[POWERPC] Make syscall restart code more common

This patch moves the code in signal_32.c and signal_64.c for handling
syscall restart into a common signal.c file and converge around a single
implementation that is based on the 32 bits one, using trap, ccr
and r3 rather than the special "result" field for deciding what to do.

The "result" field is now pretty much deprecated. We still set it for
the sake of whatever might rely on it in userland but we no longer use
it's content.

This, along with a previous patch that enables ptracers to write to
"trap" and "orig_r3" should allow gdb to properly handle syscall
restarting.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
new file mode 100644
index 00000000000..88a12544e8b
--- /dev/null
+++ b/arch/powerpc/kernel/signal.c
@@ -0,0 +1,65 @@
+/*
+ * Common signal handling code for both 32 and 64 bits
+ *
+ *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Coproration
+ *    Extracted from signal_32.c and signal_64.c
+ *
+ * This file is subject to the terms and conditions of the GNU General
+ * Public License.  See the file README.legal in the main directory of
+ * this archive for more details.
+ */
+
+#include <linux/ptrace.h>
+#include <linux/signal.h>
+#include <asm/unistd.h>
+
+void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
+			   int has_handler)
+{
+	unsigned long ret = regs->gpr[3];
+	int restart = 1;
+
+	/* syscall ? */
+	if (TRAP(regs) != 0x0C00)
+		return;
+
+	/* error signalled ? */
+	if (!(regs->ccr & 0x10000000))
+		return;
+
+	switch (ret) {
+	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.
+		 */
+		restart = !has_handler;
+		break;
+	case ERESTARTSYS:
+		/* ERESTARTSYS means to restart the syscall if there is no
+		 * handler or the handler was registered with SA_RESTART
+		 */
+		restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
+		break;
+	case ERESTARTNOINTR:
+		/* ERESTARTNOINTR means that the syscall should be
+		 * called again after the signal handler returns.
+		 */
+		break;
+	default:
+		return;
+	}
+	if (restart) {
+		if (ret == ERESTART_RESTARTBLOCK)
+			regs->gpr[0] = __NR_restart_syscall;
+		else
+			regs->gpr[3] = regs->orig_gpr3;
+		regs->nip -= 4;
+		regs->result = 0;
+	} else {
+		regs->result = -EINTR;
+		regs->gpr[3] = EINTR;
+		regs->ccr |= 0x10000000;
+	}
+}