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kernel_optimize_test/arch/tile/kernel/compat_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 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>
struct compat_sigaction {
compat_uptr_t sa_handler;
compat_ulong_t sa_flags;
compat_uptr_t sa_restorer;
sigset_t sa_mask __packed;
};
struct compat_sigaltstack {
compat_uptr_t ss_sp;
int ss_flags;
compat_size_t ss_size;
};
struct compat_ucontext {
compat_ulong_t uc_flags;
compat_uptr_t uc_link;
struct compat_sigaltstack uc_stack;
struct sigcontext uc_mcontext;
sigset_t uc_sigmask; /* mask last for extensibility */
};
#define COMPAT_SI_PAD_SIZE ((SI_MAX_SIZE - 3 * sizeof(int)) / sizeof(int))
struct compat_siginfo {
int si_signo;
int si_errno;
int si_code;
union {
int _pad[COMPAT_SI_PAD_SIZE];
/* kill() */
struct {
unsigned int _pid; /* sender's pid */
unsigned int _uid; /* sender's uid */
} _kill;
/* POSIX.1b timers */
struct {
compat_timer_t _tid; /* timer id */
int _overrun; /* overrun count */
compat_sigval_t _sigval; /* same as below */
int _sys_private; /* not to be passed to user */
int _overrun_incr; /* amount to add to overrun */
} _timer;
/* POSIX.1b signals */
struct {
unsigned int _pid; /* sender's pid */
unsigned int _uid; /* sender's uid */
compat_sigval_t _sigval;
} _rt;
/* SIGCHLD */
struct {
unsigned int _pid; /* which child */
unsigned int _uid; /* sender's uid */
int _status; /* exit code */
compat_clock_t _utime;
compat_clock_t _stime;
} _sigchld;
/* SIGILL, SIGFPE, SIGSEGV, SIGBUS */
struct {
unsigned int _addr; /* faulting insn/memory ref. */
#ifdef __ARCH_SI_TRAPNO
int _trapno; /* TRAP # which caused the signal */
#endif
} _sigfault;
/* SIGPOLL */
struct {
int _band; /* POLL_IN, POLL_OUT, POLL_MSG */
int _fd;
} _sigpoll;
} _sifields;
};
struct compat_rt_sigframe {
unsigned char save_area[C_ABI_SAVE_AREA_SIZE]; /* caller save area */
struct compat_siginfo info;
struct compat_ucontext uc;
};
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
long compat_sys_rt_sigaction(int sig, struct compat_sigaction __user *act,
struct compat_sigaction __user *oact,
size_t sigsetsize)
{
struct k_sigaction new_sa, old_sa;
int ret = -EINVAL;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
goto out;
if (act) {
compat_uptr_t handler, restorer;
if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
__get_user(handler, &act->sa_handler) ||
__get_user(new_sa.sa.sa_flags, &act->sa_flags) ||
__get_user(restorer, &act->sa_restorer) ||
__copy_from_user(&new_sa.sa.sa_mask, &act->sa_mask,
sizeof(sigset_t)))
return -EFAULT;
new_sa.sa.sa_handler = compat_ptr(handler);
new_sa.sa.sa_restorer = compat_ptr(restorer);
}
ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
if (!ret && oact) {
if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
__put_user(ptr_to_compat(old_sa.sa.sa_handler),
&oact->sa_handler) ||
__put_user(ptr_to_compat(old_sa.sa.sa_restorer),
&oact->sa_restorer) ||
__put_user(old_sa.sa.sa_flags, &oact->sa_flags) ||
__copy_to_user(&oact->sa_mask, &old_sa.sa.sa_mask,
sizeof(sigset_t)))
return -EFAULT;
}
out:
return ret;
}
long compat_sys_rt_sigqueueinfo(int pid, int sig,
struct compat_siginfo __user *uinfo)
{
siginfo_t info;
int ret;
mm_segment_t old_fs = get_fs();
if (copy_siginfo_from_user32(&info, uinfo))
return -EFAULT;
set_fs(KERNEL_DS);
ret = sys_rt_sigqueueinfo(pid, sig, (siginfo_t __force __user *)&info);
set_fs(old_fs);
return ret;
}
int copy_siginfo_to_user32(struct compat_siginfo __user *to, siginfo_t *from)
{
int err;
if (!access_ok(VERIFY_WRITE, to, sizeof(struct compat_siginfo)))
return -EFAULT;
/* If you change siginfo_t structure, please make sure that
this code is fixed accordingly.
It should never copy any pad contained in the structure
to avoid security leaks, but must copy the generic
3 ints plus the relevant union member. */
err = __put_user(from->si_signo, &to->si_signo);
err |= __put_user(from->si_errno, &to->si_errno);
err |= __put_user((short)from->si_code, &to->si_code);
if (from->si_code < 0) {
err |= __put_user(from->si_pid, &to->si_pid);
err |= __put_user(from->si_uid, &to->si_uid);
err |= __put_user(ptr_to_compat(from->si_ptr), &to->si_ptr);
} else {
/*
* First 32bits of unions are always present:
* si_pid === si_band === si_tid === si_addr(LS half)
*/
err |= __put_user(from->_sifields._pad[0],
&to->_sifields._pad[0]);
switch (from->si_code >> 16) {
case __SI_FAULT >> 16:
break;
case __SI_CHLD >> 16:
err |= __put_user(from->si_utime, &to->si_utime);
err |= __put_user(from->si_stime, &to->si_stime);
err |= __put_user(from->si_status, &to->si_status);
/* FALL THROUGH */
default:
case __SI_KILL >> 16:
err |= __put_user(from->si_uid, &to->si_uid);
break;
case __SI_POLL >> 16:
err |= __put_user(from->si_fd, &to->si_fd);
break;
case __SI_TIMER >> 16:
err |= __put_user(from->si_overrun, &to->si_overrun);
err |= __put_user(ptr_to_compat(from->si_ptr),
&to->si_ptr);
break;
/* This is not generated by the kernel as of now. */
case __SI_RT >> 16:
case __SI_MESGQ >> 16:
err |= __put_user(from->si_uid, &to->si_uid);
err |= __put_user(from->si_int, &to->si_int);
break;
}
}
return err;
}
int copy_siginfo_from_user32(siginfo_t *to, struct compat_siginfo __user *from)
{
int err;
u32 ptr32;
if (!access_ok(VERIFY_READ, from, sizeof(struct compat_siginfo)))
return -EFAULT;
err = __get_user(to->si_signo, &from->si_signo);
err |= __get_user(to->si_errno, &from->si_errno);
err |= __get_user(to->si_code, &from->si_code);
err |= __get_user(to->si_pid, &from->si_pid);
err |= __get_user(to->si_uid, &from->si_uid);
err |= __get_user(ptr32, &from->si_ptr);
to->si_ptr = compat_ptr(ptr32);
return err;
}
long compat_sys_sigaltstack(const struct compat_sigaltstack __user *uss_ptr,
struct compat_sigaltstack __user *uoss_ptr,
struct pt_regs *regs)
{
stack_t uss, uoss;
int ret;
mm_segment_t seg;
if (uss_ptr) {
u32 ptr;
memset(&uss, 0, sizeof(stack_t));
if (!access_ok(VERIFY_READ, uss_ptr, sizeof(*uss_ptr)) ||
__get_user(ptr, &uss_ptr->ss_sp) ||
__get_user(uss.ss_flags, &uss_ptr->ss_flags) ||
__get_user(uss.ss_size, &uss_ptr->ss_size))
return -EFAULT;
uss.ss_sp = compat_ptr(ptr);
}
seg = get_fs();
set_fs(KERNEL_DS);
ret = do_sigaltstack(uss_ptr ? (stack_t __user __force *)&uss : NULL,
(stack_t __user __force *)&uoss,
(unsigned long)compat_ptr(regs->sp));
set_fs(seg);
if (ret >= 0 && uoss_ptr) {
if (!access_ok(VERIFY_WRITE, uoss_ptr, sizeof(*uoss_ptr)) ||
__put_user(ptr_to_compat(uoss.ss_sp), &uoss_ptr->ss_sp) ||
__put_user(uoss.ss_flags, &uoss_ptr->ss_flags) ||
__put_user(uoss.ss_size, &uoss_ptr->ss_size))
ret = -EFAULT;
}
return ret;
}
/* The assembly shim for this function arranges to ignore the return value. */
long compat_sys_rt_sigreturn(struct pt_regs *regs)
{
struct compat_rt_sigframe __user *frame =
(struct compat_rt_sigframe __user *) compat_ptr(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 (compat_sys_sigaltstack(&frame->uc.uc_stack, NULL, regs) != 0)
goto badframe;
return 0;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
/*
* Determine which stack to use..
*/
static inline void __user *compat_get_sigframe(struct k_sigaction *ka,
struct pt_regs *regs,
size_t frame_size)
{
unsigned long sp;
/* Default to using normal stack */
sp = (unsigned long)compat_ptr(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;
}
int compat_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
sigset_t *set, struct pt_regs *regs)
{
unsigned long restorer;
struct compat_rt_sigframe __user *frame;
int err = 0;
int usig;
frame = compat_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_user32(&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(0, &frame->uc.uc_link);
err |= __put_user(ptr_to_compat((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);
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 = ptr_to_compat_reg(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.
*/
regs->pc = ptr_to_compat_reg(ka->sa.sa_handler);
regs->ex1 = PL_ICS_EX1(USER_PL, 1); /* set crit sec in handler */
regs->sp = ptr_to_compat_reg(frame);
regs->lr = restorer;
regs->regs[0] = (unsigned long) usig;
if (ka->sa.sa_flags & SA_SIGINFO) {
/* Need extra arguments, so mark to restore caller-saves. */
regs->regs[1] = ptr_to_compat_reg(&frame->info);
regs->regs[2] = ptr_to_compat_reg(&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;
}
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