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linux-stable/arch/tile/kernel/signal.c
Chris Metcalf 81711cee93 arch/tile: handle rt_sigreturn() more cleanly 
The current tile rt_sigreturn() syscall pattern uses the common idiom
of loading up pt_regs with all the saved registers from the time of
the signal, then anticipating the fact that we will clobber the ABI
"return value" register (r0) as we return from the syscall by setting
the rt_sigreturn return value to whatever random value was in the pt_regs
for r0.

However, this breaks in our 64-bit kernel when running "compat" tasks,
since we always sign-extend the "return value" register to properly
handle returned pointers that are in the upper 2GB of the 32-bit compat
address space.  Doing this to the sigreturn path then causes occasional
random corruption of the 64-bit r0 register.

Instead, we stop doing the crazy "load the return-value register"
hack in sigreturn.  We already have some sigreturn-specific assembly
code that we use to pass the pt_regs pointer to C code.  We extend that
code to also set the link register to point to a spot a few instructions
after the usual syscall return address so we don't clobber the saved r0.
Now it no longer matters what the rt_sigreturn syscall returns, and the
pt_regs structure can be cleanly and completely reloaded.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
2010-12-17 16:59:29 -05:00

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/*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright 2010 Tilera Corporation. All Rights Reserved.
*
* 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, version 2.
*
* This program 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, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for
* more details.
*/
#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/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/suspend.h>
#include <linux/ptrace.h>
#include <linux/elf.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/sigframe.h>
#include <asm/syscalls.h>
#include <arch/interrupts.h>
#define DEBUG_SIG 0
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
SYSCALL_DEFINE3(sigaltstack, const stack_t __user *, uss,
stack_t __user *, uoss, struct pt_regs *, regs)
{
return do_sigaltstack(uss, uoss, regs->sp);
}
/*
* Do a signal return; undo the signal stack.
*/
int restore_sigcontext(struct pt_regs *regs,
struct sigcontext __user *sc)
{
int err = 0;
int i;
/* Always make any pending restarted system calls return -EINTR */
current_thread_info()->restart_block.fn = do_no_restart_syscall;
/*
* Enforce that sigcontext is like pt_regs, and doesn't mess
* up our stack alignment rules.
*/
BUILD_BUG_ON(sizeof(struct sigcontext) != sizeof(struct pt_regs));
BUILD_BUG_ON(sizeof(struct sigcontext) % 8 != 0);
for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
err |= __get_user(regs->regs[i], &sc->gregs[i]);
/* Ensure that the PL is always set to USER_PL. */
regs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(regs->ex1));
regs->faultnum = INT_SWINT_1_SIGRETURN;
return err;
}
/* The assembly shim for this function arranges to ignore the return value. */
SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs)
{
struct rt_sigframe __user *frame =
(struct rt_sigframe __user *)(regs->sp);
sigset_t set;
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 (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
goto badframe;
return 0;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
/*
* Set up a signal frame.
*/
int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
{
int i, err = 0;
for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
err |= __put_user(regs->regs[i], &sc->gregs[i]);
return err;
}
/*
* Determine which stack to use..
*/
static inline void __user *get_sigframe(struct k_sigaction *ka,
struct pt_regs *regs,
size_t frame_size)
{
unsigned long sp;
/* Default to using normal stack */
sp = regs->sp;
/*
* 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 (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
return (void __user __force *)-1UL;
/* This is the X/Open sanctioned signal stack switching. */
if (ka->sa.sa_flags & SA_ONSTACK) {
if (sas_ss_flags(sp) == 0)
sp = current->sas_ss_sp + current->sas_ss_size;
}
sp -= frame_size;
/*
* Align the stack pointer according to the TILE ABI,
* i.e. so that on function entry (sp & 15) == 0.
*/
sp &= -16UL;
return (void __user *) sp;
}
static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
sigset_t *set, struct pt_regs *regs)
{
unsigned long restorer;
struct rt_sigframe __user *frame;
int err = 0;
int usig;
frame = get_sigframe(ka, regs, sizeof(*frame));
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto give_sigsegv;
usig = current_thread_info()->exec_domain
&& current_thread_info()->exec_domain->signal_invmap
&& sig < 32
? current_thread_info()->exec_domain->signal_invmap[sig]
: sig;
/* Always write at least the signal number for the stack backtracer. */
if (ka->sa.sa_flags & SA_SIGINFO) {
/* At sigreturn time, restore the callee-save registers too. */
err |= copy_siginfo_to_user(&frame->info, info);
regs->flags |= PT_FLAGS_RESTORE_REGS;
} else {
err |= __put_user(info->si_signo, &frame->info.si_signo);
}
/* Create the ucontext. */
err |= __clear_user(&frame->save_area, sizeof(frame->save_area));
err |= __put_user(0, &frame->uc.uc_flags);
err |= __put_user(NULL, &frame->uc.uc_link);
err |= __put_user((void __user *)(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);
err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
if (err)
goto give_sigsegv;
restorer = VDSO_BASE;
if (ka->sa.sa_flags & SA_RESTORER)
restorer = (unsigned long) ka->sa.sa_restorer;
/*
* Set up registers for signal handler.
* Registers that we don't modify keep the value they had from
* user-space at the time we took the signal.
* We always pass siginfo and mcontext, regardless of SA_SIGINFO,
* since some things rely on this (e.g. glibc's debug/segfault.c).
*/
regs->pc = (unsigned long) ka->sa.sa_handler;
regs->ex1 = PL_ICS_EX1(USER_PL, 1); /* set crit sec in handler */
regs->sp = (unsigned long) frame;
regs->lr = restorer;
regs->regs[0] = (unsigned long) usig;
regs->regs[1] = (unsigned long) &frame->info;
regs->regs[2] = (unsigned long) &frame->uc;
regs->flags |= PT_FLAGS_CALLER_SAVES;
/*
* Notify any tracer that was single-stepping it.
* The tracer may want to single-step inside the
* handler too.
*/
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
return 0;
give_sigsegv:
force_sigsegv(sig, current);
return -EFAULT;
}
/*
* OK, we're invoking a handler
*/
static int handle_signal(unsigned long sig, siginfo_t *info,
struct k_sigaction *ka, sigset_t *oldset,
struct pt_regs *regs)
{
int ret;
/* Are we from a system call? */
if (regs->faultnum == INT_SWINT_1) {
/* If so, check system call restarting.. */
switch (regs->regs[0]) {
case -ERESTART_RESTARTBLOCK:
case -ERESTARTNOHAND:
regs->regs[0] = -EINTR;
break;
case -ERESTARTSYS:
if (!(ka->sa.sa_flags & SA_RESTART)) {
regs->regs[0] = -EINTR;
break;
}
/* fallthrough */
case -ERESTARTNOINTR:
/* Reload caller-saves to restore r0..r5 and r10. */
regs->flags |= PT_FLAGS_CALLER_SAVES;
regs->regs[0] = regs->orig_r0;
regs->pc -= 8;
}
}
/* Set up the stack frame */
#ifdef CONFIG_COMPAT
if (is_compat_task())
ret = compat_setup_rt_frame(sig, ka, info, oldset, regs);
else
#endif
ret = setup_rt_frame(sig, ka, info, oldset, regs);
if (ret == 0) {
/* This code is only called from system calls or from
* the work_pending path in the return-to-user code, and
* either way we can re-enable interrupts unconditionally.
*/
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);
}
return ret;
}
/*
* 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.
*/
void do_signal(struct pt_regs *regs)
{
siginfo_t info;
int signr;
struct k_sigaction ka;
sigset_t *oldset;
/*
* i386 will check if we're coming from kernel mode and bail out
* here. In my experience this just turns weird crashes into
* weird spin-hangs. But if we find a case where this seems
* helpful, we can reinstate the check on "!user_mode(regs)".
*/
if (current_thread_info()->status & TS_RESTORE_SIGMASK)
oldset = &current->saved_sigmask;
else
oldset = &current->blocked;
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
/* Whee! Actually deliver the signal. */
if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
/*
* 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 TS_RESTORE_SIGMASK flag.
*/
current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
}
goto done;
}
/* Did we come from a system call? */
if (regs->faultnum == INT_SWINT_1) {
/* Restart the system call - no handlers present */
switch (regs->regs[0]) {
case -ERESTARTNOHAND:
case -ERESTARTSYS:
case -ERESTARTNOINTR:
regs->flags |= PT_FLAGS_CALLER_SAVES;
regs->regs[0] = regs->orig_r0;
regs->pc -= 8;
break;
case -ERESTART_RESTARTBLOCK:
regs->flags |= PT_FLAGS_CALLER_SAVES;
regs->regs[TREG_SYSCALL_NR] = __NR_restart_syscall;
regs->pc -= 8;
break;
}
}
/* If there's no signal to deliver, just put the saved sigmask back. */
if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
}
done:
/* Avoid double syscall restart if there are nested signals. */
regs->faultnum = INT_SWINT_1_SIGRETURN;
}
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