diff options
Diffstat (limited to 'arch/ia64/kernel/signal.c')
| -rw-r--r-- | arch/ia64/kernel/signal.c | 691 |
1 files changed, 691 insertions, 0 deletions
diff --git a/arch/ia64/kernel/signal.c b/arch/ia64/kernel/signal.c new file mode 100644 index 000000000000..6891d86937d9 --- /dev/null +++ b/arch/ia64/kernel/signal.c @@ -0,0 +1,691 @@ +/* + * Architecture-specific signal handling support. + * + * Copyright (C) 1999-2004 Hewlett-Packard Co + * David Mosberger-Tang <davidm@hpl.hp.com> + * + * Derived from i386 and Alpha versions. + */ + +#include <linux/config.h> +#include <linux/errno.h> +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/ptrace.h> +#include <linux/sched.h> +#include <linux/signal.h> +#include <linux/smp.h> +#include <linux/smp_lock.h> +#include <linux/stddef.h> +#include <linux/tty.h> +#include <linux/binfmts.h> +#include <linux/unistd.h> +#include <linux/wait.h> + +#include <asm/ia32.h> +#include <asm/intrinsics.h> +#include <asm/uaccess.h> +#include <asm/rse.h> +#include <asm/sigcontext.h> + +#include "sigframe.h" + +#define DEBUG_SIG 0 +#define STACK_ALIGN 16 /* minimal alignment for stack pointer */ +#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP))) + +#if _NSIG_WORDS > 1 +# define PUT_SIGSET(k,u) __copy_to_user((u)->sig, (k)->sig, sizeof(sigset_t)) +# define GET_SIGSET(k,u) __copy_from_user((k)->sig, (u)->sig, sizeof(sigset_t)) +#else +# define PUT_SIGSET(k,u) __put_user((k)->sig[0], &(u)->sig[0]) +# define GET_SIGSET(k,u) __get_user((k)->sig[0], &(u)->sig[0]) +#endif + +long +ia64_rt_sigsuspend (sigset_t __user *uset, size_t sigsetsize, struct sigscratch *scr) +{ + sigset_t oldset, set; + + /* XXX: Don't preclude handling different sized sigset_t's. */ + if (sigsetsize != sizeof(sigset_t)) + return -EINVAL; + + if (!access_ok(VERIFY_READ, uset, sigsetsize)) + return -EFAULT; + + if (GET_SIGSET(&set, uset)) + return -EFAULT; + + sigdelsetmask(&set, ~_BLOCKABLE); + + spin_lock_irq(¤t->sighand->siglock); + { + oldset = current->blocked; + current->blocked = set; + recalc_sigpending(); + } + spin_unlock_irq(¤t->sighand->siglock); + + /* + * The return below usually returns to the signal handler. We need to + * pre-set the correct error code here to ensure that the right values + * get saved in sigcontext by ia64_do_signal. + */ + scr->pt.r8 = EINTR; + scr->pt.r10 = -1; + + while (1) { + current->state = TASK_INTERRUPTIBLE; + schedule(); + if (ia64_do_signal(&oldset, scr, 1)) + return -EINTR; + } +} + +asmlinkage long +sys_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, long arg2, + long arg3, long arg4, long arg5, long arg6, long arg7, + struct pt_regs regs) +{ + return do_sigaltstack(uss, uoss, regs.r12); +} + +static long +restore_sigcontext (struct sigcontext __user *sc, struct sigscratch *scr) +{ + unsigned long ip, flags, nat, um, cfm; + long err; + + /* Always make any pending restarted system calls return -EINTR */ + current_thread_info()->restart_block.fn = do_no_restart_syscall; + + /* restore scratch that always needs gets updated during signal delivery: */ + err = __get_user(flags, &sc->sc_flags); + err |= __get_user(nat, &sc->sc_nat); + err |= __get_user(ip, &sc->sc_ip); /* instruction pointer */ + err |= __get_user(cfm, &sc->sc_cfm); + err |= __get_user(um, &sc->sc_um); /* user mask */ + err |= __get_user(scr->pt.ar_rsc, &sc->sc_ar_rsc); + err |= __get_user(scr->pt.ar_unat, &sc->sc_ar_unat); + err |= __get_user(scr->pt.ar_fpsr, &sc->sc_ar_fpsr); + err |= __get_user(scr->pt.ar_pfs, &sc->sc_ar_pfs); + err |= __get_user(scr->pt.pr, &sc->sc_pr); /* predicates */ + err |= __get_user(scr->pt.b0, &sc->sc_br[0]); /* b0 (rp) */ + err |= __get_user(scr->pt.b6, &sc->sc_br[6]); /* b6 */ + err |= __copy_from_user(&scr->pt.r1, &sc->sc_gr[1], 8); /* r1 */ + err |= __copy_from_user(&scr->pt.r8, &sc->sc_gr[8], 4*8); /* r8-r11 */ + err |= __copy_from_user(&scr->pt.r12, &sc->sc_gr[12], 2*8); /* r12-r13 */ + err |= __copy_from_user(&scr->pt.r15, &sc->sc_gr[15], 8); /* r15 */ + + scr->pt.cr_ifs = cfm | (1UL << 63); + + /* establish new instruction pointer: */ + scr->pt.cr_iip = ip & ~0x3UL; + ia64_psr(&scr->pt)->ri = ip & 0x3; + scr->pt.cr_ipsr = (scr->pt.cr_ipsr & ~IA64_PSR_UM) | (um & IA64_PSR_UM); + + scr->scratch_unat = ia64_put_scratch_nat_bits(&scr->pt, nat); + + if (!(flags & IA64_SC_FLAG_IN_SYSCALL)) { + /* Restore most scratch-state only when not in syscall. */ + err |= __get_user(scr->pt.ar_ccv, &sc->sc_ar_ccv); /* ar.ccv */ + err |= __get_user(scr->pt.b7, &sc->sc_br[7]); /* b7 */ + err |= __get_user(scr->pt.r14, &sc->sc_gr[14]); /* r14 */ + err |= __copy_from_user(&scr->pt.ar_csd, &sc->sc_ar25, 2*8); /* ar.csd & ar.ssd */ + err |= __copy_from_user(&scr->pt.r2, &sc->sc_gr[2], 2*8); /* r2-r3 */ + err |= __copy_from_user(&scr->pt.r16, &sc->sc_gr[16], 16*8); /* r16-r31 */ + } + + if ((flags & IA64_SC_FLAG_FPH_VALID) != 0) { + struct ia64_psr *psr = ia64_psr(&scr->pt); + + __copy_from_user(current->thread.fph, &sc->sc_fr[32], 96*16); + psr->mfh = 0; /* drop signal handler's fph contents... */ + if (psr->dfh) + ia64_drop_fpu(current); + else { + /* We already own the local fph, otherwise psr->dfh wouldn't be 0. */ + __ia64_load_fpu(current->thread.fph); + ia64_set_local_fpu_owner(current); + } + } + return err; +} + +int +copy_siginfo_to_user (siginfo_t __user *to, siginfo_t *from) +{ + if (!access_ok(VERIFY_WRITE, to, sizeof(siginfo_t))) + return -EFAULT; + if (from->si_code < 0) { + if (__copy_to_user(to, from, sizeof(siginfo_t))) + return -EFAULT; + return 0; + } else { + int err; + + /* + * If you change siginfo_t structure, please be sure this code is fixed + * accordingly. It should never copy any pad contained in the structure + * to avoid security leaks, but must copy the generic 3 ints plus the + * relevant union member. + */ + err = __put_user(from->si_signo, &to->si_signo); + err |= __put_user(from->si_errno, &to->si_errno); + err |= __put_user((short)from->si_code, &to->si_code); + switch (from->si_code >> 16) { + case __SI_FAULT >> 16: + err |= __put_user(from->si_flags, &to->si_flags); + err |= __put_user(from->si_isr, &to->si_isr); + case __SI_POLL >> 16: + err |= __put_user(from->si_addr, &to->si_addr); + err |= __put_user(from->si_imm, &to->si_imm); + break; + case __SI_TIMER >> 16: + err |= __put_user(from->si_tid, &to->si_tid); + err |= __put_user(from->si_overrun, &to->si_overrun); + err |= __put_user(from->si_ptr, &to->si_ptr); + break; + case __SI_RT >> 16: /* Not generated by the kernel as of now. */ + case __SI_MESGQ >> 16: + err |= __put_user(from->si_uid, &to->si_uid); + err |= __put_user(from->si_pid, &to->si_pid); + err |= __put_user(from->si_ptr, &to->si_ptr); + break; + case __SI_CHLD >> 16: + err |= __put_user(from->si_utime, &to->si_utime); + err |= __put_user(from->si_stime, &to->si_stime); + err |= __put_user(from->si_status, &to->si_status); + default: + err |= __put_user(from->si_uid, &to->si_uid); + err |= __put_user(from->si_pid, &to->si_pid); + break; + } + return err; + } +} + +long +ia64_rt_sigreturn (struct sigscratch *scr) +{ + extern char ia64_strace_leave_kernel, ia64_leave_kernel; + struct sigcontext __user *sc; + struct siginfo si; + sigset_t set; + long retval; + + sc = &((struct sigframe __user *) (scr->pt.r12 + 16))->sc; + + /* + * When we return to the previously executing context, r8 and r10 have already + * been setup the way we want them. Indeed, if the signal wasn't delivered while + * in a system call, we must not touch r8 or r10 as otherwise user-level state + * could be corrupted. + */ + retval = (long) &ia64_leave_kernel; + if (test_thread_flag(TIF_SYSCALL_TRACE)) + /* + * strace expects to be notified after sigreturn returns even though the + * context to which we return may not be in the middle of a syscall. + * Thus, the return-value that strace displays for sigreturn is + * meaningless. + */ + retval = (long) &ia64_strace_leave_kernel; + + if (!access_ok(VERIFY_READ, sc, sizeof(*sc))) + goto give_sigsegv; + + if (GET_SIGSET(&set, &sc->sc_mask)) + goto give_sigsegv; + + sigdelsetmask(&set, ~_BLOCKABLE); + + spin_lock_irq(¤t->sighand->siglock); + { + current->blocked = set; + recalc_sigpending(); + } + spin_unlock_irq(¤t->sighand->siglock); + + if (restore_sigcontext(sc, scr)) + goto give_sigsegv; + +#if DEBUG_SIG + printk("SIG return (%s:%d): sp=%lx ip=%lx\n", + current->comm, current->pid, scr->pt.r12, scr->pt.cr_iip); +#endif + /* + * It is more difficult to avoid calling this function than to + * call it and ignore errors. + */ + do_sigaltstack(&sc->sc_stack, NULL, scr->pt.r12); + return retval; + + give_sigsegv: + si.si_signo = SIGSEGV; + si.si_errno = 0; + si.si_code = SI_KERNEL; + si.si_pid = current->pid; + si.si_uid = current->uid; + si.si_addr = sc; + force_sig_info(SIGSEGV, &si, current); + return retval; +} + +/* + * This does just the minimum required setup of sigcontext. + * Specifically, it only installs data that is either not knowable at + * the user-level or that gets modified before execution in the + * trampoline starts. Everything else is done at the user-level. + */ +static long +setup_sigcontext (struct sigcontext __user *sc, sigset_t *mask, struct sigscratch *scr) +{ + unsigned long flags = 0, ifs, cfm, nat; + long err; + + ifs = scr->pt.cr_ifs; + + if (on_sig_stack((unsigned long) sc)) + flags |= IA64_SC_FLAG_ONSTACK; + if ((ifs & (1UL << 63)) == 0) + /* if cr_ifs doesn't have the valid bit set, we got here through a syscall */ + flags |= IA64_SC_FLAG_IN_SYSCALL; + cfm = ifs & ((1UL << 38) - 1); + ia64_flush_fph(current); + if ((current->thread.flags & IA64_THREAD_FPH_VALID)) { + flags |= IA64_SC_FLAG_FPH_VALID; + __copy_to_user(&sc->sc_fr[32], current->thread.fph, 96*16); + } + + nat = ia64_get_scratch_nat_bits(&scr->pt, scr->scratch_unat); + + err = __put_user(flags, &sc->sc_flags); + err |= __put_user(nat, &sc->sc_nat); + err |= PUT_SIGSET(mask, &sc->sc_mask); + err |= __put_user(cfm, &sc->sc_cfm); + err |= __put_user(scr->pt.cr_ipsr & IA64_PSR_UM, &sc->sc_um); + err |= __put_user(scr->pt.ar_rsc, &sc->sc_ar_rsc); + err |= __put_user(scr->pt.ar_unat, &sc->sc_ar_unat); /* ar.unat */ + err |= __put_user(scr->pt.ar_fpsr, &sc->sc_ar_fpsr); /* ar.fpsr */ + err |= __put_user(scr->pt.ar_pfs, &sc->sc_ar_pfs); + err |= __put_user(scr->pt.pr, &sc->sc_pr); /* predicates */ + err |= __put_user(scr->pt.b0, &sc->sc_br[0]); /* b0 (rp) */ + err |= __put_user(scr->pt.b6, &sc->sc_br[6]); /* b6 */ + err |= __copy_to_user(&sc->sc_gr[1], &scr->pt.r1, 8); /* r1 */ + err |= __copy_to_user(&sc->sc_gr[8], &scr->pt.r8, 4*8); /* r8-r11 */ + err |= __copy_to_user(&sc->sc_gr[12], &scr->pt.r12, 2*8); /* r12-r13 */ + err |= __copy_to_user(&sc->sc_gr[15], &scr->pt.r15, 8); /* r15 */ + err |= __put_user(scr->pt.cr_iip + ia64_psr(&scr->pt)->ri, &sc->sc_ip); + + if (flags & IA64_SC_FLAG_IN_SYSCALL) { + /* Clear scratch registers if the signal interrupted a system call. */ + err |= __put_user(0, &sc->sc_ar_ccv); /* ar.ccv */ + err |= __put_user(0, &sc->sc_br[7]); /* b7 */ + err |= __put_user(0, &sc->sc_gr[14]); /* r14 */ + err |= __clear_user(&sc->sc_ar25, 2*8); /* ar.csd & ar.ssd */ + err |= __clear_user(&sc->sc_gr[2], 2*8); /* r2-r3 */ + err |= __clear_user(&sc->sc_gr[16], 16*8); /* r16-r31 */ + } else { + /* Copy scratch regs to sigcontext if the signal didn't interrupt a syscall. */ + err |= __put_user(scr->pt.ar_ccv, &sc->sc_ar_ccv); /* ar.ccv */ + err |= __put_user(scr->pt.b7, &sc->sc_br[7]); /* b7 */ + err |= __put_user(scr->pt.r14, &sc->sc_gr[14]); /* r14 */ + err |= __copy_to_user(&sc->sc_ar25, &scr->pt.ar_csd, 2*8); /* ar.csd & ar.ssd */ + err |= __copy_to_user(&sc->sc_gr[2], &scr->pt.r2, 2*8); /* r2-r3 */ + err |= __copy_to_user(&sc->sc_gr[16], &scr->pt.r16, 16*8); /* r16-r31 */ + } + return err; +} + +/* + * Check whether the register-backing store is already on the signal stack. + */ +static inline int +rbs_on_sig_stack (unsigned long bsp) +{ + return (bsp - current->sas_ss_sp < current->sas_ss_size); +} + +static long +force_sigsegv_info (int sig, void __user *addr) +{ + unsigned long flags; + struct siginfo si; + + if (sig == SIGSEGV) { + /* + * Acquiring siglock around the sa_handler-update is almost + * certainly overkill, but this isn't a + * performance-critical path and I'd rather play it safe + * here than having to debug a nasty race if and when + * something changes in kernel/signal.c that would make it + * no longer safe to modify sa_handler without holding the + * lock. + */ + spin_lock_irqsave(¤t->sighand->siglock, flags); + current->sighand->action[sig - 1].sa.sa_handler = SIG_DFL; + spin_unlock_irqrestore(¤t->sighand->siglock, flags); + } + si.si_signo = SIGSEGV; + si.si_errno = 0; + si.si_code = SI_KERNEL; + si.si_pid = current->pid; + si.si_uid = current->uid; + si.si_addr = addr; + force_sig_info(SIGSEGV, &si, current); + return 0; +} + +static long +setup_frame (int sig, struct k_sigaction *ka, siginfo_t *info, sigset_t *set, + struct sigscratch *scr) +{ + extern char __kernel_sigtramp[]; + unsigned long tramp_addr, new_rbs = 0; + struct sigframe __user *frame; + long err; + + frame = (void __user *) scr->pt.r12; + tramp_addr = (unsigned long) __kernel_sigtramp; + if ((ka->sa.sa_flags & SA_ONSTACK) && sas_ss_flags((unsigned long) frame) == 0) { + frame = (void __user *) ((current->sas_ss_sp + current->sas_ss_size) + & ~(STACK_ALIGN - 1)); + /* + * We need to check for the register stack being on the signal stack + * separately, because it's switched separately (memory stack is switched + * in the kernel, register stack is switched in the signal trampoline). + */ + if (!rbs_on_sig_stack(scr->pt.ar_bspstore)) + new_rbs = (current->sas_ss_sp + sizeof(long) - 1) & ~(sizeof(long) - 1); + } + frame = (void __user *) frame - ((sizeof(*frame) + STACK_ALIGN - 1) & ~(STACK_ALIGN - 1)); + + if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) + return force_sigsegv_info(sig, frame); + + err = __put_user(sig, &frame->arg0); + err |= __put_user(&frame->info, &frame->arg1); + err |= __put_user(&frame->sc, &frame->arg2); + err |= __put_user(new_rbs, &frame->sc.sc_rbs_base); + err |= __put_user(0, &frame->sc.sc_loadrs); /* initialize to zero */ + err |= __put_user(ka->sa.sa_handler, &frame->handler); + + err |= copy_siginfo_to_user(&frame->info, info); + + err |= __put_user(current->sas_ss_sp, &frame->sc.sc_stack.ss_sp); + err |= __put_user(current->sas_ss_size, &frame->sc.sc_stack.ss_size); + err |= __put_user(sas_ss_flags(scr->pt.r12), &frame->sc.sc_stack.ss_flags); + err |= setup_sigcontext(&frame->sc, set, scr); + + if (unlikely(err)) + return force_sigsegv_info(sig, frame); + + scr->pt.r12 = (unsigned long) frame - 16; /* new stack pointer */ + scr->pt.ar_fpsr = FPSR_DEFAULT; /* reset fpsr for signal handler */ + scr->pt.cr_iip = tramp_addr; + ia64_psr(&scr->pt)->ri = 0; /* start executing in first slot */ + ia64_psr(&scr->pt)->be = 0; /* force little-endian byte-order */ + /* + * Force the interruption function mask to zero. This has no effect when a + * system-call got interrupted by a signal (since, in that case, scr->pt_cr_ifs is + * ignored), but it has the desirable effect of making it possible to deliver a + * signal with an incomplete register frame (which happens when a mandatory RSE + * load faults). Furthermore, it has no negative effect on the getting the user's + * dirty partition preserved, because that's governed by scr->pt.loadrs. + */ + scr->pt.cr_ifs = (1UL << 63); + + /* + * Note: this affects only the NaT bits of the scratch regs (the ones saved in + * pt_regs), which is exactly what we want. + */ + scr->scratch_unat = 0; /* ensure NaT bits of r12 is clear */ + +#if DEBUG_SIG + printk("SIG deliver (%s:%d): sig=%d sp=%lx ip=%lx handler=%p\n", + current->comm, current->pid, sig, scr->pt.r12, frame->sc.sc_ip, frame->handler); +#endif + return 1; +} + +static long +handle_signal (unsigned long sig, struct k_sigaction *ka, siginfo_t *info, sigset_t *oldset, + struct sigscratch *scr) +{ + if (IS_IA32_PROCESS(&scr->pt)) { + /* send signal to IA-32 process */ + if (!ia32_setup_frame1(sig, ka, info, oldset, &scr->pt)) + return 0; + } else + /* send signal to IA-64 process */ + if (!setup_frame(sig, ka, info, oldset, scr)) + return 0; + + if (!(ka->sa.sa_flags & SA_NODEFER)) { + spin_lock_irq(¤t->sighand->siglock); + { + sigorsets(¤t->blocked, ¤t->blocked, &ka->sa.sa_mask); + sigaddset(¤t->blocked, sig); + recalc_sigpending(); + } + spin_unlock_irq(¤t->sighand->siglock); + } + return 1; +} + +/* + * Note that `init' is a special process: it doesn't get signals it doesn't want to + * handle. Thus you cannot kill init even with a SIGKILL even by mistake. + */ +long +ia64_do_signal (sigset_t *oldset, struct sigscratch *scr, long in_syscall) +{ + struct k_sigaction ka; + siginfo_t info; + long restart = in_syscall; + long errno = scr->pt.r8; +# define ERR_CODE(c) (IS_IA32_PROCESS(&scr->pt) ? -(c) : (c)) + + /* + * In the ia64_leave_kernel code path, we want the common case to go fast, which + * is why we may in certain cases get here from kernel mode. Just return without + * doing anything if so. + */ + if (!user_mode(&scr->pt)) + return 0; + + if (!oldset) + oldset = ¤t->blocked; + + /* + * This only loops in the rare cases of handle_signal() failing, in which case we + * need to push through a forced SIGSEGV. + */ + while (1) { + int signr = get_signal_to_deliver(&info, &ka, &scr->pt, NULL); + + /* + * get_signal_to_deliver() may have run a debugger (via notify_parent()) + * and the debugger may have modified the state (e.g., to arrange for an + * inferior call), thus it's important to check for restarting _after_ + * get_signal_to_deliver(). + */ + if (IS_IA32_PROCESS(&scr->pt)) { + if (in_syscall) { + if (errno >= 0) + restart = 0; + else + errno = -errno; + } + } else if ((long) scr->pt.r10 != -1) + /* + * A system calls has to be restarted only if one of the error codes + * ERESTARTNOHAND, ERESTARTSYS, or ERESTARTNOINTR is returned. If r10 + * isn't -1 then r8 doesn't hold an error code and we don't need to + * restart the syscall, so we can clear the "restart" flag here. + */ + restart = 0; + + if (signr <= 0) + break; + + if (unlikely(restart)) { + switch (errno) { + case ERESTART_RESTARTBLOCK: + case ERESTARTNOHAND: + scr->pt.r8 = ERR_CODE(EINTR); + /* note: scr->pt.r10 is already -1 */ + break; + + case ERESTARTSYS: + if ((ka.sa.sa_flags & SA_RESTART) == 0) { + scr->pt.r8 = ERR_CODE(EINTR); + /* note: scr->pt.r10 is already -1 */ + break; + } + case ERESTARTNOINTR: + if (IS_IA32_PROCESS(&scr->pt)) { + scr->pt.r8 = scr->pt.r1; + scr->pt.cr_iip -= 2; + } else + ia64_decrement_ip(&scr->pt); + restart = 0; /* don't restart twice if handle_signal() fails... */ + } + } + + /* + * Whee! Actually deliver the signal. If the delivery failed, we need to + * continue to iterate in this loop so we can deliver the SIGSEGV... + */ + if (handle_signal(signr, &ka, &info, oldset, scr)) + return 1; + } + + /* Did we come from a system call? */ + if (restart) { + /* Restart the system call - no handlers present */ + if (errno == ERESTARTNOHAND || errno == ERESTARTSYS || errno == ERESTARTNOINTR + || errno == ERESTART_RESTARTBLOCK) + { + if (IS_IA32_PROCESS(&scr->pt)) { + scr->pt.r8 = scr->pt.r1; + scr->pt.cr_iip -= 2; + if (errno == ERESTART_RESTARTBLOCK) + scr->pt.r8 = 0; /* x86 version of __NR_restart_syscall */ + } else { + /* + * Note: the syscall number is in r15 which is saved in + * pt_regs so all we need to do here is adjust ip so that + * the "break" instruction gets re-executed. + */ + ia64_decrement_ip(&scr->pt); + if (errno == ERESTART_RESTARTBLOCK) + scr->pt.r15 = __NR_restart_syscall; + } + } + } + return 0; +} + +/* Set a delayed signal that was detected in MCA/INIT/NMI/PMI context where it + * could not be delivered. It is important that the target process is not + * allowed to do any more work in user space. Possible cases for the target + * process: + * + * - It is sleeping and will wake up soon. Store the data in the current task, + * the signal will be sent when the current task returns from the next + * interrupt. + * + * - It is running in user context. Store the data in the current task, the + * signal will be sent when the current task returns from the next interrupt. + * + * - It is running in kernel context on this or another cpu and will return to + * user context. Store the data in the target task, the signal will be sent + * to itself when the target task returns to user space. + * + * - It is running in kernel context on this cpu and will sleep before + * returning to user context. Because this is also the current task, the + * signal will not get delivered and the task could sleep indefinitely. + * Store the data in the idle task for this cpu, the signal will be sent + * after the idle task processes its next interrupt. + * + * To cover all cases, store the data in the target task, the current task and + * the idle task on this cpu. Whatever happens, the signal will be delivered + * to the target task before it can do any useful user space work. Multiple + * deliveries have no unwanted side effects. + * + * Note: This code is executed in MCA/INIT/NMI/PMI context, with interrupts + * disabled. It must not take any locks nor use kernel structures or services + * that require locks. + */ + +/* To ensure that we get the right pid, check its start time. To avoid extra + * include files in thread_info.h, convert the task start_time to unsigned long, + * giving us a cycle time of > 580 years. + */ +static inline unsigned long +start_time_ul(const struct task_struct *t) +{ + return t->start_time.tv_sec * NSEC_PER_SEC + t->start_time.tv_nsec; +} + +void +set_sigdelayed(pid_t pid, int signo, int code, void __user *addr) +{ + struct task_struct *t; + unsigned long start_time = 0; + int i; + + for (i = 1; i <= 3; ++i) { + switch (i) { + case 1: + t = find_task_by_pid(pid); + if (t) + start_time = start_time_ul(t); + break; + case 2: + t = current; + break; + default: + t = idle_task(smp_processor_id()); + break; + } + + if (!t) + return; + t->thread_info->sigdelayed.signo = signo; + t->thread_info->sigdelayed.code = code; + t->thread_info->sigdelayed.addr = addr; + t->thread_info->sigdelayed.start_time = start_time; + t->thread_info->sigdelayed.pid = pid; + wmb(); + set_tsk_thread_flag(t, TIF_SIGDELAYED); + } +} + +/* Called from entry.S when it detects TIF_SIGDELAYED, a delayed signal that + * was detected in MCA/INIT/NMI/PMI context where it could not be delivered. + */ + +void +do_sigdelayed(void) +{ + struct siginfo siginfo; + pid_t pid; + struct task_struct *t; + + clear_thread_flag(TIF_SIGDELAYED); + memset(&siginfo, 0, sizeof(siginfo)); + siginfo.si_signo = current_thread_info()->sigdelayed.signo; + siginfo.si_code = current_thread_info()->sigdelayed.code; + siginfo.si_addr = current_thread_info()->sigdelayed.addr; + pid = current_thread_info()->sigdelayed.pid; + t = find_task_by_pid(pid); + if (!t) + return; + if (current_thread_info()->sigdelayed.start_time != start_time_ul(t)) + return; + force_sig_info(siginfo.si_signo, &siginfo, t); +} |
