From 1d299bc7732c34d85bd43ac1a8745f5a2fed2078 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Mon, 14 Nov 2011 20:32:16 -0800 Subject: sparc: Fix handling of orig_i0 wrt. debugging when restarting syscalls. Although we provide a proper way for a debugger to control whether syscall restart occurs, we run into problems because orig_i0 is not saved and restored properly. Luckily we can solve this problem without having to make debuggers aware of the issue. Across system calls, several registers are considered volatile and can be safely clobbered. Therefore we use the pt_regs save area of one of those registers, %g2, as a place to save and restore orig_i0. Debuggers transparently will do the right thing because they save and restore this register already. Signed-off-by: David S. Miller --- arch/sparc/kernel/signal32.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'arch/sparc/kernel/signal32.c') diff --git a/arch/sparc/kernel/signal32.c b/arch/sparc/kernel/signal32.c index 2caa556db86d..2e86fd1ddc7b 100644 --- a/arch/sparc/kernel/signal32.c +++ b/arch/sparc/kernel/signal32.c @@ -822,21 +822,23 @@ static inline void syscall_restart32(unsigned long orig_i0, struct pt_regs *regs * want to handle. Thus you cannot kill init even with a SIGKILL even by * mistake. */ -void do_signal32(sigset_t *oldset, struct pt_regs * regs, - int restart_syscall, unsigned long orig_i0) +void do_signal32(sigset_t *oldset, struct pt_regs * regs) { struct k_sigaction ka; + unsigned long orig_i0; + int restart_syscall; siginfo_t info; int signr; signr = get_signal_to_deliver(&info, &ka, regs, NULL); - /* If the debugger messes with the program counter, it clears - * the "in syscall" bit, directing us to not perform a syscall - * restart. - */ - if (restart_syscall && !pt_regs_is_syscall(regs)) - restart_syscall = 0; + restart_syscall = 0; + orig_i0 = 0; + if (pt_regs_is_syscall(regs) && + (regs->tstate & (TSTATE_XCARRY | TSTATE_ICARRY))) { + restart_syscall = 1; + orig_i0 = regs->u_regs[UREG_G2]; + } if (signr > 0) { if (restart_syscall) -- cgit From e88d2468718b0789b4c33da2f7e1cef2a1eee279 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 15 Nov 2011 12:57:00 -0800 Subject: sparc: Stash orig_i0 into %g6 instead of %g2 As per the comments added by this commit, %g2 turns out to not be a usable place to save away orig_i0 for syscall restart handling. In fact all of %g2, %g3, %g4, and %g5 are assumed to be saved across a system call by various bits of code in glibc. %g1 can't be used because that holds the syscall number, which would need to be saved and restored for syscall restart handling too, and that would only compound our problems :-) This leaves us with %g6 and %g7 which are for "system use". %g7 is used as the "thread register" by glibc, but %g6 is used as a compiler and assembler temporary scratch register. And in no instance is %g6 used to hold a value across a system call. Therefore %g6 is safe for storing away orig_i0, at least for now. Signed-off-by: David S. Miller --- arch/sparc/kernel/signal32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/sparc/kernel/signal32.c') diff --git a/arch/sparc/kernel/signal32.c b/arch/sparc/kernel/signal32.c index 2e86fd1ddc7b..023b8860dc97 100644 --- a/arch/sparc/kernel/signal32.c +++ b/arch/sparc/kernel/signal32.c @@ -837,7 +837,7 @@ void do_signal32(sigset_t *oldset, struct pt_regs * regs) if (pt_regs_is_syscall(regs) && (regs->tstate & (TSTATE_XCARRY | TSTATE_ICARRY))) { restart_syscall = 1; - orig_i0 = regs->u_regs[UREG_G2]; + orig_i0 = regs->u_regs[UREG_G6]; } if (signr > 0) { -- cgit