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linux/arch/xtensa/kernel/signal.c
Chris Zankel 44c64e6b15 [XTENSA] Add support for the sa_restorer function 
Supporting the sa_restorer function allows for better security
since the sigreturn system call doesn't need to be placed on
the stack, so the stack doesn't need to be executable. This
requires support from the c-library as it has to provide the
restorer function.

Signed-off-by: Chris Zankel <chris@zankel.net>
2008-02-13 17:42:31 -08:00

578 lines
14 KiB
C
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/*
* arch/xtensa/kernel/signal.c
*
* Default platform functions.
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2005, 2006 Tensilica Inc.
* Copyright (C) 1991, 1992 Linus Torvalds
* 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
*
* Chris Zankel <chris@zankel.net>
* Joe Taylor <joe@tensilica.com>
*/
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/personality.h>
#include <linux/freezer.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/coprocessor.h>
#include <asm/unistd.h>
#define DEBUG_SIG 0
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
asmlinkage int do_signal(struct pt_regs *regs, sigset_t *oldset);
extern struct task_struct *coproc_owners[];
struct rt_sigframe
{
struct siginfo info;
struct ucontext uc;
struct {
xtregs_opt_t opt;
xtregs_user_t user;
#if XTENSA_HAVE_COPROCESSORS
xtregs_coprocessor_t cp;
#endif
} xtregs;
unsigned char retcode[6];
unsigned int window[4];
};
/*
* Flush register windows stored in pt_regs to stack.
* Returns 1 for errors.
*/
int
flush_window_regs_user(struct pt_regs *regs)
{
const unsigned long ws = regs->windowstart;
const unsigned long wb = regs->windowbase;
unsigned long sp = 0;
unsigned long wm;
int err = 1;
int base;
/* Return if no other frames. */
if (regs->wmask == 1)
return 0;
/* Rotate windowmask and skip empty frames. */
wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
/* For call8 or call12 frames, we need the previous stack pointer. */
if ((regs->wmask & 2) == 0)
if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
goto errout;
/* Spill frames to stack. */
while (base < XCHAL_NUM_AREGS / 4) {
int m = (wm >> base);
int inc = 0;
/* Save registers a4..a7 (call8) or a4...a11 (call12) */
if (m & 2) { /* call4 */
inc = 1;
} else if (m & 4) { /* call8 */
if (copy_to_user((void*)(sp - 32),
&regs->areg[(base + 1) * 4], 16))
goto errout;
inc = 2;
} else if (m & 8) { /* call12 */
if (copy_to_user((void*)(sp - 48),
&regs->areg[(base + 1) * 4], 32))
goto errout;
inc = 3;
}
/* Save current frame a0..a3 under next SP */
sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
if (copy_to_user((void*)(sp - 16), &regs->areg[base * 4], 16))
goto errout;
/* Get current stack pointer for next loop iteration. */
sp = regs->areg[base * 4 + 1];
base += inc;
}
regs->wmask = 1;
regs->windowstart = 1 << wb;
return 0;
errout:
return err;
}
/*
* Note: We don't copy double exception 'regs', we have to finish double exc.
* first before we return to signal handler! This dbl.exc.handler might cause
* another double exception, but I think we are fine as the situation is the
* same as if we had returned to the signal handerl and got an interrupt
* immediately...
*/
static int
setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
{
struct sigcontext __user *sc = &frame->uc.uc_mcontext;
struct thread_info *ti = current_thread_info();
int err = 0;
#define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
COPY(pc);
COPY(ps);
COPY(lbeg);
COPY(lend);
COPY(lcount);
COPY(sar);
#undef COPY
err |= flush_window_regs_user(regs);
err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
err |= __put_user(0, &sc->sc_xtregs);
if (err)
return err;
#if XTENSA_HAVE_COPROCESSORS
coprocessor_flush_all(ti);
coprocessor_release_all(ti);
err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
sizeof (frame->xtregs.cp));
#endif
err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
sizeof (xtregs_opt_t));
err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
sizeof (xtregs_user_t));
err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
return err;
}
static int
restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
{
struct sigcontext __user *sc = &frame->uc.uc_mcontext;
struct thread_info *ti = current_thread_info();
unsigned int err = 0;
unsigned long ps;
#define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
COPY(pc);
COPY(lbeg);
COPY(lend);
COPY(lcount);
COPY(sar);
#undef COPY
/* All registers were flushed to stack. Start with a prestine frame. */
regs->wmask = 1;
regs->windowbase = 0;
regs->windowstart = 1;
regs->syscall = -1; /* disable syscall checks */
/* For PS, restore only PS.CALLINC.
* Assume that all other bits are either the same as for the signal
* handler, or the user mode value doesn't matter (e.g. PS.OWB).
*/
err |= __get_user(ps, &sc->sc_ps);
regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
/* Additional corruption checks */
if ((regs->lcount > 0)
&& ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
err = 1;
err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
if (err)
return err;
/* The signal handler may have used coprocessors in which
* case they are still enabled. We disable them to force a
* reloading of the original task's CP state by the lazy
* context-switching mechanisms of CP exception handling.
* Also, we essentially discard any coprocessor state that the
* signal handler created. */
#if XTENSA_HAVE_COPROCESSORS
coprocessor_release_all(ti);
err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
sizeof (frame->xtregs.cp));
#endif
err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
sizeof (xtregs_user_t));
err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
sizeof (xtregs_opt_t));
return err;
}
/*
* Do a signal return; undo the signal stack.
*/
asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
long a4, long a5, struct pt_regs *regs)
{
struct rt_sigframe __user *frame;
sigset_t set;
int ret;
if (regs->depc > 64)
panic("rt_sigreturn in double exception!\n");
frame = (struct rt_sigframe __user *) regs->areg[1];
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))
goto badframe;
ret = regs->areg[2];
if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->areg[1]) == -EFAULT)
goto badframe;
return ret;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
/*
* Set up a signal frame.
*/
static int
gen_return_code(unsigned char *codemem)
{
int err = 0;
/*
* The 12-bit immediate is really split up within the 24-bit MOVI
* instruction. As long as the above system call numbers fit within
* 8-bits, the following code works fine. See the Xtensa ISA for
* details.
*/
#if __NR_rt_sigreturn > 255
# error Generating the MOVI instruction below breaks!
#endif
#ifdef __XTENSA_EB__ /* Big Endian version */
/* Generate instruction: MOVI a2, __NR_rt_sigreturn */
err |= __put_user(0x22, &codemem[0]);
err |= __put_user(0x0a, &codemem[1]);
err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
/* Generate instruction: SYSCALL */
err |= __put_user(0x00, &codemem[3]);
err |= __put_user(0x05, &codemem[4]);
err |= __put_user(0x00, &codemem[5]);
#elif defined __XTENSA_EL__ /* Little Endian version */
/* Generate instruction: MOVI a2, __NR_rt_sigreturn */
err |= __put_user(0x22, &codemem[0]);
err |= __put_user(0xa0, &codemem[1]);
err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
/* Generate instruction: SYSCALL */
err |= __put_user(0x00, &codemem[3]);
err |= __put_user(0x50, &codemem[4]);
err |= __put_user(0x00, &codemem[5]);
#else
# error Must use compiler for Xtensa processors.
#endif
/* Flush generated code out of the data cache */
if (err == 0) {
__invalidate_icache_range((unsigned long)codemem, 6UL);
__flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
}
return err;
}
static void setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
sigset_t *set, struct pt_regs *regs)
{
struct rt_sigframe *frame;
int err = 0;
int signal;
unsigned long sp, ra;
sp = regs->areg[1];
if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! on_sig_stack(sp)) {
sp = current->sas_ss_sp + current->sas_ss_size;
}
frame = (void *)((sp - sizeof(*frame)) & -16ul);
if (regs->depc > 64)
panic ("Double exception sys_sigreturn\n");
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
goto give_sigsegv;
}
signal = current_thread_info()->exec_domain
&& current_thread_info()->exec_domain->signal_invmap
&& sig < 32
? current_thread_info()->exec_domain->signal_invmap[sig]
: sig;
if (ka->sa.sa_flags & SA_SIGINFO) {
err |= copy_siginfo_to_user(&frame->info, info);
}
/* Create the user context. */
err |= __put_user(0, &frame->uc.uc_flags);
err |= __put_user(0, &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->areg[1]),
&frame->uc.uc_stack.ss_flags);
err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
err |= setup_sigcontext(frame, regs);
err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
if (ka->sa.sa_flags & SA_RESTORER) {
ra = (unsigned long)ka->sa.sa_restorer;
} else {
/* Create sys_rt_sigreturn syscall in stack frame */
err |= gen_return_code(frame->retcode);
if (err) {
goto give_sigsegv;
}
ra = (unsigned long) frame->retcode;
}
/*
* Create signal handler execution context.
* Return context not modified until this point.
*/
/* Set up registers for signal handler */
start_thread(regs, (unsigned long) ka->sa.sa_handler,
(unsigned long) frame);
/* Set up a stack frame for a call4
* Note: PS.CALLINC is set to one by start_thread
*/
regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
regs->areg[6] = (unsigned long) signal;
regs->areg[7] = (unsigned long) &frame->info;
regs->areg[8] = (unsigned long) &frame->uc;
/* Set access mode to USER_DS. Nomenclature is outdated, but
* functionality is used in uaccess.h
*/
set_fs(USER_DS);
#if DEBUG_SIG
printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
current->comm, current->pid, signal, frame, regs->pc);
#endif
return;
give_sigsegv:
if (sig == SIGSEGV)
ka->sa.sa_handler = SIG_DFL;
force_sig(SIGSEGV, current);
}
/*
* Atomically swap in the new signal mask, and wait for a signal.
*/
asmlinkage long xtensa_rt_sigsuspend(sigset_t __user *unewset,
size_t sigsetsize,
long a2, long a3, long a4, long a5,
struct pt_regs *regs)
{
sigset_t saveset, newset;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
if (copy_from_user(&newset, unewset, sizeof(newset)))
return -EFAULT;
sigdelsetmask(&newset, ~_BLOCKABLE);
spin_lock_irq(&current->sighand->siglock);
saveset = current->blocked;
current->blocked = newset;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
regs->areg[2] = -EINTR;
while (1) {
current->state = TASK_INTERRUPTIBLE;
schedule();
if (do_signal(regs, &saveset))
return -EINTR;
}
}
asmlinkage long xtensa_sigaltstack(const stack_t __user *uss,
stack_t __user *uoss,
long a2, long a3, long a4, long a5,
struct pt_regs *regs)
{
return do_sigaltstack(uss, uoss, regs->areg[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.
*
* Note that we go through the signals twice: once to check the signals that
* the kernel can handle, and then we build all the user-level signal handling
* stack-frames in one go after that.
*/
int do_signal(struct pt_regs *regs, sigset_t *oldset)
{
siginfo_t info;
int signr;
struct k_sigaction ka;
if (!user_mode(regs))
return 0;
if (try_to_freeze())
goto no_signal;
if (!oldset)
oldset = &current->blocked;
task_pt_regs(current)->icountlevel = 0;
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
/* Are we from a system call? */
if ((signed)regs->syscall >= 0) {
/* If so, check system call restarting.. */
switch (regs->areg[2]) {
case -ERESTARTNOHAND:
case -ERESTART_RESTARTBLOCK:
regs->areg[2] = -EINTR;
break;
case -ERESTARTSYS:
if (!(ka.sa.sa_flags & SA_RESTART)) {
regs->areg[2] = -EINTR;
break;
}
/* fallthrough */
case -ERESTARTNOINTR:
regs->areg[2] = regs->syscall;
regs->pc -= 3;
break;
default:
/* nothing to do */
if (regs->areg[2] != 0)
break;
}
}
/* Whee! Actually deliver the signal. */
/* Set up the stack frame */
setup_frame(signr, &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, signr);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
if (current->ptrace & PT_SINGLESTEP)
task_pt_regs(current)->icountlevel = 1;
return 1;
}
no_signal:
/* Did we come from a system call? */
if ((signed) regs->syscall >= 0) {
/* Restart the system call - no handlers present */
switch (regs->areg[2]) {
case -ERESTARTNOHAND:
case -ERESTARTSYS:
case -ERESTARTNOINTR:
regs->areg[2] = regs->syscall;
regs->pc -= 3;
break;
case -ERESTART_RESTARTBLOCK:
regs->areg[2] = __NR_restart_syscall;
regs->pc -= 3;
break;
}
}
if (current->ptrace & PT_SINGLESTEP)
task_pt_regs(current)->icountlevel = 1;
return 0;
}
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