Fix parameters of signal handlers for linuxppc.

Linux passes the arguments in registers, but our compiler expects
arguments on the stack.  Signal handlers got garbage instead of the
signal number.  Some handlers, like the one in lang/m2/libm2/sigtrp.c,
need the correct signal number.

I write a "bridge" in PowerPC assembly that moves the arguments to the
stack.  I put the bridge in sigaction(), so I provide a signal() that
calls sigaction().  I remove the *.c glob or wildcard from build.lua,
so linuxppc only compiles its own signal.c, not the other signal.c for
linux386 and linux68k.

My bridge uses sigprocmask(), so I also add sigprocmask().  Because
linux386 and linux68k use globs, they also get sigprocmask().  I sync
the header files so all three Linux platforms declare execve(),
sigprocmask(), and unlink(), but not remove(), because we have
remove() in <stdio.h>.

I am using sigaction.s to test some features that we recently added to
our PowerPC assembler.  These are the "hi16[...]" and "lo16[...]"
syntax, and also the extended names like "beq", "cmpwi", "li", "subi".

plat/linux/libsys/sigprocmask.c

@@ -0,0 +1,7 @@
+#include <signal.h>
+#include "libsys.h"
+
+int sigprocmask(int flags, const sigset_t *new, sigset_t *old)
+{
+	return _syscall(__NR_sigprocmask, flags, (quad) new, (quad) old);
+}

plat/linux386/include/unistd.h

@@ -56,7 +56,6 @@ extern int write(int fd, void* buffer, size_t count);
 extern off_t lseek(int fildes, off_t offset, int whence);
 extern int fcntl(int fd, int op, ...);
 extern int unlink(const char* path);
-extern int remove(const char* path);
 
 /* Special variables */
 
@@ -117,8 +116,16 @@ typedef int sig_atomic_t;
 
 #define _NSIG           32      /* Biggest signal number + 1
                                    (not including real-time signals).  */
+
+/* sigprocmask */
+#define SIG_BLOCK       0
+#define SIG_UNBLOCK     1
+#define SIG_SETMASK     2
+typedef unsigned long sigset_t;
+
 typedef void (*sighandler_t)(int);
 extern sighandler_t signal(int signum, sighandler_t handler);
+extern int sigprocmask(int, const sigset_t *, sigset_t *);
 extern int raise(int signum);
 
 

plat/linux68k/include/unistd.h

@@ -55,6 +55,7 @@ extern int read(int fd, void* buffer, size_t count);
 extern int write(int fd, void* buffer, size_t count);
 extern off_t lseek(int fildes, off_t offset, int whence);
 extern int fcntl(int fd, int op, ...);
+extern int unlink(const char* path);
 
 /* Special variables */
 
@@ -67,6 +68,7 @@ extern pid_t getpid(void);
 extern int brk(void* ptr);
 extern void* sbrk(int increment);
 extern int isatty(int d);
+extern int execve(const char *path, char *const argv[], char *const envp[]);
 
 /* Signal handling */
 
@@ -114,8 +116,16 @@ typedef int sig_atomic_t;
 
 #define _NSIG           32      /* Biggest signal number + 1
                                    (not including real-time signals).  */
+
+/* sigprocmask */
+#define SIG_BLOCK       0
+#define SIG_UNBLOCK     1
+#define SIG_SETMASK     2
+typedef unsigned long sigset_t;
+
 typedef void (*sighandler_t)(int);
 extern sighandler_t signal(int signum, sighandler_t handler);
+extern int sigprocmask(int, const sigset_t *, sigset_t *);
 extern int raise(int signum);
 
 

plat/linuxppc/include/unistd.h

@@ -55,6 +55,7 @@ extern int read(int fd, void* buffer, size_t count);
 extern int write(int fd, void* buffer, size_t count);
 extern off_t lseek(int fildes, off_t offset, int whence);
 extern int fcntl(int fd, int op, ...);
+extern int unlink(const char* path);
 
 /* Special variables */
 
@@ -115,8 +116,34 @@ typedef int sig_atomic_t;
 
 #define _NSIG           32      /* Biggest signal number + 1
                                    (not including real-time signals).  */
+
+/* sigprocmask */
+#define SIG_BLOCK       0
+#define SIG_UNBLOCK     1
+#define SIG_SETMASK     2
+typedef unsigned long sigset_t;
+
+/* sa_flags */
+#define SA_NODEFER      0x40000000UL
+#define SA_RESETHAND    0x80000000UL
+
+struct __siginfo;
+struct sigaction {
+	union {
+		void (*__sa_handler)(int);
+		void (*__sa_sigaction)(int, struct __siginfo *, void *);
+	} __sigaction_u;
+	sigset_t sa_mask;
+	unsigned long sa_flags;
+	void (*sa_restorer)(void);
+};
+#define sa_handler __sigaction_u.__sa_handler
+#define sa_sigaction __sigaction_u.__sa_sigaction
+
 typedef void (*sighandler_t)(int);
+extern int sigaction(int, const struct sigaction *, struct sigaction *);
 extern sighandler_t signal(int signum, sighandler_t handler);
+extern int sigprocmask(int, const sigset_t *, sigset_t *);
 extern int raise(int signum);
 
 

plat/linuxppc/libsys/build.lua

@@ -1,9 +1,29 @@
 acklibrary {
 	name = "lib",
 	srcs = {
-        "./*.s",
+		"./_syscall.s",
-        "plat/linux/libsys/*.c",
+		"./sigaction.s",
-        "plat/linux/libsys/*.s",
+		"./signal.c",
+		"./trap.s",
+		"plat/linux/libsys/_exit.c",
+		"plat/linux/libsys/_hol0.s",
+		"plat/linux/libsys/close.c",
+		"plat/linux/libsys/creat.c",
+		"plat/linux/libsys/errno.s",
+		"plat/linux/libsys/execve.c",
+		"plat/linux/libsys/getpid.c",
+		"plat/linux/libsys/gettimeofday.c",
+		"plat/linux/libsys/ioctl.c",
+		"plat/linux/libsys/isatty.c",
+		"plat/linux/libsys/kill.c",
+		"plat/linux/libsys/lseek.c",
+		"plat/linux/libsys/open.c",
+		"plat/linux/libsys/read.c",
+		"plat/linux/libsys/sbrk.c",
+		-- omit signal.c
+		"plat/linux/libsys/sigprocmask.c",
+		"plat/linux/libsys/unlink.c",
+		"plat/linux/libsys/write.c",
 	},
 	deps = {
 		"lang/cem/libcc.ansi/headers+headers",

plat/linuxppc/libsys/sigaction.s

@@ -0,0 +1,156 @@
+#define __NR_sigaction		67
+#define SIG_BLOCK		0
+#define SIG_SETMASK		2
+#define MAXSIG			32
+
+/* offsets into our stack frame */
+#define mynew	16	/* new sigaction */
+#define mynset	32	/* new signal set */
+#define myoset	36	/* old signal set */
+#define mysave	40
+#define mysize	56
+
+.sect .text; .sect .rodata; .sect .data; .sect .bss
+
+/*
+ * Linux calls signal handlers with arguments in registers, but the
+ * ACK expects arguments on the stack.  This sigaction() uses a
+ * "bridge" to move the arguments.
+ */
+.sect .text
+.define _sigaction
+_sigaction:
+	mflr	r0
+	subi	r1, r1, mysize
+	stw	r31, mysave+8(r1)
+	stw	r30, mysave+4(r1)
+	stw	r29, mysave(r1)
+	stw	r0, mysave+12(r1)
+	li	r3, 0
+	stw	r3, mynset(r1)	   	! mynset = 0
+	lwz	r29, mysize(r1)		! r29 = signal number
+	lwz	r30, mysize+4(r1)	! r30 = new action
+	lwz	r31, mysize+8(r1)	! r31 = old action
+	/*
+	 * If the new action is non-NULL, the signal number is in
+	 * range 1 to MAXSIG, and the new handler is not SIG_DFL 0
+	 * or SIG_IGN 1, then we interpose our bridge.
+	 */
+	cmpwi	cr0, r30, 0
+	subi	r7, r29, 1		! r7 = index in handlers
+	cmplwi	cr7, r7, MAXSIG		! unsigned comparison
+	beq	cr0, kernel
+	bge	cr7, kernel
+	lwz	r3, 0(r30)		! r3 = new handler
+	clrrwi.	r3, r3, 1
+	beq	cr0, kernel
+	/*
+	 * Block the signal while we build the bridge.  Prevents a
+	 * race if a signal arrives after we change the bridge but
+	 * before we change the action in the kernel.
+	 */
+	li	r4, 1
+	slw	r4, r4, r7
+	stw	r4, mynset(r1)		! mynmask = 1 << (signal - 1)
+	li	r3, SIG_BLOCK
+	la	r4, mynset(r1)
+	la	r5, myoset(r1)
+	stw	r3, 0(r1)
+	stw	r4, 4(r1)
+	stw	r5, 8(r1)
+	bl	_sigprocmask
+	/*
+	 * Point our bridge to the new signal handler.  Then copy the
+	 * new sigaction but point it to our bridge.
+	 */
+	lis	r6, hi16[handlers]
+	ori	r6, r6, lo16[handlers]
+	subi	r7, r29, 1
+	slwi	r7, r7, 2
+	lwz	r3, 0(r30)		! r3 = new handler
+	stwx	r3, r6, r7		! put it in array of handlers
+	lis	r3, hi16[bridge]
+	ori	r3, r3, lo16[bridge]
+	lwz	r4, 4(r30)
+	lwz	r5, 8(r30)
+	lwz	r6, 12(r30)
+	stw	r3, mynew(r1)		! sa_handler or sa_sigaction
+	stw	r4, mynew+4(r1)		! sa_mask
+	stw	r5, mynew+8(r1)		! sa_flags
+	stw	r6, mynew+12(r1)	! sa_restorer
+	la	r30, mynew(r1)
+kernel:
+	li	r3, __NR_sigaction
+	stw	r3, 0(r1)
+	stw	r29, 4(r1)
+	stw	r30, 8(r1)
+	stw	r31, 12(r1)
+	bl	__syscall
+	/*
+	 * If we blocked the signal, then restore the old signal mask.
+	 */
+	lwz	r3, mynset(r1)
+	cmpwi	cr0, r3, 0
+	beq	cr0, fixold
+	li	r3, SIG_SETMASK
+	la	r4, myoset(r1)
+	li	r5, 0
+	stw	r3, 0(r1)
+	stw	r4, 4(r1)
+	stw	r5, 8(r1)
+	bl	_sigprocmask
+	/*
+	 * If the old sigaction is non-NULL and points to our bridge,
+	 * then point it to the signal handler.
+	 */
+fixold:
+	cmpwi	cr0, r31, 0
+	beq	cr0, leave
+	lis	r3, hi16[bridge]
+	ori	r3, r3, lo16[bridge]
+	lwz	r4, 0(r31)
+	cmpw	cr0, r3, r4
+	bne	cr0, leave
+	lis	r6, hi16[handlers]
+	ori	r6, r6, lo16[handlers]
+	subi	r7, r29, 1
+	slwi	r7, r7, 2
+	lwzx	r3, r6, r7	! get it from array of handlers
+	stw	r3, 0(r31)	! put it in old sigaction
+leave:
+	lwz	r0, mysave+12(r1)
+	lwz	r29, mysave(r1)
+	lwz	r30, mysave+4(r1)
+	lwz	r31, mysave+8(r1)
+	addi	r1, r1, mysize
+	mtlr	r0
+	blr			! return from sigaction
+
+/*
+ * Linux calls bridge(signum) or bridge(signum, info, context) with
+ * arguments in registers r3, r4, r5.
+ */
+bridge:
+	mflr	r0
+	subi	r1, r1, 16
+	stw	r0, 12(r1)
+	stw	r3, 0(r1)	! signal number
+	stw	r4, 4(r1)	! info
+	stw	r5, 8(r1)	! context
+
+	lis	r6, hi16[handlers]
+	ori	r6, r6, lo16[handlers]
+	subi	r7, r3, 1
+	slwi	r7, r7, 2
+	lwzx	r6, r6, r7
+	mtctr	r6
+	bctrl			! call our signal handler
+
+	lwz	r0, 12(r1)
+	addi	r1, r1, 16
+	mtlr	r0
+	blr			! return from bridge
+
+.sect .bss
+handlers:
+	.space 4 * MAXSIG	! array of signal handlers

plat/linuxppc/libsys/signal.c

@@ -0,0 +1,19 @@
+#include <signal.h>
+
+/*
+ * Uses our bridge in sigaction.s when calling the signal handler.
+ * Mimics Linux __NR_signal by using SA_NODEFER | SA_RESETHAND.
+ */
+sighandler_t signal(int signum, sighandler_t handler) {
+	struct sigaction new, old;
+	int i;
+
+	new.sa_handler = handler;
+	new.sa_mask = 0; /* empty set */
+	new.sa_flags = SA_NODEFER | SA_RESETHAND;
+
+	i = sigaction(signum, &new, &old);
+	if (i < 0)
+		return SIG_ERR;
+	return old.sa_handler;
+}