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linux-next/arch/arm/kernel/signal.c
Arnd Bergmann 2af68df02f ARM: 6892/1: handle ptrace requests to change PC during interrupted system calls 
GDB's interrupt.exp test cases currenly fail on ARM.  The problem is how do_signal
handled restarting interrupted system calls:

The entry.S assembler code determines that we come from a system call; and that
information is passed as "syscall" parameter to do_signal.  That routine then
calls get_signal_to_deliver [*] and if a signal is to be delivered, calls into
handle_signal.  If a system call is to be restarted either after the signal
handler returns, or if no handler is to be called in the first place, the PC
is updated after the get_signal_to_deliver call, either in handle_signal (if
we have a handler) or at the end of do_signal (otherwise).

Now the problem is that during [*], the call to get_signal_to_deliver, a ptrace
intercept may happen.  During this intercept, the debugger may change registers,
including the PC.  This is done by GDB if it wants to execute an "inferior call",
i.e. the execution of some code in the debugged program triggered by GDB.

To this purpose, GDB will save all registers, allocate a stack frame, set up
PC and arguments as appropriate for the call, and point the link register to
a dummy breakpoint instruction.  Once the process is restarted, it will execute
the call and then trap back to the debugger, at which point GDB will restore
all registers and continue original execution.

This generally works fine.  However, now consider what happens when GDB attempts
to do exactly that while the process was interrupted during execution of a to-be-
restarted system call:  do_signal is called with the syscall flag set; it calls
get_signal_to_deliver, at which point the debugger takes over and changes the PC
to point to a completely different place.  Now get_signal_to_deliver returns
without a signal to deliver; but now do_signal decides it should be restarting
a system call, and decrements the PC by 2 or 4 -- so it now points to 2 or 4
bytes before the function GDB wants to call -- which leads to a subsequent crash.

To fix this problem, two things need to be supported:
- do_signal must be able to recognize that get_signal_to_deliver changed the PC
  to a different location, and skip the restart-syscall sequence
- once the debugger has restored all registers at the end of the inferior call
  sequence, do_signal must recognize that *now* it needs to restart the pending
  system call, even though it was now entered from a breakpoint instead of an
  actual svc instruction

This set of issues is solved on other platforms, usually by one of two
mechanisms:

- The status information "do_signal is handling a system call that may need
  restarting" is itself carried in some register that can be accessed via
  ptrace.  This is e.g. on Intel the "orig_eax" register; on Sparc the kernel
  defines a magic extra bit in the flags register for this purpose.
  This allows GDB to manage that state: reset it when doing an inferior call,
  and restore it after the call is finished.

- On s390, do_signal transparently handles this problem without requiring
  GDB interaction, by performing system call restarting in the following
  way: first, adjust the PC as necessary for restarting the call.  Then,
  call get_signal_to_deliver; and finally just continue execution at the
  PC.  This way, if GDB does not change the PC, everything is as before.
  If GDB *does* change the PC, execution will simply continue there --
  and once GDB restores the PC it saved at that point, it will automatically
  point to the *restarted* system call.  (There is the minor twist how to
  handle system calls that do *not* need restarting -- do_signal will undo
  the PC change in this case, after get_signal_to_deliver has returned, and
  only if ptrace did not change the PC during that call.)

Because there does not appear to be any obvious register to carry the
syscall-restart information on ARM, we'd either have to introduce a new
artificial ptrace register just for that purpose, or else handle the issue
transparently like on s390.  The patch below implements the second option;
using this patch makes the interrupt.exp test cases pass on ARM, with no
regression in the GDB test suite otherwise.

Cc: patches@linaro.org
Signed-off-by: Ulrich Weigand <ulrich.weigand@linaro.org>
Signed-off-by: Arnd Bergmann <arnd.bergmann@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-05-12 10:52:00 +01:00

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/*
* linux/arch/arm/kernel/signal.c
*
* Copyright (C) 1995-2009 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/personality.h>
#include <linux/freezer.h>
#include <linux/uaccess.h>
#include <linux/tracehook.h>
#include <asm/elf.h>
#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/unistd.h>
#include <asm/vfp.h>
#include "signal.h"
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
/*
* For ARM syscalls, we encode the syscall number into the instruction.
*/
#define SWI_SYS_SIGRETURN (0xef000000|(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE))
#define SWI_SYS_RT_SIGRETURN (0xef000000|(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE))
#define SWI_SYS_RESTART (0xef000000|__NR_restart_syscall|__NR_OABI_SYSCALL_BASE)
/*
* With EABI, the syscall number has to be loaded into r7.
*/
#define MOV_R7_NR_SIGRETURN (0xe3a07000 | (__NR_sigreturn - __NR_SYSCALL_BASE))
#define MOV_R7_NR_RT_SIGRETURN (0xe3a07000 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))
/*
* For Thumb syscalls, we pass the syscall number via r7. We therefore
* need two 16-bit instructions.
*/
#define SWI_THUMB_SIGRETURN (0xdf00 << 16 | 0x2700 | (__NR_sigreturn - __NR_SYSCALL_BASE))
#define SWI_THUMB_RT_SIGRETURN (0xdf00 << 16 | 0x2700 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))
const unsigned long sigreturn_codes[7] = {
MOV_R7_NR_SIGRETURN, SWI_SYS_SIGRETURN, SWI_THUMB_SIGRETURN,
MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN,
};
/*
* Either we support OABI only, or we have EABI with the OABI
* compat layer enabled. In the later case we don't know if
* user space is EABI or not, and if not we must not clobber r7.
* Always using the OABI syscall solves that issue and works for
* all those cases.
*/
const unsigned long syscall_restart_code[2] = {
SWI_SYS_RESTART, /* swi __NR_restart_syscall */
0xe49df004, /* ldr pc, [sp], #4 */
};
/*
* atomically swap in the new signal mask, and wait for a signal.
*/
asmlinkage int sys_sigsuspend(int restart, unsigned long oldmask, old_sigset_t mask)
{
mask &= _BLOCKABLE;
spin_lock_irq(&current->sighand->siglock);
current->saved_sigmask = current->blocked;
siginitset(&current->blocked, mask);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
current->state = TASK_INTERRUPTIBLE;
schedule();
set_restore_sigmask();
return -ERESTARTNOHAND;
}
asmlinkage int
sys_sigaction(int sig, const struct old_sigaction __user *act,
struct old_sigaction __user *oact)
{
struct k_sigaction new_ka, old_ka;
int ret;
if (act) {
old_sigset_t mask;
if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
__get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
__get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
return -EFAULT;
__get_user(new_ka.sa.sa_flags, &act->sa_flags);
__get_user(mask, &act->sa_mask);
siginitset(&new_ka.sa.sa_mask, mask);
}
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
__put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
__put_user(old_ka.sa.sa_restorer, &oact->sa_restorer))
return -EFAULT;
__put_user(old_ka.sa.sa_flags, &oact->sa_flags);
__put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
}
return ret;
}
#ifdef CONFIG_CRUNCH
static int preserve_crunch_context(struct crunch_sigframe __user *frame)
{
char kbuf[sizeof(*frame) + 8];
struct crunch_sigframe *kframe;
/* the crunch context must be 64 bit aligned */
kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
kframe->magic = CRUNCH_MAGIC;
kframe->size = CRUNCH_STORAGE_SIZE;
crunch_task_copy(current_thread_info(), &kframe->storage);
return __copy_to_user(frame, kframe, sizeof(*frame));
}
static int restore_crunch_context(struct crunch_sigframe __user *frame)
{
char kbuf[sizeof(*frame) + 8];
struct crunch_sigframe *kframe;
/* the crunch context must be 64 bit aligned */
kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
if (__copy_from_user(kframe, frame, sizeof(*frame)))
return -1;
if (kframe->magic != CRUNCH_MAGIC ||
kframe->size != CRUNCH_STORAGE_SIZE)
return -1;
crunch_task_restore(current_thread_info(), &kframe->storage);
return 0;
}
#endif
#ifdef CONFIG_IWMMXT
static int preserve_iwmmxt_context(struct iwmmxt_sigframe *frame)
{
char kbuf[sizeof(*frame) + 8];
struct iwmmxt_sigframe *kframe;
/* the iWMMXt context must be 64 bit aligned */
kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
kframe->magic = IWMMXT_MAGIC;
kframe->size = IWMMXT_STORAGE_SIZE;
iwmmxt_task_copy(current_thread_info(), &kframe->storage);
return __copy_to_user(frame, kframe, sizeof(*frame));
}
static int restore_iwmmxt_context(struct iwmmxt_sigframe *frame)
{
char kbuf[sizeof(*frame) + 8];
struct iwmmxt_sigframe *kframe;
/* the iWMMXt context must be 64 bit aligned */
kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
if (__copy_from_user(kframe, frame, sizeof(*frame)))
return -1;
if (kframe->magic != IWMMXT_MAGIC ||
kframe->size != IWMMXT_STORAGE_SIZE)
return -1;
iwmmxt_task_restore(current_thread_info(), &kframe->storage);
return 0;
}
#endif
#ifdef CONFIG_VFP
static int preserve_vfp_context(struct vfp_sigframe __user *frame)
{
struct thread_info *thread = current_thread_info();
struct vfp_hard_struct *h = &thread->vfpstate.hard;
const unsigned long magic = VFP_MAGIC;
const unsigned long size = VFP_STORAGE_SIZE;
int err = 0;
vfp_sync_hwstate(thread);
__put_user_error(magic, &frame->magic, err);
__put_user_error(size, &frame->size, err);
/*
* Copy the floating point registers. There can be unused
* registers see asm/hwcap.h for details.
*/
err |= __copy_to_user(&frame->ufp.fpregs, &h->fpregs,
sizeof(h->fpregs));
/*
* Copy the status and control register.
*/
__put_user_error(h->fpscr, &frame->ufp.fpscr, err);
/*
* Copy the exception registers.
*/
__put_user_error(h->fpexc, &frame->ufp_exc.fpexc, err);
__put_user_error(h->fpinst, &frame->ufp_exc.fpinst, err);
__put_user_error(h->fpinst2, &frame->ufp_exc.fpinst2, err);
return err ? -EFAULT : 0;
}
static int restore_vfp_context(struct vfp_sigframe __user *frame)
{
struct thread_info *thread = current_thread_info();
struct vfp_hard_struct *h = &thread->vfpstate.hard;
unsigned long magic;
unsigned long size;
unsigned long fpexc;
int err = 0;
__get_user_error(magic, &frame->magic, err);
__get_user_error(size, &frame->size, err);
if (err)
return -EFAULT;
if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
return -EINVAL;
/*
* Copy the floating point registers. There can be unused
* registers see asm/hwcap.h for details.
*/
err |= __copy_from_user(&h->fpregs, &frame->ufp.fpregs,
sizeof(h->fpregs));
/*
* Copy the status and control register.
*/
__get_user_error(h->fpscr, &frame->ufp.fpscr, err);
/*
* Sanitise and restore the exception registers.
*/
__get_user_error(fpexc, &frame->ufp_exc.fpexc, err);
/* Ensure the VFP is enabled. */
fpexc |= FPEXC_EN;
/* Ensure FPINST2 is invalid and the exception flag is cleared. */
fpexc &= ~(FPEXC_EX | FPEXC_FP2V);
h->fpexc = fpexc;
__get_user_error(h->fpinst, &frame->ufp_exc.fpinst, err);
__get_user_error(h->fpinst2, &frame->ufp_exc.fpinst2, err);
if (!err)
vfp_flush_hwstate(thread);
return err ? -EFAULT : 0;
}
#endif
/*
* Do a signal return; undo the signal stack. These are aligned to 64-bit.
*/
struct sigframe {
struct ucontext uc;
unsigned long retcode[2];
};
struct rt_sigframe {
struct siginfo info;
struct sigframe sig;
};
static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
{
struct aux_sigframe __user *aux;
sigset_t set;
int err;
err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
if (err == 0) {
sigdelsetmask(&set, ~_BLOCKABLE);
spin_lock_irq(&current->sighand->siglock);
current->blocked = set;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
}
__get_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
__get_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
__get_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
__get_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
__get_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
__get_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
__get_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
__get_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
__get_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
__get_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
__get_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
__get_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
__get_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
__get_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
__get_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
__get_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
__get_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);
err |= !valid_user_regs(regs);
aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
#ifdef CONFIG_CRUNCH
if (err == 0)
err |= restore_crunch_context(&aux->crunch);
#endif
#ifdef CONFIG_IWMMXT
if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
err |= restore_iwmmxt_context(&aux->iwmmxt);
#endif
#ifdef CONFIG_VFP
if (err == 0)
err |= restore_vfp_context(&aux->vfp);
#endif
return err;
}
asmlinkage int sys_sigreturn(struct pt_regs *regs)
{
struct sigframe __user *frame;
/* Always make any pending restarted system calls return -EINTR */
current_thread_info()->restart_block.fn = do_no_restart_syscall;
/*
* Since we stacked the signal on a 64-bit boundary,
* then 'sp' should be word aligned here. If it's
* not, then the user is trying to mess with us.
*/
if (regs->ARM_sp & 7)
goto badframe;
frame = (struct sigframe __user *)regs->ARM_sp;
if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
goto badframe;
if (restore_sigframe(regs, frame))
goto badframe;
return regs->ARM_r0;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
{
struct rt_sigframe __user *frame;
/* Always make any pending restarted system calls return -EINTR */
current_thread_info()->restart_block.fn = do_no_restart_syscall;
/*
* Since we stacked the signal on a 64-bit boundary,
* then 'sp' should be word aligned here. If it's
* not, then the user is trying to mess with us.
*/
if (regs->ARM_sp & 7)
goto badframe;
frame = (struct rt_sigframe __user *)regs->ARM_sp;
if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
goto badframe;
if (restore_sigframe(regs, &frame->sig))
goto badframe;
if (do_sigaltstack(&frame->sig.uc.uc_stack, NULL, regs->ARM_sp) == -EFAULT)
goto badframe;
return regs->ARM_r0;
badframe:
force_sig(SIGSEGV, current);
return 0;
}
static int
setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
{
struct aux_sigframe __user *aux;
int err = 0;
__put_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
__put_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
__put_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
__put_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
__put_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
__put_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
__put_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
__put_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
__put_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
__put_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
__put_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
__put_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
__put_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
__put_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
__put_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
__put_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
__put_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);
__put_user_error(current->thread.trap_no, &sf->uc.uc_mcontext.trap_no, err);
__put_user_error(current->thread.error_code, &sf->uc.uc_mcontext.error_code, err);
__put_user_error(current->thread.address, &sf->uc.uc_mcontext.fault_address, err);
__put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);
err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
#ifdef CONFIG_CRUNCH
if (err == 0)
err |= preserve_crunch_context(&aux->crunch);
#endif
#ifdef CONFIG_IWMMXT
if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
err |= preserve_iwmmxt_context(&aux->iwmmxt);
#endif
#ifdef CONFIG_VFP
if (err == 0)
err |= preserve_vfp_context(&aux->vfp);
#endif
__put_user_error(0, &aux->end_magic, err);
return err;
}
static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, int framesize)
{
unsigned long sp = regs->ARM_sp;
void __user *frame;
/*
* This is the X/Open sanctioned signal stack switching.
*/
if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
sp = current->sas_ss_sp + current->sas_ss_size;
/*
* ATPCS B01 mandates 8-byte alignment
*/
frame = (void __user *)((sp - framesize) & ~7);
/*
* Check that we can actually write to the signal frame.
*/
if (!access_ok(VERIFY_WRITE, frame, framesize))
frame = NULL;
return frame;
}
static int
setup_return(struct pt_regs *regs, struct k_sigaction *ka,
unsigned long __user *rc, void __user *frame, int usig)
{
unsigned long handler = (unsigned long)ka->sa.sa_handler;
unsigned long retcode;
int thumb = 0;
unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
cpsr |= PSR_ENDSTATE;
/*
* Maybe we need to deliver a 32-bit signal to a 26-bit task.
*/
if (ka->sa.sa_flags & SA_THIRTYTWO)
cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
#ifdef CONFIG_ARM_THUMB
if (elf_hwcap & HWCAP_THUMB) {
/*
* The LSB of the handler determines if we're going to
* be using THUMB or ARM mode for this signal handler.
*/
thumb = handler & 1;
if (thumb) {
cpsr |= PSR_T_BIT;
#if __LINUX_ARM_ARCH__ >= 7
/* clear the If-Then Thumb-2 execution state */
cpsr &= ~PSR_IT_MASK;
#endif
} else
cpsr &= ~PSR_T_BIT;
}
#endif
if (ka->sa.sa_flags & SA_RESTORER) {
retcode = (unsigned long)ka->sa.sa_restorer;
} else {
unsigned int idx = thumb << 1;
if (ka->sa.sa_flags & SA_SIGINFO)
idx += 3;
if (__put_user(sigreturn_codes[idx], rc) ||
__put_user(sigreturn_codes[idx+1], rc+1))
return 1;
if (cpsr & MODE32_BIT) {
/*
* 32-bit code can use the new high-page
* signal return code support.
*/
retcode = KERN_SIGRETURN_CODE + (idx << 2) + thumb;
} else {
/*
* Ensure that the instruction cache sees
* the return code written onto the stack.
*/
flush_icache_range((unsigned long)rc,
(unsigned long)(rc + 2));
retcode = ((unsigned long)rc) + thumb;
}
}
regs->ARM_r0 = usig;
regs->ARM_sp = (unsigned long)frame;
regs->ARM_lr = retcode;
regs->ARM_pc = handler;
regs->ARM_cpsr = cpsr;
return 0;
}
static int
setup_frame(int usig, struct k_sigaction *ka, sigset_t *set, struct pt_regs *regs)
{
struct sigframe __user *frame = get_sigframe(ka, regs, sizeof(*frame));
int err = 0;
if (!frame)
return 1;
/*
* Set uc.uc_flags to a value which sc.trap_no would never have.
*/
__put_user_error(0x5ac3c35a, &frame->uc.uc_flags, err);
err |= setup_sigframe(frame, regs, set);
if (err == 0)
err = setup_return(regs, ka, frame->retcode, frame, usig);
return err;
}
static int
setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
sigset_t *set, struct pt_regs *regs)
{
struct rt_sigframe __user *frame = get_sigframe(ka, regs, sizeof(*frame));
stack_t stack;
int err = 0;
if (!frame)
return 1;
err |= copy_siginfo_to_user(&frame->info, info);
__put_user_error(0, &frame->sig.uc.uc_flags, err);
__put_user_error(NULL, &frame->sig.uc.uc_link, err);
memset(&stack, 0, sizeof(stack));
stack.ss_sp = (void __user *)current->sas_ss_sp;
stack.ss_flags = sas_ss_flags(regs->ARM_sp);
stack.ss_size = current->sas_ss_size;
err |= __copy_to_user(&frame->sig.uc.uc_stack, &stack, sizeof(stack));
err |= setup_sigframe(&frame->sig, regs, set);
if (err == 0)
err = setup_return(regs, ka, frame->sig.retcode, frame, usig);
if (err == 0) {
/*
* For realtime signals we must also set the second and third
* arguments for the signal handler.
* -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
*/
regs->ARM_r1 = (unsigned long)&frame->info;
regs->ARM_r2 = (unsigned long)&frame->sig.uc;
}
return err;
}
/*
* OK, we're invoking a handler
*/
static int
handle_signal(unsigned long sig, struct k_sigaction *ka,
siginfo_t *info, sigset_t *oldset,
struct pt_regs * regs)
{
struct thread_info *thread = current_thread_info();
struct task_struct *tsk = current;
int usig = sig;
int ret;
/*
* translate the signal
*/
if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
usig = thread->exec_domain->signal_invmap[usig];
/*
* Set up the stack frame
*/
if (ka->sa.sa_flags & SA_SIGINFO)
ret = setup_rt_frame(usig, ka, info, oldset, regs);
else
ret = setup_frame(usig, ka, oldset, regs);
/*
* Check that the resulting registers are actually sane.
*/
ret |= !valid_user_regs(regs);
if (ret != 0) {
force_sigsegv(sig, tsk);
return ret;
}
/*
* Block the signal if we were successful.
*/
spin_lock_irq(&tsk->sighand->siglock);
sigorsets(&tsk->blocked, &tsk->blocked,
&ka->sa.sa_mask);
if (!(ka->sa.sa_flags & SA_NODEFER))
sigaddset(&tsk->blocked, sig);
recalc_sigpending();
spin_unlock_irq(&tsk->sighand->siglock);
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, int syscall)
{
unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
struct k_sigaction ka;
siginfo_t info;
int signr;
/*
* 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;
/*
* If we were from a system call, check for system call restarting...
*/
if (syscall) {
continue_addr = regs->ARM_pc;
restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
retval = regs->ARM_r0;
/*
* Prepare for system call restart. We do this here so that a
* debugger will see the already changed PSW.
*/
switch (retval) {
case -ERESTARTNOHAND:
case -ERESTARTSYS:
case -ERESTARTNOINTR:
regs->ARM_r0 = regs->ARM_ORIG_r0;
regs->ARM_pc = restart_addr;
break;
case -ERESTART_RESTARTBLOCK:
regs->ARM_r0 = -EINTR;
break;
}
}
if (try_to_freeze())
goto no_signal;
/*
* Get the signal to deliver. When running under ptrace, at this
* point the debugger may change all our registers ...
*/
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
sigset_t *oldset;
/*
* Depending on the signal settings we may need to revert the
* decision to restart the system call. But skip this if a
* debugger has chosen to restart at a different PC.
*/
if (regs->ARM_pc == restart_addr) {
if (retval == -ERESTARTNOHAND
|| (retval == -ERESTARTSYS
&& !(ka.sa.sa_flags & SA_RESTART))) {
regs->ARM_r0 = -EINTR;
regs->ARM_pc = continue_addr;
}
}
if (test_thread_flag(TIF_RESTORE_SIGMASK))
oldset = &current->saved_sigmask;
else
oldset = &current->blocked;
if (handle_signal(signr, &ka, &info, 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 TIF_RESTORE_SIGMASK flag.
*/
if (test_thread_flag(TIF_RESTORE_SIGMASK))
clear_thread_flag(TIF_RESTORE_SIGMASK);
}
return;
}
no_signal:
if (syscall) {
/*
* Handle restarting a different system call. As above,
* if a debugger has chosen to restart at a different PC,
* ignore the restart.
*/
if (retval == -ERESTART_RESTARTBLOCK
&& regs->ARM_pc == continue_addr) {
if (thumb_mode(regs)) {
regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE;
regs->ARM_pc -= 2;
} else {
#if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT)
regs->ARM_r7 = __NR_restart_syscall;
regs->ARM_pc -= 4;
#else
u32 __user *usp;
regs->ARM_sp -= 4;
usp = (u32 __user *)regs->ARM_sp;
if (put_user(regs->ARM_pc, usp) == 0) {
regs->ARM_pc = KERN_RESTART_CODE;
} else {
regs->ARM_sp += 4;
force_sigsegv(0, current);
}
#endif
}
}
/* If there's no signal to deliver, 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);
}
}
}
asmlinkage void
do_notify_resume(struct pt_regs *regs, unsigned int thread_flags, int syscall)
{
if (thread_flags & _TIF_SIGPENDING)
do_signal(regs, syscall);
if (thread_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
tracehook_notify_resume(regs);
if (current->replacement_session_keyring)
key_replace_session_keyring();
}
}
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