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linux/arch/powerpc/kernel/signal_64.c
David Woodhouse 401d1f029b [PATCH] syscall entry/exit revamp 
This cleanup patch speeds up the null syscall path on ppc64 by about 3%,
and brings the ppc32 and ppc64 code slightly closer together.

The ppc64 code was checking current_thread_info()->flags twice in the
syscall exit path; once for TIF_SYSCALL_T_OR_A before disabling
interrupts, and then again for TIF_SIGPENDING|TIF_NEED_RESCHED etc after
disabling interrupts. Now we do the same as ppc32 -- check the flags
only once in the fast path, and re-enable interrupts if necessary in the
ptrace case.

The patch abolishes the 'syscall_noerror' member of struct thread_info
and replaces it with a TIF_NOERROR bit in the flags, which is handled in
the slow path. This shortens the syscall entry code, which no longer
needs to clear syscall_noerror.

The patch adds a TIF_SAVE_NVGPRS flag which causes the syscall exit slow
path to save the non-volatile GPRs into a signal frame. This removes the
need for the assembly wrappers around sys_sigsuspend(),
sys_rt_sigsuspend(), et al which existed solely to save those registers
in advance. It also means I don't have to add new wrappers for ppoll()
and pselect(), which is what I was supposed to be doing when I got
distracted into this...

Finally, it unifies the ppc64 and ppc32 methods of handling syscall exit
directly into a signal handler (as required by sigsuspend et al) by
introducing a TIF_RESTOREALL flag which causes _all_ the registers to be
reloaded from the pt_regs by taking the ret_from_exception path, instead
of the normal syscall exit path which stomps on the callee-saved GPRs.

It appears to pass an LTP test run on ppc64, and passes basic testing on
ppc32 too. Brief tests of ptrace functionality with strace and gdb also
appear OK. I wouldn't send it to Linus for 2.6.15 just yet though :)

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2006-01-09 14:49:01 +11:00

594 lines
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/*
* linux/arch/ppc64/kernel/signal.c
*
* PowerPC version
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
*
* Derived from "arch/i386/kernel/signal.c"
* Copyright (C) 1991, 1992 Linus Torvalds
* 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
*
* 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; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/config.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.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/elf.h>
#include <linux/ptrace.h>
#include <linux/module.h>
#include <asm/sigcontext.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>
#include <asm/vdso.h>
#define DEBUG_SIG 0
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
#define GP_REGS_SIZE min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
#define FP_REGS_SIZE sizeof(elf_fpregset_t)
#define TRAMP_TRACEBACK 3
#define TRAMP_SIZE 6
/*
* When we have signals to deliver, we set up on the user stack,
* going down from the original stack pointer:
* 1) a rt_sigframe struct which contains the ucontext
* 2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
* frame for the signal handler.
*/
struct rt_sigframe {
/* sys_rt_sigreturn requires the ucontext be the first field */
struct ucontext uc;
unsigned long _unused[2];
unsigned int tramp[TRAMP_SIZE];
struct siginfo *pinfo;
void *puc;
struct siginfo info;
/* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
char abigap[288];
} __attribute__ ((aligned (16)));
/*
* Atomically swap in the new signal mask, and wait for a signal.
*/
long sys_rt_sigsuspend(sigset_t __user *unewset, size_t sigsetsize, int p3, int p4,
int p6, int p7, 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->result = -EINTR;
regs->gpr[3] = EINTR;
regs->ccr |= 0x10000000;
while (1) {
current->state = TASK_INTERRUPTIBLE;
schedule();
if (do_signal(&saveset, regs)) {
set_thread_flag(TIF_RESTOREALL);
return 0;
}
}
}
long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss, unsigned long r5,
unsigned long r6, unsigned long r7, unsigned long r8,
struct pt_regs *regs)
{
return do_sigaltstack(uss, uoss, regs->gpr[1]);
}
/*
* Set up the sigcontext for the signal frame.
*/
static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
int signr, sigset_t *set, unsigned long handler)
{
/* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
* process never used altivec yet (MSR_VEC is zero in pt_regs of
* the context). This is very important because we must ensure we
* don't lose the VRSAVE content that may have been set prior to
* the process doing its first vector operation
* Userland shall check AT_HWCAP to know wether it can rely on the
* v_regs pointer or not
*/
#ifdef CONFIG_ALTIVEC
elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
#endif
long err = 0;
flush_fp_to_thread(current);
#ifdef CONFIG_ALTIVEC
err |= __put_user(v_regs, &sc->v_regs);
/* save altivec registers */
if (current->thread.used_vr) {
flush_altivec_to_thread(current);
/* Copy 33 vec registers (vr0..31 and vscr) to the stack */
err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
/* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
* contains valid data.
*/
regs->msr |= MSR_VEC;
}
/* We always copy to/from vrsave, it's 0 if we don't have or don't
* use altivec.
*/
err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
#else /* CONFIG_ALTIVEC */
err |= __put_user(0, &sc->v_regs);
#endif /* CONFIG_ALTIVEC */
err |= __put_user(&sc->gp_regs, &sc->regs);
if (!FULL_REGS(regs)) {
/* Zero out the unsaved GPRs to avoid information
leak, and set TIF_SAVE_NVGPRS to ensure that the
registers do actually get saved later. */
memset(&regs->gpr[14], 0, 18 * sizeof(unsigned long));
set_thread_flag(TIF_SAVE_NVGPRS);
current_thread_info()->nvgprs_frame = &sc->gp_regs;
}
err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
err |= __put_user(signr, &sc->signal);
err |= __put_user(handler, &sc->handler);
if (set != NULL)
err |= __put_user(set->sig[0], &sc->oldmask);
return err;
}
/*
* Restore the sigcontext from the signal frame.
*/
static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
struct sigcontext __user *sc)
{
#ifdef CONFIG_ALTIVEC
elf_vrreg_t __user *v_regs;
#endif
unsigned long err = 0;
unsigned long save_r13 = 0;
elf_greg_t *gregs = (elf_greg_t *)regs;
#ifdef CONFIG_ALTIVEC
unsigned long msr;
#endif
int i;
/* If this is not a signal return, we preserve the TLS in r13 */
if (!sig)
save_r13 = regs->gpr[13];
/* copy everything before MSR */
err |= __copy_from_user(regs, &sc->gp_regs,
PT_MSR*sizeof(unsigned long));
/* skip MSR and SOFTE */
for (i = PT_MSR+1; i <= PT_RESULT; i++) {
if (i == PT_SOFTE)
continue;
err |= __get_user(gregs[i], &sc->gp_regs[i]);
}
if (!sig)
regs->gpr[13] = save_r13;
err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
if (set != NULL)
err |= __get_user(set->sig[0], &sc->oldmask);
#ifdef CONFIG_ALTIVEC
err |= __get_user(v_regs, &sc->v_regs);
err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
if (err)
return err;
/* Copy 33 vec registers (vr0..31 and vscr) from the stack */
if (v_regs != 0 && (msr & MSR_VEC) != 0)
err |= __copy_from_user(current->thread.vr, v_regs,
33 * sizeof(vector128));
else if (current->thread.used_vr)
memset(current->thread.vr, 0, 33 * sizeof(vector128));
/* Always get VRSAVE back */
if (v_regs != 0)
err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
else
current->thread.vrsave = 0;
#endif /* CONFIG_ALTIVEC */
#ifndef CONFIG_SMP
preempt_disable();
if (last_task_used_math == current)
last_task_used_math = NULL;
if (last_task_used_altivec == current)
last_task_used_altivec = NULL;
preempt_enable();
#endif
/* Force reload of FP/VEC */
regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
return err;
}
/*
* Allocate space for the signal frame
*/
static inline void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
size_t frame_size)
{
unsigned long newsp;
/* Default to using normal stack */
newsp = regs->gpr[1];
if (ka->sa.sa_flags & SA_ONSTACK) {
if (! on_sig_stack(regs->gpr[1]))
newsp = (current->sas_ss_sp + current->sas_ss_size);
}
return (void __user *)((newsp - frame_size) & -16ul);
}
/*
* Setup the trampoline code on the stack
*/
static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
{
int i;
long err = 0;
/* addi r1, r1, __SIGNAL_FRAMESIZE # Pop the dummy stackframe */
err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
/* li r0, __NR_[rt_]sigreturn| */
err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
/* sc */
err |= __put_user(0x44000002UL, &tramp[2]);
/* Minimal traceback info */
for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
err |= __put_user(0, &tramp[i]);
if (!err)
flush_icache_range((unsigned long) &tramp[0],
(unsigned long) &tramp[TRAMP_SIZE]);
return err;
}
/*
* Restore the user process's signal mask (also used by signal32.c)
*/
void restore_sigmask(sigset_t *set)
{
sigdelsetmask(set, ~_BLOCKABLE);
spin_lock_irq(&current->sighand->siglock);
current->blocked = *set;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
}
/*
* Handle {get,set,swap}_context operations
*/
int sys_swapcontext(struct ucontext __user *old_ctx,
struct ucontext __user *new_ctx,
long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
{
unsigned char tmp;
sigset_t set;
/* Context size is for future use. Right now, we only make sure
* we are passed something we understand
*/
if (ctx_size < sizeof(struct ucontext))
return -EINVAL;
if (old_ctx != NULL) {
if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
|| setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
|| __copy_to_user(&old_ctx->uc_sigmask,
&current->blocked, sizeof(sigset_t)))
return -EFAULT;
}
if (new_ctx == NULL)
return 0;
if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
|| __get_user(tmp, (u8 __user *) new_ctx)
|| __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
return -EFAULT;
/*
* If we get a fault copying the context into the kernel's
* image of the user's registers, we can't just return -EFAULT
* because the user's registers will be corrupted. For instance
* the NIP value may have been updated but not some of the
* other registers. Given that we have done the access_ok
* and successfully read the first and last bytes of the region
* above, this should only happen in an out-of-memory situation
* or if another thread unmaps the region containing the context.
* We kill the task with a SIGSEGV in this situation.
*/
if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
do_exit(SIGSEGV);
restore_sigmask(&set);
if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
do_exit(SIGSEGV);
/* This returns like rt_sigreturn */
set_thread_flag(TIF_RESTOREALL);
return 0;
}
/*
* Do a signal return; undo the signal stack.
*/
int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
unsigned long r6, unsigned long r7, unsigned long r8,
struct pt_regs *regs)
{
struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
sigset_t set;
/* Always make any pending restarted system calls return -EINTR */
current_thread_info()->restart_block.fn = do_no_restart_syscall;
if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
goto badframe;
if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
goto badframe;
restore_sigmask(&set);
if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
goto badframe;
/* do_sigaltstack expects a __user pointer and won't modify
* what's in there anyway
*/
do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
set_thread_flag(TIF_RESTOREALL);
return 0;
badframe:
#if DEBUG_SIG
printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
regs, uc, &uc->uc_mcontext);
#endif
force_sig(SIGSEGV, current);
return 0;
}
static int setup_rt_frame(int signr, struct k_sigaction *ka, siginfo_t *info,
sigset_t *set, struct pt_regs *regs)
{
/* Handler is *really* a pointer to the function descriptor for
* the signal routine. The first entry in the function
* descriptor is the entry address of signal and the second
* entry is the TOC value we need to use.
*/
func_descr_t __user *funct_desc_ptr;
struct rt_sigframe __user *frame;
unsigned long newsp = 0;
long err = 0;
frame = get_sigframe(ka, regs, sizeof(*frame));
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto badframe;
err |= __put_user(&frame->info, &frame->pinfo);
err |= __put_user(&frame->uc, &frame->puc);
err |= copy_siginfo_to_user(&frame->info, info);
if (err)
goto badframe;
/* Create the ucontext. */
err |= __put_user(0, &frame->uc.uc_flags);
err |= __put_user(0, &frame->uc.uc_link);
err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
err |= __put_user(sas_ss_flags(regs->gpr[1]),
&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, signr, NULL,
(unsigned long)ka->sa.sa_handler);
err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
if (err)
goto badframe;
/* Make sure signal handler doesn't get spurious FP exceptions */
current->thread.fpscr.val = 0;
/* Set up to return from userspace. */
if (vdso64_rt_sigtramp && current->thread.vdso_base) {
regs->link = current->thread.vdso_base + vdso64_rt_sigtramp;
} else {
err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
if (err)
goto badframe;
regs->link = (unsigned long) &frame->tramp[0];
}
funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
/* Allocate a dummy caller frame for the signal handler. */
newsp = (unsigned long)frame - __SIGNAL_FRAMESIZE;
err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
/* Set up "regs" so we "return" to the signal handler. */
err |= get_user(regs->nip, &funct_desc_ptr->entry);
regs->gpr[1] = newsp;
err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
regs->gpr[3] = signr;
regs->result = 0;
if (ka->sa.sa_flags & SA_SIGINFO) {
err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
regs->gpr[6] = (unsigned long) frame;
} else {
regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
}
if (err)
goto badframe;
return 1;
badframe:
#if DEBUG_SIG
printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
regs, frame, newsp);
#endif
force_sigsegv(signr, current);
return 0;
}
/*
* 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)
{
int ret;
/* Set up Signal Frame */
ret = setup_rt_frame(sig, ka, info, oldset, regs);
if (ret) {
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;
}
static inline void syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
{
switch ((int)regs->result) {
case -ERESTART_RESTARTBLOCK:
case -ERESTARTNOHAND:
/* ERESTARTNOHAND means that the syscall should only be
* restarted if there was no handler for the signal, and since
* we only get here if there is a handler, we dont restart.
*/
regs->result = -EINTR;
regs->gpr[3] = EINTR;
regs->ccr |= 0x10000000;
break;
case -ERESTARTSYS:
/* ERESTARTSYS means to restart the syscall if there is no
* handler or the handler was registered with SA_RESTART
*/
if (!(ka->sa.sa_flags & SA_RESTART)) {
regs->result = -EINTR;
regs->gpr[3] = EINTR;
regs->ccr |= 0x10000000;
break;
}
/* fallthrough */
case -ERESTARTNOINTR:
/* ERESTARTNOINTR means that the syscall should be
* called again after the signal handler returns.
*/
regs->gpr[3] = regs->orig_gpr3;
regs->nip -= 4;
regs->result = 0;
break;
}
}
/*
* 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.
*/
int do_signal(sigset_t *oldset, struct pt_regs *regs)
{
siginfo_t info;
int signr;
struct k_sigaction ka;
/*
* If the current thread is 32 bit - invoke the
* 32 bit signal handling code
*/
if (test_thread_flag(TIF_32BIT))
return do_signal32(oldset, regs);
if (!oldset)
oldset = &current->blocked;
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
/* Whee! Actually deliver the signal. */
if (TRAP(regs) == 0x0C00)
syscall_restart(regs, &ka);
/*
* Reenable the DABR before delivering the signal to
* user space. The DABR will have been cleared if it
* triggered inside the kernel.
*/
if (current->thread.dabr)
set_dabr(current->thread.dabr);
return handle_signal(signr, &ka, &info, oldset, regs);
}
if (TRAP(regs) == 0x0C00) { /* System Call! */
if ((int)regs->result == -ERESTARTNOHAND ||
(int)regs->result == -ERESTARTSYS ||
(int)regs->result == -ERESTARTNOINTR) {
regs->gpr[3] = regs->orig_gpr3;
regs->nip -= 4; /* Back up & retry system call */
regs->result = 0;
} else if ((int)regs->result == -ERESTART_RESTARTBLOCK) {
regs->gpr[0] = __NR_restart_syscall;
regs->nip -= 4;
regs->result = 0;
}
}
return 0;
}
EXPORT_SYMBOL(do_signal);
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