From dc5dc7e6d71ca9fd1ea01a1418150af3b2937489 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Wed, 7 May 2008 18:54:05 -0700 Subject: sparc: Fix SA_ONSTACK signal handling. We need to be more liberal about the alignment of the buffer given to us by sigaltstack(). The user should not need to be mindful of all of the alignment constraints we have for the stack frame. This mirrors how we handle this situation in clone() as well. Also, we align the stack even in non-SA_ONSTACK cases so that signals due to bad stack alignment can be delivered properly. This makes such errors easier to debug and recover from. Finally, add the sanity check x86 has to make sure we won't overflow the signal stack. This fixes glibc testcases nptl/tst-cancel20.c and nptl/tst-cancelx20.c Signed-off-by: David S. Miller --- arch/sparc/kernel/signal.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) (limited to 'arch/sparc/kernel/signal.c') diff --git a/arch/sparc/kernel/signal.c b/arch/sparc/kernel/signal.c index 3c312290c3c2..368157926d24 100644 --- a/arch/sparc/kernel/signal.c +++ b/arch/sparc/kernel/signal.c @@ -245,15 +245,29 @@ static inline int invalid_frame_pointer(void __user *fp, int fplen) static inline void __user *get_sigframe(struct sigaction *sa, struct pt_regs *regs, unsigned long framesize) { - unsigned long sp; + unsigned long sp = regs->u_regs[UREG_FP]; - sp = regs->u_regs[UREG_FP]; + /* + * 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 - framesize))) + return (void __user *) -1L; /* This is the X/Open sanctioned signal stack switching. */ if (sa->sa_flags & SA_ONSTACK) { - if (!on_sig_stack(sp) && !((current->sas_ss_sp + current->sas_ss_size) & 7)) + if (sas_ss_flags(sp) == 0) sp = current->sas_ss_sp + current->sas_ss_size; } + + /* Always align the stack frame. This handles two cases. First, + * sigaltstack need not be mindful of platform specific stack + * alignment. Second, if we took this signal because the stack + * is not aligned properly, we'd like to take the signal cleanly + * and report that. + */ + sp &= ~7UL; + return (void __user *)(sp - framesize); } -- cgit v1.2.3 From 28e6103665301ce60634e8a77f0b657c6cc099de Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Sun, 11 May 2008 02:07:19 -0700 Subject: sparc: Fix debugger syscall restart interactions. So, forever, we've had this ptrace_signal_deliver implementation which tries to handle all of the nasties that can occur when the debugger looks at a process about to take a signal. It's meant to address all of these issues inside of the kernel so that the debugger need not be mindful of such things. Problem is, this doesn't work. The idea was that we should do the syscall restart business first, so that the debugger captures that state. Otherwise, if the debugger for example saves the child's state, makes the child execute something else, then restores the saved state, we won't handle the syscall restart properly because we lose the "we're in a syscall" state. The code here worked for most cases, but if the debugger actually passes the signal through to the child unaltered, it's possible that we would do a syscall restart when we shouldn't have. In particular this breaks the case of debugging a process under a gdb which is being debugged by yet another gdb. gdb uses sigsuspend to wait for SIGCHLD of the inferior, but if gdb itself is being debugged by a top-level gdb we get a ptrace_stop(). The top-level gdb does a PTRACE_CONT with SIGCHLD to let the inferior gdb see the signal. But ptrace_signal_deliver() assumed the debugger would cancel out the signal and therefore did a syscall restart, because the return error was ERESTARTNOHAND. Fix this by simply making ptrace_signal_deliver() a nop, and providing a way for the debugger to control system call restarting properly: 1) Report a "in syscall" software bit in regs->{tstate,psr}. It is set early on in trap entry to a system call and is fully visible to the debugger via ptrace() and regsets. 2) Test this bit right before doing a syscall restart. We have to do a final recheck right after get_signal_to_deliver() in case the debugger cleared the bit during ptrace_stop(). 3) Clear the bit in trap return so we don't accidently try to set that bit in the real register. As a result we also get a ptrace_{is,clear}_syscall() for sparc32 just like sparc64 has. M68K has this same exact bug, and is now the only other user of the ptrace_signal_deliver hook. It needs to be fixed in the same exact way as sparc. Signed-off-by: David S. Miller --- arch/sparc/kernel/signal.c | 64 ++++++++++++++++++++-------------------------- 1 file changed, 28 insertions(+), 36 deletions(-) (limited to 'arch/sparc/kernel/signal.c') diff --git a/arch/sparc/kernel/signal.c b/arch/sparc/kernel/signal.c index 368157926d24..3fd1df9f9ba7 100644 --- a/arch/sparc/kernel/signal.c +++ b/arch/sparc/kernel/signal.c @@ -145,6 +145,9 @@ asmlinkage void do_sigreturn(struct pt_regs *regs) regs->psr = (up_psr & ~(PSR_ICC | PSR_EF)) | (regs->psr & (PSR_ICC | PSR_EF)); + /* Prevent syscall restart. */ + pt_regs_clear_syscall(regs); + err |= __get_user(fpu_save, &sf->fpu_save); if (fpu_save) @@ -199,6 +202,9 @@ asmlinkage void do_rt_sigreturn(struct pt_regs *regs) regs->psr = (regs->psr & ~PSR_ICC) | (psr & PSR_ICC); + /* Prevent syscall restart. */ + pt_regs_clear_syscall(regs); + err |= __get_user(fpu_save, &sf->fpu_save); if (fpu_save) @@ -507,26 +513,36 @@ static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs, * want to handle. Thus you cannot kill init even with a SIGKILL even by * mistake. */ -asmlinkage void do_signal(struct pt_regs * regs, unsigned long orig_i0, int restart_syscall) +asmlinkage void do_signal(struct pt_regs * regs, unsigned long orig_i0) { - siginfo_t info; - struct sparc_deliver_cookie cookie; struct k_sigaction ka; - int signr; + int restart_syscall; sigset_t *oldset; + siginfo_t info; + int signr; - cookie.restart_syscall = restart_syscall; - cookie.orig_i0 = orig_i0; + if (pt_regs_is_syscall(regs) && (regs->psr & PSR_C)) + restart_syscall = 1; + else + restart_syscall = 0; if (test_thread_flag(TIF_RESTORE_SIGMASK)) oldset = ¤t->saved_sigmask; else oldset = ¤t->blocked; - signr = get_signal_to_deliver(&info, &ka, regs, &cookie); + signr = get_signal_to_deliver(&info, &ka, regs, NULL); + + /* If the debugger messes with the program counter, it clears + * the software "in syscall" bit, directing us to not perform + * a syscall restart. + */ + if (restart_syscall && !pt_regs_is_syscall(regs)) + restart_syscall = 0; + if (signr > 0) { - if (cookie.restart_syscall) - syscall_restart(cookie.orig_i0, regs, &ka.sa); + if (restart_syscall) + syscall_restart(orig_i0, regs, &ka.sa); handle_signal(signr, &ka, &info, oldset, regs); /* a signal was successfully delivered; the saved @@ -538,16 +554,16 @@ asmlinkage void do_signal(struct pt_regs * regs, unsigned long orig_i0, int rest clear_thread_flag(TIF_RESTORE_SIGMASK); return; } - if (cookie.restart_syscall && + if (restart_syscall && (regs->u_regs[UREG_I0] == ERESTARTNOHAND || regs->u_regs[UREG_I0] == ERESTARTSYS || regs->u_regs[UREG_I0] == ERESTARTNOINTR)) { /* replay the system call when we are done */ - regs->u_regs[UREG_I0] = cookie.orig_i0; + regs->u_regs[UREG_I0] = orig_i0; regs->pc -= 4; regs->npc -= 4; } - if (cookie.restart_syscall && + if (restart_syscall && regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) { regs->u_regs[UREG_G1] = __NR_restart_syscall; regs->pc -= 4; @@ -599,27 +615,3 @@ do_sys_sigstack(struct sigstack __user *ssptr, struct sigstack __user *ossptr, out: return ret; } - -void ptrace_signal_deliver(struct pt_regs *regs, void *cookie) -{ - struct sparc_deliver_cookie *cp = cookie; - - if (cp->restart_syscall && - (regs->u_regs[UREG_I0] == ERESTARTNOHAND || - regs->u_regs[UREG_I0] == ERESTARTSYS || - regs->u_regs[UREG_I0] == ERESTARTNOINTR)) { - /* replay the system call when we are done */ - regs->u_regs[UREG_I0] = cp->orig_i0; - regs->pc -= 4; - regs->npc -= 4; - cp->restart_syscall = 0; - } - - if (cp->restart_syscall && - regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) { - regs->u_regs[UREG_G1] = __NR_restart_syscall; - regs->pc -= 4; - regs->npc -= 4; - cp->restart_syscall = 0; - } -} -- cgit v1.2.3