2018-10-01 Nathan Sidwell <nathan@acm.org>
* configure.ac (checkfuncs): Add pipe2.
* config.in, configure: Rebuilt.
* pex-unix.c (pex_unix_exec_child): Comminicate errors from child
to parent with a pipe, when possible.
===================================================================
@@ -195,6 +195,9 @@
/* Define to 1 if you have the `on_exit' function. */
#undef HAVE_ON_EXIT
+/* Define to 1 if you have the `pipe2' function. */
+#undef HAVE_PIPE2
+
/* Define to 1 if you have the <process.h> header file. */
#undef HAVE_PROCESS_H
===================================================================
@@ -5727,7 +5727,7 @@ funcs="$funcs setproctitle"
vars="sys_errlist sys_nerr sys_siglist"
checkfuncs="__fsetlocking canonicalize_file_name dup3 getrlimit getrusage \
- getsysinfo gettimeofday on_exit psignal pstat_getdynamic pstat_getstatic \
+ getsysinfo gettimeofday on_exit pipe2 psignal pstat_getdynamic pstat_getstatic \
realpath setrlimit sbrk spawnve spawnvpe strerror strsignal sysconf sysctl \
sysmp table times wait3 wait4"
@@ -5743,7 +5743,7 @@ if test "x" = "y"; then
index insque \
memchr memcmp memcpy memmem memmove memset mkstemps \
on_exit \
- psignal pstat_getdynamic pstat_getstatic putenv \
+ pipe2 psignal pstat_getdynamic pstat_getstatic putenv \
random realpath rename rindex \
sbrk setenv setproctitle setrlimit sigsetmask snprintf spawnve spawnvpe \
stpcpy stpncpy strcasecmp strchr strdup \
===================================================================
@@ -391,7 +391,7 @@ funcs="$funcs setproctitle"
vars="sys_errlist sys_nerr sys_siglist"
checkfuncs="__fsetlocking canonicalize_file_name dup3 getrlimit getrusage \
- getsysinfo gettimeofday on_exit psignal pstat_getdynamic pstat_getstatic \
+ getsysinfo gettimeofday on_exit pipe2 psignal pstat_getdynamic pstat_getstatic \
realpath setrlimit sbrk spawnve spawnvpe strerror strsignal sysconf sysctl \
sysmp table times wait3 wait4"
@@ -407,7 +407,7 @@ if test "x" = "y"; then
index insque \
memchr memcmp memcpy memmem memmove memset mkstemps \
on_exit \
- psignal pstat_getdynamic pstat_getstatic putenv \
+ pipe2 psignal pstat_getdynamic pstat_getstatic putenv \
random realpath rename rindex \
sbrk setenv setproctitle setrlimit sigsetmask snprintf spawnve spawnvpe \
stpcpy stpncpy strcasecmp strchr strdup \
===================================================================
@@ -569,6 +569,38 @@ pex_unix_exec_child (struct pex_obj *obj
int toclose, const char **errmsg, int *err)
{
pid_t pid = -1;
+ /* Tuple to communicate error from child to parent. We can safely
+ transfer string literal pointers as both run with identical
+ address mappings. */
+ struct fn_err
+ {
+ const char *fn;
+ int err;
+ };
+ volatile int do_pipe = 0;
+ volatile int pipes[2]; /* [0]:reader,[1]:writer. */
+#ifdef O_CLOEXEC
+ do_pipe = 1;
+#endif
+ if (do_pipe)
+ {
+#ifdef HAVE_PIPE2
+ if (pipe2 ((int *)pipes, O_CLOEXEC))
+ do_pipe = 0;
+#else
+ if (pipe ((int *)pipes))
+ do_pipe = 0;
+ else
+ {
+ if (fcntl (pipes[1], F_SETFD, FD_CLOEXEC) == -1)
+ {
+ close (pipes[0]);
+ close (pipes[1]);
+ do_pipe = 0;
+ }
+ }
+#endif
+ }
/* We declare these to be volatile to avoid warnings from gcc about
them being clobbered by vfork. */
@@ -579,8 +611,9 @@ pex_unix_exec_child (struct pex_obj *obj
This clobbers the parent's environ so we need to restore it.
It would be nice to use one of the exec* functions that takes an
environment as a parameter, but that may have portability
- issues. */
- char **save_environ = environ;
+ issues. It is marked volatile so the child doesn't consider it a
+ dead variable and therefore clobber where ever it is stored. */
+ char **volatile save_environ = environ;
for (retries = 0; retries < 4; ++retries)
{
@@ -594,6 +627,11 @@ pex_unix_exec_child (struct pex_obj *obj
switch (pid)
{
case -1:
+ if (do_pipe)
+ {
+ close (pipes[0]);
+ close (pipes[1]);
+ }
*err = errno;
*errmsg = VFORK_STRING;
return (pid_t) -1;
@@ -601,40 +639,43 @@ pex_unix_exec_child (struct pex_obj *obj
case 0:
/* Child process. */
{
- const char *bad_fn = NULL;
+ struct fn_err failed;
+ failed.fn = NULL;
- if (!bad_fn && in != STDIN_FILE_NO)
+ if (do_pipe)
+ close (pipes[0]);
+ if (!failed.fn && in != STDIN_FILE_NO)
{
if (dup2 (in, STDIN_FILE_NO) < 0)
- bad_fn = "dup2";
+ failed.fn = "dup2", failed.err = errno;
else if (close (in) < 0)
- bad_fn = "close";
+ failed.fn = "close", failed.err = errno;
}
- if (!bad_fn && out != STDOUT_FILE_NO)
+ if (!failed.fn && out != STDOUT_FILE_NO)
{
if (dup2 (out, STDOUT_FILE_NO) < 0)
- bad_fn = "dup2";
+ failed.fn = "dup2", failed.err = errno;
else if (close (out) < 0)
- bad_fn = "close";
+ failed.fn = "close", failed.err = errno;
}
- if (!bad_fn && errdes != STDERR_FILE_NO)
+ if (!failed.fn && errdes != STDERR_FILE_NO)
{
if (dup2 (errdes, STDERR_FILE_NO) < 0)
- bad_fn = "dup2";
+ failed.fn = "dup2", failed.err = errno;
else if (close (errdes) < 0)
- bad_fn = "close";
+ failed.fn = "close", failed.err = errno;
}
- if (!bad_fn && toclose >= 0)
+ if (!failed.fn && toclose >= 0)
{
if (close (toclose) < 0)
- bad_fn = "close";
+ failed.fn = "close", failed.err = errno;
}
- if (!bad_fn && (flags & PEX_STDERR_TO_STDOUT) != 0)
+ if (!failed.fn && (flags & PEX_STDERR_TO_STDOUT) != 0)
{
if (dup2 (STDOUT_FILE_NO, STDERR_FILE_NO) < 0)
- bad_fn = "dup2";
+ failed.fn = "dup2", failed.err = errno;
}
- if (!bad_fn)
+ if (!failed.fn)
{
if (env)
/* NOTE: In a standard vfork implementation this clobbers
@@ -644,30 +685,35 @@ pex_unix_exec_child (struct pex_obj *obj
if ((flags & PEX_SEARCH) != 0)
{
execvp (executable, to_ptr32 (argv));
- bad_fn = "execvp";
+ failed.fn = "execvp", failed.err = errno;
}
else
{
execv (executable, to_ptr32 (argv));
- bad_fn = "execv";
+ failed.fn = "execv", failed.err = errno;
}
}
/* Something failed, report an error. We don't use stdio
routines, because we might be here due to a vfork call. */
ssize_t retval = 0;
- int eno = errno;
-
+
+ if (!do_pipe
+ || write (pipes[1], &failed, sizeof (failed)) != sizeof (failed))
+ {
+ /* The parent will not see our scream above, so write to
+ stdout. */
#define writeerr(s) (retval |= write (STDERR_FILE_NO, s, strlen (s)))
- writeerr (obj->pname);
- writeerr (": error trying to exec '");
- writeerr (executable);
- writeerr ("': ");
- writeerr (bad_fn);
- writeerr (": ");
- writeerr (xstrerror (eno));
- writeerr ("\n");
+ writeerr (obj->pname);
+ writeerr (": error trying to exec '");
+ writeerr (executable);
+ writeerr ("': ");
+ writeerr (failed.fn);
+ writeerr (": ");
+ writeerr (xstrerror (failed.err));
+ writeerr ("\n");
#undef writeerr
+ }
/* Exit with -2 if the error output failed, too. */
_exit (retval < 0 ? -2 : -1);
@@ -678,8 +724,6 @@ pex_unix_exec_child (struct pex_obj *obj
default:
/* Parent process. */
{
- const char *bad_fn = NULL;
-
/* Restore environ. Note that the parent either doesn't run
until the child execs/exits (standard vfork behaviour), or
if it does run then vfork is behaving more like fork. In
@@ -687,24 +731,34 @@ pex_unix_exec_child (struct pex_obj *obj
copy of environ. */
environ = save_environ;
- if (!bad_fn && in != STDIN_FILE_NO)
+ struct fn_err failed;
+ failed.fn = NULL;
+ if (do_pipe)
+ {
+ close (pipes[1]);
+ ssize_t len = read (pipes[0], &failed, sizeof (failed));
+ if (len < 0)
+ failed.fn = NULL;
+ close (pipes[0]);
+ }
+
+ if (!failed.fn && in != STDIN_FILE_NO)
if (close (in) < 0)
- bad_fn = "close";
- if (!bad_fn && out != STDOUT_FILE_NO)
+ failed.fn = "close", failed.err = errno;
+ if (!failed.fn && out != STDOUT_FILE_NO)
if (close (out) < 0)
- bad_fn = "close";
- if (!bad_fn && errdes != STDERR_FILE_NO)
+ failed.fn = "close", failed.err = errno;
+ if (!failed.fn && errdes != STDERR_FILE_NO)
if (close (errdes) < 0)
- bad_fn = "close";
+ failed.fn = "close", failed.err = errno;
- if (bad_fn)
+ if (failed.fn)
{
- *err = errno;
- *errmsg = bad_fn;
+ *err = failed.err;
+ *errmsg = failed.fn;
return (pid_t) -1;
}
}
-
return pid;
}
}