[PATCH 2/4] UML - Move signal handlers to arch code
From: Jeff Dike
Date: Wed Aug 02 2006 - 15:57:12 EST
Have most signals go through an arch-provided handler which recovers
the sigcontext and then calls a generic handler. This replaces the
ARCH_GET_SIGCONTEXT macro, which was somewhat fragile. On x86_64,
recovering %rdx (which holds the sigcontext pointer) must be the first
thing that happens. sig_handler duly invokes that first, but there is
no guarantee that I can see that instructions won't be reordered such
that %rdx is used before that. Having the arch provide the handler
seems much more robust.
Some signals in some parts of UML require their own handlers - these
places don't call set_handler any more. They call sigaction or signal
themselves.
Signed-off-by: Jeff Dike <jdike@xxxxxxxxxxx>
Index: linux-2.6.18-rc2-mm1/arch/um/include/sysdep-i386/signal.h
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/include/sysdep-i386/signal.h 2006-08-02 15:53:33.000000000 -0400
+++ /dev/null 1970-01-01 00:00:00.000000000 +0000
@@ -1,27 +0,0 @@
-/*
- * Copyright (C) 2004 PathScale, Inc
- * Licensed under the GPL
- */
-
-#ifndef __I386_SIGNAL_H_
-#define __I386_SIGNAL_H_
-
-#include <signal.h>
-
-#define ARCH_SIGHDLR_PARAM int sig
-
-#define ARCH_GET_SIGCONTEXT(sc, sig) \
- do sc = (struct sigcontext *) (&sig + 1); while(0)
-
-#endif
-
-/*
- * 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:
- */
Index: linux-2.6.18-rc2-mm1/arch/um/include/sysdep-x86_64/signal.h
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/include/sysdep-x86_64/signal.h 2006-08-02 15:53:33.000000000 -0400
+++ /dev/null 1970-01-01 00:00:00.000000000 +0000
@@ -1,29 +0,0 @@
-/*
- * Copyright (C) 2004 PathScale, Inc
- * Licensed under the GPL
- */
-
-#ifndef __X86_64_SIGNAL_H_
-#define __X86_64_SIGNAL_H_
-
-#define ARCH_SIGHDLR_PARAM int sig
-
-#define ARCH_GET_SIGCONTEXT(sc, sig_addr) \
- do { \
- struct ucontext *__uc; \
- asm("movq %%rdx, %0" : "=r" (__uc)); \
- sc = (struct sigcontext *) &__uc->uc_mcontext; \
- } while(0)
-
-#endif
-
-/*
- * 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:
- */
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/sys-i386/signal.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/sys-i386/signal.c 2006-08-02 15:53:39.000000000 -0400
@@ -0,0 +1,15 @@
+/*
+ * Copyright (C) 2006 Jeff Dike (jdike@xxxxxxxxxxx)
+ * Licensed under the GPL
+ */
+
+#include <signal.h>
+
+extern void (*handlers[])(int sig, struct sigcontext *sc);
+
+void hard_handler(int sig)
+{
+ struct sigcontext *sc = (struct sigcontext *) (&sig + 1);
+
+ (*handlers[sig])(sig, sc);
+}
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/sys-x86_64/signal.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/sys-x86_64/signal.c 2006-08-02 15:53:39.000000000 -0400
@@ -0,0 +1,16 @@
+/*
+ * Copyright (C) 2006 Jeff Dike (jdike@xxxxxxxxxxx)
+ * Licensed under the GPL
+ */
+
+#include <signal.h>
+
+extern void (*handlers[])(int sig, struct sigcontext *sc);
+
+void hard_handler(int sig)
+{
+ struct ucontext *uc;
+ asm("movq %%rdx, %0" : "=r" (uc));
+
+ (*handlers[sig])(sig, (struct sigcontext *) &uc->uc_mcontext);
+}
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/signal.c
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/os-Linux/signal.c 2006-08-02 15:53:33.000000000 -0400
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/signal.c 2006-08-02 15:53:39.000000000 -0400
@@ -15,7 +15,6 @@
#include "user.h"
#include "signal_kern.h"
#include "sysdep/sigcontext.h"
-#include "sysdep/signal.h"
#include "sigcontext.h"
#include "mode.h"
#include "os.h"
@@ -38,18 +37,10 @@
static int signals_enabled = 1;
static int pending = 0;
-void sig_handler(ARCH_SIGHDLR_PARAM)
+void sig_handler(int sig, struct sigcontext *sc)
{
- struct sigcontext *sc;
int enabled;
- /* Must be the first thing that this handler does - x86_64 stores
- * the sigcontext in %rdx, and we need to save it before it has a
- * chance to get trashed.
- */
-
- ARCH_GET_SIGCONTEXT(sc, sig);
-
enabled = signals_enabled;
if(!enabled && (sig == SIGIO)){
pending |= SIGIO_MASK;
@@ -84,13 +75,10 @@ static void real_alarm_handler(int sig,
}
-void alarm_handler(ARCH_SIGHDLR_PARAM)
+void alarm_handler(int sig, struct sigcontext *sc)
{
- struct sigcontext *sc;
int enabled;
- ARCH_GET_SIGCONTEXT(sc, sig);
-
enabled = signals_enabled;
if(!signals_enabled){
if(sig == SIGVTALRM)
@@ -126,6 +114,10 @@ void remove_sigstack(void)
panic("disabling signal stack failed, errno = %d\n", errno);
}
+void (*handlers[_NSIG])(int sig, struct sigcontext *sc);
+
+extern void hard_handler(int sig);
+
void set_handler(int sig, void (*handler)(int), int flags, ...)
{
struct sigaction action;
@@ -133,13 +125,15 @@ void set_handler(int sig, void (*handler
sigset_t sig_mask;
int mask;
- va_start(ap, flags);
action.sa_handler = handler;
+
sigemptyset(&action.sa_mask);
- while((mask = va_arg(ap, int)) != -1){
+
+ va_start(ap, flags);
+ while((mask = va_arg(ap, int)) != -1)
sigaddset(&action.sa_mask, mask);
- }
va_end(ap);
+
action.sa_flags = flags;
action.sa_restorer = NULL;
if(sigaction(sig, &action, NULL) < 0)
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/process.c
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/os-Linux/process.c 2006-08-02 15:53:33.000000000 -0400
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/process.c 2006-08-02 15:53:39.000000000 -0400
@@ -246,7 +246,17 @@ void init_new_thread_stack(void *sig_sta
set_sigstack(sig_stack, pages * page_size());
flags = SA_ONSTACK;
}
- if(usr1_handler) set_handler(SIGUSR1, usr1_handler, flags, -1);
+ if(usr1_handler){
+ struct sigaction sa;
+
+ sa.sa_handler = usr1_handler;
+ sigemptyset(&sa.sa_mask);
+ sa.sa_flags = flags;
+ sa.sa_restorer = NULL;
+ if(sigaction(SIGUSR1, &sa, NULL) < 0)
+ panic("init_new_thread_stack - sigaction failed - "
+ "errno = %d\n", errno);
+ }
}
void init_new_thread_signals(void)
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/time.c
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/os-Linux/time.c 2006-08-02 15:53:33.000000000 -0400
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/time.c 2006-08-02 15:53:39.000000000 -0400
@@ -40,8 +40,8 @@ void disable_timer(void)
printk("disnable_timer - setitimer failed, errno = %d\n",
errno);
/* If there are signals already queued, after unblocking ignore them */
- set_handler(SIGALRM, SIG_IGN, 0, -1);
- set_handler(SIGVTALRM, SIG_IGN, 0, -1);
+ signal(SIGALRM, SIG_IGN);
+ signal(SIGVTALRM, SIG_IGN);
}
void switch_timers(int to_real)
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/irq.c
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/os-Linux/irq.c 2006-08-02 15:53:33.000000000 -0400
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/irq.c 2006-08-02 15:53:39.000000000 -0400
@@ -132,7 +132,7 @@ void os_set_pollfd(int i, int fd)
void os_set_ioignore(void)
{
- set_handler(SIGIO, SIG_IGN, 0, -1);
+ signal(SIGIO, SIG_IGN);
}
void init_irq_signals(int on_sigstack)
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/main.c
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/os-Linux/main.c 2006-08-02 15:53:33.000000000 -0400
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/main.c 2006-08-02 15:53:39.000000000 -0400
@@ -67,13 +67,32 @@ static __init void do_uml_initcalls(void
static void last_ditch_exit(int sig)
{
- signal(SIGINT, SIG_DFL);
- signal(SIGTERM, SIG_DFL);
- signal(SIGHUP, SIG_DFL);
uml_cleanup();
exit(1);
}
+static void install_fatal_handler(int sig)
+{
+ struct sigaction action;
+
+ /* All signals are enabled in this handler ... */
+ sigemptyset(&action.sa_mask);
+
+ /* ... including the signal being handled, plus we want the
+ * handler reset to the default behavior, so that if an exit
+ * handler is hanging for some reason, the UML will just die
+ * after this signal is sent a second time.
+ */
+ action.sa_flags = SA_RESETHAND | SA_NODEFER;
+ action.sa_restorer = NULL;
+ action.sa_handler = last_ditch_exit;
+ if(sigaction(sig, &action, NULL) < 0){
+ printf("failed to install handler for signal %d - errno = %d\n",
+ errno);
+ exit(1);
+ }
+}
+
#define UML_LIB_PATH ":/usr/lib/uml"
static void setup_env_path(void)
@@ -158,9 +177,12 @@ int main(int argc, char **argv, char **e
}
new_argv[argc] = NULL;
- set_handler(SIGINT, last_ditch_exit, SA_ONESHOT | SA_NODEFER, -1);
- set_handler(SIGTERM, last_ditch_exit, SA_ONESHOT | SA_NODEFER, -1);
- set_handler(SIGHUP, last_ditch_exit, SA_ONESHOT | SA_NODEFER, -1);
+ /* Allow these signals to bring down a UML if all other
+ * methods of control fail.
+ */
+ install_fatal_handler(SIGINT);
+ install_fatal_handler(SIGTERM);
+ install_fatal_handler(SIGHUP);
scan_elf_aux( envp);
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/skas/process.c
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/os-Linux/skas/process.c 2006-08-02 15:53:33.000000000 -0400
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/skas/process.c 2006-08-02 15:53:39.000000000 -0400
@@ -189,14 +189,25 @@ static int userspace_tramp(void *stack)
}
}
if(!ptrace_faultinfo && (stack != NULL)){
+ struct sigaction sa;
+
unsigned long v = UML_CONFIG_STUB_CODE +
(unsigned long) stub_segv_handler -
(unsigned long) &__syscall_stub_start;
set_sigstack((void *) UML_CONFIG_STUB_DATA, page_size());
- set_handler(SIGSEGV, (void *) v, SA_ONSTACK,
- SIGIO, SIGWINCH, SIGALRM, SIGVTALRM,
- SIGUSR1, -1);
+ sigemptyset(&sa.sa_mask);
+ sigaddset(&sa.sa_mask, SIGIO);
+ sigaddset(&sa.sa_mask, SIGWINCH);
+ sigaddset(&sa.sa_mask, SIGALRM);
+ sigaddset(&sa.sa_mask, SIGVTALRM);
+ sigaddset(&sa.sa_mask, SIGUSR1);
+ sa.sa_flags = SA_ONSTACK;
+ sa.sa_handler = (void *) v;
+ sa.sa_restorer = NULL;
+ if(sigaction(SIGSEGV, &sa, NULL) < 0)
+ panic("userspace_tramp - setting SIGSEGV handler "
+ "failed - errno = %d\n", errno);
}
os_stop_process(os_getpid());
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/sys-i386/Makefile
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/os-Linux/sys-i386/Makefile 2006-08-02 15:53:33.000000000 -0400
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/sys-i386/Makefile 2006-08-02 15:53:39.000000000 -0400
@@ -3,7 +3,7 @@
# Licensed under the GPL
#
-obj-$(CONFIG_MODE_SKAS) = registers.o tls.o
+obj-$(CONFIG_MODE_SKAS) = registers.o signal.o tls.o
USER_OBJS := $(obj-y)
Index: linux-2.6.18-rc2-mm1/arch/um/os-Linux/sys-x86_64/Makefile
===================================================================
--- linux-2.6.18-rc2-mm1.orig/arch/um/os-Linux/sys-x86_64/Makefile 2006-08-02 15:53:33.000000000 -0400
+++ linux-2.6.18-rc2-mm1/arch/um/os-Linux/sys-x86_64/Makefile 2006-08-02 15:53:39.000000000 -0400
@@ -3,7 +3,7 @@
# Licensed under the GPL
#
-obj-$(CONFIG_MODE_SKAS) = registers.o
+obj-$(CONFIG_MODE_SKAS) = registers.o signal.o
USER_OBJS := $(obj-y)
-
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