klibc - Aug 2020 - [klibc:master] signal: Add sysconfig setting to force SA_SIGINFO on

Commit-ID:  2a2a0b6b79c2470f529daabd5c193f58fe188337
Gitweb:    
http://git.kernel.org/?p=libs/klibc/klibc.git;a=commit;h=2a2a0b6b79c2470f529daabd5c193f58fe188337
Author:     Ben Hutchings <ben at decadent.org.uk>
AuthorDate: Tue, 25 Aug 2020 01:05:28 +0100
Committer:  Ben Hutchings <ben at decadent.org.uk>
CommitDate: Thu, 27 Aug 2020 15:00:33 +0100

[klibc] signal: Add sysconfig setting to force SA_SIGINFO on

On alpha, arm, i386, m68k, powerpc, s390, sh, and sparc (32-bit), the
kernel sets up the signal stack frame differently depending on the
SA_SIGINFO flag, not whether the sigaction() or rt_sigaction() system
call was used to install the handler.

On alpha and sparc, we are going to start providing our own restorer
that will call rt_sigaction(), so will need to ensure this flag is
always set.

Signed-off-by: Ben Hutchings <ben at decadent.org.uk>

---
 usr/include/klibc/sysconfig.h | 14 ++++++++++++++
 usr/klibc/sigaction.c         | 21 ++++++++++++++-------
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/usr/include/klibc/sysconfig.h b/usr/include/klibc/sysconfig.h
index 4e38b1fd..5722e04f 100644
--- a/usr/include/klibc/sysconfig.h
+++ b/usr/include/klibc/sysconfig.h
@@ -162,6 +162,20 @@
 #endif
 
 
+/*
+ * _KLIBC_NEEDS_SA_SIGINFO:
+ *
+ *	On some architectures, the signal stack frame is set up for
+ *	either sigreturn() or rt_sigreturn() depending on whether
+ *	SA_SIGINFO is set.  Where this is the case, and we provide our
+ *	own restorer function, this must also be set so that the
+ *	restorer can always use rt_sigreturn().
+ */
+#ifndef _KLIBC_NEEDS_SA_SIGINFO
+# define _KLIBC_NEEDS_SA_SIGINFO 0
+#endif
+
+
 /*
  * _KLIBC_STATFS_F_TYPE_64:
  *
diff --git a/usr/klibc/sigaction.c b/usr/klibc/sigaction.c
index 966bc1c6..0d7c5c9d 100644
--- a/usr/klibc/sigaction.c
+++ b/usr/klibc/sigaction.c
@@ -22,19 +22,26 @@ __extern int __rt_sigaction(int, const struct sigaction *,
struct sigaction *,
 
 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact)
 {
-	int rv;
-
+	unsigned int needed_flags = 0
 #if _KLIBC_NEEDS_SA_RESTORER
+		| SA_RESTORER
+#endif
+#if _KLIBC_NEEDS_SA_SIGINFO
+		| SA_SIGINFO
+#endif
+		;
 	struct sigaction sa;
+	int rv;
 
-	if (act && !(act->sa_flags & SA_RESTORER)) {
+	if (act && (act->sa_flags & needed_flags) != needed_flags) {
 		sa = *act;
+		sa.sa_flags |= needed_flags;
+#if _KLIBC_NEEDS_SA_RESTORER
+		if (!(act->sa_flags & SA_RESTORER))
+			sa.sa_restorer = &__sigreturn;
+#endif
 		act = &sa;
-
-		sa.sa_flags |= SA_RESTORER;
-		sa.sa_restorer = &__sigreturn;
 	}
-#endif
 
 #if _KLIBC_USE_RT_SIG
 	/* Check that we have the right signal API definitions */