int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
{
int error = -ESRCH;
struct task_struct *p;
rcu_read_lock();
retry:
p = pid_task(pid, PIDTYPE_PID);
if (p) {
error = group_send_sig_info(sig, info, p);
if (unlikely(error == -ESRCH))
/*
* The task was unhashed in between, try again.
* If it is dead, pid_task() will return NULL,
* if we race with de_thread() it will find the
* new leader.
*/
goto retry;
}
rcu_read_unlock();
return error;
}
/*
* send signal info to all the members of a group
*/
int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
{
int ret;
rcu_read_lock();
ret = check_kill_permission(sig, info, p);
rcu_read_unlock();
if (!ret && sig)
ret = do_send_sig_info(sig, info, p, true);
return ret;
}
int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
bool group)
{
unsigned long flags;
int ret = -ESRCH;
if (lock_task_sighand(p, &flags)) {
ret = send_signal(sig, info, p, group);
unlock_task_sighand(p, &flags);
}
return ret;
}
static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
int group)
{
int from_ancestor_ns = 0;
#ifdef CONFIG_PID_NS
from_ancestor_ns = si_fromuser(info) &&
!task_pid_nr_ns(current, task_active_pid_ns(t));
#endif
return __send_signal(sig, info, t, group, from_ancestor_ns);
}
static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
int group, int from_ancestor_ns)
{
struct sigpending *pending;
struct sigqueue *q;
int override_rlimit;
int ret = 0, result;
assert_spin_locked(&t->sighand->siglock);
result = TRACE_SIGNAL_IGNORED;
if (!prepare_signal(sig, t,
from_ancestor_ns || (info == SEND_SIG_FORCED)))
goto ret;
pending = group ? &t->signal->shared_pending : &t->pending;
/*
* Short-circuit ignored signals and support queuing
* exactly one non-rt signal, so that we can get more
* detailed information about the cause of the signal.
*/
result = TRACE_SIGNAL_ALREADY_PENDING;
if (legacy_queue(pending, sig))
goto ret;
result = TRACE_SIGNAL_DELIVERED;
/*
* fast-pathed signals for kernel-internal things like SIGSTOP
* or SIGKILL.
*/
if (info == SEND_SIG_FORCED)
goto out_set;
/*
* Real-time signals must be queued if sent by sigqueue, or
* some other real-time mechanism. It is implementation
* defined whether kill() does so. We attempt to do so, on
* the principle of least surprise, but since kill is not
* allowed to fail with EAGAIN when low on memory we just
* make sure at least one signal gets delivered and don't
* pass on the info struct.
*/
if (sig < SIGRTMIN)
override_rlimit = (is_si_special(info) || info->si_code >= 0);
else
override_rlimit = 0;
q = __sigqueue_alloc(sig, t, GFP_ATOMIC | __GFP_NOTRACK_FALSE_POSITIVE,
override_rlimit); //分配sigqueue
if (q) {
list_add_tail(&q->list, &pending->list); //将新的sigqueue加入到pending链表中
switch ((unsigned long) info) {//开始检查info结构
case (unsigned long) SEND_SIG_NOINFO:
q->info.si_signo = sig;
q->info.si_errno = 0;
q->info.si_code = SI_USER;
q->info.si_pid = task_tgid_nr_ns(current,
task_active_pid_ns(t));
q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
break;
case (unsigned long) SEND_SIG_PRIV:
q->info.si_signo = sig;
q->info.si_errno = 0;
q->info.si_code = SI_KERNEL;
q->info.si_pid = 0;
q->info.si_uid = 0;
break;
default:
copy_siginfo(&q->info, info); //将info信息填入sigqueue中
if (from_ancestor_ns)
q->info.si_pid = 0;
break;
}
userns_fixup_signal_uid(&q->info, t);
} else if (!is_si_special(info)) {
if (sig >= SIGRTMIN && info->si_code != SI_USER) {
/*
* Queue overflow, abort. We may abort if the
* signal was rt and sent by user using something
* other than kill().
*/
result = TRACE_SIGNAL_OVERFLOW_FAIL;
ret = -EAGAIN;
goto ret;
} else {
/*
* This is a silent loss of information. We still
* send the signal, but the *info bits are lost.
*/
result = TRACE_SIGNAL_LOSE_INFO;
}
}
out_set:
signalfd_notify(t, sig);
sigaddset(&pending->signal, sig); //设置pending中的等待信号位图
complete_signal(sig, t, group);
ret:
trace_signal_generate(sig, info, t, group, result);
return ret;
}
sigqueue结构代表一个要处理的信号，kill将sigqueue挂到pending链表中，等待处理。
signal的处理
signal的处理时机是在系统调用退出时 和 在异常（中断）退出时。
在syscall_exit中会调用do_notify_resume处理signal。 do_signal函数中有 get_signal_to_deliver函数：用来处理需要内核处理的信号
handle_signal函数： 处理用户注册的信号，设置寄存器和栈里边的数据 准备返回用户层handler中。
/*
* notification of userspace execution resumption
* - triggered by the TIF_WORK_MASK flags
*/
asmlinkage void do_notify_resume(struct pt_regs *regs, void *unused,
__u32 thread_info_flags)
{
local_irq_enable();
user_exit();
/* deal with pending signal delivery */
if (thread_info_flags & _TIF_SIGPENDING)
do_signal(regs);
if (thread_info_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
tracehook_notify_resume(regs);
}
user_enter();
}
static void do_signal(struct pt_regs *regs)
{
struct k_sigaction ka;
siginfo_t info;
int signr;
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
/* Whee! Actually deliver the signal. */
handle_signal(signr, &info, &ka, regs);
return;
}
if (regs->regs[0]) {
switch (regs->regs[2]) {
case ERESTARTNOHAND:
case ERESTARTSYS:
case ERESTARTNOINTR:
regs->regs[2] = regs->regs[0];
regs->regs[7] = regs->regs[26];
regs->cp0_epc -= 4;
break;
case ERESTART_RESTARTBLOCK:
regs->regs[2] = current->thread.abi->restart;
regs->regs[7] = regs->regs[26];
regs->cp0_epc -= 4;
break;
}
regs->regs[0] = 0; /* Don't deal with this again. */
}
/*
* If there's no signal to deliver, we just put the saved sigmask
* back
*/
restore_saved_sigmask();
}
int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
struct pt_regs *regs, void *cookie)
{
struct sighand_struct *sighand = current->sighand;
struct signal_struct *signal = current->signal;
int signr;
if (unlikely(current->task_works))
task_work_run();
if (unlikely(uprobe_deny_signal()))
return 0;
/*
* Do this once, we can't return to user-mode if freezing() == T.
* do_signal_stop() and ptrace_stop() do freezable_schedule() and
* thus do not need another check after return.
*/
try_to_freeze();
relock:
spin_lock_irq(&sighand->siglock);
/*
* Every stopped thread goes here after wakeup. Check to see if
* we should notify the parent, prepare_signal(SIGCONT) encodes
* the CLD_ si_code into SIGNAL_CLD_MASK bits.
*/
if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
int why;
if (signal->flags & SIGNAL_CLD_CONTINUED)
why = CLD_CONTINUED;
else
why = CLD_STOPPED;
signal->flags &= ~SIGNAL_CLD_MASK;
spin_unlock_irq(&sighand->siglock);
/*
* Notify the parent that we're continuing. This event is
* always per-process and doesn't make whole lot of sense
* for ptracers, who shouldn't consume the state via
* wait(2) either, but, for backward compatibility, notify
* the ptracer of the group leader too unless it's gonna be
* a duplicate.
*/
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current, false, why);
if (ptrace_reparented(current->group_leader))
do_notify_parent_cldstop(current->group_leader,
true, why);
read_unlock(&tasklist_lock);
goto relock;
}
for (;;) { //处理所有接收到的信号
struct k_sigaction *ka;
if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
do_signal_stop(0))
goto relock;
if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) {
do_jobctl_trap();
spin_unlock_irq(&sighand->siglock);
goto relock;
}
signr = dequeue_signal(current, ¤t->blocked, info); //移除代表信号的sigqueue结构
if (!signr)
break; /* will return 0 */
if (unlikely(current->ptrace) && signr != SIGKILL) {
signr = ptrace_signal(signr, info);
if (!signr)
continue;
}
ka = &sighand->action[signr-1]; //获得接收信号的操作结构
/* Trace actually delivered signals. */
trace_signal_deliver(signr, info, ka);
if (ka->sa.sa_handler == SIG_IGN) /* Do nothing. */ // 设置为被忽略的
continue;
if (ka->sa.sa_handler != SIG_DFL) { //当不是默认的操作，已经被用户捕获时返回这个操作结构
/* Run the handler. */
*return_ka = *ka; //返回
if (ka->sa.sa_flags & SA_ONESHOT) //kill默认设置这个只执行一次的标志
ka->sa.sa_handler = SIG_DFL;
break; /* will return non-zero "signr" value */ //退出准备执行上层注册函数
}
/*
* Now we are doing the default action for this signal.
*/
if (sig_kernel_ignore(signr)) /* Default is nothing. */ //如果被忽略的
continue;
/*
* Global init gets no signals it doesn't want.
* Container-init gets no signals it doesn't want from same
* container.
*
* Note that if global/container-init sees a sig_kernel_only()
* signal here, the signal must have been generated internally
* or must have come from an ancestor namespace. In either
* case, the signal cannot be dropped.
*/
if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
!sig_kernel_only(signr))
continue;
if (sig_kernel_stop(signr)) {
/*
* The default action is to stop all threads in
* the thread group. The job control signals
* do nothing in an orphaned pgrp, but SIGSTOP
* always works. Note that siglock needs to be
* dropped during the call to is_orphaned_pgrp()
* because of lock ordering with tasklist_lock.
* This allows an intervening SIGCONT to be posted.
* We need to check for that and bail out if necessary.
*/
if (signr != SIGSTOP) {
spin_unlock_irq(&sighand->siglock);
/* signals can be posted during this window */
if (is_current_pgrp_orphaned())
goto relock;
spin_lock_irq(&sighand->siglock);
}
if (likely(do_signal_stop(info->si_signo))) {
/* It released the siglock. */
goto relock;
}
/*
* We didn't actually stop, due to a race
* with SIGCONT or something like that.
*/
continue;
}
spin_unlock_irq(&sighand->siglock);
/*
* Anything else is fatal, maybe with a core dump.
*/
current->flags |= PF_SIGNALED;
if (sig_kernel_coredump(signr)) {
if (print_fatal_signals)
print_fatal_signal(info->si_signo);
proc_coredump_connector(current);
/*
* If it was able to dump core, this kills all
* other threads in the group and synchronizes with
* their demise. If we lost the race with another
* thread getting here, it set group_exit_code
* first and our do_group_exit call below will use
* that value and ignore the one we pass it.
*/
do_coredump(info);
}
/*
* Death signals, no core dump. 如果这个信号未被捕获，默认情况下是使进程退出跟SIGKILL效果相同
*/
do_group_exit(info->si_signo);
/* NOTREACHED */
}
spin_unlock_irq(&sighand->siglock);
return signr;
}
static void handle_signal(unsigned long sig, siginfo_t *info,
struct k_sigaction *ka, struct pt_regs *regs)
{
sigset_t *oldset = sigmask_to_save();
int ret;
struct mips_abi *abi = current->thread.abi;
#ifdef CONFIG_CPU_MICROMIPS
void *vdso;
unsigned int tmp = (unsigned int)current->mm->context.vdso;
set_isa16_mode(tmp);
vdso = (void *)tmp;
#else
void *vdso = current->mm->context.vdso;
#endif
if (regs->regs[0]) {
switch(regs->regs[2]) {
case ERESTART_RESTARTBLOCK:
case ERESTARTNOHAND:
regs->regs[2] = EINTR;
break;
case ERESTARTSYS:
if (!(ka->sa.sa_flags & SA_RESTART)) {
regs->regs[2] = EINTR;
break;
}
/* fallthrough */
case ERESTARTNOINTR:
regs->regs[7] = regs->regs[26];
regs->regs[2] = regs->regs[0];
regs->cp0_epc -= 4;
}
regs->regs[0] = 0; /* Don't deal with this again. */
}
if (sig_uses_siginfo(ka))
ret = abi->setup_rt_frame(vdso + abi->rt_signal_return_offset,
ka, regs, sig, oldset, info);
else
ret = abi->setup_frame(vdso + abi->signal_return_offset,
ka, regs, sig, oldset);
if (ret)
return;
signal_delivered(sig, info, ka, regs, 0);
}
setup_rt_frame设置寄存器和栈数据准备返回用户层
static int setup_rt_frame(void *sig_return, struct k_sigaction *ka,
struct pt_regs *regs, int signr, sigset_t *set,
siginfo_t *info)
{
struct rt_sigframe __user *frame;
int err = 0;
frame = get_sigframe(ka, regs, sizeof(*frame));
if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
goto give_sigsegv;
/* Create siginfo. */
err |= copy_siginfo_to_user(&frame->rs_info, info);
/* Create the ucontext. */
err |= __put_user(0, &frame->rs_uc.uc_flags);
err |= __put_user(NULL, &frame->rs_uc.uc_link);
err |= __save_altstack(&frame->rs_uc.uc_stack, regs->regs[29]);
err |= setup_sigcontext(regs, &frame->rs_uc.uc_mcontext);
err |= __copy_to_user(&frame->rs_uc.uc_sigmask, set, sizeof(*set));
if (err)
goto give_sigsegv;
/*
* Arguments to signal handler:
*
* a0 = signal number
* a1 = 0 (should be cause)
* a2 = pointer to ucontext
*
* $25 and c0_epc point to the signal handler, $29 points to
* the struct rt_sigframe.
*/
regs->regs[ 4] = signr;
regs->regs[ 5] = (unsigned long) &frame->rs_info;
regs->regs[ 6] = (unsigned long) &frame->rs_uc;
regs->regs[29] = (unsigned long) frame;
regs->regs[31] = (unsigned long) sig_return;
regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
current->comm, current->pid,
frame, regs->cp0_epc, regs->regs[31]);
return 0;
give_sigsegv:
force_sigsegv(signr, current);
return -EFAULT;
}
mips需要保存的寄存器
struct pt_regs {
#ifdef CONFIG_32BIT
/* Pad bytes for argument save space on the stack. */
unsigned long pad0[6];
#endif
/* Saved main processor registers. */
unsigned long regs[32];
/* Saved special registers. */
unsigned long cp0_status;
unsigned long hi;
unsigned long lo;
#ifdef CONFIG_CPU_HAS_SMARTMIPS
unsigned long acx;
#endif
unsigned long cp0_badvaddr;
unsigned long cp0_cause;
unsigned long cp0_epc;
#ifdef CONFIG_MIPS_MT_SMTC
unsigned long cp0_tcstatus;
#endif /* CONFIG_MIPS_MT_SMTC */
} __attribute__ ((aligned (8)));
killall 和killall -9的区别
killall默认发送SIGTERM信号， killall -9 指定发送SIGKILL信号， SIGTERM可以被用户层捕获， SIGKILL不能被捕获。
捕获SIGTERM的作用一般是获取到结束信息，设置结束标志，然后用户层自己主动退出。
SIGKILL是强制当前进程退出，退出使用的是do_group_exit, 跟用户执行exit()函数是相同的，都能释放内存，close打开的文件等。因为是强制退出，驱动中的资源不能通过close文件释放的节点不会被释放。
如果SIGTERM没有被上层捕获，它的效果跟SIGKILL完全相同。
