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linux/arch/xtensa/kernel/signal.c
Max Filippov 062b1c19b8 xtensa: clean up access to spilled registers locations 
Define macros SPILL_SLOT* that return a reference to the stack location
of the spill slot for specific register and use them instead of opencoded
address calculations.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
2017-05-01 10:34:43 -07:00

500 lines
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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/tracehook.h>
#include <linux/sched/task_stack.h>
#include <asm/ucontext.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/coprocessor.h>
#include <asm/unistd.h>
#define DEBUG_SIG 0
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(&SPILL_SLOT_CALL8(sp, 4),
&regs->areg[(base + 1) * 4], 16))
goto errout;
inc = 2;
} else if (m & 8) { /* call12 */
if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4),
&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(&SPILL_SLOT(sp, 0), &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;
/* Always make any pending restarted system calls return -EINTR */
current->restart_block.fn = do_no_restart_syscall;
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;
set_current_blocked(&set);
if (restore_sigcontext(regs, frame))
goto badframe;
ret = regs->areg[2];
if (restore_altstack(&frame->uc.uc_stack))
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 int setup_frame(struct ksignal *ksig, sigset_t *set,
struct pt_regs *regs)
{
struct rt_sigframe *frame;
int err = 0, sig = ksig->sig;
unsigned long sp, ra, tp;
sp = regs->areg[1];
if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
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))) {
return -EFAULT;
}
if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
err |= copy_siginfo_to_user(&frame->info, &ksig->info);
}
/* Create the user context. */
err |= __put_user(0, &frame->uc.uc_flags);
err |= __put_user(0, &frame->uc.uc_link);
err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
err |= setup_sigcontext(frame, regs);
err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
if (ksig->ka.sa.sa_flags & SA_RESTORER) {
ra = (unsigned long)ksig->ka.sa.sa_restorer;
} else {
/* Create sys_rt_sigreturn syscall in stack frame */
err |= gen_return_code(frame->retcode);
if (err) {
return -EFAULT;
}
ra = (unsigned long) frame->retcode;
}
/*
* Create signal handler execution context.
* Return context not modified until this point.
*/
/* Set up registers for signal handler; preserve the threadptr */
tp = regs->threadptr;
start_thread(regs, (unsigned long) ksig->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) sig;
regs->areg[7] = (unsigned long) &frame->info;
regs->areg[8] = (unsigned long) &frame->uc;
regs->threadptr = tp;
#if DEBUG_SIG
printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
current->comm, current->pid, sig, frame, regs->pc);
#endif
return 0;
}
/*
* 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.
*/
static void do_signal(struct pt_regs *regs)
{
struct ksignal ksig;
task_pt_regs(current)->icountlevel = 0;
if (get_signal(&ksig)) {
int ret;
/* 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 (!(ksig.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 */
ret = setup_frame(&ksig, sigmask_to_save(), regs);
signal_setup_done(ret, &ksig, 0);
if (current->ptrace & PT_SINGLESTEP)
task_pt_regs(current)->icountlevel = 1;
return;
}
/* 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 there's no signal to deliver, we just restore the saved mask. */
restore_saved_sigmask();
if (current->ptrace & PT_SINGLESTEP)
task_pt_regs(current)->icountlevel = 1;
return;
}
void do_notify_resume(struct pt_regs *regs)
{
if (test_thread_flag(TIF_SIGPENDING))
do_signal(regs);
if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
tracehook_notify_resume(regs);
}
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