[RFC PATCH] New SA_NOPRNOTIF sigaction flag

From: Bhavesh P. Davda
Date: Mon Sep 26 2005 - 12:40:34 EST


Sometimes when a task is being ptraced (e.g. by a debugger), one would
like to handle a certain signal (e.g. SIGSEGV) within the task without
having to notify the ptracing task.

An example of this is if one would like to detect the rate at which pages
are being modified, and therefore mprotect() the pages. The SIGSEGV
handler just keeps track of how many writes are happening on each of the
mprotect()ed pages, but you don't want to bother the debugger with these
SIGSEGVs.

I'm proposing the addition of a new SA_NOPRNOTIF flag to struct sigaction
{ sa_flags }, which makes the kernel skip notifying the ptracing parent if
the flag is set for a sighandler for a particular signal.

This trivial patch achieves just that.

Comments?

Thanks

- Bhavesh

ps: wonder why POSIX, SUSV3, SVR4, etc. didn't have this option. Seems
like a handy flag to have...


Bhavesh P. Davda | Distinguished Member of Technical Staff | Avaya |
1300 West 120th Avenue | B3-B03 | Westminster, CO 80234 | U.S.A. |
Voice/Fax: 303.538.4438 | bhavesh@xxxxxxxxx
diff --git a/include/asm-alpha/signal.h b/include/asm-alpha/signal.h
--- a/include/asm-alpha/signal.h
+++ b/include/asm-alpha/signal.h
@@ -99,6 +99,10 @@ typedef unsigned long sigset_t;
#define SA_ONESHOT SA_RESETHAND
#define SA_NOMASK SA_NODEFER
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

/*
* sigaltstack controls
diff --git a/include/asm-arm/signal.h b/include/asm-arm/signal.h
--- a/include/asm-arm/signal.h
+++ b/include/asm-arm/signal.h
@@ -102,6 +102,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT


/*
diff --git a/include/asm-arm26/signal.h b/include/asm-arm26/signal.h
--- a/include/asm-arm26/signal.h
+++ b/include/asm-arm26/signal.h
@@ -102,6 +102,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT


/*
diff --git a/include/asm-cris/signal.h b/include/asm-cris/signal.h
--- a/include/asm-cris/signal.h
+++ b/include/asm-cris/signal.h
@@ -96,6 +96,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-frv/signal.h b/include/asm-frv/signal.h
--- a/include/asm-frv/signal.h
+++ b/include/asm-frv/signal.h
@@ -95,6 +95,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-h8300/signal.h b/include/asm-h8300/signal.h
--- a/include/asm-h8300/signal.h
+++ b/include/asm-h8300/signal.h
@@ -95,6 +95,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-i386/signal.h b/include/asm-i386/signal.h
--- a/include/asm-i386/signal.h
+++ b/include/asm-i386/signal.h
@@ -98,6 +98,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-ia64/signal.h b/include/asm-ia64/signal.h
--- a/include/asm-ia64/signal.h
+++ b/include/asm-ia64/signal.h
@@ -77,6 +77,10 @@
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-m32r/signal.h b/include/asm-m32r/signal.h
--- a/include/asm-m32r/signal.h
+++ b/include/asm-m32r/signal.h
@@ -102,6 +102,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-m68k/signal.h b/include/asm-m68k/signal.h
--- a/include/asm-m68k/signal.h
+++ b/include/asm-m68k/signal.h
@@ -95,6 +95,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

/*
* sigaltstack controls
diff --git a/include/asm-m68knommu/signal.h b/include/asm-m68knommu/signal.h
--- a/include/asm-m68knommu/signal.h
+++ b/include/asm-m68knommu/signal.h
@@ -95,6 +95,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

/*
* sigaltstack controls
diff --git a/include/asm-mips/signal.h b/include/asm-mips/signal.h
--- a/include/asm-mips/signal.h
+++ b/include/asm-mips/signal.h
@@ -86,6 +86,10 @@ typedef unsigned long old_sigset_t; /*
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000 /* Only for o32 */

diff --git a/include/asm-parisc/signal.h b/include/asm-parisc/signal.h
--- a/include/asm-parisc/signal.h
+++ b/include/asm-parisc/signal.h
@@ -70,6 +70,10 @@
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000 /* obsolete -- ignored */

diff --git a/include/asm-ppc/signal.h b/include/asm-ppc/signal.h
--- a/include/asm-ppc/signal.h
+++ b/include/asm-ppc/signal.h
@@ -88,6 +88,10 @@ typedef struct {
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-ppc64/signal.h b/include/asm-ppc64/signal.h
--- a/include/asm-ppc64/signal.h
+++ b/include/asm-ppc64/signal.h
@@ -85,6 +85,10 @@ typedef struct {
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000u /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000u

diff --git a/include/asm-s390/signal.h b/include/asm-s390/signal.h
--- a/include/asm-s390/signal.h
+++ b/include/asm-s390/signal.h
@@ -105,6 +105,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-sh/signal.h b/include/asm-sh/signal.h
--- a/include/asm-sh/signal.h
+++ b/include/asm-sh/signal.h
@@ -96,6 +96,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-sh64/signal.h b/include/asm-sh64/signal.h
--- a/include/asm-sh64/signal.h
+++ b/include/asm-sh64/signal.h
@@ -95,6 +95,10 @@ typedef struct {
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-sparc/signal.h b/include/asm-sparc/signal.h
--- a/include/asm-sparc/signal.h
+++ b/include/asm-sparc/signal.h
@@ -142,6 +142,10 @@ struct sigstack {
#define SA_RESTART _SV_INTR
#define SA_ONESHOT _SV_RESET
#define SA_INTERRUPT 0x10u
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT
#define SA_NOMASK 0x20u
#define SA_NOCLDWAIT 0x100u
#define SA_SIGINFO 0x200u
diff --git a/include/asm-sparc64/signal.h b/include/asm-sparc64/signal.h
--- a/include/asm-sparc64/signal.h
+++ b/include/asm-sparc64/signal.h
@@ -144,6 +144,10 @@ struct sigstack {
#define SA_RESTART _SV_INTR
#define SA_ONESHOT _SV_RESET
#define SA_INTERRUPT 0x10u
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT
#define SA_NOMASK 0x20u
#define SA_NOCLDWAIT 0x100u
#define SA_SIGINFO 0x200u
diff --git a/include/asm-v850/signal.h b/include/asm-v850/signal.h
--- a/include/asm-v850/signal.h
+++ b/include/asm-v850/signal.h
@@ -98,6 +98,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-x86_64/signal.h b/include/asm-x86_64/signal.h
--- a/include/asm-x86_64/signal.h
+++ b/include/asm-x86_64/signal.h
@@ -104,6 +104,10 @@ typedef unsigned long sigset_t;
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/include/asm-xtensa/signal.h b/include/asm-xtensa/signal.h
--- a/include/asm-xtensa/signal.h
+++ b/include/asm-xtensa/signal.h
@@ -96,6 +96,10 @@ typedef struct {
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
#define SA_INTERRUPT 0x20000000 /* dummy -- ignored */
+/*
+ * Let's reuse SA_INTERRUPT since it is unused anymore
+ */
+#define SA_NOPRNOTIF SA_INTERRUPT

#define SA_RESTORER 0x04000000

diff --git a/kernel/signal.c b/kernel/signal.c
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1849,7 +1849,11 @@ relock:
if (!signr)
break; /* will return 0 */

- if ((current->ptrace & PT_PTRACED) && signr != SIGKILL) {
+ ka = &current->sighand->action[signr-1];
+
+ if ((current->ptrace & PT_PTRACED) && (signr != SIGKILL)
+ && !(ka->sa.sa_flags & SA_NOPRNOTIF))
+ {
ptrace_signal_deliver(regs, cookie);

/* Let the debugger run. */