path: root/src/process
diff options
authorRich Felker <>2014-05-29 21:01:32 -0400
committerRich Felker <>2014-05-29 21:01:32 -0400
commitdd5f50da6f6c3df5647e922e47f8568a8896a752 (patch)
treec5ab9a1006d2ab4c449f8fa922ce3237acad30e4 /src/process
parent2e55da911896a91e95b24ab5dc8a9d9b0718f4de (diff)
support linux kernel apis (new archs) with old syscalls removed
such archs are expected to omit definitions of the SYS_* macros for syscalls their kernels lack from arch/$ARCH/bits/syscall.h. the preprocessor is then able to select the an appropriate implementation for affected functions. two basic strategies are used on a case-by-case basis: where the old syscalls correspond to deprecated library-level functions, the deprecated functions have been converted to wrappers for the modern function, and the modern function has fallback code (omitted at the preprocessor level on new archs) to make use of the old syscalls if the new syscall fails with ENOSYS. this also improves functionality on older kernels and eliminates the incentive to program with deprecated library-level functions for the sake of compatibility with older kernels. in other situations where the old syscalls correspond to library-level functions which are not deprecated but merely lack some new features, such as the *at functions, the old syscalls are still used on archs which support them. this may change at some point in the future if or when fallback code is added to the new functions to make them usable (possibly with reduced functionality) on old kernels.
Diffstat (limited to 'src/process')
2 files changed, 21 insertions, 2 deletions
diff --git a/src/process/fork.c b/src/process/fork.c
index 864c7d7a..f8cf21e7 100644
--- a/src/process/fork.c
+++ b/src/process/fork.c
@@ -1,5 +1,6 @@
#include <unistd.h>
#include <string.h>
+#include <signal.h>
#include "syscall.h"
#include "libc.h"
#include "pthread_impl.h"
@@ -16,7 +17,11 @@ pid_t fork(void)
sigset_t set;
+#ifdef SYS_fork
ret = syscall(SYS_fork);
+ ret = syscall(SYS_clone, SIGCHLD, 0);
if (libc.has_thread_pointer && !ret) {
pthread_t self = __pthread_self();
self->tid = self->pid = __syscall(SYS_getpid);
diff --git a/src/process/posix_spawn.c b/src/process/posix_spawn.c
index 08644f51..08928b0e 100644
--- a/src/process/posix_spawn.c
+++ b/src/process/posix_spawn.c
@@ -22,6 +22,20 @@ struct args {
void __get_handler_set(sigset_t *);
+static int __sys_dup2(int old, int new)
+#ifdef SYS_dup2
+ return __syscall(SYS_dup2, old, new);
+ if (old==new) {
+ int r = __syscall(SYS_fcntl, old, F_GETFD);
+ return r<0 ? r : old;
+ } else {
+ return __syscall(SYS_dup3, old, new, 0);
+ }
static int child(void *args_vp)
int i, ret;
@@ -92,14 +106,14 @@ static int child(void *args_vp)
goto fail;
case FDOP_DUP2:
- if ((ret=__syscall(SYS_dup2, op->srcfd, op->fd))<0)
+ if ((ret=__sys_dup2(op->srcfd, op->fd))<0)
goto fail;
fd = __sys_open(op->path, op->oflag, op->mode);
if ((ret=fd) < 0) goto fail;
if (fd != op->fd) {
- if ((ret=__syscall(SYS_dup2, fd, op->fd))<0)
+ if ((ret=__sys_dup2(fd, op->fd))<0)
goto fail;
__syscall(SYS_close, fd);