overhaul implementation-internal signal protections

the new approach relies on the fact that the only ways to create
sigset_t objects without invoking UB are to use the sig*set()
functions, or from the masks returned by sigprocmask, sigaction, etc.
or in the ucontext_t argument to a signal handler. thus, as long as
sigfillset and sigaddset avoid adding the "protected" signals, there
is no way the application will ever obtain a sigset_t including these
bits, and thus no need to add the overhead of checking/clearing them
when sigprocmask or sigaction is called.

note that the old code actually *failed* to remove the bits from
sa_mask when sigaction was called.

the new implementations are also significantly smaller, simpler, and
faster due to ignoring the useless "GNU HURD signals" 65-1024, which
are not used and, if there's any sanity in the world, never will be
used.

diff --git a/dist/config.mak b/dist/config.mak
index 691e3ce1bb8ce100466524c05c23f332f7ff50c2..66aa44cd822c6d83fe301646b201670bee54fa29 100644 (file)
--- a/dist/config.mak
+++ b/dist/config.mak
@@ -18,7 +18,7 @@ exec_prefix = /usr/local
 #CFLAGS += -fomit-frame-pointer -mno-accumulate-outgoing-args
 
 # Uncomment for warnings (as errors). Might need tuning to your gcc version.
-#CFLAGS += -Werror -Wall -Wpointer-arith -Wcast-align -Wno-parentheses -Wno-char-subscripts -Wno-uninitialized -Wno-sequence-point -Wno-missing-braces -Wno-unused-value
+#CFLAGS += -Werror -Wall -Wpointer-arith -Wcast-align -Wno-parentheses -Wno-char-subscripts -Wno-uninitialized -Wno-sequence-point -Wno-missing-braces -Wno-unused-value -Wno-overflow -Wno-int-to-pointer-cast
 
 # Uncomment if you want to build a shared library (experimental).
 #LIBC_LIBS += lib/libc.so

diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h
index 049f5dfb4ddd4e1f2f5303e20e6e5cc1b44f11fb..24cbeb25d136b06f29ab33b03e832d348f9d75c2 100644 (file)
--- a/src/internal/pthread_impl.h
+++ b/src/internal/pthread_impl.h
@@ -75,9 +75,12 @@ struct __timer {
 
 #include "pthread_arch.h"
 
-#define SIGCANCEL 32
-#define SIGSYSCALL 33
-#define SIGTIMER 34
+#define SIGTIMER 32
+#define SIGCANCEL 33
+#define SIGSYSCALL 34
+
+#define SIGPT_SET ((sigset_t){{[sizeof(long)==4] = 3<<(32*(sizeof(long)>4))}})
+#define SIGTIMER_SET ((sigset_t){{ 0x80000000 }})
 
 int __set_thread_area(void *);
 int __libc_sigaction(int, const struct sigaction *, struct sigaction *);

diff --git a/src/signal/raise.c b/src/signal/raise.c
index 9948f4189bc7dce65196fa8652c4f0c95998200f..71e0505b0f598d1c3184e3f38cd78d57204a05ad 100644 (file)
--- a/src/signal/raise.c
+++ b/src/signal/raise.c
@@ -1,18 +1,16 @@
 #include <signal.h>
 #include <errno.h>
+#include <stdint.h>
 #include "syscall.h"
 
-int __sigprocmask(int, const sigset_t *, sigset_t *);
-
 int raise(int sig)
 {
        int pid, tid, ret;
        sigset_t set;
-       sigfillset(&set);
-       __sigprocmask(SIG_BLOCK, &set, &set);
+       __syscall(SYS_rt_sigprocmask, SIG_BLOCK, (uint64_t[]){-1}, &set, 8);
        tid = syscall(SYS_gettid);
        pid = syscall(SYS_getpid);
        ret = syscall(SYS_tgkill, pid, tid, sig);
-       __sigprocmask(SIG_SETMASK, &set, 0);
+       __syscall(SYS_rt_sigprocmask, SIG_SETMASK, &set, 0, 8);
        return ret;
 }

diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index 887bbc4f70989e4f837e12bcc5d6326221747016..18956c6b24a84724143df86e1679fcc52a683620 100644 (file)
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -35,7 +35,7 @@ int __libc_sigaction(int sig, const struct sigaction *sa, struct sigaction *old)
 
 int __sigaction(int sig, const struct sigaction *sa, struct sigaction *old)
 {
-       if (sig-SIGCANCEL < 3U) {
+       if (sig-32U < 3) {
                errno = EINVAL;
                return -1;
        }

diff --git a/src/signal/sigaddset.c b/src/signal/sigaddset.c
index 23e655dbf1ca1aa97f896e323e442696e3e7ff70..d632c6fbe4c33f35b83bf724d23639f60e852888 100644 (file)
--- a/src/signal/sigaddset.c
+++ b/src/signal/sigaddset.c
@@ -4,7 +4,7 @@
 int sigaddset(sigset_t *set, int sig)
 {
        unsigned s = sig-1;
-       if (s >= 8*sizeof(sigset_t)) {
+       if (s >= 8*sizeof(sigset_t) || s-32U<3) {
                errno = EINVAL;
                return -1;
        }

diff --git a/src/signal/sigdelset.c b/src/signal/sigdelset.c
index 14042fb8fa8bfee53c12da1b2fb6a1d65cf25302..f8794ad6a155473919995831cb9f0d234889def4 100644 (file)
--- a/src/signal/sigdelset.c
+++ b/src/signal/sigdelset.c
@@ -4,7 +4,7 @@
 int sigdelset(sigset_t *set, int sig)
 {
        unsigned s = sig-1;
-       if (s >= 8*sizeof(sigset_t)) {
+       if (s >= 8*sizeof(sigset_t) || s-32U<3) {
                errno = EINVAL;
                return -1;
        }

diff --git a/src/signal/sigemptyset.c b/src/signal/sigemptyset.c
index 91f77adf3a7b4c5361cff4d73382b9ca82b53dbb..ca9b89207f97bb59f6c6b754a6bb2ebbe50b5f01 100644 (file)
--- a/src/signal/sigemptyset.c
+++ b/src/signal/sigemptyset.c
@@ -3,6 +3,7 @@
 
 int sigemptyset(sigset_t *set)
 {
-       memset(set, 0, sizeof *set);
+       set->__bits[0] = 0;
+       if (sizeof(long)==4) set->__bits[1] = 0;
        return 0;
 }

diff --git a/src/signal/sigfillset.c b/src/signal/sigfillset.c
index fab50a528649a8dad07ea7655761dfa2f511dbe0..6c84b9b7859b03472fe91e8ad5575f45afa54c1d 100644 (file)
--- a/src/signal/sigfillset.c
+++ b/src/signal/sigfillset.c
@@ -1,8 +1,14 @@
 #include <signal.h>
 #include <string.h>
+#include <limits.h>
 
 int sigfillset(sigset_t *set)
 {
-       memset(set, -1, sizeof *set);
+#if ULONG_MAX == 0xffffffff
+       set->__bits[0] = 0x7ffffffful;
+       set->__bits[1] = 0xfffffffcul;
+#else
+       set->__bits[0] = 0xfffffffc7ffffffful;
+#endif
        return 0;
 }

diff --git a/src/signal/sigismember.c b/src/signal/sigismember.c
index afd29e523b83ab50e35f2815f67e12e9028c3e4d..d3de6efb8f5bbfe9460ed45202325be3209fee9b 100644 (file)
--- a/src/signal/sigismember.c
+++ b/src/signal/sigismember.c
@@ -4,7 +4,7 @@
 int sigismember(const sigset_t *set, int sig)
 {
        unsigned s = sig-1;
-       if (s >= 8*sizeof(sigset_t)) {
+       if (s >= 8*sizeof(sigset_t) || s-32U<3) {
                errno = EINVAL;
                return -1;
        }

diff --git a/src/signal/sigprocmask.c b/src/signal/sigprocmask.c
index a272c10d301df8fef5b9ea58f7b1a41d96a7130c..3f003afbef890b8965dd17c45db50787246ca89e 100644 (file)
--- a/src/signal/sigprocmask.c
+++ b/src/signal/sigprocmask.c
@@ -4,27 +4,11 @@
 #include "libc.h"
 #include "pthread_impl.h"
 
-int __libc_sigprocmask(int how, const sigset_t *set, sigset_t *old)
+int sigprocmask(int how, const sigset_t *set, sigset_t *old)
 {
-       return syscall(SYS_rt_sigprocmask, how, set, old, 8);
-}
-
-int __sigprocmask(int how, const sigset_t *set, sigset_t *old)
-{
-       sigset_t tmp;
        if (how > 2U) {
                errno = EINVAL;
                return -1;
        }
-       /* Disallow blocking thread control signals */
-       if (set && how != SIG_UNBLOCK) {
-               tmp = *set;
-               set = &tmp;
-               sigdelset(&tmp, SIGCANCEL);
-               sigdelset(&tmp, SIGSYSCALL);
-               sigdelset(&tmp, SIGTIMER);
-       }
-       return __libc_sigprocmask(how, set, old);
+       return syscall(SYS_rt_sigprocmask, how, set, old, 8);
 }
-
-weak_alias(__sigprocmask, sigprocmask);

diff --git a/src/thread/__rsyscall.c b/src/thread/__rsyscall.c
index 61d41df76b4b3466a549be50b27789ee829bbbed..e885d9e7ac4fe0b640739bc12b384caa013dcdd7 100644 (file)
--- a/src/thread/__rsyscall.c
+++ b/src/thread/__rsyscall.c
@@ -56,8 +56,7 @@ int __rsyscall(int nr, long a, long b, long c, long d, long e, long f)
        while ((i=rs.blocks))
                __wait(&rs.blocks, 0, i, 1);
 
-       sigfillset(&set);
-       __libc_sigprocmask(SIG_BLOCK, &set, &set);
+       __syscall(SYS_rt_sigprocmask, SIG_BLOCK, (uint64_t[]){-1}, &set, 8);
 
        if (!rs.init) {
                struct sigaction sa = {
@@ -88,7 +87,7 @@ int __rsyscall(int nr, long a, long b, long c, long d, long e, long f)
        }
 
        /* Handle any lingering signals with no-op */
-       __libc_sigprocmask(SIG_UNBLOCK, &set, &set);
+       __syscall(SYS_rt_sigprocmask, SIG_SETMASK, &set, &set, 8);
 
        /* Resume other threads' signal handlers and wait for them */
        rs.hold = 0;

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 0d2c17bbe8a623902b85efef8ae82718a1cd2fde..6545539b5c979f5dd6248d14cf01c8557099f207 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -34,7 +34,7 @@ void __pthread_unwind_next(struct __ptcb *cb)
        if (!n) exit(0);
 
        if (self->detached && self->map_base) {
-               __syscall(SYS_rt_sigprocmask, SIG_BLOCK, (long)(uint64_t[1]){-1},0,8);
+               __syscall(SYS_rt_sigprocmask, SIG_BLOCK, (uint64_t[]){-1},0,8);
                __unmapself(self->map_base, self->map_size);
        }
 
@@ -44,12 +44,8 @@ void __pthread_unwind_next(struct __ptcb *cb)
 static int start(void *p)
 {
        struct pthread *self = p;
-       if (self->unblock_cancel) {
-               sigset_t set;
-               sigemptyset(&set);
-               sigaddset(&set, SIGCANCEL);
-               __libc_sigprocmask(SIG_UNBLOCK, &set, 0);
-       }
+       if (self->unblock_cancel)
+               __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, &SIGPT_SET, 0, 8);
        pthread_exit(self->start(self->start_arg));
        return 0;
 }
@@ -72,11 +68,7 @@ int pthread_create(pthread_t *res, const pthread_attr_t *attr, void *(*entry)(vo
 
        if (!self) return ENOSYS;
        if (!libc.threaded) {
-               sigset_t set;
-               sigemptyset(&set);
-               sigaddset(&set, SIGSYSCALL);
-               sigaddset(&set, SIGCANCEL);
-               __libc_sigprocmask(SIG_UNBLOCK, &set, 0);
+               __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, &SIGPT_SET, 0, 8);
                libc.threaded = 1;
        }
 

diff --git a/src/time/timer_create.c b/src/time/timer_create.c
index cc10bef08b7b0bebc5977dcd360a20dacb052ddc..3bcfa951d92e5342828e9b58d51bd8dc9b9c565b 100644 (file)
--- a/src/time/timer_create.c
+++ b/src/time/timer_create.c
@@ -51,8 +51,7 @@ static void install_handler()
                .sa_flags = SA_SIGINFO | SA_RESTART
        };
        __libc_sigaction(SIGTIMER, &sa, 0);
-       sigaddset(&sa.sa_mask, SIGTIMER);
-       __libc_sigprocmask(SIG_UNBLOCK, &sa.sa_mask, 0);
+       __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, &SIGTIMER_SET, 0, 8);
 }
 
 static void *start(void *arg)