[klibc] [klibc:master] sig{set, long}jmp: do not ignore sigsetjmp's second argument

[klibc-bot for mirabilos]

Commit-ID:  eb10cf8c3128612a089ace8489a81bc4ffd5d07a
Gitweb:     http://git.kernel.org/?p=libs/klibc/klibc.git;a=commit;h=eb10cf8c3128612a089ace8489a81bc4ffd5d07a
Author:     mirabilos <tg at debian.org>
AuthorDate: Wed, 5 May 2021 21:02:37 +0200
Committer:  Ben Hutchings <ben at decadent.org.uk>
CommitDate: Sun, 26 Dec 2021 18:55:27 +0100

sig{set,long}jmp: do not ignore sigsetjmp's second argument

Save and restore the signal mask only if that argument is nonzero,
as required by the standards.  (Closes: Debian #988027)

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

---
 usr/include/setjmp.h   | 7 ++++++-
 usr/klibc/CAVEATS      | 3 +--
 usr/klibc/siglongjmp.c | 3 ++-
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/usr/include/setjmp.h b/usr/include/setjmp.h
index abebccde..5916cd8a 100644
--- a/usr/include/setjmp.h
+++ b/usr/include/setjmp.h
@@ -27,6 +27,7 @@ __extern __noreturn longjmp(jmp_buf, int);
 struct __sigjmp_buf {
 	jmp_buf __jmpbuf;
 	sigset_t __sigs;
+	unsigned char __sigs_saved;
 };
 
 typedef struct __sigjmp_buf sigjmp_buf[1];
@@ -34,7 +35,11 @@ typedef struct __sigjmp_buf sigjmp_buf[1];
 #define sigsetjmp(__env, __save) \
 ({ \
   struct __sigjmp_buf *__e = (__env); \
-  sigprocmask(0, NULL, &__e->__sigs); \
+  if (__save) { \
+    sigprocmask(0, NULL, &__e->__sigs); \
+    __e->__sigs_saved = 1; \
+  } else \
+    __e->__sigs_saved = 0; \
   setjmp(__e->__jmpbuf); \
 })
 
diff --git a/usr/klibc/CAVEATS b/usr/klibc/CAVEATS
index 5e991cb7..39949c28 100644
--- a/usr/klibc/CAVEATS
+++ b/usr/klibc/CAVEATS
@@ -13,8 +13,7 @@ Compiling with -O0 is more likely to work on gcc 3.
 setjmp()/longjmp():
 -------------------
 setjmp() and longjmp() *do not* save signal state.  sigsetjmp() and
-siglongjmp() *do* save the signal mask -- regardless of the value of
-the extra argument.
+siglongjmp() *do* save the signal mask if the extra argument is nonzero.
 
 The standards actually state that if you pass longjmp() a final value
 of zero the library should change that to a 1!  Presumably the reason
diff --git a/usr/klibc/siglongjmp.c b/usr/klibc/siglongjmp.c
index 31042cbd..45f4e400 100644
--- a/usr/klibc/siglongjmp.c
+++ b/usr/klibc/siglongjmp.c
@@ -10,6 +10,7 @@
 
 __noreturn siglongjmp(sigjmp_buf buf, int retval)
 {
-	sigprocmask(SIG_SETMASK, &buf->__sigs, NULL);
+	if (buf->__sigs_saved)
+		sigprocmask(SIG_SETMASK, &buf->__sigs, NULL);
 	longjmp(buf->__jmpbuf, retval);
 }