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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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