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    Subject[PATCH v3 04/19] OpenRISC: Signal handling
    Date

    Signed-off-by: Jonas Bonn <jonas@southpole.se>
    Reviewed-by: Arnd Bergmann <arnd@arndb.de>
    ---
    arch/openrisc/include/asm/sigcontext.h | 38 +++
    arch/openrisc/kernel/signal.c | 396 ++++++++++++++++++++++++++++++++
    2 files changed, 434 insertions(+), 0 deletions(-)
    create mode 100644 arch/openrisc/include/asm/sigcontext.h
    create mode 100644 arch/openrisc/kernel/signal.c

    diff --git a/arch/openrisc/include/asm/sigcontext.h b/arch/openrisc/include/asm/sigcontext.h
    new file mode 100644
    index 0000000..54a5c50
    --- /dev/null
    +++ b/arch/openrisc/include/asm/sigcontext.h
    @@ -0,0 +1,38 @@
    +/*
    + * OpenRISC Linux
    + *
    + * Linux architectural port borrowing liberally from similar works of
    + * others. All original copyrights apply as per the original source
    + * declaration.
    + *
    + * OpenRISC implementation:
    + * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
    + * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
    + * et al.
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of the GNU General Public License as published by
    + * the Free Software Foundation; either version 2 of the License, or
    + * (at your option) any later version.
    + */
    +
    +#ifndef __ASM_OPENRISC_SIGCONTEXT_H
    +#define __ASM_OPENRISC_SIGCONTEXT_H
    +
    +#include <asm/ptrace.h>
    +
    +/* This struct is saved by setup_frame in signal.c, to keep the current
    + context while a signal handler is executed. It's restored by sys_sigreturn.
    +
    + To keep things simple, we use pt_regs here even though normally you just
    + specify the list of regs to save. Then we can use copy_from_user on the
    + entire regs instead of a bunch of get_user's as well...
    +*/
    +
    +struct sigcontext {
    + struct pt_regs regs; /* needs to be first */
    + unsigned long oldmask;
    + unsigned long usp; /* usp before stacking this gunk on it */
    +};
    +
    +#endif /* __ASM_OPENRISC_SIGCONTEXT_H */
    diff --git a/arch/openrisc/kernel/signal.c b/arch/openrisc/kernel/signal.c
    new file mode 100644
    index 0000000..5f759c7
    --- /dev/null
    +++ b/arch/openrisc/kernel/signal.c
    @@ -0,0 +1,396 @@
    +/*
    + * OpenRISC signal.c
    + *
    + * Linux architectural port borrowing liberally from similar works of
    + * others. All original copyrights apply as per the original source
    + * declaration.
    + *
    + * Modifications for the OpenRISC architecture:
    + * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
    + * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
    + *
    + * This program is free software; you can redistribute it and/or
    + * modify it under the terms of the GNU General Public License
    + * as published by the Free Software Foundation; either version
    + * 2 of the License, or (at your option) any later version.
    + */
    +
    +#include <linux/sched.h>
    +#include <linux/mm.h>
    +#include <linux/smp.h>
    +#include <linux/kernel.h>
    +#include <linux/signal.h>
    +#include <linux/errno.h>
    +#include <linux/wait.h>
    +#include <linux/ptrace.h>
    +#include <linux/unistd.h>
    +#include <linux/stddef.h>
    +#include <linux/tracehook.h>
    +
    +#include <asm/processor.h>
    +#include <asm/ucontext.h>
    +#include <asm/uaccess.h>
    +
    +#define DEBUG_SIG 0
    +
    +#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
    +
    +asmlinkage long
    +_sys_sigaltstack(const stack_t *uss, stack_t *uoss, struct pt_regs *regs)
    +{
    + return do_sigaltstack(uss, uoss, regs->sp);
    +}
    +
    +struct rt_sigframe {
    + struct siginfo *pinfo;
    + void *puc;
    + struct siginfo info;
    + struct ucontext uc;
    + unsigned char retcode[16]; /* trampoline code */
    +};
    +
    +static int restore_sigcontext(struct pt_regs *regs, struct sigcontext *sc)
    +{
    + unsigned int err = 0;
    + unsigned long old_usp;
    +
    + /* Alwys make any pending restarted system call return -EINTR */
    + current_thread_info()->restart_block.fn = do_no_restart_syscall;
    +
    + /* restore the regs from &sc->regs (same as sc, since regs is first)
    + * (sc is already checked for VERIFY_READ since the sigframe was
    + * checked in sys_sigreturn previously)
    + */
    +
    + if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
    + goto badframe;
    +
    + /* make sure the SM-bit is cleared so user-mode cannot fool us */
    + regs->sr &= ~SPR_SR_SM;
    +
    + /* restore the old USP as it was before we stacked the sc etc.
    + * (we cannot just pop the sigcontext since we aligned the sp and
    + * stuff after pushing it)
    + */
    +
    + err |= __get_user(old_usp, &sc->usp);
    +
    + regs->sp = old_usp;
    +
    + /* TODO: the other ports use regs->orig_XX to disable syscall checks
    + * after this completes, but we don't use that mechanism. maybe we can
    + * use it now ?
    + */
    +
    + return err;
    +
    +badframe:
    + return 1;
    +}
    +
    +asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
    +{
    + struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
    + sigset_t set;
    + stack_t st;
    +
    + /*
    + * Since we stacked the signal on a dword boundary,
    + * then frame should be dword aligned here. If it's
    + * not, then the user is trying to mess with us.
    + */
    + if (((long)frame) & 3)
    + goto badframe;
    +
    + if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
    + goto badframe;
    + if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
    + goto badframe;
    +
    + sigdelsetmask(&set, ~_BLOCKABLE);
    + spin_lock_irq(&current->sighand->siglock);
    + current->blocked = set;
    + recalc_sigpending();
    + spin_unlock_irq(&current->sighand->siglock);
    +
    + if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
    + goto badframe;
    +
    + if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
    + goto badframe;
    + /* It is more difficult to avoid calling this function than to
    + call it and ignore errors. */
    + do_sigaltstack(&st, NULL, regs->sp);
    +
    + return regs->gpr[11];
    +
    +badframe:
    + force_sig(SIGSEGV, current);
    + return 0;
    +}
    +
    +/*
    + * Set up a signal frame.
    + */
    +
    +static int setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs,
    + unsigned long mask)
    +{
    + int err = 0;
    + unsigned long usp = regs->sp;
    +
    + /* copy the regs. they are first in sc so we can use sc directly */
    +
    + err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));
    +
    + /* then some other stuff */
    +
    + err |= __put_user(mask, &sc->oldmask);
    +
    + err |= __put_user(usp, &sc->usp);
    +
    + return err;
    +}
    +
    +static inline unsigned long align_sigframe(unsigned long sp)
    +{
    + return sp & ~3UL;
    +}
    +
    +/*
    + * Work out where the signal frame should go. It's either on the user stack
    + * or the alternate stack.
    + */
    +
    +static inline void __user *get_sigframe(struct k_sigaction *ka,
    + struct pt_regs *regs, size_t frame_size)
    +{
    + unsigned long sp = regs->sp;
    + int onsigstack = on_sig_stack(sp);
    +
    + /* redzone */
    + sp -= STACK_FRAME_OVERHEAD;
    +
    + /* This is the X/Open sanctioned signal stack switching. */
    + if ((ka->sa.sa_flags & SA_ONSTACK) && !onsigstack) {
    + if (current->sas_ss_size)
    + sp = current->sas_ss_sp + current->sas_ss_size;
    + }
    +
    + sp = align_sigframe(sp - frame_size);
    +
    + /*
    + * If we are on the alternate signal stack and would overflow it, don't.
    + * Return an always-bogus address instead so we will die with SIGSEGV.
    + */
    + if (onsigstack && !likely(on_sig_stack(sp)))
    + return (void __user *)-1L;
    +
    + return (void __user *)sp;
    +}
    +
    +/* grab and setup a signal frame.
    + *
    + * basically we stack a lot of state info, and arrange for the
    + * user-mode program to return to the kernel using either a
    + * trampoline which performs the syscall sigreturn, or a provided
    + * user-mode trampoline.
    + */
    +static void setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
    + sigset_t *set, struct pt_regs *regs)
    +{
    + struct rt_sigframe *frame;
    + unsigned long return_ip;
    + int err = 0;
    +
    + frame = get_sigframe(ka, regs, sizeof(*frame));
    +
    + if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
    + goto give_sigsegv;
    +
    + err |= __put_user(&frame->info, &frame->pinfo);
    + err |= __put_user(&frame->uc, &frame->puc);
    +
    + if (ka->sa.sa_flags & SA_SIGINFO)
    + err |= copy_siginfo_to_user(&frame->info, info);
    + if (err)
    + goto give_sigsegv;
    +
    + /* Clear all the bits of the ucontext we don't use. */
    + err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
    + err |= __put_user(0, &frame->uc.uc_flags);
    + err |= __put_user(NULL, &frame->uc.uc_link);
    + err |= __put_user((void *)current->sas_ss_sp,
    + &frame->uc.uc_stack.ss_sp);
    + err |= __put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags);
    + err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
    + err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
    +
    + err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
    +
    + if (err)
    + goto give_sigsegv;
    +
    + /* trampoline - the desired return ip is the retcode itself */
    + return_ip = (unsigned long)&frame->retcode;
    + /* This is l.ori r11,r0,__NR_sigreturn, l.sys 1 */
    + err |= __put_user(0xa960, (short *)(frame->retcode + 0));
    + err |= __put_user(__NR_rt_sigreturn, (short *)(frame->retcode + 2));
    + err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
    + err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
    +
    + if (err)
    + goto give_sigsegv;
    +
    + /* TODO what is the current->exec_domain stuff and invmap ? */
    +
    + /* Set up registers for signal handler */
    + regs->pc = (unsigned long)ka->sa.sa_handler; /* what we enter NOW */
    + regs->gpr[9] = (unsigned long)return_ip; /* what we enter LATER */
    + regs->gpr[3] = (unsigned long)sig; /* arg 1: signo */
    + regs->gpr[4] = (unsigned long)&frame->info; /* arg 2: (siginfo_t*) */
    + regs->gpr[5] = (unsigned long)&frame->uc; /* arg 3: ucontext */
    +
    + /* actually move the usp to reflect the stacked frame */
    + regs->sp = (unsigned long)frame;
    +
    + return;
    +
    +give_sigsegv:
    + if (sig == SIGSEGV)
    + ka->sa.sa_handler = SIG_DFL;
    + force_sig(SIGSEGV, current);
    +}
    +
    +static inline void
    +handle_signal(unsigned long sig,
    + siginfo_t *info, struct k_sigaction *ka,
    + sigset_t *oldset, struct pt_regs *regs)
    +{
    + setup_rt_frame(sig, ka, info, oldset, regs);
    +
    + if (ka->sa.sa_flags & SA_ONESHOT)
    + ka->sa.sa_handler = SIG_DFL;
    +
    + spin_lock_irq(&current->sighand->siglock);
    + sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
    + if (!(ka->sa.sa_flags & SA_NODEFER))
    + sigaddset(&current->blocked, sig);
    + recalc_sigpending();
    +
    + spin_unlock_irq(&current->sighand->siglock);
    +}
    +
    +/*
    + * 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.
    + *
    + * Also note that the regs structure given here as an argument, is the latest
    + * pushed pt_regs. It may or may not be the same as the first pushed registers
    + * when the initial usermode->kernelmode transition took place. Therefore
    + * we can use user_mode(regs) to see if we came directly from kernel or user
    + * mode below.
    + */
    +
    +void do_signal(struct pt_regs *regs)
    +{
    + siginfo_t info;
    + int signr;
    + struct k_sigaction ka;
    +
    + /*
    + * 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(regs))
    + return;
    +
    + signr = get_signal_to_deliver(&info, &ka, regs, NULL);
    +
    + /* If we are coming out of a syscall then we need
    + * to check if the syscall was interrupted and wants to be
    + * restarted after handling the signal. If so, the original
    + * syscall number is put back into r11 and the PC rewound to
    + * point at the l.sys instruction that resulted in the
    + * original syscall. Syscall results other than the four
    + * below mean that the syscall executed to completion and no
    + * restart is necessary.
    + */
    + if (regs->syscallno) {
    + int restart = 0;
    +
    + switch (regs->gpr[11]) {
    + case -ERESTART_RESTARTBLOCK:
    + case -ERESTARTNOHAND:
    + /* Restart if there is no signal handler */
    + restart = (signr <= 0);
    + break;
    + case -ERESTARTSYS:
    + /* Restart if there no signal handler or
    + * SA_RESTART flag is set */
    + restart = (signr <= 0 || (ka.sa.sa_flags & SA_RESTART));
    + break;
    + case -ERESTARTNOINTR:
    + /* Always restart */
    + restart = 1;
    + break;
    + }
    +
    + if (restart) {
    + if (regs->gpr[11] == -ERESTART_RESTARTBLOCK)
    + regs->gpr[11] = __NR_restart_syscall;
    + else
    + regs->gpr[11] = regs->orig_gpr11;
    + regs->pc -= 4;
    + } else {
    + regs->gpr[11] = -EINTR;
    + }
    + }
    +
    + if (signr <= 0) {
    + /* no signal to deliver so we just put the saved sigmask
    + * back */
    + if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
    + clear_thread_flag(TIF_RESTORE_SIGMASK);
    + sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
    + }
    +
    + } else { /* signr > 0 */
    + sigset_t *oldset;
    +
    + if (current_thread_info()->flags & _TIF_RESTORE_SIGMASK)
    + oldset = &current->saved_sigmask;
    + else
    + oldset = &current->blocked;
    +
    + /* Whee! Actually deliver the signal. */
    + handle_signal(signr, &info, &ka, oldset, regs);
    + /* a signal was successfully delivered; the saved
    + * sigmask will have been stored in the signal frame,
    + * and will be restored by sigreturn, so we can simply
    + * clear the TIF_RESTORE_SIGMASK flag */
    + if (test_thread_flag(TIF_RESTORE_SIGMASK))
    + clear_thread_flag(TIF_RESTORE_SIGMASK);
    +
    + tracehook_signal_handler(signr, &info, &ka, regs,
    + test_thread_flag(TIF_SINGLESTEP));
    + }
    +
    + return;
    +}
    +
    +asmlinkage void do_notify_resume(struct pt_regs *regs)
    +{
    + if (current_thread_info()->flags & _TIF_SIGPENDING)
    + do_signal(regs);
    +
    + if (current_thread_info()->flags & _TIF_NOTIFY_RESUME) {
    + clear_thread_flag(TIF_NOTIFY_RESUME);
    + tracehook_notify_resume(regs);
    + if (current->replacement_session_keyring)
    + key_replace_session_keyring();
    + }
    +}
    --
    1.7.4.1


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