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linux/arch/um/sys-x86_64/signal.c
Jeff Dike 98c18238f1 [PATCH] uml: fix segfault on signal delivery 
This fixes a process segfault where a signal was being delivered such that a
new stack page needed to be allocated to hold the signal frame.  This was
tripping some logic in the page fault handler which wouldn't allocate the page
if the faulting address was more that 32 bytes lower than the current stack
pointer.  Since a signal frame is greater than 32 bytes, this exercised that
case.

It's fixed by updating the SP in the pt_regs before starting to copy the
signal frame.  Since those are the registers that will be copied on to the
stack, we have to be careful to put the original SP, not the new one which
points to the signal frame, on the stack.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:38 -08:00

311 lines
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/*
* Copyright (C) 2003 PathScale, Inc.
* Licensed under the GPL
*/
#include "linux/stddef.h"
#include "linux/errno.h"
#include "linux/personality.h"
#include "linux/ptrace.h"
#include "asm/current.h"
#include "asm/uaccess.h"
#include "asm/sigcontext.h"
#include "asm/ptrace.h"
#include "asm/arch/ucontext.h"
#include "choose-mode.h"
#include "sysdep/ptrace.h"
#include "frame_kern.h"
#ifdef CONFIG_MODE_SKAS
#include "skas.h"
static int copy_sc_from_user_skas(struct pt_regs *regs,
struct sigcontext *from)
{
int err = 0;
#define GETREG(regs, regno, sc, regname) \
__get_user((regs)->regs.skas.regs[(regno) / sizeof(unsigned long)], \
&(sc)->regname)
err |= GETREG(regs, R8, from, r8);
err |= GETREG(regs, R9, from, r9);
err |= GETREG(regs, R10, from, r10);
err |= GETREG(regs, R11, from, r11);
err |= GETREG(regs, R12, from, r12);
err |= GETREG(regs, R13, from, r13);
err |= GETREG(regs, R14, from, r14);
err |= GETREG(regs, R15, from, r15);
err |= GETREG(regs, RDI, from, rdi);
err |= GETREG(regs, RSI, from, rsi);
err |= GETREG(regs, RBP, from, rbp);
err |= GETREG(regs, RBX, from, rbx);
err |= GETREG(regs, RDX, from, rdx);
err |= GETREG(regs, RAX, from, rax);
err |= GETREG(regs, RCX, from, rcx);
err |= GETREG(regs, RSP, from, rsp);
err |= GETREG(regs, RIP, from, rip);
err |= GETREG(regs, EFLAGS, from, eflags);
err |= GETREG(regs, CS, from, cs);
#undef GETREG
return(err);
}
int copy_sc_to_user_skas(struct sigcontext *to, struct _fpstate *to_fp,
struct pt_regs *regs, unsigned long mask,
unsigned long sp)
{
struct faultinfo * fi = &current->thread.arch.faultinfo;
int err = 0;
err |= __put_user(0, &to->gs);
err |= __put_user(0, &to->fs);
#define PUTREG(regs, regno, sc, regname) \
__put_user((regs)->regs.skas.regs[(regno) / sizeof(unsigned long)], \
&(sc)->regname)
err |= PUTREG(regs, RDI, to, rdi);
err |= PUTREG(regs, RSI, to, rsi);
err |= PUTREG(regs, RBP, to, rbp);
/* Must use orignal RSP, which is passed in, rather than what's in
* the pt_regs, because that's already been updated to point at the
* signal frame.
*/
err |= __put_user(sp, &to->rsp);
err |= PUTREG(regs, RBX, to, rbx);
err |= PUTREG(regs, RDX, to, rdx);
err |= PUTREG(regs, RCX, to, rcx);
err |= PUTREG(regs, RAX, to, rax);
err |= PUTREG(regs, R8, to, r8);
err |= PUTREG(regs, R9, to, r9);
err |= PUTREG(regs, R10, to, r10);
err |= PUTREG(regs, R11, to, r11);
err |= PUTREG(regs, R12, to, r12);
err |= PUTREG(regs, R13, to, r13);
err |= PUTREG(regs, R14, to, r14);
err |= PUTREG(regs, R15, to, r15);
err |= PUTREG(regs, CS, to, cs); /* XXX x86_64 doesn't do this */
err |= __put_user(fi->cr2, &to->cr2);
err |= __put_user(fi->error_code, &to->err);
err |= __put_user(fi->trap_no, &to->trapno);
err |= PUTREG(regs, RIP, to, rip);
err |= PUTREG(regs, EFLAGS, to, eflags);
#undef PUTREG
err |= __put_user(mask, &to->oldmask);
return(err);
}
#endif
#ifdef CONFIG_MODE_TT
int copy_sc_from_user_tt(struct sigcontext *to, struct sigcontext *from,
int fpsize)
{
struct _fpstate *to_fp, *from_fp;
unsigned long sigs;
int err;
to_fp = to->fpstate;
sigs = to->oldmask;
err = copy_from_user(to, from, sizeof(*to));
from_fp = to->fpstate;
to->fpstate = to_fp;
to->oldmask = sigs;
if(to_fp != NULL)
err |= copy_from_user(to_fp, from_fp, fpsize);
return(err);
}
int copy_sc_to_user_tt(struct sigcontext *to, struct _fpstate *fp,
struct sigcontext *from, int fpsize, unsigned long sp)
{
struct _fpstate *to_fp, *from_fp;
int err;
to_fp = (fp ? fp : (struct _fpstate *) (to + 1));
from_fp = from->fpstate;
err = copy_to_user(to, from, sizeof(*to));
/* The SP in the sigcontext is the updated one for the signal
* delivery. The sp passed in is the original, and this needs
* to be restored, so we stick it in separately.
*/
err |= copy_to_user(&SC_SP(to), sp, sizeof(sp));
if(from_fp != NULL){
err |= copy_to_user(&to->fpstate, &to_fp, sizeof(to->fpstate));
err |= copy_to_user(to_fp, from_fp, fpsize);
}
return err;
}
#endif
static int copy_sc_from_user(struct pt_regs *to, void __user *from)
{
int ret;
ret = CHOOSE_MODE(copy_sc_from_user_tt(UPT_SC(&to->regs), from,
sizeof(struct _fpstate)),
copy_sc_from_user_skas(to, from));
return(ret);
}
static int copy_sc_to_user(struct sigcontext *to, struct _fpstate *fp,
struct pt_regs *from, unsigned long mask,
unsigned long sp)
{
return(CHOOSE_MODE(copy_sc_to_user_tt(to, fp, UPT_SC(&from->regs),
sizeof(*fp), sp),
copy_sc_to_user_skas(to, fp, from, mask, sp)));
}
struct rt_sigframe
{
char *pretcode;
struct ucontext uc;
struct siginfo info;
};
#define round_down(m, n) (((m) / (n)) * (n))
int setup_signal_stack_si(unsigned long stack_top, int sig,
struct k_sigaction *ka, struct pt_regs * regs,
siginfo_t *info, sigset_t *set)
{
struct rt_sigframe __user *frame;
struct _fpstate __user *fp = NULL;
unsigned long save_sp = PT_REGS_RSP(regs);
int err = 0;
struct task_struct *me = current;
frame = (struct rt_sigframe __user *)
round_down(stack_top - sizeof(struct rt_sigframe), 16) - 8;
frame = (struct rt_sigframe *) ((unsigned long) frame - 128);
if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
goto out;
#if 0 /* XXX */
if (save_i387(fp) < 0)
err |= -1;
#endif
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto out;
if (ka->sa.sa_flags & SA_SIGINFO) {
err |= copy_siginfo_to_user(&frame->info, info);
if (err)
goto out;
}
/* Update SP now because the page fault handler refuses to extend
* the stack if the faulting address is too far below the current
* SP, which frame now certainly is. If there's an error, the original
* value is restored on the way out.
* When writing the sigcontext to the stack, we have to write the
* original value, so that's passed to copy_sc_to_user, which does
* the right thing with it.
*/
PT_REGS_RSP(regs) = (unsigned long) frame;
/* Create the ucontext. */
err |= __put_user(0, &frame->uc.uc_flags);
err |= __put_user(0, &frame->uc.uc_link);
err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
err |= __put_user(sas_ss_flags(save_sp),
&frame->uc.uc_stack.ss_flags);
err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
err |= copy_sc_to_user(&frame->uc.uc_mcontext, fp, regs, set->sig[0],
save_sp);
err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
if (sizeof(*set) == 16) {
__put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
__put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
}
else
err |= __copy_to_user(&frame->uc.uc_sigmask, set,
sizeof(*set));
/* Set up to return from userspace. If provided, use a stub
already in userspace. */
/* x86-64 should always use SA_RESTORER. */
if (ka->sa.sa_flags & SA_RESTORER)
err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
else
/* could use a vstub here */
goto restore_sp;
if (err)
goto restore_sp;
/* Set up registers for signal handler */
{
struct exec_domain *ed = current_thread_info()->exec_domain;
if (unlikely(ed && ed->signal_invmap && sig < 32))
sig = ed->signal_invmap[sig];
}
PT_REGS_RDI(regs) = sig;
/* In case the signal handler was declared without prototypes */
PT_REGS_RAX(regs) = 0;
/* This also works for non SA_SIGINFO handlers because they expect the
next argument after the signal number on the stack. */
PT_REGS_RSI(regs) = (unsigned long) &frame->info;
PT_REGS_RDX(regs) = (unsigned long) &frame->uc;
PT_REGS_RIP(regs) = (unsigned long) ka->sa.sa_handler;
out:
return err;
restore_sp:
PT_REGS_RSP(regs) = save_sp;
return err;
}
long sys_rt_sigreturn(struct pt_regs *regs)
{
unsigned long sp = PT_REGS_SP(&current->thread.regs);
struct rt_sigframe __user *frame =
(struct rt_sigframe __user *)(sp - 8);
struct ucontext __user *uc = &frame->uc;
sigset_t set;
if(copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
goto segfault;
sigdelsetmask(&set, ~_BLOCKABLE);
spin_lock_irq(&current->sighand->siglock);
current->blocked = set;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
if(copy_sc_from_user(&current->thread.regs, &uc->uc_mcontext))
goto segfault;
/* Avoid ERESTART handling */
PT_REGS_SYSCALL_NR(&current->thread.regs) = -1;
return(PT_REGS_SYSCALL_RET(&current->thread.regs));
segfault:
force_sig(SIGSEGV, current);
return 0;
}
/*
* Overrides for Emacs so that we follow Linus's tabbing style.
* Emacs will notice this stuff at the end of the file and automatically
* adjust the settings for this buffer only. This must remain at the end
* of the file.
* ---------------------------------------------------------------------------
* Local variables:
* c-file-style: "linux"
* End:
*/
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