Linux: Use our own signalfd wrapper, rather than libstddjb

selfpipe already does a fine job of interfacing to signalfd. But Debian and Ubuntu want us to depend on the skalibs-dev package rather than build libstddjb ourselves. That would be fine except that skalibs-dev has static libraries only, and they aren't built with -fPIC. This interferes with building mosh-{client,server} as position-independent executables, which is a desirable security measure. So we have our own wrapper, which invokes either signalfd or selfpipe. And we build it ourselves with our own flags, because it's part of the Mosh project proper. (closes #108)
2012-04-12 05:24:50 -04:00
parent 93325d3ef0
commit 0eec0b60f0
10 changed files with 180 additions and 46 deletions
@@ -0,0 +1,75 @@
+/*
+    Mosh: the mobile shell
+    Copyright 2012 Keith Winstein
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <errno.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/signalfd.h>
+
+#include "fatal_assert.h"
+
+static sigset_t caught;
+static int fd = -1;
+
+#define SIGNALFD_FLAGS ( SFD_NONBLOCK | SFD_CLOEXEC )
+
+int sigfd_init( void )
+{
+  if ( fd != -1 ) {
+    errno = EBUSY;
+    return -1;
+  }
+  sigemptyset( &caught );
+  fd = signalfd( -1, &caught, SIGNALFD_FLAGS );
+  return fd;
+}
+
+int sigfd_trap( int sig )
+{
+  /* The callers all fatal_assert on error, so we can do the same here.
+     We still return 'int' in order to have the same API as libstddjb. */
+  fatal_assert( 0 <= fd );
+  fatal_assert( 0 <= sigaddset( &caught, sig ) );
+  fatal_assert( 0 <= sigprocmask( SIG_BLOCK, &caught, NULL ) );
+  fatal_assert( 0 <= signalfd( fd, &caught, SIGNALFD_FLAGS ) );
+  return 0;
+}
+
+int sigfd_read( void )
+{
+  int r;
+  struct signalfd_siginfo si;
+
+  do {
+    r = read( fd, &si, sizeof( si ) );
+  } while ( ( r == -1 ) && ( errno == EINTR ) );
+
+  if ( r == -1 ) {
+    if ( errno == EAGAIN || errno == EWOULDBLOCK )
+      /* No signal available */
+      return 0;
+    return -1;
+  } else if ( r != sizeof( si ) ) {
+    /* Should never happen?
+       Includes r = 0, i.e. end of file */
+    errno = EPIPE;
+    return -1;
+  }
+
+  return (int) si.ssi_signo;
+}