klibc - Aug 2020 - [klibc:master] signal: Note another reason to define _KLIBC_NEEDS_SA_RESTORER

Commit-ID:  ccc5c14c44f3fa76f61b8aae947cf3b853a6c833
Gitweb:    
http://git.kernel.org/?p=libs/klibc/klibc.git;a=commit;h=ccc5c14c44f3fa76f61b8aae947cf3b853a6c833
Author:     Ben Hutchings <ben at decadent.org.uk>
AuthorDate: Tue, 25 Aug 2020 00:43:33 +0100
Committer:  Ben Hutchings <ben at decadent.org.uk>
CommitDate: Thu, 27 Aug 2020 15:00:33 +0100

[klibc] signal: Note another reason to define _KLIBC_NEEDS_SA_RESTORER

On some architectures we should set SA_RESTORER to avoid the need for
a signal trampoline and executable stack.

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

---
 usr/include/klibc/sysconfig.h | 3 ++-
 usr/klibc/sigaction.c         | 2 --
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/usr/include/klibc/sysconfig.h b/usr/include/klibc/sysconfig.h
index c91d5b85..4e38b1fd 100644
--- a/usr/include/klibc/sysconfig.h
+++ b/usr/include/klibc/sysconfig.h
@@ -154,7 +154,8 @@
  *
  *	Some architectures, like x86-64 and some i386 Fedora kernels,
  *	do not provide a default sigreturn, and therefore must have
- *	SA_RESTORER set.
+ *	SA_RESTORER set.  On others, the default sigreturn requires an
+ *	executable stack, which we should avoid.
  */
 #ifndef _KLIBC_NEEDS_SA_RESTORER
 # define _KLIBC_NEEDS_SA_RESTORER 0
diff --git a/usr/klibc/sigaction.c b/usr/klibc/sigaction.c
index 30ef39ef..966bc1c6 100644
--- a/usr/klibc/sigaction.c
+++ b/usr/klibc/sigaction.c
@@ -31,8 +31,6 @@ int sigaction(int sig, const struct sigaction *act, struct
sigaction *oact)
 		sa = *act;
 		act = &sa;
 
-		/* The kernel can't be trusted to have a valid default
-		   restorer */
 		sa.sa_flags |= SA_RESTORER;
 		sa.sa_restorer = &__sigreturn;
 	}